12v foghorn system?

[davethedog]

Hello all and just after recommendations for a 12v foghorn system for a sailboat. Already have a set of wiring ran up the mast and into the boat for a speaker to be fitted.

Cheers

DTD

 

[AntarcticPilot]

You'll need good batteries and a robust charging system - a system audible at a distance is likely to need a lot of power. My dad always forbade us from sounding the car's horn without the engine running, because it flattened the batteries.

 

[LittleSister]

I doubt the amount of power used is a huge issue*. Even horns powerful enough to be as much noise as you'd want to tolerate on board (might need some ear plugs/defenders) don't draw that much, and you'd only normally be using a it few seconds every couple of minutes.

I've been intending to mount on my boat a compact but scarily loud horn I previously bought for a motorbike but never fitted. Ideally I'd want it on the pulpit, as far away from the crew's ears as possible, but I suspect it would have a limited life in all the salt-water spray and be vulnerable to damage. I was therefore contemplating putting it in some sort of a downward facing hood on the front of the bottom of the mast.

I would still carry an emergency pump up or blown horn as a back-up/supplement, but they are pathetically feeble in volume.

*p.s. Stebel Nautilus horn, advertised as 139db (ouch!), apparently draws 18 amps. I reckon that would work out roughly equivalent to a continuous draw of 1amp over the period in use. (I'm v. tired so might need to check my maths etc.: Sailing vessel in fog 1 long @ 5 secs + 2 short @ 1 sec, every 2 minutes = 3.5 secs per minute = 220 secs per hour = 5.83% of the time. 18 amps x 0.0583 = 1.05 amps.

p.p.s. Percentage above originally wrongly stated, now corrected.

 

[AntarcticPilot]

I doubt the amount of power used is a huge issue*. Even horns powerful enough to be as much noise as you'd want to tolerate on board (might need some ear plugs/defenders) don't draw that much, and you'd only normally be using a it few seconds every couple of minutes.

I've been intending to mount on my boat a compact but scarily loud horn I previously bought for a motorbike but never fitted. Ideally I'd want it on the pulpit, as far away from the crew's ears as possible, but I suspect it would have a limited life in all the salt-water spray and be vulnerable to damage. I was therefore contemplating putting it in some sort of a downward facing hood on the front of the bottom of the mast.

I would still carry an emergency pump up or blown horn as a back-up/supplement, but they are pathetically feeble in volume.

*p.s. Stebel Nautilus horn, advertised as 139db (ouch!), apparently draws 18 amps. I reckon that would work out roughly equivalent to a continuous draw of 1amp over the period in use. (I'm v. tired so might need to check my maths etc.: Sailing vessel in fog 1 long @ 5 secs + 2 short @ 1 sec, every 2 minutes = 3.5 secs per minute = 220 secs per hour = 0.583% of the time. 18 amps x 0.0583 = 1.05 amps.

There's a mistake in your calculation; I think you've slipped a decimal place and it's 10.5 Ah per hour.

 

[Aeolus]

Little Sister erred in that it's 5.83%, not 0.583% however the value she actually used in the calculation of 0.0583 is correct, as is the end result of 1.05 Amps per hour.

Think about it - if something draws 18 Amps, then it would have to be active for over half of the time to consume 10.5 amps per hour.

 

[differentroads]

Yes, there's an error in the way the calculation is written out but I worked out that the horn would be drawing current 5.8% of the time too, so 18A x 5.8% of 1 hour = a touch over 1Ah. Manageable by any reasonable battery bank, I think.
18A over the length of wiring to run up the mast will involve some power loss though unless the wire is a fairly heavy gauge - 4mm diameter cable would give you a 10% loss over a 10m cable run (10m positive, 10m negative) if I read the table in Caldwell correctly.
Apologies for digressing from the OP's question, but I'm interested both in the recommendations and the installation problem. Longest I've been out in fog is 12 hours rounding Cape St Vincent at the southern tip of Portugal. The two of us could keep up the manual foghorn for only an hour. The sound so close to our ears was stressful and fatiguing even though it seemed too feeble to be heard from the bridge of a ship or fishing boat. One of my winter jobs is to fit an electric one.

 

[dolabriform]

I've just been chatting with a colleague, and we reckon we could put a system together for around £50.
This would include the horn, and a control box with simple functionality. Select the type of signal you need ( sail / motor ) and hit go. It would then produce the correct signals at the required intervals until told to stop.
Anyone interested?

Edit: we should probably add a manual trigger button as well!

 

[lw395]

I'd forget the automated novelty.
What happens in fog is you want to listen.
You don't want your own toys going off just when you think you hear something.

 

[LittleSister]

Little Sister erred in that it's 5.83%, not 0.583% however the value she actually used in the calculation of 0.0583 is correct, as is the end result of 1.05 Amps per hour.

Thanks for checking and for the correction. Yes, I slipped a decimal point in writing out as a percentage the value I had calculated (but not in the calculation itself). I've now corrected it above.

 

[LittleSister]

18A over the length of wiring to run up the mast will involve some power loss though unless the wire is a fairly heavy gauge

Yes, which is why I am thinking of installing mine close to the foot of the mast.

 

[GHA]

Anyone using the foghorn option on an Icom gx2100e?
Manual says it can listen as well through the speaker.

 

[Refueler]

I'd forget the automated novelty.
What happens in fog is you want to listen.
You don't want your own toys going off just when you think you hear something.

Agreed ... the signals designated for each type of vessel are initial .. once you make audio contact with another - you both would then change to frequent blasts to give indication of where you are as well as any turns you make ...

Now some smart arse is going to argue that ..

 

[differentroads]

Anyone using the foghorn option on an Icom gx2100e?
Manual says it can listen as well through the speaker.

I'm about to wire up a loudspeaker to my Icom M423 to see what its foghorn function is like. But the manual says just 10W output, so I'm expecting it not to be very loud.

Edit. The range was 250m standing in line of sight in front of the speaker in F4-5 cross wind. My hearing is fairly reasonable so I'm taking that as my benchmark of 'not loud enough as a foghorn'. I wonder how many decibels this would have been? I'd guess it was about the same loudness as a modern car horn, supposedly around 100db. The air horn style at 139db will be ambulance siren level of loudness. Thats what I want ?

 

[differentroads]

I've just been chatting with a colleague, and we reckon we could put a system together for around £50.
This would include the horn, and a control box with simple functionality. Select the type of signal you need ( sail / motor ) and hit go. It would then produce the correct signals at the required intervals until told to stop.
Anyone interested?

Edit: we should probably add a manual trigger button as well!

Despite some people expressing scepticism, I'd be interested. Its not a huge premium to automate a chore that can take attention away from scanning for dangers by ears and eyes (including AIS and radar screens). LittleSister's calcs showed us that the horn would be sounding 6% of the time, so I'd be listening 94% of the time without losing attention to fiddling with equipment. A pretty fair tradeoff, I think.
My experience is that I've hardly ever heard other vessels sounding horns in fog, including two recent foggy crossings of the Straits of Gibraltar, really busy with shipping.
I'd sooner give vessels a chance to avoid me cos I'm reliably making a racket rather than trust that I'll hear them. Because experience tells me I won't. Experience also tells me that I can't sustain hours of regular foghorn button pressing.

 

[dolabriform]

Despite some people expressing scepticism, I'd be interested. Its not a huge premium to automate a chore that can take attention away from scanning for dangers by ears and eyes (including AIS and radar screens). LittleSister's calcs showed us that the horn would be sounding 6% of the time, so I'd be listening 94% of the time without losing attention to fiddling with equipment. A pretty fair tradeoff, I think.
My experience is that I've hardly ever heard other vessels sounding horns in fog, including two recent foggy crossings of the Straits of Gibraltar, really busy with shipping.
I'd sooner give vessels a chance to avoid me cos I'm reliably making a racket rather than trust that I'll hear them. Because experience tells me I won't. Experience also tells me that I can't sustain hours of regular foghorn button pressing.

Thanks for the positive feedback.

One situation that comes to mind is lots of small boats "listening" and not transmitting AIS.

The layout I'm thinking of is as follows.
Switch to select between signals for sailing or motoring.
Button to start it. which then becomes stop button once it's running.
Button to sound the horn so you can use it for signalling ( 5 blasts etc ).

I was thinking of LED status lights instead of an LCD display to keep it simple.

I'll play around with a prototype. and let you know how I get on.

@LW
If you think you heard something hit the stop switch!

 

[pvb]

Lots of VHF radios have built-in automatic foghorn functionality, typically with 30W output. Worth checking your VHF specs first.

 

[Refueler]

Always hated fog at sea ... eery feeling.

Just a story that may amuse ....

20,000 tonner going into Placentia Bay Canada ... dense fog ... I'm up on focsle with an AB keeping lookout for bouys ... bridge calls on walkie talkie ... keep eye out for stbd marker buoy should see it soon ...

AB and I looking ... staring into the dense fog cannot see a thing ... then we hear BONK BONK BONK ... as it dances down ships side !!

 

[differentroads]

I'm about to wire up a loudspeaker to my Icom M423 to see what its foghorn function is like. But the manual says just 10W output, so I'm expecting it not to be very loud.

Just back from testing. Audible range of the 10W output into a 30W horn speaker was 250m or so in line of sight standing in front of the speaker.

Lots of VHF radios have built-in automatic foghorn functionality, typically with 30W output. Worth checking your VHF specs first.

Yeah, I wish my Icom could put out that much audio. Mind you, 30W audio output is a fair chunk of power for small devices like modern VHFs to deal with alongside the hardware to manage 25W of radio output. Well it was when I used to run to hi-fi amps and VHF radios that I could repair thirty years ago. Stuff is more efficient nowadays.

 

[differentroads]

Always hated fog at sea ... eery feeling.

Just a story that may amuse ....

20,000 tonner going into Placentia Bay Canada ... dense fog ... I'm up on focsle with an AB keeping lookout for bouys ... bridge calls on walkie talkie ... keep eye out for stbd marker buoy should see it soon ...

AB and I looking ... staring into the dense fog cannot see a thing ... then we hear BONK BONK BONK ... as it dances down ships side !!

I'm with you on that. Mostly because of the thought of big b*ggers like you scraping small b*ggers like me down the side!!
Kidding aside, AIS has been a game-changer in fog for me. Being able to call up a ships bridge, check they have me on radar and who will do what is a huge help. The professionalism of merchant mariners always impresses me. I'd be interested to hear if and how well watch officers hear fog signals from small vessels like yachts and fishing boats.

 

[ithet]

I have been considering something similar, but using a small horn mounted on the mast rather than a loudhailer, e.g. Stainless Steel Compact Horn

Anyone have experience with these?

I was thinking about combining the horn control with navigation light selection.