Sealing Depth Transducers

[noelex 77]

I need to install 2 new depth transducers. They are plastic into an alumiminium hull. I am looking for recommendations to bed/seal them.
Lifeseal etc that is commonly suggested is not available here, but Sikaflex products are. I have read the Sikaflex data sheets, but I still not sure the best product. I would prefer to be able to remove the transduces at a later date if this can be done without compromising the seal.
Is Sikaflex 291 my best option ?

[gauchocat]

I have successfully done this three times; however, only with fiberglass hulls but not aluminum...

I have never been a fan of drilling through my hull to place a transducer.

In all cases I purchased a clear plexiglass tube approximately 6" in diameter and approximately 8 - 10" in length. I shaped one end of the tube to the contour of the inside of the hull, off the center line away from the keel. Once the tube meets the contour I used silicone to hold it in place and seal it to the hull. With a flat piece of clear plexiglass I fabricated a cover.

Suspend the transducer from the cover (drill a hole through the cover and use the supplied nut from the transducer) so the transducer is close to the hull. Fill the tube with water and you're in business.

By using clear plexiglass you can always check to see that your tube if full. The set-up works well and my depth sounders never let me down, i.e. never ran aground. The manufacturers will tell you that you will lose sensitivity and that may be more so with an aluminum hull. Also, you may choose to use another fluid like baby oil instead of water since the transduce sensitivity decreases as the density of the media changes.

[Lancerbye]

I have done the inside hull mounted system on a commercial boat and it worked great even better in aluminum than Fiberglass. I used glycerine as a tranducer medium. The higher the liquid density the better. Used the same idea in Industry many times.

[noelex 77]

Thanks for the suggestion. I used this system on my old fiberglass boat,( although gauchocats system with a clear tube to check the liquid contents is a great idea). My understanding was that it did not work at all on metal hulls, given lancerbyes comment it looks like I may have been wrong.
Anyway the transducers will be replacing the previous depth and speed transducers which already have cut outs. The instruments were damaged by lightening as I am planning to go with depth and a fishfinder. The fishfinder is mainly to provide a back up depth instrument.

[Downthere]

I recently made a fish finder/depth finder that I can use as a backup by buying an inexpensive (but high pixel count) fishfinder and mounting the transducer on an epoxied stick that I bungee to the back of the boat when I need it. I put on a cigarette lighter style 12V plug for power.

It works great for bottom fishing over a shipwreck or live bottom. Here in South Carolina you will either catch nothing (when bottom fishing) if you are over sand, or you will get great sea bass, grouper, and snapper if over a ledge or wreck or artificial reef.

I keep it all wrapped up in the storage locker until I need it. When sailing, I just use the digital depth finder.

Maybe you could have one less hole in the boat?

Steve

[GordMay]

Originally Posted by noelex 77

... Is Sikaflex 291 my best option ?

Sikaflex “291" is a very tenacious Polyurethane (PU) Adhesive/Sealant, like 3M’s “5200" (tho’ faster curing). Like all Pu’s, “291" can only be removed mechanically*, once cured.

BoatLife “Lifeseal” is a hybrid Polyurethane/Silicone sealant. Hardware, bedded with “Lifeseal” can be more easily removed (than pure PU’s) once cured; but the silicone residue must still be removed mechanically (nothing sticks to silicone, including silicone itself).

* DeBond Corp. claims that it's DeBond Marine Formula will:
“remove and clean up cured 3M 5200 (polyurethane adhesive sealant) in addition to silicones, caulk and common marine adhesives without damaging the boat or accessory.”
Marine Formula

[Capitain Mike]

Originally Posted by GordMay

Sikaflex “291" is a very tenacious Polyurethane (PU) Adhesive/Sealant, like 3M’s “5200" (tho’ faster curing). Like all Pu’s, “291" can only be removed mechanically*, once cured.

BoatLife “Lifeseal” is a hybrid Polyurethane/Silicone sealant. Hardware, bedded with “Lifeseal” can be more easily removed (than pure PU’s) once cured; but the silicone residue must still be removed mechanically (nothing sticks to silicone, including silicone itself).

* DeBond Corp. claims that it's DeBond Marine Formula will:
“remove and clean up cured 3M 5200 (polyurethane adhesive sealant) in addition to silicones, caulk and common marine adhesives without damaging the boat or accessory.”
Marine Formula

Hi Gorgon,
Do you know if The Debond Corporation AK Marine Formula still exist. I get no reply to my emails