Why don't yachts have foghorns?

prv said:
That's rather the point of the thread :p

I have a hailer/horn driven by the VHF - it's good for fog signals, but as the OP says, it's not really convenient for unanticipated manoeuvering signals (unlike him I don't need to go below and fiddle with glasses and so on, but it still takes a few button-presses on the handset at the helm to get it ready to sound). Ideally the VHF would have an input wire (short to ground, or apply 12v, to immediately generate a horn tone) that could be wired to a dedicated button, but they don't. I have a plan to put together a signal generator and an audio relay, that switches the speaker away from the VHF and then sends a tone to it, and I actually added the "horn" button for it to the helm along with some other work. But so far I've been a bit hampered by my lack of analogue electronics knowledge and haven't built the driver circuit.

Pete
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I suppose you could just pick up the mike and hoot into it. :D
 
prv said:
That's rather the point of the thread :p


Pete
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Well obviously. So to claim the average yachts sound signals can be heard on the bridge of any size of ship is somewhat fanciful. Of the dozens and dozens of different yachts Ive sailed, only one had a decent foghorn up the mast. Motorboats, well different, most fitted with something effective.
 
The problem with sailing yacht is where to fit your "whistle" such that it won't snag the genoa when tacking. Under the radar mount seems popular but I don't have one of those.

Those Kahlenberg horns are rather shiny and allegedly colregs compliant but heinously expensive...
 
Over here, all vessels have to carry a horn, except 'beach toys'. Standard for small boats is a plastic jobby like an old posties horn. Also obliged to carry an anchor (of choice:) ) with rope, a compass and three red flares, along with a copy of the buoys and regs.
 
DownWest said:
Over here, all vessels have to carry a horn, except 'beach toys'. Standard for small boats is a plastic jobby like an old posties horn.
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I have one of these:

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Its sole use is to let bridge keepers on the Crinan Canal know we're coming.
 
A recording of a liner foghorn played down the VHF speaker works well in the marina -dont think I have ever had to use at sea and I think I would prefer to keep my eyes on AIS and radar as opposed to believing any large ship might actually be listening .
The greatest danger might be from fishing boats though IMHO
 
JumbleDuck said:
I have one of these:

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Its sole use is to let bridge keepers on the Crinan Canal know we're coming.
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Had one of those on the yacht I sailed for the last two weeks on the Algarve. In the first week we had three mornings of drifting fog banks and it got well used. One long two shorts. but as useful really on a yacht as an umbrella.....:)
 
I thought nearly ever boat had one of those gas canister horns?

We have a set of car horns, used for starting dinghy races.
 
ashtead said:
A recording of a liner foghorn played down the VHF speaker works well in the marina ...
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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?
 
JumbleDuck said:
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?
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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.
 
lw395 said:
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.
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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.
 
JumbleDuck said:
But can a VHF speaker really produce 120dB in the cockpit?
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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
 
The benefit of using your VHF as a horn is that it’s 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.
 
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