Cut thru hull for transducer

LouisR

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We have a 2001 Sailfish 282, we often fish deep at 300 meters for Tuna, the transom mounted transducer is not up to it and Furuno have recommended a 2kW transduce unit and a 600W widebeam transducer linked to a FCV295 fish finder. But cutting two holes thru my hull worries me, especially fibreglass separation issues that may result from not sealing off the balsa-core of the Grady. Any experiences or comments to share?
 

seasick

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LouisR said:
We have a 2001 Sailfish 282, we often fish deep at 300 meters for Tuna, the transom mounted transducer is not up to it and Furuno have recommended a 2kW transduce unit and a 600W widebeam transducer linked to a FCV295 fish finder. But cutting two holes thru my hull worries me, especially fibreglass separation issues that may result from not sealing off the balsa-core of the Grady. Any experiences or comments to share?
I didn't think that the hull on that vessel was balsa cored. I suspect it is not. Regardless, making and sealing the penetration is not difficult. The hard part is selecting the best spot for the transducer. The hole should be sealed with epoxy and left to cure. The transducer would then be bedded with 5200. Make sure you have the correct angle transducer or an appropriate faring block.
 

ElyseM

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GW are not cored below the waterline. your hull is about an inch of fiberglass. you can call GW customer service and they will put your mind at ease. good luck, ron
 

DennisG01

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I'll start by mentioning that if you're worried about, it might be best to hire someone to do it. On average, you'll probably find that two holes (and running the wires) should be about 3-4 hours. A little more, depending on circumstances - limited access to the spot can certainly increase that.

That said, what you'll do is verify (a few times!) that you're cutting in the right spot. Take a piece of 3/4" MARINE plywood and make a backing plate to be epoxied on the inside. It should be roughly twice the size (square is OK) of the ducer. You can pre-coat this piece with epoxy ahead of time (and sand lightly, after washing the amine blush off). Now, sand the interior surface where the block will be epoxied - sand about an extra 4"-6" in each direction. Next, epoxy the piece in place and cover with fiberglass.

Now you're ready to cut the hole. If space permits, I usually like to make a pilot hole from the inside to make sure I get the right position. If not, measure a few times from known objects (keel, lifting strakes, etc.). Once your big hole is cut, bevel the inside and outside edge of the cut. I didn't realize the boat had a balsa core there, but in that case then what you want to do is remove about 1/2" of the balsa all the way around the inside perimeter of the cut (sometimes it might be easier to do this before epoxying the block in place) and then come back and fill with thickened epoxy (first coat the balsa and inside area of this "relieved" section with straight epoxy). Coat the inside edge of the blocking at the same time.

Seal the 'ducer with something like BoatLife LifeCalk or 3M 4200 (after again removing the amine blush and a light sand). DO NOT use 3M5200. Again... DO NOT use 5200.
 

LouisR

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Ok, this is all great information for me and sets my mind at ease. I do intend getting the work done by a shipwright. I was under the impression the bottom of the hull had a balsa-core but if not, then that's even simpler. I will contact GW and confirm. Thanks again for the advice guys.
 

onoahimahi

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The hull of my 94 Sailfish has two factory "flats" molded into the bottom for thru-hull transducers, one on each side. Thus the transducers would shoot straight down without needing any wedging which is convenient and would make for an easy install.

-Scott
 

LouisR

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Thanks for all the tips guys. I have confirmed with GW Customer Service that there is no core in the hull bottom of my Sailfish 282 and it is 100% hand laid fiberglass. Cheers.
 

LouisR

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For the record, after four years with transducers through the hull, no problems and they work really well hooked up to the Furuno NavNet TZT.
LouisR
 

Fishtales

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check out a shoot thru ducer set up. Good alternative.