gary3029
regular
Reged: 22/07/2005
Posts: 227
Loc: Poole Dorset
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I need a new depth gauge and don't want anything fancy. The Nasa Target 2 meets the criteria as basic and cheap. Given I have a wooden boat I don't want to be drilling holes for the transducer. Will this unit work if I don't put the transducer through the hull. As anyone got this unit in a wooden hull?
Thanks
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"We need to make a sacrifice to the boat gods, find me a young virgin... oh,
and bring something to kill"
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oldharry
regular
Reged: 30/05/2001
Posts: 3796
Loc: North from the Nab about 10 mi...
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No, AFAIK there is no sounder which will work through wood - its too soft and deadens the ultrasound. It either has to go through - and some authorities insist you use a bronze transducer housing, as timber swells and may crack a plastic housing with disasterous results - or you have to find some way of going round outside like with a transom mount.
But maybe somebody knows different?
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If you cant fix it, get a bigger hammer...
Edited by oldharry (17/03/2008 22:58)
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Tranona
regular
Reged: 10/11/2007
Posts: 1377
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No, you are right. Although a plastic transducer might be OK through stable Plywood - I have one for my log impellor, you need bronze to go through wood which might swell. Apart from the extra cost of the bronze transducer, there is no downside to having the hole through a plank, or better still through the deadwood in front of the keel with a shaped fairing piece so that it is vertical. It will not work inside anyway. So, bite the bullet and do it properly! or cast yourself a lead!
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KenMcCulloch
regular
Reged: 22/04/2007
Posts: 865
Loc: Edinburgh, Scotland
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Quote:
No, you are right. Although a plastic transducer might be OK through stable Plywood - I have one for my log impellor, you need bronze to go through wood which might swell.
The shipwright who was working on Border Maid recently opined that this stuff about bronze transducers is a load of nonsense. He has seen dozens of plastic through-hull transducers like mine in wooden boats and none of them were cracked. The only qualification might be that a new wooden boat (or a new plank) might possibly swell enough to cause a problem.
Cue dozens of posts from people whose old gaffers have sunk because of plastic transducers 
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Ken McCulloch
Border Maid
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Clifford_Pope
regular
Reged: 28/10/2005
Posts: 741
Loc: Pembrokeshire
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Even if plastic is proved to be 100% safe, do you really want your lovely wooden boat to be plugged with the stuff?
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TMLondon
regular
Reged: 10/03/2008
Posts: 54
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I use one with a bronze fitting on a plywood full, fits lovely, but as always, holes in the hull are a constant source of concern. -Especially as I get enough water in through my leaky roof / deck!
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www.yachtshoestring.co.uk
1969 Wooden Folkboat
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PyroJames
regular
Reged: 09/08/2002
Posts: 996
Loc: Cambridge
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I'd agree. I had plastic transducers in my old boat, and although one of them did break (my fault for over tightning it) they never leaked a drop. If in doubt, bed it on stickflex and leave the nut off until its been in the water a week.
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Tranona
regular
Reged: 10/11/2007
Posts: 1377
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Nasa seem to only offer a plastic transducer that can be used in-hull in GRP or as a through hull. Even if you are happy using it through a plank, there is still an issue of getting it vertical and clear of the keel for good performance.
I fitted mine by drilling a hole vertically through the stem just in front of the keel, counterboring inside to give a square bearing surface for the lock nut and fitted a fairing piece on the outside to take the head of the transducer. The hole is about 1mm dia oversize and when I assembled it I filled the hole with sealer so the threaded stem of the transducer is not in contact with the wood. Been there for over 15 years now! However, it is bronze from Raymarine. They now have a range of bronze through hulls with fairing blocks - details on their website, but don't know whether they work with Nasa.
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Casey
regular
Reged: 16/01/2003
Posts: 275
Loc: New Forest, Hampshire, England
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On Kala Sona I have both log and depth sounder through the hull and they are both plastic. Six or Seven years ago I had to replace the log and found that the hole was too big so I turned some mahogany to reduce the hole to the correct size, glued it in with epoxy and followed NASA's instructions for fitting. I have had no problems at that end with either of them. The unit in the cockpit is a different matter as I did not seal the log unit properly and the consequent ingress of water ruined the head. More expense!!
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Kala Sona is for sale. A bargain waiting for someone.
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KenMcCulloch
regular
Reged: 22/04/2007
Posts: 865
Loc: Edinburgh, Scotland
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Quote:
Even if plastic is proved to be 100% safe, do you really want your lovely wooden boat to be plugged with the stuff?
Well all things being equal probably not. They are there however, have been for at least 15 years and I see no reason to mess with things that are working perfectly.
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Ken McCulloch
Border Maid
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