sailboat sound signal in fog

Inshore Fishing
Offshore Fishing

Download ALL AT SEA
Subscribe to All At Sea
Advertising – All At Sea – Caribbean

Sound Signals in Restricted Visibility and Rule 35

You know you want it...

Mocka Jumbies and Rum...

Fog, mist, falling snow, heavy rainstorms, sandstorms or any other similar causes can make conditions that hamper visibility. Sound signals for vessels in restricted visibility, whether underway, at anchor or aground, day or night, are the subject of Rule 35 ( COLREGS ). The bell and gong are added into the mix of whistle sounds used as options for restricted visibility signals. Rule 35 is fairly complex, and it is advised to have a highlighter in hand while reading through it.

The Rules of the Road state when underway ‘vessels shall sound at intervals of not more than two minutes’ the prescribed sound signal.

Why a two minute rule? A requirement for all vessels is to maintain a proper look-out by sight and hearing. In restricted visibility, the two minutes allows the look-out to listen for sound signals from other vessels groping their way through the fog. COLREGS lists the following sound signals for vessels underway:

A power-driven vessel making way shall sound one prolonged blast.
A power-driven vessel underway but stopped shall sound two prolonged blasts.
A pilot vessel , engaged in pilotage duty, may also sound four short blasts in addition to the sound signals required by a power-driven vessel.
Vessels that are encumbered , due to their maneuverability or their ranking in the hierarchy of responsibilities between vessels in Rule 18, shall sound one prolonged blast followed by two short blasts. These encumbered vessels are those not under command, restricted in their ability maneuver due to their work, constrained by draft, sailing , engaged in commercial fishing and towing or pushing another vessel.

If a vessel being towed is manned, that tow or barge shall sound one prolonged blast followed by three short blasts. The tug itself first sounds its own signal for an encumbered vessel, and if possible, the manned tow sounds its own signal immediately after.
While at anchor , ringing the ship’s bell rapidly for about five seconds at intervals of no more than one minute is the primary sound signal for smaller vessels.
Larger vessels, those 100m (328ft) or more in length, also use a gong.

For these large yachts and ships, the bell is rapidly sounded from the foredeck, and immediately followed by the gong sounded rapidly from the afterdeck, both for about five seconds.

In addition, any vessel at anchor can also sound one short, one prolonged and one short blasts as a collision avoidance warning.

There are two classes of working vessels that do not use the bell and gong signals while at anchor.

Commercial fishing boats that are fishing while at anchor, and vessels restricted in their ability to maneuver that are carrying out their work while at anchor must use the encumbered vessel sound signal of one prolonged and two short blasts.

If aground , a vessel shall give the bell signal and if required the (at anchor) gong signal prescribed … and shall, in addition, give three separate and distinct strokes on the bell immediately before and after the rapid ringing of the bell.

To further finesse Rule 35, The International Regulations for Preventing Collisions at Sea (IRPCS), doesn’t oblige the bell signals to be used at anchor and when aground for vessels 12m (39ft) or more, but less than 20m (65.6ft) in length. Instead, she shall make some other efficient sound signal at intervals of not more than two minutes.

Vessels less than 12m LOA are NOT required to use any of the sound signals required for vessels in restricted visibility. They also can make some other efficient sound signal at intervals of not more than two minutes.

With the large number of sound signals available for use in restricted visibility, remembering all the possibilities can be difficult. Trying to quickly look up a sound signal heard in the fog by turning to Rule 35 in COLREGS can be a bit of a challenge.

A good alternative is to use one of the many laminated visual shorthand versions of COLREGS sold at ship chandleries.

For sound signals, a Morse code dot represents the short blast of about one-second duration. And a Morse code dash represents the prolonged blast of four to six seconds long.

Here’s the link to reference the Related, Rule 34 describing maneuvering and warning for powered vessels underweigh in international waters

If you like this, you’ll love:

Why do Yachts and Ships have Whistles Bells and Gongs?
Much Maligned Rays Part III

Don't Miss a Beat!

Stay in the loop with the Caribbean

International Regulations for Preventing Collisions at Sea (IRPCS)

Culebra Island Guide: Top 10 Must-Visit Spots for a Caribbean Escape

Uncovering the gems of st. martin and st. barts: a top 10 chronicle, miss pfaff rocks: the unlikely companion of our cruising voyage on s&s 41 sy pitufa, so caribbean you can almost taste the rum....

EDITOR PICKS

Talkative posts, the seven words you can’t put in a boat name, saying “no”, program for financing older boats – tips and suggestions, popular category.

Cruise 1742
St. Thomas, US Virgin Islands 514
Tortola, British Virgin Islands 432
Caribbean 424

How to sail and navigate through fog safely

Fog at sea can be far more treacherous than rough conditions with high winds and large waves, particularly for smaller vessels. Visibility may be almost zero, increasing the risk of colliding with other boats, the shore, or other obstacles. If fog draws in at sea, your first priority should be to ensure the safety of your crew, start using appropriate signals and take steps to make your boat as visible as possible.

Orientate yourself in fog using all your senses

Poor or near-zero visibility may be the main concern when navigating in fog , but it is not the only challenge for the crew. Fog also distorts and dampens sound, causing it to reflect and travel in unusual ways which can make it difficult to determine which direction a sound is coming from. Even with sophisticated technology like navigation, GPS, and radar, it is possible to lose track of a boat's position and its heading in foggy conditions.

But that doesn't mean that sailing in fog is impossible. It just places significantly greater demands on the sailors and their experience and ability. In general, if the fog is close to shore and you are not sure if it will clear at sea, it is worth postponing departure from the marina or anchorage. If you are caught by fog at sea , several steps should be taken to maintain safety and minimize potential damage, based on sailing regulations as well as the expertise of experienced mariners.

The first steps to take when the fog starts rolling in

Avoid sailing in fog if you can, especially if sailing is more of a leisure activity for you and you haven't logged thousands of nautical miles. This means watching the weather forecast before setting sail and, if necessary, using your experience to judge whether fog is likely to develop during your trip. If there is already fog in port, it is better to wait until it clears so you can enjoy the beauty of sailing unhindered.

Out at sea, however, fog can easily catch you off guard and if this happens, you must act quickly. The safety of the crew comes first. All members should be fully-clothed and wearing life jackets, because, in the event of a collision, there may be no time to get dressed. Crew members should be secured to the boat using safety lines or harnesses that are loose enough to allow movement around the boat and easy to undo. Safety harnesses are essential because if someone falls overboard in fog, it will be near impossible to find them in the sea.

YACHTING.COM TIP: Do you know how to rescue a person who has fallen overboard? Despite all safeguards, sometimes it is unavoidable, so every crew member should know exactly what to do. Go over the main guidelines and steps to take in our article — Man Over Board (MOB): a step-by-step guide .

Turn on the radar reflector and navigation lights so the boat can be seen in the fog

As well as ensuring the safety of the crew, it is also crucial to focus on the boat itself and minimise the risk of collision . The moment fog sets in, the skipper or navigator should plot the boat's position as precisely as possible on the chart or determine its most likely position. The radar reflector should be switched on. If it is not fixed on the boat, place it as high as possible on the rigging. As the vast majority of vessels on the open sea use radar to avoid a collision, this will increase the chances of being noticed by a passing vessel. Next, turn on your navigation lights.

Don't forget to sound signals in fog

It is not just enough to improve the visibility of your boat; you also need to sound the signals prescribed by international law.

These are the usual sound signals in fog:

Under sail: one long and two short blasts every 2 minutes

Under engine power: two long blasts every 2 minutes

Unmanageable vessel, vessel with restricted movement: one long tone and two short blasts every two minutes

At anchor: ring the bell rapidly for 5 seconds every minute (one short, one long and one short ring)

More sailing tips:

Medicanes in Greece

The ultimate yacht cleaning kit

New Year's resolution: let's sail more eco

How to have a nautical Christmas

What to pack for a tropical sailing

How to gear up for the 2024 sailing season

Use your eyes.

Even though visibility is greatly reduced in foggy conditions, it is still important to keep a watchful eye on the situation rather than relying solely on radar and navigation systems. The ideal place to be is out on the deck, where the glass in the windows and the glow of the monitors won't impair your view. Depending on the type of fog, visibility is usually best at the surface or at height.

Don't be afraid to move around the deck to find the best vantage point with the best visibility. At least one crew member should be monitoring the situation, ideally more, and another person should be assigned to the radar to keep an eye on it constantly. If you are sailing in fog at night , you can further improve the visibility of the boat by shining or flashing lights onto the sails using a powerful flashlight.

YACHTING.COM TIP: Are you concerned about encountering foggy conditions at sea and don't have enough experience sailing in more demanding conditions? Rent one of our charter boats along with an experienced skipper and enjoy a stress-free sailing holiday. Our sales team will be happy to help you with both.

Get to know fog with your ears

Fog not only reduces overall visibility, it also distorts the way sound travels . A sound can easily be perceived as coming from a short distance ahead when in reality it is a warning signal coming from far behind you. This is why it pays to use all of your senses as well as the available technology to navigate through the fog and reach safe waters.

Hearing is an important sense when navigating fog, especially when combined with sailing know-how. One proven strategy adopted by experienced sailors is setting an appropriate course . Generally, sound carries downwind so if you're heading upwind, you have a better chance of hearing any sound signals ahead of you. Conversely, if you are travelling downwind, the sound will carry with you, making it much harder to detect and identify its source.

Beams of light from the lighthouse reflecting in the mist in the darkness.

If you are not travelling under sail but using engine power , aim to cruise at a slower speed of around 3 to 5 knots (depending on the conditions). This means the engine will not drown out surrounding sounds. Turn off the engine every now and again and listen for any sounds or signals. In some cases, sound may get lost even when just two people are talking. It is therefore important to keep your ears open and monitor the situation closely. Of course, it is essential you know the fog sound signals described above, as well as the signals emitted by the neighbouring buoys, lighthouses and other marked sites, in order to navigate safely and prevent a collision.

YACHTING.COM TIP: Lighthouses are extremely useful when sailing in foggy conditions. Did you know that each has its own specific sound and light signals? Plus, they are real architectural gems, so take a look at our article on the 15 beautiful lighthouses you must visit .

Feel your surroundings with your whole body

To some extent, even your sense of touch or the sensations on your skin can assist you to navigate fog. And, while this is more of a supplementary aid when trying to get to a port or anchorage safely, every little thing counts.

Keep in mind that fog is caused by significant differences between air and sea/land temperatures . Therefore, you should head for a place where these differences are not so marked. Focus on how the air feels on your skin . For example, if the air feels warm while the water is cold, head for shallower waters where the sea is likely to be warmer and closer to the air temperature. Conversely, if the air is cool, head for the open sea where there is more depth and the water is cooler. 10–15

Don't forget your sense of smell

Even if you can't see or hear anything, smells may tell you a lot about what's going on around you. Smell is a complementary sense that can help you pinpoint the location of something that does not produce a sound. For example, the smell of fish can indicate the proximity of a fishing boat, just like diesel fumes can indicate the presence of a motorboat or boat nearby, etc.

YACHTING.COM TIP: Wondering what type of signals to use when sailing in fog? Sign up for a sailing course with us and learn everything you need to know under experienced professionals.

Need a skipper's license or just some more practice? Try our sailing courses...

Electronics and modern technology on board.

Most boats nowadays are equipped with modern navigation systems and equipment , (such as radar, GPS, radio, etc.) that pinpoint your current position and the position of vessels or obstacles around you. Electronics on board are of a very high standard, but they are not omnipotent. So, always consider electronics as an aid and a reference point, rather than the absolute truth.

Onboard radar system monitors for potential obstacles and other vessels

The moment fog rolls in, you should immediately turn on the radar . If you do not have it permanently installed on your boat, place it as far up on the rigging as possible to maximise its range. One crew member should be assigned to constantly monitor the radar and report to the helmsman or skipper about the presence of other vessels or hazards. Communication should be brief and to the point so that the helmsman can remain focussed on what they can see and hear around them.

GPS will help you to navigate your yacht

GPS is now the standard method of finding your location and searching for routes, even on smartphones, so it's no surprise that it's also an essential piece of equipment on a boat . However, like other electronic systems, GPS can be incorrect or inaccurate, especially when determining precise position or speed. Therefore, always use GPS in combination with your own observations . If you have a choice, go a GPS system that allows you to see where you had previously been sailing. When sailing in fog, this can be a useful way of finding your way back. Simply sail back in the opposite direction along your original course.

Radio can provide other useful information

An onboard radio is standard on most boats and is a useful aid when sailing in fog . If you have access to all the data you need, you can use the radio to communicate your position and intentions to nearby boats. This usually includes the name of the ship, its type and size, position (latitude and longitude), course and speed. To avoid any misunderstandings or distractions to you or other boats, always use simple and clear sentences in radio communication.

Now all that's left to do is pick a boat:

We have a large selection of boats available, as well as contacts with excellent skippers. Get in contact.

Denisa Nguyenová

Faq how to sail in fog.

Sailing In The Fog – What You Need To Know And Do

Ben Eriksen Carey July 15, 2014 Words 1 Comment

Sound Signals and VHF Protocol in the Fog

Our recent 3 day Morse Alpha sail training expedition in beautiful Maine offered a wide variety of sailing conditions. We saw gusts to 30 knots the first day out, thick fog the second, and light winds the third. The perfect course… a little bit of everything, couldn’t have planned it better myself.

We had fun tucking in a 2nd reef, then a 3rd, then shaking them all, and re-tucking them! We experimented with balance, moving our center of effort forward then aft to feel the effects of each sail individually.

But when the fog rolled in overnight, and the southeasterly winds persisted the next morning, we knew we weren’t going to be able to avoid traveling in the fog. We delayed as much as possible, spending time below going over sail theory, sail trim and learning the nuts and bolts of navigation in the fog. But 1100 came, and we had to catch the tide.

The Scenario

We conservatively motored our way through the Casco Passage, a tight channel with a strong 2-3 knot current and about a thousand lobster traps, or so it seemed—we were too busy to count. Making our way west towards The Deer Island Thorofare we heard the schooner Mary Day on the VHF giving a securité (pronounced “secure-a-tay”) call, announcing their name, location, direction of travel, and that they were under sail. They were just making their way past Stonington, eastbound. It was obviously socked in there too, bad news.

A sailing vessel replied to their securité call and asked for clarification on the Mary Day’s direction of travel and exact location (on a working channel, NOT 16). Then went on to ask how thick the fog was there. Captain Barry let him know he was “ socked-in just north of Russ Island “. To which the sailboat replied, “D o you think I should drop anchor here, right where I am if it’s really thick there?”

“Well Cap, I can’t really say. That’s up to you to decide.” Barry responded.

“Well, I think I’ll keep going then.” the yachtsman stated.

“Just keep sounding your horn, and we should pass each other safely” said Barry.

“We don’t have a horn.”

“Oh. Well Cap, that’s not good” said Barry calmly, surely holding back a few expletives and his opinion of the yachtsman’s seamanship on this public VHF forum.

A Sound Solution

As a sailing vessel with an auxiliary engine, we are required, under normal circumstances, to sound one of two (we are either a sailing vessel or a power-driven vessel) different sound signals in the fog as started clearly by Rule 35. It’s not an option! And besides, we kinda like to toot our horn!

Rule 35 – Sound Signals in Restricted Visibility (view full rule)

(a) A power-driven vessel making way through the water shall sound at intervals of not more than 2 minutes one prolonged blast. (—)

(c) A vessel not under command , a vessel restricted in her ability to maneuver whether underway or at anchor , a vessel constrained by her draft , a sailing vessel , a vessel engaged in fishing whether underway or at anchor and a vessel engaged in towing or pushing another vessel shall, instead of the signals prescribed in paragraph (a) or (b) of this Rule, sound at intervals of not more than 2 minutes three blasts in succession, namely one prolonged followed by two short blasts. (— • •)

*note: prolonged = 4-6 seconds, short = 1 second.

A Radio Solution

All vessels are allowed to give securité calls on the VHF, you don’t have to be large or restricted in your ability to maneuver. Securité calls are preferably made on channel 13, but unfortunately not everyone monitors 13. So channel 16 is used frequently. Please monitor channel 13! As a recreational vessel, we exercise diligence when giving securité calls, trying to reserve their use to narrow channels, busy commercial lanes, or when radar targets of concern are within a mile or two. But if there is ever doubt, we get on the radio and broadcast a securité.

How To Give An Effective Securité Call

Securité, Securité, Securité.

This is the forty-four foot sailing vessel Rocinante .

We are motor-sailing eastbound through the Fox Island Thorofare, just passing red nun number ten, off Iron Point.

Any concerned traffic please respond on channel one-three or one-six.

This is the sailing vessel Rocinante standing by on one-three and one-six.

The Prudent Solution

But no matter what we decide to do, underlying many of the decisions we make aboard Rocinante is the desire to be able to explain our actions in a court of law. We often ask ourselves, if an accident were to happen, would we be able to justify our every action and prove that we acted in the most prudent, responsible manner, and maintained the highest standards of seamanship. This may seem like a fearful way of living and sailing, but we don’t see it that way. Rather, it provides a very clear guideline for making decisions. If our yachtsman in the conversation above were to have had a collision with the Mary Da y, surely his lack of a horn would not hold up well in court. A very simple, inexpensive piece of gear could cost him his entire vessel (insurance payout).

Very timely! I am getting ready to head out today and I anticipate fog all weekend here in the Puget Sound. Your article was a good refresher for me. I just finished mounting and wiring my horn yesterday!

Sailing in fog: Pro navigator Mike Broughton shares his top tips

November 26, 2020

Just a few minutes of sailing in dense fog takes most sailors well out of their comfort zones: it’s disorientating and, quite frankly, scary for many. Here are some tips on how to prepare for, and deal with, a ‘pea soup’

sailing-in-fog-2017-fastnet-race-aerial-view-credit-carlo-borlenghi

Sailing in fog can be exhausting and disorientating. Photo: Carlo Borlenghi

At sea, fog can be summed up as condensed water vapour or just thick cloud on the surface. Sea fog, or advection fog, forms when relatively warm moist air moves over colder water and cools to its dew point temperature, causing the air to saturate.

Unlike land fog, or radiation fog, sea fog can occur at any time of day and still exist with quite strong winds. It only really clears with a change of air mass – usually with the passage of a cold front. Without the passage of a cold front, it can last for days.

While radiation fog usually occurs on cold, still winter days, sea fog or advection fog is more prevalent in early summer. June can be a particularly bad month in the English Channel , when the water is still relatively cold, with warm moist air coming up from the south-west.

These Sat24.com website images reveal that what appears to be cloud in the satellite view…

Looking out for the forecasts of fog is important, but one simple trick is to go online and use satellite imagery. Sat24.com is a great website to see the last three hours of visual imagery, where fog often shows as a dull, grey and featureless cloud. Next, do a quick comparison with the infra-red satellite imagery and the fog seems to miraculously disappear, whereas other clouds tops still show up.

This is due to the fog being approximately the same temperature as the sea, hence giving a neat confirmation of the existence of fog on the visual picture. You can then return to the visual imagery and more accurately plot the extent of the fog and potentially take avoiding action.

Caught in fog

If you unexpectedly end up sailing in fog, first consider whether you need to keep heading further into it? Would it make more sense to do a quick 180° turn and head back out into clearer visibility?

sailing-in-fog-europe-infrared-satellite-view

…is in fact fog that disappears in the infrared view as shown here in the Celtic Sea and North Atlantic

Once we realise we’re sailing in fog, we need to work through a checklist of actions. Note your compass heading. Do we need a more experienced helmsman? It’s easy to quickly find you’re 30° or 40° off course and not notice. Steering is more exacting and even exhausting.

Could it be less stressful to use the autopilot , to allow you to focus on lookout? Just be ready to immediately switch to manual if you need to at a moment’s notice.

Slowing down is certainly good seamanship and the requirement to proceed at a safe speed appropriate to the conditions is detailed clearly in the International Regulations for the Prevention of Collision at Sea (IRPCS Rule 6 – Safe Speed).

Article continues below…

Knowing how your variety of fog has formed will give you a better idea of how long it is going to last.

Weather expert Chris Tibbs on how to predict and cope with fog at sea

Radar and AIS help to make navigating in fog safer, but it is still an unnerving experience to sail in…

Navigation briefing: Mike Broughton explains why you still need radar

In a recent feature in Yachting World, my friend and highly respected yachting journalist Ed Gorman wrote a revealing article…

With an increased risk of collision, it’s good practise to ensure everyone is wearing a lifejacket . Maintaining a proper lookout is essential. In ‘pea soup’ fog, stationing a person forwards near the bow can help enormously. If motoring, the bow is a good place to escape the noise to allow the lookout crew member to listen for fog signals, or other hazards. On several occasions when I’ve been sailing in fog, the lookout at the bow has provided vital information to avoid a hazard or navigation mark.

In areas of dense shipping, remember to look up as well as straight ahead, I’m sure I am not the only person to have sighted a large vessel from the helm at the angle of the first spreader!

When ‘in or near areas of restricted visibility’ IRPCS states we shall make the prescribed sound signal, which for sailing vessels is one long blast, followed by two short blasts at intervals not more than two minutes. We need to have a working knowledge of sound signals of other vessels: many don’t appreciate that the fog signal for yachts is the same as vessels involved with fishing, towing, and even vessels ‘constrained by draught’ and ‘not under command’.

Make yourself visible

To help other ships see us, our best chance is to ensure we are clearly seen by the equipment on the bridge, which is radar and AIS (automated information system). Radar is a great help, but not all yachts have it, and it does take concerted focus and an understanding of how best to use it. Nearly all yachts have radar reflectors. Disappointingly tests have shown radar reflectors are not as effective at enhancing our radar signature as many people think. Active radar transponders show up much better.

AIS has been a real step change to aid collision avoidance when sailing in fog, though always remember that not all vessels use it and it is only an aid, albeit a very useful one. AIS can give the speed and course of a vessel as well as the closest point of approach (CPA) and time to the CPA: this is really useful data when navigating in fog. AIS also gives the vessel name, call sign, type and size.

Navigation lights are essential in foggy conditions. In a really thick fog the bow navigation lights can reflect back off the fog, leaving you with an eerie red or green glow.

Do you know how to make the prescribed sound signal in restricted visibility?

The amount of radio traffic tends to rise when sailing in fog, though beware using VHF radio to communicate with the watch keeper of another vessel, which can be fraught with problems.

There have been at least three occasions in the Dover Straits where watch keepers have opted to use radio to try to negotiate collision avoidance, which has ended unhappily in a collision!

These have often come about through misidentification and language difficulties, when both watch keepers should have prioritised normal rules of the road and not allowed themselves to be distracted in an important close quarters situation.

One tactic for dealing with fog on small vessels is to head away from busy shipping channels and sail to shallow water and anchor. Once tethered to the seabed remember to sound your fog signal (for vessels over 12m, ringing a bell for five seconds every minute). Many sailors may not be familiar with the additional signal of one short, one long, one short blast that can be made after the bell if you are concerned of a risk of collision while you are an anchor.

Stopping and racing in fog

Racing in fog creates extra challenges. Fog by night can take you by surprise and it is easy to lose hard fought gains, if the helmsperson loses awareness. If you have the choice of tacking into fog or not when racing, I would take the clear option every time: humans concentrate better when they can see.

The disorientation and confusion that sailing fog can create can easily generate high levels of stress. Mat Sweetman, captain of the J Class yacht Rainbow , suggests: “It is easy to get freaked out in fog, [but] look at is as if it was just a dark night and it gets a whole load less stressful.”

One clue as to the existence of fog at night is an absence of ambient lights and low altitude stars. If you are on the helm and getting close to fog, it is a good idea to start a scan of your yacht instruments. Like a pilot flying into cloud, it is imperative to ‘believe in your instruments’.

A regular scan is most effective but is both tiring and exacting over a long period of time. On top of normal sailing skills such as utilising the feel of your helm, tell tales (if you can still see them) and heel angle, we now need to bring in regular glances at true wind angle, boat speed, and heading. Working out a pattern for your scan is a good discipline for sailing in fog.

Sea fog is renowned over the Grand Banks. On the Transatlantic Race in 2005, fog prevailed for over six days with sustained wind speeds of 25-30 knots. Visibility was mostly less than 150 metres. Sailing in fog for nearly a week is tough going!

Using radar for collision avoidance

Periodically cycle through the ranges and don’t leave it just on long range. Zoom in to only three miles in busy shipping and even closer when tracking a vessel of interest.
Leave the sensitivity and clutter settings on auto. Modern radars handle them well.
If you want to look through a rain cloud, alter ‘rain clutter’ control very briefly, then revert it to automatic every time.
Use a split screen with radar on dual range, or radar and chartplotter lined up alongside, or radar ‘overlaid’ on the chartplotter.
Experiment with this before you hit fog.
Consider setting up an alarm zone to help you detect contacts.
If your radar display is below decks, have a tested system for communicating to the helm. Some yachts use a private VHF channel.
Stay clear of busy ferry routes

First published in the November 2020 issue of Yachting World.

Sound Signals for Vessels

The basic sound signals you should know are shown below. This information is embedded in the NauticEd Skipper Course and the NauticEd RYA Day Skipper Course.

Also, download our Navigation Rules eBook for iPad where the complete set of Navigation Rules are given and explained with animations – ONLY $2.99.

Tap each image to hear an example sound.

Between each successive signal you should wait 10 seconds or more.

These sounds are to made by power-driven vessels greater than 12 meters (39ft) in length and when operating in a narrow channel and have sighted each other.

The danger signal is general and can be used by anyone to signal disagreement with another vessel’s signal, which may lead to danger or just danger in general to anyone.

Sailboat in Fog

When operating in areas of restricted visibility IE fog, a Sailboat must make the following signal.

Remember this by an average sailboat normally has two sails- thus the two shorts toots.

Powerboat if Fog

Where prolonged is a prolonged blast (lasting 4 to 6 seconds) and signals are not more than 2 minutes apart. This signal above (one prolonged and two short) is also the signal for other vessels operating in fog such as vessels towing, broken down, commercial fishing, or restricted in ability to maneuver.

Power driven vessels operating in fog must make the following signal not more than 2 minutes apart.

These are international rules. The above list of signals is not exhaustive. For a list of all sound signals visit Rules 32 through 37 of the USCG regs (which again are international).

Finally, a piece of advice: Make sure you have a loud sound making device at hand at all times near the helm available with in 1-2 seconds. The day you will need it is the day you will thank yourself for heeding this advice.

Oh and BTW, that day WILL come – read this story about how it was too late

Recent Posts

NauticEd uses the SailTies GPS Tracking App - March 29, 2024
Sea of Cortez Flotilla – February 2025 - March 8, 2024
British Virgin Islands Flotilla – March 2025 - March 2, 2024

Top ten safe boating tips - wearing a lifevest

TWEET ABOUT

FIGHT CHILDHOOD CANCER

NauticEd is a fully recognized education and certification platform for sailing students combining online and on-the-water real instruction ( and now VR ). NauticEd offers +24 online courses , a free sailor's toolkit that includes 2 free courses, and six ranks of certification – all integrated into NauticEd’s proprietary platform. The USCG and NASBLA recognize NauticEd as having met the established American National Standards. Learn more at www.nauticed.org .

The NauticEd Vacations team are Expert Global Yacht Charter Agents – when you book a sailing vacation or bareboat charter through NauticEd, we don’t charge you a fee – we often save you money since we can compare prices from all yacht charter companies. PLUS, we can give you advice on which destination or charter company will suit your needs best. Inquire about a Sailing Vacation or Charter .

Online Sailing Courses Sailing Vacations | Charters Practical Sailing Courses Sailing Certification | License

Sign up for 2 FREE Sailing Courses Try sailing in Virtual Reality! Gift a Friend a Sailing Course Sailing Events | Opportunities

About NauticEd Contact Us NauticEd Support Privacy Policy

RYA Powerboat Training

Powerboat Course Overview
RYA Powerboat Level 2
RYA Powerboat Level 1
Own Boat Training
ICC Qualification
Course Calendar
News, Articles & Customer Stories
Have a question?
Christchurch MBC
Our location

Sound signals in reduced visibility (fog)

The best way to remember these sound signals is to split them by ship condition: 1. Making way and unrestricted in their ability to manoeuvre: 2. Making way but restricted in their ability to manoeuvre; 3. At anchor or underway but not making way; or finally aground

The first set - Making way and unrestricted in their ability to manoeuvre

The only boats classed as unrestricted in their ability to manoeuvre are power boats of all shapes and sizes, making way, but not engaged in any restrictive works such as fishing, dredging or towing, nor constrained by their draft.

Ships in this state all should make the same sound signal : One long blast every two minutes or less.

A ship or boat that is merely stationary but not at anchor (underway, but not making way) gives two long blasts every two minutes or less.

A pilot boat, for some reason, is allowed to add a further signal to its powerboat sound � four short blasts.

You don´t have to worry to much about the size of the vessel. The blast the Queen Mary II makes will not be confused with the sound your berth neighbour´s Sea Ray emits.

It is worth remembering the very large ships can neither turn, stop or reverse in order to avoid you. So if you hear a ‘large vessel blast’ you should be extra alert.

The second set � Making way but restricted in their ability to manoeuvre

This covers lots of boat types. Power boats engaged in work that makes them less manoeuvrable such as boats fishing, dredging, and towing, ships constrained by their draft and all sailing boats.

These ships and boats sound as follows. One long blast followed immediately by two short blasts (again, every two minutes or less).

Towing vessels should make an additional sound signal to alert other shipping to the extra hazard they represent. While the towing vessel makes the sound for a vessel restricted in its ability to manoeuvre, the vessel being towed has a sound signal all of its own and that is one long blast followed immediately by THREE short blasts. These sounds should be co-ordinated into a set. The towing vessel should do its one long and two short and then, after a SHORT pause, the vessel being towed should emit one long and three short blasts.

The third set: At anchor or aground

Ships under 100m, at anchor, ring a bell for 5 seconds at least every minute. Ships longer than 100m ring the bell at the bow end and follow it with beating a gong for five seconds at the stern.

If the ship is aground, rather than at anchor, it should preceed and follow the rapid ringing with three single strikes. If over 100m, the same goes for the gong.

If they become concerned that an approaching vessel is on a collision course, they may add one short, one long and one short blast from their hooter.

That means that a ship over 100m aground and alarmed you might be on a collision course will do the following: 1. Three distinct strikes of a bell; 2. Rapid ringing of the bell for 5 sec; 3. Three distinct strikes of the bell; 4. Three distinct strikes of the gong; 5. Rapid striking of the gong for 5 sec; 6. Three distinct strikes of the gong; and 7. One short, one, long and one short blast from its hooter.

That ought to get your attention!

Season 2023/24

Season 2023/24 Call Will for all boat training requirements on 01202 836721

Bespoke Tuition to suit your requirements, can also include crew training on your boat. Call Will to discuss on 01202 836721

Our Details:

Saltwater Experience Bailey Bridge Marina, 10 Bailey Drive, Christchurch, Dorset BH23 2BN

Tel: 01202 836721

Principal: Will Eveleigh Chief Instructor: Lloyd James

[email protected]

On the water:
Int Certificate of Competence
Shorebased courses:
Diesel maintenance
VHF Radio course
Complaint Procedure

Design by Signatures Design . Hosted by Radikls

Our Stumble Into The Cruising Life

Low Flite Facebook
Low Flite Twitter
Low Flite Google+
Low Flite YouTube
Low Flite Instagram
Low Flite Email

Sound Signals and VHF Protocol in the Fog

By admin
April 26, 2015
No Comments

We’re starting to look forward to getting back to North America, and thinking about the various places that we can do some sailing.

Growing up on the East Coast we are familiar with the rather high number of days with very thick fog, and while looking for some information about sailing in the fog, we came across this topical blog post from Sailing Simplicity .

The Scenario

“Well Cap, I can’t really say. That’s up to you to decide.” Barry responded.

“Well, I think I’ll keep going then.” the yachtsman stated.

“Just keep sounding your horn, and we should pass each other safely” said Barry.

“We don’t have a horn.”

“Oh. Well Cap, that’s not good” said Barry calmly, surely holding back a few expletives and his opinion of the yachtsman’s seamanship on this public VHF forum.

A Sound Solution

Rule 35 – Sound Signals in Restricted Visibility (view full rule)

(a) A power-driven vessel making way through the water shall sound at intervals of not more than 2 minutes one prolonged blast. (—)

(c) A vessel not under command, a vessel restricted in her ability to maneuver whether underway or at anchor , a vessel constrained by her draft , a sailing vessel , a vessel engaged in fishing whether underway or at anchor and a vessel engaged in towing or pushing another vessel shall, instead of the signals prescribed in paragraph (a) or (b) of this Rule, sound at intervals of not more than 2 minutes three blasts in succession, namely one prolonged followed by two short blasts. (— • •)

*note: prolonged = 4-6 seconds, short = 1 second.

A Radio Solution

How To Give An Effective Securité Call

Securité, Securité, Securité.

This is the forty-four foot sailing vessel Rocinante .

We are motor-sailing eastbound through the Fox Island Thorofare, just passing red nun number ten, off Iron Point.

Any concerned traffic please respond on channel one-three or one-six.

This is the sailing vessel Rocinante standing by on one-three and one-six.

The Prudent Solution

Boat Sound Signals: Time To Sound Off

When caught in a situation with restricted visibility, you'll need know how to let others know where you're located — and interpret where they are.

Photo: Stacey Nedrow-Wigmore

While the term "restricted visibility" may sound like there's something in your path that obstructs or blocks the view of where you're going, in maritime terms, it describes not only a situation where an operator can't see hazards in their path and around them, but also one that prevents your boat from being seen by others. Two common examples of this would be operating a vessel at night or during inclement weather. But restricted visibility can also occur due to unusual circumstances, such as dust storms or even smoke from nearby forest fires.

Boats need to be aware of each other's position at all times to operate safely, which is why adherence to navigational rules (such as the proper display of lights and use of sound signals) during periods of restricted visibility is so crucial.

Similar to the visual information provided by navigational lighting, sound signals provide an audible means of conveying your intentions, while also helping you understand what other boats around you are doing. This is especially important in situations of restricted visibility, such as fog, heavy rain, or when transiting areas where a vessel operator may experience limited visibility due to physical characteristics (a sharp bend in a narrow river, for example). In situations like these the effectiveness of navigation lights may be reduced or eliminated altogether.

Inland Vs. International

In some cases, the sound signals for International Rules may differ slightly from those described in the Inland Rules (the focus of this article). If traveling overseas, be sure to consult and familiarize yourself with the International Rules beforehand as provided in the Navigation Rules. While every boat owner should have sound-signal information on board for quick reference, a printed copy of the Navigation Rules is mandatory for vessels over 12 meters (39.4 feet) in length.

Sound-Producing Devices And Characteristics

Sound signals are described as "blasts," of which there are two types: A "short blast" means a blast of about 1 second, while a "prolonged blast" is 4 to 6 seconds.

The word "whistle" is defined in the Navigation Rules as any sound-signaling device capable of producing the required blasts as described by Annex III of the Rules. While Annex III provides the technical details of what constitutes a proper blast (such as frequencies and intensity) a simple interpretation for most recreational boaters would be how far the blast can be heard. For example, the minimum audibility range for a whistle or horn (both can be used interchangeably) required for a vessel 20 meters (65.6 feet), but less than 75 meters (246 feet) in length is 1 nautical mile. The minimum range for a vessel 12 meters (39.4 feet), but less than 20 meters is .5 nautical miles.

Most every vessel is required to carry some form of sound-producing device, and even those that are not would do well to have one on board, regardless of mandated carriage requirements.

That said, the Navigation Rules state a vessel 12 meters or more in length shall be provided with a whistle and a bell. Vessels of 100 meters or more in length shall additionally carry a gong, the tone and sound of which cannot be confused with that of the bell. The bell and gong may be replaced by equipment having the same respective sound characteristics, provided that manual sounding of the prescribed signals is always possible. An example of this would be an electronic loud hailer system that can generate the required sounds.

Acceptable sound-producing devices on board a boat can include an air horn, bell, or whistle, depending on the boat. (Photos: Air horn: Getty Images/gabrieletamborrelli; Bell: Getty Images/Yury Karamanenko)

Vessels less than 12 meters in length are required only to carry an "efficient" sound-producing device, such as a bell, air horn, or whistle. While banging on that galley pot may technically qualify as meeting the letter of the law, do yourself (and everyone else) a favor and carry an appropriate a sound-producing device. As the goal here is to be heard, ditch that wimpy horn and get one that makes the other boats think the Queen Mary is headed their way!

Sound Signals During Restricted Visibility

The below summary focuses on sound signals applicable for recreational vessels during restricted visibility. Keep in mind, however, that vessels engaged in other activities (towing, for example) will often have different or additional sound signal requirements and that sometimes variations may apply. When in doubt, always refer to the Navigation Rules .

Power vessels making way through the water must sound one prolonged blast at not more than 2 minute intervals.
A power vessel underway but stopped (not making way) must sound two prolonged blasts roughly 2 seconds apart at intervals of not more than 2 minutes.
A sailing vessel, a vessel not under command, a vessel restricted in her ability to maneuver (whether underway or at anchor), or a vessel engaged in fishing (underway or at anchor) must sound three blasts in succession (one prolonged followed by two short blasts) at intervals of not more than 2 minutes.
A vessel at anchor must ring a bell rapidly for about 5 seconds at intervals of not more than 1 minute apart. For vessels 100 meters or more in length (which require both a bell and gong), the bell shall be sounded in the forepart of the vessel and immediately after the ringing of the bell, the gong shall be sounded rapidly for about 5 seconds in the after part of the vessel. A vessel at anchor may, in addition, sound three blasts in succession; namely, one short, one prolonged and one short blast, to give warning of her position and of the possibility of collision to an approaching vessel. When anchored in a special anchorage area designated by the Secretary, vessels less than 20 meters in length, barges, canal boats, scows, or other nondescript craft are not required to give the sound signals described above for anchored vessels.

While vessels less than 12 meters in length are not required to give the above signals, they are required to make some type of efficient sound signal at intervals not more than 2 minutes apart. While there is leeway regarding sound signals for vessels less than 12 meters, why try to reinvent the wheel here? Having a proper sound-signaling device on smaller vessels and using the same sound signals (where practical and permitted by the rules) are a win-win for everyone on the water, in my opinion.

Finally, a vessel nearing a bend or an area of a channel or fairway where other vessels may be obscured by an intervening obstruction must sound one prolonged blast. This signal must be answered with a prolonged blast by any approaching vessel that may be within hearing around the bend or behind the intervening obstruction.

Remember these sound signal rules (we recommend carrying a cheat sheet on board), and you can cruise with the confidence of having added to your boating safety skill set.

The truth about ceramic coatings for boats.

Our editor investigates the marketing claims of consumer-grade ceramic coatings.

Fine-Tune Your Side Scan Fishfinder

Take your side-scanning fishfinder off auto mode, and you’ll be spotting your prey from afar in no time

DIY Boat Foam Decking

Closed-cell foam flooring helps make boating more comfortable. Here’s how to install it on your vessel

Click to explore related articles

Frank Lanier

Contributing Editor, BoatUS Magazine

Capt. Frank Lanier is a SAMS Accredited Marine Surveyor with more than 40 years of experience in the marine and diving industries. He’s also an author, public speaker, and multiple award-winning journalist whose articles on boat maintenance, repair, and seamanship appear regularly in numerous marine publications worldwide. He can be reached via his YouTube channel “Everything Boats with Capt. Frank Lanier” and website captfklanier.com.

BoatUS Magazine Is A Benefit Of BoatUS Membership

Membership Benefits Include:

Subscription to the print version of BoatUS Magazine

4% back on purchases from West Marine stores or online at WestMarine.com

Discounts on fuel, transient slips, repairs and more at over 1,200 businesses

Deals on cruises, charters, car rentals, hotel stays and more…

All for only $25/year!

We use cookies to enhance your visit to our website and to improve your experience. By continuing to use our website, you’re agreeing to our cookie policy.

Yachting Monthly

Digital edition

How to avoid collisions in fog

Andy Du Port
April 8, 2020

Not many of us would happily set sail in fog but sometimes it is unavoidable, and knowing how to avoid collisions is crucial, says Andy du Port

Fog, even if it is localised, changes which navigation rules you follow. Would you know what to do?

Sir John Harvey-Jones, erstwhile chairman of ICI, once said, ‘Planning is an unnatural process; the nicest thing about not planning is that failure comes as a complete surprise rather than being preceded by a period of worry and doubt.’

When you see the fog rolling towards you, it is too late to start planning.

Not many of us would happily set sail in fog but sometimes it is unavoidable, either out at sea or as we make our way into harbour.

Sailing in poor visibility – fog, heavy rain, even snow – can be disorientating and worrying but some prior thought and basic preparation will help to keep the heart rate near normal and, vitally, you and your crew safe.

With any luck you won’t be in fog for long but while you are, you have two objectives: safe navigation and collision avoidance.

In open waters your attention will be on collision avoidance, but closer inshore you will probably be busy dodging other vessels while at the same time keeping yourself in safe water.

When planning your cruise think about how you would deal with fog

There is lots of good advice elsewhere about ‘blind’ navigation, so here I will focus on collision avoidance.

This is covered in the Colregs by Rule 19: Conduct of vessels in restricted visibility, which is possibly the most misunderstood rule in the book.

The actions you should take to avoid collision are quite different from those when vessels are in sight of one another: there is no ‘give way’ vessel and no ‘stand on’ vessel.

Even the usual manoeuvring sound signals don’t apply.

In poor visibility your best bet is to avoid all close quarters situations.

In other words, keep the opposition at arm’s length rather than nipping under the stern as you might in clear weather.

One-mile clearance of a big ship in fog is quite close enough for me.

‘A collision at sea can ruin your entire day’ may not have been said by Thucydides, to whom it is often attributed, but whoever actually said it made an indisputable point.

Preparation for fog

You want to be ‘seen’ in fog so invest in a good radar reflector and permanently fit it as high as possible.

A radar reflector is one of the few SOLAS V requirements for small craft.

Which one you choose will depend on the depth of your pocket, but be wary of going for cheap and cheerful.

Knowing how to interpret a radar picture properly will pay dividends in fog

You can spend hundreds of pounds on a radar target enhancer, or you can buy a passive reflector for much less.

If you go for a traditional tetrahedral reflector just make sure you hoist it in the ‘rain-catching’ mode, not point up.

AIS does not yet feature in the Colregs but it can be an invaluable anti-collision aid.

If you have radar fitted, take time to get to know how to use it and interpret what is shows

Even receive-only sets will make life much safer.

However, AIS is not a radar (whatever some manufacturers may claim), and many small craft are not fitted with it; even larger vessels may not have it set up correctly or even turned on.

Like AIS, the use of VHF is not mentioned in the Colregs, and you should be very wary, even in clear weather, of causing unnecessary confusion by calling another ship to negotiate actions to avoid a close-quarters situation, unless you have both positively identified each other.

This applies in poor visibility when a third vessel may be tempted to take avoiding action based on an overheard conversation.

AIS is no replacement for proper radar equipment

That said, particularly in busy areas, a listening watch will help you to build up a general picture of shipping movements around you.

So, have your set tuned to the relevant channel(s): Ch 16 when offshore as well as the local harbour or VTS channels when appropriate.

If you feel you must check your radio before sailing, try to do so on a working channel and avoid cluttering up Ch 16.

The advantage of radar over AIS is that, when used properly, it will show all other vessels, and not just those fitted with corresponding equipment.

A tetrahedral radar reflector on a yacht

A tetrahedral radar reflector reflector must be mounted in the right orientation

With either AIS or radar, however, the information you are given still needs interpretation.

You should be able to read it and ascertain another vessel’s closest point of approach (CPA), it’s time to CPA (TCPA), and where it will be in relation to your vessel at that time.

If you have radar, it is a requirement of Rule 19 that you make proper use of it in reduced visibility.

Permanently mounting a passive radar reflector is good sense

Therefore, tune it for best reception and know how to get the most out of it.

Unless you are already an experienced operator, book yourself onto a course then practise in clear visibility.

You won’t regret it when your safety depends on it.

Entering fog

You will probably have some warning before being enveloped in fog.

You may see it looming ahead of you but, if you are not keeping a good all-round lookout, it could roll in from astern and catch you by surprise.

When everything starts to look grey take the following actions as soon as possible.

Some of them will need your careful judgement.

Navigation light on a yacht to help navigate in fog

Turn on your navigation lights.

The aim is to be seen at all costs, and dense fog probably justifies bending the rules and showing as many lights as you can – perhaps including an all-round white anchor light at the masthead.

Better, I suggest, to risk a rebuke for showing incorrect lights than be involved in a potentially disastrous collision.

Make yourself visible. If you are motoring, keep the mainsail hoisted and consider having the headsail at least partially unfurled so long as it doesn’t obscure your view.

To keep your options open for rapid manoeuvring, however, lower spinnakers and cruising chutes, avoid poling out headsails and unrig preventers.

Instruments on the cockpit of a Hallberg Rassy

A yacht is unlikely to be able to exceed a ‘safe speed’, but sailing too slowly just prolongs the misery and makes any alterations of course less obvious on another vessel’s radar.

In these conditions, motoring might make sense.

A skipper with his hand on the engine throttle

Have it running or ready for immediate use.

The noise of the engine will reduce your ability to hear other ships, but you may think that instant manoeuvrability is more important in the circumstances.

If you are sailing well and are confident that the engine will start on demand, I would leave it off (but see the point above).

5. Lifejackets and harnesses

Wear a lifejacket when sailing especially in fog and heavy weather

Put on lifejackets. Not only is this a sensible precaution, it also alerts the crew that conditions may become serious.

In calm weather (quite likely in fog), you don’t want to be tethered to the boat in the event of a collision, so probably best not to hook on.

This has to be weighed against the risk of someone falling over the side, as recovering an MOB in fog or rough seas is going to be much more difficult.

6. Liferaft

Prepare a liftraft in case of a collision in fog

Have it ready to deploy. If it is normally stowed in a locker, get it out and secure its painter to a strongpoint.

If you don’t carry a liferaft, a possible alternative is to inflate the dinghy and tow it astern.

It’s also worth having your EPIRB or PLB, and a flare ready to hand if the worst were indeed to happen.

Use your radar, chartplotter, GPS and AIS to build a picture of what is around you, and know how to track vessels’ courses

The rules require that proper use shall be made of radar, if fitted.

This includes plotting and assessing contacts, so give the job to the most experienced operator. As the skipper, this may be you.

At the chart table, you are well placed to build up a picture of what is around you using radar, AIS, VHF and any reports from your team on deck in order to make the right decisions.

8. Sound signals

There is no way your fog horn is going to be heard inside the bridge of a large ship, but it will alert other yachts to your presence.

Anyhow, the rules say it ‘shall be used’.

On our boat, we use a referees’ whistle for making sound signals.

It is just as audible as a canister fog horn, and it doesn’t run out of gas.

A good lookout, by both sight and hearing (Rule 5), is essential. Brief your crew to report anything they hear or see.

Warn them that direction can be ambiguous in fog, so ‘I think I can hear a big ship’s engines somewhere to port’ is likely to be more use to you than a guess at a precise bearing – which is quite liable to be wrong.

Collision avoidance

Unless you are in confined waters, your main worry will be collision avoidance.

This is where Rule 19 kicks in, and it is absolutely vital that you understand what it says.

The full text is shown below. Rules 11 to 18 deal with the conduct of vessels in sight of one another, but they do not apply in fog.

It doesn’t make any difference whether you are sailing, motoring, fishing or flying your seaplane, no one has a ‘right of way’ (a term, incidentally, which does not feature anywhere in the Colregs, only ‘stand on vessel’), no one is a ‘give way’ vessel, and the usual manoeuvring and warning sound signals (Rule 34) only apply in good visibility.

It is Rule 35 that tells us what sound signals to make in fog.

Rule 19 does not only apply when you are in fog.

You may be in bright sunshine but the actions to avoid collision with a ship you can’t see because she is in a nearby fog bank, a rain squall, or even a snow shower, are dictated by Rule 19.

What this means

Rule 19 says that unless you have determined that a risk of collision or close-quarters situation does not exist, then you must assume that it does and act accordingly.

It goes on to say that if you hear a fog signal ahead of the beam and have not yet determined if it poses a risk, you shall reduce your speed to a minimum.

This is not really applicable to most sailing yachts but the principle stands, and you should not plough on at full speed unless you are quite sure that there is no risk of getting uncomfortably close to the other ship.

A mere reduction in speed (from 6 knots to 3 knots, say) is rarely practicable as it won’t be readily apparent on another vessel’s radar.

Make MOB buoys, liferafts and flares ready for use, as events can unfold quickly

As we have already seen, the steering rules for vessels in sight of one another no longer apply, but Rule 19 rather confusingly only tells us what we should not do.

If you turn this around, it makes more sense.

Put simply: always turn to starboard to avoid a collision or close-quarters situation unless: a) The other vessel is on your starboard quarter (green 90° to right astern), in which case you should alter course to port, or b) You are overtaking, in which case you may alter course whichever way achieves the aim.

Whatever you do, Rule 19 insists that you do it ‘in ample time’.

As always, any actions you take must be ‘positive and readily apparent to the other vessel’.

In other words, act early and don’t faff around with small alterations of course. A turn of 90° or more may be necessary to make your intentions obvious.

Worth the risk

Andy Du Port is a Yachtmaster Offshore, and formerly an RN specialist navigating officer and RYA Cruising Instructor

To end on a sobering note, if you do have an incident while underway in fog, you may have to explain to the authorities your decision to sail.

A written passage plan which shows all the factors you have taken into account, and a note of your preparations, would certainly help.

However, while I said at the start that few of us would willingly set sail in fog, there are times when it is foggy close inshore but known to be clear just a few miles out.

The harbourmaster or local VTS may have reports from ships offshore, or you could ask the coastguard or nearby National Coastwatch Institution (NCI) station, available on VHF Channel 65.

In these situations you may justifiably decide to leave the safety of your berth knowing that the gloom won’t last long. Similarly, a forecast for occasional fog patches may be worth the risk.

Conduct of vessels in restricted visibility:

(a) This Rule applies to vessels not in sight of one another when navigating in or near an area of restricted visibility.

(b) Every vessel shall proceed at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility. A power-driven vessel shall have her engines ready for immediate manoeuvre.

(c) Every vessel shall have due regard to the prevailing circumstances and conditions of restricted visibility when complying with the Rules of Section I of this Part.

(d) A vessel which detects by radar alone the presence of another vessel shall determine if a close-quarters situation is developing and/or risk of collision exists.

If so, she shall take avoiding action in ample time, provided that when such action consists of an alteration of course, so far as possible the following shall be avoided:

(i) an alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken;

(ii) an alteration of course towards a vessel abeam or abaft the beam.

(e) Except where it has been determined that a risk of collision does not exist, every vessel which hears apparently forward of her beam the fog signal of another vessel, or which cannot avoid a close-quarters situation with another vessel forward of her beam, shall reduce her speed to the minimum at which she can be kept on her course.

She shall, if necessary, take all her way off and in any event navigate with extreme caution until danger of collision is over.

Boat Navigation In Fog (Safety rules to follow)

Being lost in the fog is frightening, but there are some things you can do to protect yourself. If you have a GPS or navigation chart with compass readings, use these tools to find your location. If you are not sure about your location or where you are going, it’s best to stop boat navigation until the fog clears up.

Many boat owners install fog horns on their boats to help other boaters locate them. If you have a boat horn, use it to signal your boat’s location to other boaters.

Boat Navigation In Fog – Boating In Fog Safety Tips

Let’s have a look at some navigation rules & tips.

When you’re setting sail, it’s important to have all your boat equipment on board. That includes a GPS, compass, horn, and safety gear. But there are other things that will keep you safe too.

Also, listen to the weather forecast before you set out so you can avoid unexpected navigation challenges like being caught in the fog.

Reduce speed

If you’re out on the water in foggy conditions, there are a few things that will help keep your boat safe. First, reduce speed as much as possible and take your boat out of the channel if there is any doubt about where you should be going. If you come across another boat, stay away from it to avoid a collision. Always ensure you are maintaining a safe speed for your boat.

Turn Light on

Boating safety is important, and one of the most common ways to stay safe on the water is by making sure your boat lights are turned on. When you’re out at sea and visibility drops with a foggy horizon, it’s easy for boats to run into each other without realizing they were there. To avoid this from happening, make yourself as visible as possible by turning on your running lights so that others can see where you are.

Navigational equipment

Make sure you have the appropriate navigational equipment for your boat. That includes a GPS, radar, and all of the other gadgets that help you stay on track when traveling in foggy conditions.

We also suggest checking over any safety equipment like life jackets or signal lights. Don’t forget about things like flares and whistles either. If something goes wrong out there, it might be difficult to get back home without these tools at hand.

Anchor your boat

If you want to avoid a collision, it is important that your boat follows safety guidelines. One of the most common mistakes boaters make in low visibility conditions such as fog or rain is not stopping their engines while they are on the water.

If you’re in a FOG and there is high traffic, stop the movement of your vessel. For better visibility to other boats on the water, it may be best to drop anchor and wait for all traffic to pass before continuing on your way. Boating safety depends largely on common sense, use yours.

Know Fog Sound Signals

Navigating in foggy conditions can be tricky. If you’re a powerboat operator, the International Regulations for Preventing Collisions at Sea provide a set of sound signals to help others understand where your boat is and what it’s doing–whether underway or drifting.

If your ship is drifting, always give two blasts of the horn for a boat underway. When you are at anchor, sound one short – one prolong – one short blast.

Short blast – 1 second
Long blast – 4 to 6 seconds

Take care of electronics

So, if you’re a seafaring person and spend lots of time on the water, we recommend equipping your boat with radar. It will give you an edge in foggy situations and provide safety for all aboard. Radar is a great investment for safety and peace of mind when on the water.

You may also consider adding other electronics such as GPS/Chart plotters, VHF radios, AIS receivers, etc., depending on how much navigation assistance you want from your vessel. The point being – don’t forget about the power of electricity.

Post a lookout

Safety is important for everyone on board, but it becomes even more crucial when there’s a fog. This means that the crew has to be extra vigilant and focused at all times if they want to avoid accidents. The best way to ensure this happens? Assign different areas of your boat (fore, aft, port, and starboard) so you can maintain a lookout at all times with the help of your crew members.

Navigating in the fog is a challenging problem for any boater, but it becomes especially dangerous when you have to rely on your own eyesight. There are some steps you can take in order to make foggy conditions easier and safer for yourself or your crew. One of the most important things you should do is carry a VHF radio with you at all times.

The Radio station will warn about areas where there may be a danger that’s not visible from the outside, such as rocks or other boats in close proximity to yours. Never forget to switch on your VHF radio.

Fog Affects Visibility

Fog is different from mere darkness or precipitation. Darkness can be mitigated with aids to navigation and modern conveniences like gps and radar.

Sailing on a starry night while a bit nerve racking at times, can also be a magical experience for the well prepared skipper. The calming effect of nightfall on the sea can create a glass-like surface on the water and often enough, a sailboat can slide silently beneath the heavens and offer a cathartic escape from the temporal world in the evening hours.

At the very least, nightfall means relief from the heat of a dispassionate sun. But the wind and its indicators, rarely disappear entirely in times of darkness or precipitation. But in fog, the wind becomes an enigma.

The fact that you can’t see the waves, landmarks or flags and many times, can’t even see your windex at the top of your mast, means you are entirely dependent upon apparent wind.

Your sense of the true wind is eradicated in fog.

True wind is the wind as it comes from God’s perspective - the wind just as Mother Nature intended.

Apparent wind is a figment of your imagination. It’s the wind as affected by the movement of your boat and as it appears to you the sailor. So when my sense of true wind is diminished, I get nervous and start making bad decisions.

Many times with fog, the wind drops off entirely and your boat drifts at the mercy of the current.

A Brief Example

I have been floating down Long Island Sound in late spring when fog rolls in, and drifted for 20 miles without an ounce of control.

We were sailing to Block Island from Stamford one weekend in May aboard a 40 foot Tartan named “Green Hornet” some 20 years ago.

We started the race with a warm 10 knots blowing on our nose at 5 pm on Friday and we beat to windward with the following tide.

By midnight we were off New Haven with a cold drizzle falling on our decks leading a pack of a few dozen boats in our wake.

By Saturday morning we could see the cornered cliffs of Block Island and were having a great time, giving us hope that we would take first in the race by late Saturday night.

Screaming around Block and making a steady 8 knots as we passed New London at noon on Saturday, an air of celebration took over the boat as we set a full spinnaker for the downwind run to home.

But by sunset Saturday, the wind dropped off entirely and a thick blanket of fog wrapped our boat tightly, ten miles off New Haven Harbor.

For the next six hours we did all we could to hold position and not be dragged back to Montauk Point on the outgoing tide.

That entire night we sat blind and drifting, hearing the wail of the fog horn at New Haven Harbor, taunting us for our hubris assumption that we would be home on time.

A turn of the tide and a slight shift of the wind reversed our drift towards home and by 5 PM, Sundy the cannon blew and we knew we had made it, taking honors and winning bragging rights.

But just as we crossed the finish line, a US Coast Guard Patrol flashed their lights and chirped for all to hear on the PA system, “Chris German, Call your Mother.”

Apparently no one told my mother that in a sailboat race you can’t turn on your motor, and when we weren’t back Saturday afternoon, she began calling every Coast Guard station from Boston to Cape May looking for me. Sailing in Fog sucks.

Fog Affects Sound

It’s not just the wind that plays tricks in the fog. Sound itself is morphed into strange beasts when your eyes are removed from the sailing equation.

In fog, sound bounces off the water particles in the air and the stillness amplifies those sounds so that the rumble of a boat motor five miles away may sound like five feet to the sight-starved ears of a wayward watch stander.

Water lapping at a rock pile takes on the appearance of an impending tsunami when the heightened awareness and nerves of fog set in.

And nothing sets a chill to the spine like the sound of an unexpected gong, horn or worst all, bell in a fog bank.

The Gong oftentimes is a safe water mark or perhaps a huge tanker at anchor. The fact that it is unexpected is bad, but if it is a gong you hear, you know you are at least in deep water.

If it’s a horn you hear, you are nervous because it could be a boat underway or not, fishing or not, sailing or not.

You really should know your fog signals but who really does these days? All you really know is there is another boat or ATON nearby and a risk of collision may exist.

But the worst of all in fog is the bell. Particularly three short, one prolonged ring followed by three more short.

If you hear that in Fog, then it’s time to panic because you are near another boat who has the sense to use fog signals, but has lacked the sense to avoid going aground and you’re next to them.

In truth I have only had to use fog signals once in my career. I was in Bridgeport, CT in my 34 foot Cal that I had just purchased and was teaching a lesson.

I had four adults on board and really had just launched the boat without fully checking all the safety gear. I had to go out, because I had paying passengers, but as it is so often when the water is still cold in Long Island Sound and the warm moist air of Spring sets in, so to came the fog.

We reached the end of the channel and found ourselves in a white haze of late morning fog just off Penfield Reef light in Black Rock Harbor.

We couldn't see much at all but knew that the harbor was quite busy this time of year and the chances of a big old stinkpot running over our little sailboat were quite good.

Looking below, I found the only noisemaker the previous owner had left for me, a horn, much like those that are used at the soccer games of Europe.

Lucky enough for me, one the students on board was the tuba player for the Bridgeport Symphonic Orchestra and he had a unique gift for both keeping time and blowing long blasts on a horn.

For three hours he blew, “BWAAANNNNNHHHHH, BWAHN BWANH” every two minutes like machine. He impressed the hell out of all of us on the boat and it was entirely to his credit that we avoided a collision from Joey Bagadonuts and his 32 foot gas hog.

Did I mention that sailing in fog sucks?

Fog Is Not Always The Same

Fog is not however the same everywhere, everytime.

In North Carolina, fog is common in the winter months in evenings and early mornings but a rarity for the other 10 months of the year.

While in New England, fog has so many more chances to form given the cold waters and comes in so many different shapes, colors and densities.

Fall River, Mass has some of the best fog I have ever sailed in because it comes like clouds floating in and out from Newport and up from the North Atlantic.

Boston’s fog reminds me of what it must be like in London and would be quite lovely if not for all the rock strewn islands dotting Boston Harbor.

And in Maine’s Fox Thoroughfare, the fog is persistent, moving in like the blob and sitting there for days.

I was a lighthouse keeper at the North Haven light for one summer, where people could rent the lighthouse for a week and live remotely in the middle of the water in a Spark Plug-style lighthouse.

One couple I dropped off experienced this fog just minutes after I dropped them off at the lighthouse.

And five days later when I returned to get them, they were on the verge of madness having listened to the fog horn morning, noon and night for five days straight with nothing to see but a milky fog bank the entire time. Imagine what it was to be a sailing ship in fog 100 years ago?

One of my favorite scenes in the movie “Master and Commander”, Captain Aubrey (played by Russel Crow) and his crew is set upon by the French Navy. The French Ship Acheron blasts away the rudder chains of the HMS Surprize in a close quarters battle and the Captain orders his crew to launch the long boats and row their stricken sailboat to the safety of a fog bank.

The Acheron knowing the dangers of fog doesn’t dare follow the brave, yet foolish Surprize into that fog and it is the French timidity that causes them to lose their pursuit of the Surprize.

The author illustrates perfectly the love-hate relationship a sailor has with fog and while it may be safe for one vessel, it is certain peril for the other.

How to Navigate Through Fog

Thankfully today we have so many more tools at our disposal to navigate in fog. Charts and GPS have diminished the treachery of fog, but in no way eliminated it.

And radar for vessels that might have it, has revolutionized the visible landscape where once we were traveled in complete blindness.

But fog with its trickery can tempt you to trust your senses over instruments. Don’t be tricked into thinking you know more than the Garmin.

The GPS is linked up with satellites a thousand miles up in space who have ways of seeing through fog where you can’t.

The Military spent billions developing those satellites and those systems and made it so precise that at one time they had to dumb it down so evil doers couldn’t use it for evil purposes.

But it’s spot on accurate if you believe in it, because it works only as well as the person or the boat on which you're using it.

If you start doubting your GPS when coming up a channel you can get yourself turned around and in trouble in a hurry.

GPS was not designed for sailboats, but rather missiles and fighter jets.

Sailboats are not that fast and sometimes even go backwards. This movement can make a gps go wonky and with the light winds of a fog bank, it can be incredibly unnerving and confusing.

If you have any questions about that, look how wacky google acts when you pull into a gas station or mini-mall. While GPS is better than anything else we have ever had in boating, it can go wild at inopportune times.

So for sailing purposes, gps is only one half of the navigational equation.

Paper Charts

Paper charts do what the gps can’t, so don’t be lulled into thinking GPS is the alpha and omega.

A GPS shows you the current picture of where you are. Depending on what your scale and what your settings might be, you can miss all sorts of things that the GPS doesn’t know to show you.

A chart on the other hand, shows you God’s perspective. The whole enchilada so to speak.

Suppose you’re making way to head along the coast of Connecticut to the Connecticut River. You might set a gps course that says go 260 true and never see that that course runs smack dab over Falkner Island on a GPS.

But examine that track on a chart and you will see every hazard along the way whether you are looking for them or not.

In this push to walk away from paper charts, I believe they are an invaluable partner to the gps if you know how to use them. You can plot your position on a chart and make estimates for where your next positions might be. You can get ancillary information about an area on a chart that turns to be mission critical.

Whereas on a GPS if you don’t know look for it, you’ll have a hell of time finding it. And when you begin to doubt yourself, a chart can be a great reality check.

I’m not saying I have (wink wink) but I know many-a-sailor has lost their bearings in a fog bank after a flubbed tack.

The boat spins aimlessly adrift and the gps gets totally turned around. A plotted position on the chart can bring you back to reality when both your head and your gps go haywire in a fog bank.

And it does happen to humans regularly, even if it's uncommon in the GPS.

The Positive Side of Sailing Through Fog

But for all the ire that is sailing in fog: The wacky wind, the sinister sounds and the “find-muck” that is sailing with compromised senses. Fog really is just clouds on the water. A collection of semi-liquid water vapor suspended between layers of the earth's atmosphere.

This one just happens to occur on the surface of the water and not in the upper troposphere. It is one of the coolest weather phenomena on the planet save for maybe roll clouds and thunder snow.

But generally speaking fog does not occur with cloud to ground lightning and you don’t have to shovel your driveway after a fog bank rolls through.

But sailing in fog is one of the few times that you can truly feel what it is like to be a bird. To silently streak along through the clouds using only the wind as your propulsion.

Pilots speak of mystical feelings when their motors stop and their planes turn into gliders. No rumble of the motor, just your wing flaps and the wind currents carrying you aloft or down to your death.

And that is what a sailboat really is, a glider turned sideways with one wing in the air and the other below the sea with virtually no chance that you will crash into the ground at 600 miles an hour.

Sailing is the closest some of us will ever get to the heavens. When the moon is full in Long Island Sound off the coast of my hometown in Stratford, CT and the tide is high, the water takes on a magical feel.

Swollen with salty water pulled by the moon's gravity and cold from the relatively high latitudes and proximity to the North Atlantic currents.

Fog forms readily when combined with the stillness of the slack high water and the warm evening air.

A sailboat will be lucky to find a breath of breeze on evenings like this, but that really doesn’t matter because the fog blows by you at an astounding pace as it races along the temperature gradients that form between the air and the water.

Your skin gets cool and clammy from the condensing water that coats your spars and sails and makes your decks wet and slippery.

It’s almost like taking a shower without water, just super drenched air that soaks your clothes and hair.

It is THIS time that being on a sailboat in fog is most amazing because you are taking part in a weather phenomenon that touches your soul and makes even the most ardent deity denyers question their beliefs in an almighty power.

Wrapping Things Up

Sailing in fog sucks, almost always. I've sailed the entire Eastern Seaboard and had more than a few bad experiences sailing into and out of fog.

The winds can crap out almost entirely in a proper fog bank, the sounds can make your skin crawl and the fog can screw with the mind of the most well grounded of skippers.

Given my choice between sailing in fog and not sailing in fog, I will always choose the latter because reduced visibility is just dangerous in all its many forms.

But only by sailing in fog can you enjoy some of the most amazing things that happen on the water in a boat.

Sailing in Fog is a chance to fly with the Gods and tap into the mystical rhythms of the natural world.

Sure you’ll get there faster in a power boat and you can sneak up on stuff better in a kayak, but only by harnessing the natural forces of wind and waves can you truly become part of the atmosphere when you sail in the fog.

It’s not something I would recommend if you can avoid it, but if you can’t avoid it, you might as well enjoy it.

Be safe out there and sail far.

Capt Chris German is a life long sailor and licensed captain who has taught thousands to sail over the last 20 years. In 2007, he founded a US Sailing-based community sailing school in Bridgeport, CT for inner city youth and families. When Hurricane Sandy forced him to abandon those efforts, he moved to North Carolina where he set out to share this love for broadcasting and sailing with a growing web-based television audience through The Charted Life Television Network.

by this author

How to Sail

Most Recent

What Does "Sailing By The Lee" Mean?

Daniel Wade

October 3, 2023

The Best Sailing Schools And Programs: Reviews & Ratings

September 26, 2023

Important Legal Info

Lifeofsailing.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon. This site also participates in other affiliate programs and is compensated for referring traffic and business to these companies.

How To Choose The Right Sailing Instructor

August 16, 2023

How To Sail From California To Tahiti

July 4, 2023

How To Tow A Skier Behind A Boat

May 24, 2023

Best Liveaboard Catamaran Sailboats

December 28, 2023

Can a Novice Sail Around the World?

Elizabeth O'Malley

Best Electric Outboard Motors | Life of Sailing

4 Best Electric Outboard Motors

How Long Did It Take The Vikings To Sail To England?

10 Best Sailboat Brands | Life of Sailing

10 Best Sailboat Brands (And Why)

December 20, 2023

7 Best Places To Liveaboard A Sailboat

Get the best sailing content.

How Do Fog Horns Work: A Comprehensive Guide

by Emma Sullivan | Aug 13, 2023 | Sailing Safety

Short answer how do fog horns work:

Fog horns produce sound by passing compressed air or steam through a diaphragm, creating vibrations that resonate in a loudspeaker. The low-frequency sound waves emitted help vessels navigate during low visibility conditions such as fog or mist at sea.

Understanding the Basics: How Do Fog Horns Work?

Introduction: Fog horns, also known as fog signals or fog sirens, have been an essential part of maritime safety for centuries. These powerful devices play a critical role in alerting ships and boats to potential danger during low visibility conditions, such as dense fog . But have you ever wondered how these mighty horns work? In this blog post, we will explore the inner workings of fog horns in detail, shedding light on their mechanism and explaining why they are still relevant today.

The Physics Behind Sound Production: To understand how fog horns operate, we must first delve into the physics behind sound production. Sound is essentially a series of pressure waves travelling through a medium (such as air or water) that our ears can detect. For any sound-producing device, including fog horns, there are three key components required: a vibration source, a resonator, and an amplifier.

Vibration Source – The Diaphragm: In fog horns, the vibration source is typically an electromagnetically driven diaphragm. This thin metal disc rapidly vibrates when electrical current passes through it due to electromagnetic forces acting upon it. These vibrations emit sound waves which form the basis of the horn’s signal .

Resonator – The Horn: For any sound to travel efficiently and over long distances, it needs amplification. This is achieved with the help of a resonating chamber commonly known as the horn. By design, this conical shape allows sound waves produced by the vibrating diaphragm to amplify and project forward with greater intensity.

Amplifier – Air Pressure Differences: Now that we have established how sound is generated using vibrations and amplified through resonance via the horn structure let’s see how air pressure differentials amplify those sounds even further. Within a fog horn system, compressed air or steam is channeled into one end of the horn device called sounding aperture while outlets exist at both ends. The incoming air or steam rushes through these passages, producing low-frequency sound waves due to the interaction of the pressurized jet with the surrounding atmosphere.

Working Mechanism: When activated, either manually or automatically by a visibility sensor, fog horns go through a specific working mechanism. This mechanism involves two essential steps – vibration initiation and amplification.

Vibration Initiation: The process begins as an electrical current is supplied to the diaphragm in which suspended weights are installed around its circumference. These weights make the diaphragm unevenly weighted and help create unequal stress conditions upon vibrations. As electricity circulates through the coil surrounding the diaphragm, it initiates rapid oscillations causing air particles near it to vibrate at high frequencies.

Amplification: As these vibrations start in motion at the vibrating source (the diaphragm), they propagate into the horn structure made up of metal or other resonating materials. Due to resonance effects from the conical shape, sound waves get amplified and focused towards one specific direction – forward. The resulting amplified sound then gets radiated into the surroundings via sounding apertures strategically placed within hulls or on coastal stations.

Fog Horn Variations: Over time, different types of fog horns have emerged based on their specific mechanisms and purposes. Two notable variations include pneumatic fog horns and electrically driven sirens.

Pneumatic Fog Horns: These older versions relied on compressed air systems where passing compressed air over reeds or whistles generated sound waves amplified by a trumpet-shaped horn attached directly to them. The varying pressure of compressed air created oscillations that resulted in fog signals transmitted far distances over open water.

Electrically Driven Sirens: Modern fog signal technology has shifted towards electrically driven sirens rather than relying solely on compressed-air systems. These contemporary fog horns use electromagnetic forces acting directly upon a thin diaphragm as we discussed earlier, thereby expelling the requirement for complex air compressors. Electrically driven sirens generate intense sound waves by converting electrical energy into mechanical vibrations, making them more efficient and reliable.

Conclusion: In summary, fog horns are ingenious devices designed to ensure maritime safety during low visibility conditions such as heavy fog. By leveraging the principles of sound production, resonance, and amplification, these mechanisms produce powerful signals capable of reaching long distances over water. Whether using compressed-air systems or electrically driven sirens, fog horns play a crucial role in protecting vessels from potential collisions and guiding them through hazardous environments. Understanding the basics of how these remarkable devices work allows us to appreciate and respect their timeless significance in maritime navigation today

A Step-by-Step Guide: Unraveling the Mechanics of Fog Horns

Title: A Step-by-Step Guide: Unraveling the Mechanics of Fog Horns

Introduction: Fog horns, those hauntingly melodic instruments that pierce through the mist, have an enigmatic charm that captivates maritime enthusiasts and casual beachgoers alike. But have you ever wondered about the intricate workings behind these iconic seafaring devices? In this comprehensive guide, we will dive deep into the mesmerizing world of fog horns, uncovering their mechanics step by step. So let’s embark on an adventure where we decipher the secrets behind these remarkable auditory navigational aids.

1. The Origins of Fog Horns: Before delving into the mechanics of fog horns, it’s crucial to understand their origins. Developed in response to numerous shipwrecks caused by poor visibility at sea, fog horns became a vital safety measure for maritime traffic. Dating back to ancient times, civilizations devised ingenious methods like large bells or even cannon fire to alert sailors of impending dangers lurking in dense fog banks.

2. Anatomy 101: The Inner Workings: To comprehend how fog horns produce those resonant sounds that reverberate across vast stretches of water, we must dissect their inner workings with precision. At its core, a fog horn consists of three primary components: an air compressor or whistle mechanism, power source (usually compressed air or electricity), and an amplification system – all ingeniously designed to work in harmony.

3. Air Compressors: Breath of Sound Production: The heart and soul behind every fog horn’s sound production lies within its air compressor system. This genius contraption generates compressed air which then rushes forcefully through specially shaped openings called resonators or whistles. As this pressurized air is expelled from these openings, it sets off specific vibrations that result in distinctive sonic frequencies capable of traveling immense distances over water .

4. Resonators & Whistles: Singing Secrets Unveiled: The intricacies of the resonators and whistles bring forth the enchanting melodies emitted by fog horns. These specialized openings are meticulously designed to create vibrations that produce a fundamental frequency, which is then amplified within chambers or reflective surfaces. By adjusting the size, shape, and placement of these resonators and whistles, engineers fine-tune the sound signature unique to each fog horn .

5. Power Source: Empowering the Symphony: While compressed air stands as a traditional power source for fog horns, modern advancements have introduced electrically powered alternatives. Compressed air systems rely on machinery like diesel engines or turbines, while electrical variants employ electromagnetic coils to drive oscillations through diaphragms or other mechanisms. The choice of power source depends on factors such as efficiency, portability, and environmental considerations.

6. Amplification Systems: Propagation Perfection: To ensure optimal sound propagation across vast distances over water bodies, fog horns incorporate sophisticated amplification techniques. Reflective surfaces like parabolic dishes or trumpet-shaped funnels augment sound waves by redirecting them outward in a focused manner with minimal loss of energy. Such designs help transform modest acoustic emissions into piercing sounds capable of penetrating even the thickest maritime fogs .

Conclusion: As our eyes meet the coastline shrouded in dense fog, we now possess an intricate understanding of what goes on behind those evocative tones emanating from fog horns. This step-by-step guide has peeled back the layers encompassing their mechanics – from their ancient origins to the latest technological breakthroughs. So next time you hear that enchanting symphony echoing through a misty bay know that each note was carefully composed by complex interplay between resonators, compressed air or electricity and a welter of amplification systems united in their pursuit to keep seafarers safe amid treacherous waters – truly harmonious wonders deserving our awe and appreciation!

Frequently Asked Questions: All You Need to Know About How Fog Horns Work

Introduction: If you’ve ever been near a foggy coastal area or have seen movies featuring lighthouses, you must be familiar with the eerie and distinct sound of fog horns. These fascinating devices play a crucial role in maritime safety by warning ships of potential dangers in low visibility conditions. In this blog post, we will delve into the intricate workings of fog horns, answering some frequently asked questions about them along the way.

1. What is a fog horn? A fog horn is a powerful signaling device that produces loud and deep sounds to alert nearby ships or vessels to hazards like poor visibility due to fog, darkness, or other adverse weather conditions . Its purpose is to prevent shipwrecks and collisions by providing an audible warning.

2. How does a fog horn work ? The fundamental principle behind the functioning of a fog horn lies in its ability to generate sound waves. Traditional fog horns use compressed air produced by either steam, electricity, or air-driven sirens connected through complex mechanisms to produce their unique sound. When activated, the compressed air passes through specially designed resonators and diaphragms, causing vibrations that generate low-frequency sound waves capable of traveling long distances over water .

3. Why are fog horns so loud? Fog horns need to be exceptionally loud for two main reasons: penetrating extremely thick fog and overcoming ambient noise present at sea . Thick fog can significantly muffle sounds; therefore, it requires an intense acoustic signal with sufficient strength to cut through these dense atmospheric conditions accurately.

Additionally, since ships operate amidst various sources of background noise—waves crashing against the hulls, engines running, wind howling—a powerful signal emitted by a loud horn ensures audibility even against these environmental disturbances.

4. Are all fog horns the same? No! Fog horns come in various types depending on their design and location requirements:

– Diaphone Fog Horns: Diaphones are one of the oldest types of fog horns and work using a pair of pistons alternately driven by compressed air. They produce a deep, distinct sound with an oscillating pitch.

– Siren Fog Horns: Siren horns consist of a rotating or oscillating disk with evenly spaced holes that interrupt the flow of air, resulting in the well-known wailing sound associated with fog horns, reminiscent of old movies.

– Electrically Operated Fog Horns: These modern fog horns use electricity to generate sound waves. They are often smaller than traditional models and rely on powerful loudspeakers to emit their signals.

5. How far can fog horn sounds travel? The distance covered by fog horn signals depends on various factors such as frequency, atmospheric conditions, and ambient noise levels. Generally, low-frequency sounds produced by fog horns can travel several miles over calm waters. However, adverse weather conditions or physical obstacles such as cliffs or buildings can attenuate the sound waves’ propagation.

6. Are fog horns still used today? Indeed! While technological advancements have introduced other means of navigation and communication for ships, foghorns remain essential safety devices in many coastal areas worldwide. They serve as reliable backup systems during power outages or system failures on board ships and continue to play a critical role in preventing accidents.

In conclusion: Fog horns are remarkable inventions designed to safeguard maritime travelers against unexpected dangers in low visibility conditions. Their ability to generate deafening yet distinct sound waves ensures that ships can navigate through hazardous areas safely . Understanding how these mechanisms work enhances our appreciation for these timeless maritime marvels while highlighting their continued relevance even in today’s world of advanced technology.

The Science Behind Fog Horns: Exploring Sound and Vibration

Title: The Science Behind Fog Horns: Exploring the Intricacies of Sound and Vibration

Introduction: Have you ever stood by the coast, mesmerized by the resonant blast of a fog horn cutting through the thick mist ? Beyond being a captivating auditory experience, fog horns serve a vital purpose in maritime safety. But have you ever wondered about the science behind these awe-inspiring devices? In this blog, we will delve into the world of sound and vibration to unravel the secrets behind fog horns—a fascinating intersection of physics and engineering.

Understanding Sound Waves: To comprehend fog horns fully, we must first grasp the nature of sound itself. Sound waves are mechanical vibrations that travel through a medium—such as air or water—as compressions and rarefactions. These oscillations require both a source and a receiver for communication to occur effectively.

The Mechanics of Fog Horns: Now let’s shift our focus specifically to fog horns. These booming devices consist of several essential components working harmoniously. At its core lies an air compressor that generates high-pressure air pulses. This compressed air then passes through an orifice called a reed, causing it to vibrate at specific frequencies.

Resonance: The Secret Ingredient: What makes foghorn blasts so distinctive is resonance—the phenomenon where an object vibrates at its natural frequency when exposed to external vibrations matching that frequency. This principle acts as the secret ingredient behind all fog horn compositions.

Fog Horn Design Considerations: When it comes to designing effective fog horns, engineers incorporate various variables into their calculations. Key considerations include horn length, diameter, shape, reed design, and even environmental factors like temperature and humidity. Each element directly affects the quality, loudness, and resonance characteristics of the emitted sound waves.

Vibratory Performance Tuning: While constructing larger or more complex resonators may enhance volume levels, engineers employ another technique called vibratory performance tuning to achieve optimal results. This process involves adjusting the tension, length, and thickness of the fog horn’s vibrating reed to create just the right frequency and amplitude for maximum projection.

Propagating Sound in Fog: The primary reason fog horns exist is to aid navigation during dense foggy conditions when visibility is severely limited. Interestingly, sound waves travel differently in fog compared to clear air . Due to the tiny water droplets suspended within fog , sound encounters multiple scattering events, causing it to spread out and attenuate more rapidly. Engineers tackle this hurdle by designing fog horns with specific characteristics ensuring their sounds can penetrate through these adverse conditions effectively.

Safety Necessity: While we appreciate the scientific marvel that is a fog horn, let us not forget its essential role—maritime safety. By emitting long-range audible signals, these devices serve as crucial navigational aids for ships, warning them of nearby obstacles or hazardous weather conditions when visual cues are obscured.

Conclusion: The world of fog horns unveils an intricate web spun by physics and engineering geniuses who use sound and vibration principles to create effective maritime signaling devices. From understanding the essence of sound waves to incorporating various design considerations tailored for challenging environments like foggy expanses—they have created a symphony of science that epitomizes both aesthetics and functionality. So next time you find yourself captivated by a distant yet deafening blast from a fog horn , take a moment to marvel at the astounding ingenuity behind this timeless invention.

Dive Deeper: Explaining the Inner Workings of a Fog Horn System

Welcome back to our blog series on maritime technology! In today’s installment, we’re going to dive deeper and uncover the inner workings of a fog horn system. Prepare to be amazed as we unravel the magic behind this essential piece of equipment that plays a crucial role in maritime safety.

When visibility becomes poor due to foggy conditions, sailors rely on fog horns to navigate through treacherous waters. But have you ever wondered how these horns produce such loud and distinctive sounds ? Let’s find out!

At its core, a fog horn system consists of three major components: an air compressor, a resonator, and an actuator. These components work together seamlessly to create the sound signals that help ships avoid collisions and navigate safely.

Firstly, let’s talk about the air compressor. This mighty machine is responsible for generating compressed air, which is essential for producing sound. The compressor takes in atmospheric air and compresses it using pistons or rotary blades. This compressed air is then stored in tanks until needed.

Next comes the resonator – the star of the show! Resonators are intricate devices that amplify sound waves produced by the compressed air. They usually take the form of large horns or trumpets strategically placed within lighthouses or along coastlines. When the compressed air enters these resonators, it creates vibrations that resonate through their chambers, greatly amplifying even the faintest sounds.

To make these amplified vibrations audible from miles away, we need an actuator – essentially a device that sets everything into motion. Traditionally, fog horn systems employed massive weights or springs that released sudden bursts of compressed air into the resonator chambers. However, modern systems now use solenoids or electronically controlled valves for greater precision and control over sound output.

Now that we understand how these components work individually let’s see them in action with a simplified step-by-step breakdown:

1) When visibility drops due to fog or adverse weather conditions, the fog horn system is activated either manually or automatically. Automatic systems use sensors to detect reduced visibility and trigger the fog horn.

2) The air compressor kicks into action, drawing in atmospheric air and compressing it using its mechanical mechanisms or blades.

3) The compressed air is directed towards the resonator chambers through a network of pipes. The resonators amplify these vibrations by taking advantage of their unique shape and structure.

4) As the compressed air enters the resonator chambers, it sets off vibrations that resonate within their confines. These amplified vibrations then escape through the horn’s opening, creating a powerful and unmistakable sound signal .

5) This ear-catching signal travels across vast distances, warning nearby vessels of dangers in their path and helping them navigate safely even under thick blankets of fog .

And there you have it – an insider’s look into how a fog horn system operates! Next time you hear that characteristic “tooooot,” remember the ingenious combination of an air compressor, a resonator, and an actuator working harmoniously behind the scenes to keep sailors safe on their maritime journeys.

We hope this blog shed some light on this fascinating technology that often goes unnoticed. Stay tuned for our next installment as we continue exploring various marvels that make maritime operations possible. Until then, keep sailing safely !

Practical Uses and Safety Measures: Why Knowing How Fog Horns Work Matters

Title: Practical Uses and Safety Measures: Why Knowing How Fog Horns Work Matters

Introduction: Fog horns, also known as fog signals or sirens, have a long-standing history of providing essential navigational assistance to mariners worldwide. While their primary purpose is to warn vessels about the presence of fog or other adverse weather conditions, understanding how fog horns work carries paramount importance in terms of practical use and safety measures. In this blog post, we will delve into the intricacies of fog horns operation, explore their diverse applications, and emphasize why comprehending their functionality is crucial for sailors and coastal communities.

1. The Mechanics Behind Fog Horns: Fog horns are powered by compressed air generated either by machinery or through natural phenomena like waves crashing against specialized structures called resonators. These resonators can be seen along coastlines or on navigational aids such as lighthouses. When compressed air enters the resonator chambers, it gets channeled into specific frequencies that produce low-frequency sound waves capable of traveling long distances despite poor visibility. Understanding this mechanical process enables us to appreciate the raison d’être behind these acoustic devices.

2. Navigational Aid Applications: Fog horns play a pivotal role in maritime traffic management due to their reliable auditory signals that cut through hazardous conditions like dense fog, heavy rain, or snowfall—times when visual cues might become diminished. Their deep-toned blasts serve as distinct markers guiding ships away from potential dangers such as rocky shores, shallow water zones, wrecks, or even other vessels operating nearby. Such an indispensable navigational aid helps prevent collisions and disastrous accidents at sea.

3. Coastal Alert Systems: Beyond serving seafarers alone, fog horns extend their significance ashore by functioning as critical coastal alert systems for nearby communities. These distinctive sounds provide early warnings for any impending environmental threats like approaching hurricanes or tsunamis. In remote areas where internet connectivity may be limited, fog horns serve as a lifeline that communicates imminent danger to residents who may not have access to real-time weather updates or emergency services. By understanding their operation, locals can remain prepared and take necessary precautions in the face of nature’s fury.

4. Preservation of Maritime Tradition: While technological advancements have introduced modern navigational aids like GPS and radar systems, fog horns represent an alluring symbol of maritime heritage and tradition. Learning about the intricate workings of these historic devices allows us to acknowledge the craftsmanship and innovation that went into their creation. Embracing this knowledge ensures that the legacy of fog horns lives on and reminds sailors and coastal communities of our rich nautical past.

5. Safety Measures for Fog Horn Operators: Operating fog horns carries essential safety considerations for those assigned with their maintenance and control. Regular inspections, repairs, and equipment checks are crucial to ensure optimal functionality, guaranteeing that these vital signals are always functioning at their best when needed most. Additionally, creating awareness among operators about noise pollution regulations helps strike a balance between maintaining safety protocols while minimizing unnecessary sound disturbance in nearby residential areas.

Conclusion: Understanding how fog horns work goes beyond mere curiosity; it is an essential requirement for mariners, coastal communities, and even enthusiasts who appreciate the historical significance they hold. Familiarizing ourselves with their mechanisms empowers us to comprehend their multifaceted practical uses in navigation, early warning systems supply critical information during turbulent weather conditions while preserving maritime heritage in an ever-changing world. So let us embrace this timeless technology that continues to safeguard lives at sea by unraveling its mysteries one resounding blast at a time!

sailboat sound signal in fog

IMAGES

VIDEO

COMMENTS

Sound Signals in Restricted Visibility and Rule 35

You know you want it...

The Rules of the Road state when underway ‘vessels shall sound at intervals of not more than two minutes’ the prescribed sound signal.

There are two classes of working vessels that do not use the bell and gong signals while at anchor.

A good alternative is to use one of the many laminated visual shorthand versions of COLREGS sold at ship chandleries.

Don't Miss a Beat!

LEAVE A REPLY Cancel reply

Culebra Island Guide: Top 10 Must-Visit Spots for a Caribbean Escape

Recent Posts

EDITOR PICKS

Orientate yourself in fog using all your senses

The first steps to take when the fog starts rolling in

Turn on the radar reflector and navigation lights so the boat can be seen in the fog

Don't forget to sound signals in fog

Medicanes in Greece

The ultimate yacht cleaning kit

New Year's resolution: let's sail more eco

How to have a nautical Christmas

What to pack for a tropical sailing

How to gear up for the 2024 sailing season

Get to know fog with your ears

Feel your surroundings with your whole body

Don't forget your sense of smell

Need a skipper's license or just some more practice? Try our sailing courses...

Onboard radar system monitors for potential obstacles and other vessels

GPS will help you to navigate your yacht

Radio can provide other useful information

We have a large selection of boats available, as well as contacts with excellent skippers. Get in contact.

Denisa Nguyenová

Sailing In The Fog – What You Need To Know And Do

Sound Signals and VHF Protocol in the Fog

The Scenario

A Sound Solution

A Radio Solution

The Prudent Solution

Leave a Reply Cancel reply

Sailing in fog: Pro navigator Mike Broughton shares his top tips

Caught in fog

Weather expert Chris Tibbs on how to predict and cope with fog at sea

Navigation briefing: Mike Broughton explains why you still need radar

Make yourself visible

Stopping and racing in fog

Using radar for collision avoidance

Sound Signals for Vessels

You might also like

RYA Powerboat Training

Season 2023/24

Our Details:

Sound Signals and VHF Protocol in the Fog

The Scenario

A Sound Solution

A Radio Solution

The Prudent Solution

Leave a Comment Cancel reply

Boat Sound Signals: Time To Sound Off

When caught in a situation with restricted visibility, you'll need know how to let others know where you're located — and interpret where they are.

Inland Vs. International

Sound-Producing Devices And Characteristics

Sound Signals During Restricted Visibility

Related Articles

Fine-Tune Your Side Scan Fishfinder

DIY Boat Foam Decking

Frank Lanier

BoatUS Magazine Is A Benefit Of BoatUS Membership

Yachting Monthly

Preparation for fog

Entering fog

5. Lifejackets and harnesses

6. Liferaft

8. Sound signals

Collision avoidance

What this means

Worth the risk

Boat Navigation In Fog (Safety rules to follow)

Boat Navigation In Fog – Boating In Fog Safety Tips

Reduce speed

Turn Light on

Navigational equipment

Anchor your boat

Know Fog Sound Signals