Threaded inserts for below-the-waterline fasteners

[Capt'n Bill]

Great,

Thanks Mark. That bit of info will be quite handy.

Bill S.

[Adeline]

Thanks to everyone for their thoughts. I talked To West System about this and they believed that inserts were unneeded. However they advised that screwing into cured epoxy is not recommended. Brittle. They advised that I coat machine screws with Pam Cooking Spray and insert them into uncured epoxy. After curing, remove the screws and the thread grooves will remain. I did some mockups and found that drilling/tapping into cured epoxy offered better results with no cracking. So I went this way. First I removed my old transducer bracket and the 5200 that bedded it for 16 + years. Thankfull there was no water infusion. I filled the old holes with thickened epoxy + milled fibers(added strength). I made a cardboard template of my new transducer mounting panel and had Tap Plastics in Portland create one out of 1/2" acrylic. This stuff is really dense and I'm sure it will hold my bracket. If I'm wrong I'll redo it with 3/4"( 1/4" piece onto 1/2" piece with Testors Modeling Glue). I drilled four 3/8" diameter(.375") X 1" deep holes into the transom and filled them with the epoxy mixture. I then drilled and tapped 3/4" deep for the 8-32(.013 diameter) machine screws. I mounted the plate with a dab of 5200 at each of the holes. Finally, I mounted my new transducer bracket to the plate using 10-32 machine screws. I know some folks may think this is overkill. Especially since I'd not had a problem using 5200 alone. However, I can't see any downside and it wasn't much trouble doing it this way. It puts my mind a little more at ease. As to the threaded inserts, I still think they're a great idea and if I doubted the integrity of the epoxy mixture I would've used them here as they'd help distribute the loading. I may still use them when I install my fuel-tanks. Anyway, I posted some pictures in Adeline's photo album in case anyone wants a look. http://www.c-brats.com/modules.php?set_albumName=album207&op=modload&name=gallery&file=index&include=view_album.php

[AstoriaDave]

Like Pete, I've had good success with drilling and tapping cured epoxy. Over a very long time, it might get a little brittle, but I bet it will outlast the 'ducer! For me, the easiest way is to wait a day or so after initial layup, so the epoxy is still a tiny bit green, when it cuts easily. Another couple days and the stuff is bull strong.

Filling with microfibers is an inspired way of handling the strength issues.

I really believe in filled epoxy.

[oldgrowth]

Adeline - a nice professional looking job.