Drilling Holes

[sperzonkers2]

Hi all, What is the best way to drill holes in these cored fiberglass. My boat has a foam core inside. I have heard it is better to drill a larger hole and fill with epoxy then drill the size hole you require in the epoxy. Is this the best way to keep water out? I am installing a transducer.

[wb]

what ever you decide make sure you seal anywhere that wood or foam or anything that is not happy in water is exposed cuz water will find its way in

for larger holes i go slightly oversized then the epoxy fills in 0.030" or less and it's just the right size when done

for smaller holes like screws and such you can usually get away with the correct size or ever so slightly oversize then dab the epoxy in the hole and coat the screw assemble as usual and your done.

if you envision having to disassemble use a good quality silicone rtv sealant instead of epoxy

[sealife]

I would also use a countersink bit to cut some of the gel coat back so it does not crack when the screw is installed.

[CapBob]

Transom mount or thru hull?

[barrell]

Transom mount or thru hull?

Thats what I was wondering? If through the hull I would drill the top layer oversized but not through the bottom layer. I would then Fill the the void with a mixture of chopped fiberglass and resin back to the top surface. Then I would redrill using the proper size hole saw through the center of the new glass. This would create a solid fiberglass area for the bronze to pass through. No chance of water getting into the foam core.

[sperzonkers2]

This is a transom mount transducer.

would have replied sooner but this thing call work keeps getting in the way