Sounding through timber hull

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labrat
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Sounding through timber hull

Post by labrat » Sun Jul 29, 2018 7:25 pm

I've seen various posts related to mounting sounder transducers in the hull but can't remember any about timber hulls.

It's close to the time when I need to decide on how the sounder will be mounted in my new build so if anyone has any experience in sounding through timber can you please give me some info on what you did and how it worked out.
Cheers, Bob
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Indiedog
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Re: Sounding through timber hull

Post by Indiedog » Sun Jul 29, 2018 8:11 pm

Funny but I was talking with Ido about this very thing this afternoon. I imagine the density of the wood affects how much air is trapped within. Your timber is now doubt light so a fair bit of air. Enough to distort the signal? Not known. I was thinking you'd have to thin the hull as much as possible and then rebuild it with epoxy to eliminate the air. Tough one but interested to see a solution if indeed one is required.
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Dodge
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Re: Sounding through timber hull

Post by Dodge » Sun Jul 29, 2018 9:03 pm

Bob, had a 5 ply Hartley runabout many years ago we used for game fishing.

About mid ships inside at the keel we made a box of ply and glassed the edges onto the hull.

Varnished the box then half filled with a vegetable oil, and the transducer for an FG300 Furuno [wire stylus on paper scroll] just sat submerged and sent signal thru the hull.

Perfect signal from shallows to my deepest which was about 60 fathoms wide.
cheers RICHO

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Accept some days you're the pidgeon, but on others the statue.

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labrat
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Re: Sounding through timber hull

Post by labrat » Sun Jul 29, 2018 10:16 pm

Thanks for those replies.

Dodge, sounds like it's worth a try - I'd be surprised if the ply on a power boat would be easier to go through than 5 mm of cedar or paulownia.

Indi, I was also thinking about Ido and wondering if he'd ever tried it. Was also thinking about thinning the hull and having a small area of glass only but now I think it's worth taking the other strip kayak out on the river and doing some trials.

If it works with silicone as the coupling then I'll set up the transducer and battery behind the cockpit with access via the rear deck hatch.
Cheers, Bob
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Re: Sounding through timber hull

Post by Indiedog » Mon Jul 30, 2018 10:21 am

Bob, probably too late on this, but if you used a thinned epoxy first up and drenched the area you looked to place the transducer with several coats while still wet, that may work. If both the inner and outer surfaces are sealed, then would a matrix of small holes to say 3/4 depth through the hull on the inside which are then flooded with thinned epoxy work? Hopefully it would soak through all the timber cells to fill the voids.
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labrat
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Re: Sounding through timber hull

Post by labrat » Mon Jul 30, 2018 1:28 pm

Indi, I think you'd be surprised at how little epoxy will penetrate timber, even when thinned. If you do a test piece next time you're using epoxy, thinned or straight, and then saw through it when hard I reckon it will only be about 0.5mm deep.

The hole idea would allow it to penetrate along the grain but then there would be a pattern of different materials in the zone and this may also induce scatter. However if I have no luck with the test run in the old boat then I can make up a trial box using that method. Thanks for the idea.
Cheers, Bob
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Re: Sounding through timber hull

Post by Dodge » Mon Jul 30, 2018 4:30 pm

labrat wrote:
Sun Jul 29, 2018 10:16 pm


Dodge, sounds like it's worth a try - I'd be surprised if the ply on a power boat would be easier to go through than 5 mm of cedar or paulownia.

Bob the boat mentioned by me was about 50 years ago, ply was about 10mm thick and the laminating then would likely not be as good a quality as modern ply, we only used oil to prevent air bubbles under trannie.

In your shoes my first test would be just a sealant bond to timber under the trannie, the modern replacement for air bubbles in lieu of oil as you would know.
cheers RICHO

Kayaks: Perception Swing 400 ..... carves Anon timber lures.
Accept some days you're the pidgeon, but on others the statue.

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