"Jim Thompson" writes:

Here's yet another question about properly seating screws in laminate
fibreglass.

Transom: fibreglass over wood. I have three 1/8" holes for the
transducer mount screws.
snip

I'm doing something very similar as far as penetrating a plywood core
covered with glass.

This is what I'm doing:

1) Drill out those 1/8" holes to 1/2".

If that means the holes break out into each other, then drill out say a
1-1/4" hole with a hole saw to clean out the entire area.

2) Close off one end of the holes with some duct tape.

3) Mix some epoxy with micro-balloons to a rather stiff mix and stuff some
in each hole. Don't try to fill the entire hole, you'll be wasting your
time.

4) Allow 24 hours, the remove tape and back fill holes from both sides, if
necessary, with more epoxy/micro-balloon putty.

5) Allow to cure at least 48-72 hours, sand off excess putty, then drill
1/8" holes as req'd.

6) Seal all "raw" edges of putty with epoxy using a pipe cleaner to coat
holes. Allow to cure 24-48 hours.

7) If you need to gasket the transducer to the transom, use the old "tube
gasket" technique to build a gasket using something like SikaFlex 291 and
finishing nails as spacers.

8) If you don't need a gasket, install transducer and you are good to go.

What I have just described is a total PITA process, BUT, it insures that the
plywood core remains totally protected and will not rot.

HTH


--
Lew

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