Sounder: Shooting through plywood

martinc2

Recruit
Joined
Jul 30, 2004
Messages
4
I have a glass/ply catamaran that needs a transducer. The hull is thin (11 mm) and I would like to shoot through it rather than cutting into it. I've gotten various opinions, mostly negative, about the idea (owing to the thin layer of plywood in the sandwich). I tried flooding the bilge and placing a transducer in the water. It worked but I was in only 15' of water. I'm wondering if it will work but will just degrade the range? Any thoughts/recommendations? Also, I have about 40 degrees of deadrise and haven't found a transducer housing that will accomadate that much.
 

flashback

Rear Admiral
Joined
Jun 28, 2002
Messages
4,009
Re: Sounder: Shooting through plywood

what I have done in the past is epoxy a pvc pipe fitting with an inside diameter that is close to the transducer (I think about 2 and a half inches) to the inside of the hull, then fill the pipe with transducer and mineral oil... seal it all with the plug and it works.......
 

ThomWV

Senior Chief Petty Officer
Joined
Dec 19, 2003
Messages
701
Re: Sounder: Shooting through plywood

Stop,<br /><br />No, you can not shoot through plywood with an in-hull transducer, and it doesn't matter if you have the bilge partially flooded or not nore does it matter how you mount the in hull.<br /><br />I would be possible to simply cut out a window in the bottom of the hull and then build it back with glass and mount over top of the window, I wouldn't do it but you could. You'd be a lot better off going to a thru-hull or, as much as I dislike them, you could install a transom mounted transducer.<br /><br />I think I should tell you what I did before I installed my transducer. My boat has a solid glass bottom that is about 5/8" thick. It is an older boat. I didn't trust that my hull bottom's glass was completely solid, with no air bubbles in the laminate which would have reduced the capability of the transducer. Because of that before I mounted my in-hull I broke out the angle grinder and removed all of the glass in an area about a foot long and maybe 10" wide below where the transducer was to be mounted. This left the gel coat on the outside of course. Then I reglassed the area back to its original thickness plus a little bit to give a nearly flat surface for mounting. You could do the same thing to your hull if you wanted to. I think it took me about an hour and a half to do the glass work. Its not a big deal. My transducer mounts in a factory made tank that serves the same purpose as the PVC pipe that some folks use to mount there's. Mine is glued down to the hull bottom with 5200 to seal it, the tank itself if filled with mineral oil and the transducer is suspended above the glass in the liquid.<br /><br />Thom
 

martinc2

Recruit
Joined
Jul 30, 2004
Messages
4
Re: Sounder: Shooting through plywood

Thom and others,<br /> Thank you for the quick response. I have been dreading cutting a hole for the transducer or for the construction of a glass window. I have some friends with a lot of glass experience. I'll ask them how to go about it. The window idea solves the dead rise problem as the interior can be built up to a horizontal step. I'm assuming however, that the glass build can't be too thick. With the extreme dead rise, one edge would be pretty thick. Might be better to leave the slope and construct a tank from PVC with the exact slope cut on the bottom such that it sets vertical. Any thoughts about which approach would degrade the signal the least? I would like to reach at least 600 ft for offshore navigation by seabed contour.
 

18rabbit

Captain
Joined
Nov 14, 2003
Messages
3,202
Re: Sounder: Shooting through plywood

I question the idea of going through the process of cutting/fitting/glassing a window to improve performance than mounting the transducer in-hull. Thru-hull mounting has better performance than in-hull mounting. I would cut for a thru-hull mounting, glass reinforcing the inside of the hull if necessary and use a faring on the outside. Not much difference in the work and better transducer performance. I am presuming a typical transducer…it will get you your 600-ft soundings. If you have a large monster transducer on a disproportionably small vessel, in-hull mounting may be the best option.<br /><br />Fwiw, you can shoot sonar through plywood but with unknown results. It may work as well for you in 600-ft as it did in 15-ft of water. If you know what result you are looking for you can take it out and try it in deep water. If you are not sure, I suggest passing on the idea altogether and plan on doing some glass work.
 

ThomWV

Senior Chief Petty Officer
Joined
Dec 19, 2003
Messages
701
Re: Sounder: Shooting through plywood

Well, if you build the window, which wouldn't be too hard to do, you could build a tank with the V shapped bottom and suspend the tranducer in a tank pretty easily, and it would pretty much give you your choice of transducers.<br /><br />You didn't say what fish finder you're using so I don't know what transducers might be available to you. The in-hull transducer that I am using is now allowing me to shoot to greater than 2,000 feet. It seems to be maxing out at about 2,500 feet so far but its been pretty rough out there ever since I got it, so it may be better if we ever get to fish on a flat day. The transducer we're using is a 1kW model made by Airmar. Quite a few fish finders can use it and they make it with plugs to attach to quite a few different makes and models. Its the Airmar M260. It has 1 large transducer element for 50 kHz operation and 7 smaller transducer elements in an array for its 200 kHz side. It is a real marvel.<br /><br />Thom
 

mattttt25

Commander
Joined
Sep 29, 2002
Messages
2,661
Re: Sounder: Shooting through plywood

boating magazine ran a great article this month on the different types of transducers- thru-hull, hull mounted, and transom mounted. they conducted real life tests with the three setups and the same fishfinder. a good read.
 

18rabbit

Captain
Joined
Nov 14, 2003
Messages
3,202
Re: Sounder: Shooting through plywood

Thanks for the info on the article, Mattttt25. Now I have to go out and find a copy. :)
 
Top