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  1. #31
    Join Date
    May 2007
    Posts
    38,325

    Default Re: Why don't yachts have foghorns?

    I thought nearly ever boat had one of those gas canister horns?

    We have a set of car horns, used for starting dinghy races.

  2. #32
    Join Date
    Aug 2013
    Location
    SW Scotland
    Posts
    19,658

    Default Re: Why don't yachts have foghorns?

    Quote Originally Posted by ashtead View Post
    A recording of a liner foghorn played down the VHF speaker works well in the marina ...
    Doubling the distance reduces sound pressure by 6dB, so between 1m and - for convenience - 128m, the reduction is 42dB. A set of airhorns is about 120dB, so on the bridge of a ship 128m away they would sound about as loud as an alarm clock (80dB at 1m), which sounds about right. But can a VHF speaker really produce 120dB in the cockpit? It seems a little optimistic, but perhaps someone has measured it?
    "Seamen are always wanting to do things the proper way; and I like to do them my way."

  3. #33
    Join Date
    May 2007
    Posts
    38,325

    Default Re: Why don't yachts have foghorns?

    Quote Originally Posted by JumbleDuck View Post
    Doubling the distance reduces sound pressure by 6dB, so between 1m and - for convenience - 128m, the reduction is 42dB. A set of airhorns is about 120dB, so on the bridge of a ship 128m away they would sound about as loud as an alarm clock (80dB at 1m), which sounds about right. But can a VHF speaker really produce 120dB in the cockpit? It seems a little optimistic, but perhaps someone has measured it?
    90dB/W would be a pretty efficient speaker, so to get 120dB in the cockpit, you would want a kilowatt amp.
    Plus the liner's horn will be below the 3dB point of the cockpit speaker.
    Airhorns are way more effective.
    Plus you can point them away from you and avoid deafening yourself.

  4. #34
    Join Date
    Mar 2007
    Location
    Atlantic
    Posts
    21,369

    Default Re: Why don't yachts have foghorns?

    Quote Originally Posted by lw395 View Post
    I thought nearly ever boat had one of those gas canister horns?

    We have a set of car horns, used for starting dinghy races.
    Dont last very long in fog when sounding at intervals of not exceeding two minutes.....

  5. #35
    Join Date
    May 2007
    Posts
    38,325

    Default Re: Why don't yachts have foghorns?

    Quote Originally Posted by capnsensible View Post
    Dont last very long in fog when sounding at intervals of not exceeding two minutes.....
    Yet very few people ever use them up!

    Our club has a couple of the sort you pump up with a tyre pump. They're pretty good.

  6. #36
    Join Date
    Mar 2007
    Location
    Atlantic
    Posts
    21,369

    Default Re: Why don't yachts have foghorns?

    Quote Originally Posted by lw395 View Post
    Yet very few people ever use them up!

    Our club has a couple of the sort you pump up with a tyre pump. They're pretty good.
    Yes I had one of those on my liveaboard yacht but it fell apart after a few years.

    Gas cannister ones, well I suppose people arent in fog often enough to use up a gas cannister but I have a number of times and I would recommend an oral back up coz they dont last very long at all.

  7. #37
    Join Date
    Jul 2009
    Location
    Winter in Falmouth, summer on board Rampage.
    Posts
    5,210

    Default Re: Why don't yachts have foghorns?

    Iíve got one of the ones you blow through in the cockpit, mainly as a hired boat scarer (small, 20-40hp motorboats hired by the day in Greece). Got one of these https://www.amazon.co.uk/dp/B01AO0FM..._Y.LKDb057GQFW for when the fog comes down, as it makes more noise and is easier to use the blowing the trumpet....

  8. #38
    Join Date
    Nov 2009
    Location
    Southampton
    Posts
    35,609

    Default Re: Why don't yachts have foghorns?

    Quote Originally Posted by JumbleDuck View Post
    But can a VHF speaker really produce 120dB in the cockpit?
    Why in the cockpit? Mine’s under the radar, halfway up the mast. It doesn’t sound all that loud in the cockpit, a lot louder when I go up to the foredeck, but no, almost certainly not as loud as a big motorboat’s air horn.

    It should be enough to alert another leisure vessel at closish range, just in case they didn’t have a radar reflector and I didn’t spot a small echo in time. For the big stuff it’s not relevant, as we’ll use AIS and radar to avoid each other out of earshot of my little horn.

    Pete

  9. #39
    Join Date
    Sep 2014
    Location
    Scarborough
    Posts
    259

    Default Re: Why don't yachts have foghorns?

    The benefit of using your VHF as a horn is that itís likely got auto horn facility where you can set what you want to express, underway under power, under sail, at anchor, aground (!) or whatever and leave it to it. Manually doing fog signals for any length of time gets tedious quite quickly.

  10. #40
    Join Date
    Oct 2005
    Location
    Durham, England
    Posts
    16,563

    Default Re: Why don't yachts have foghorns?

    My boat came with a handheld foghorn powered by a soda siphon Co2 gas canister.

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