It seems from some answers to a recent post of mine and also from a recent professional installation in a friend's boat that skin fittings are often epoxied in.

The seems wrong to me because skin fittings will rarely last the life of the boat and therefore it will be necessary to remove them at some stage either because plastic ones become brittle or crack or metal ones corrode, go green...

It also seems superfluous because they are maintained in position by a large flange on the outside and a large nut on the inside plus the not inconsiderable adhesive properties of sealant like Sika 291 or equivalent.

I seem to recall an experienced YouTube channel guy (James of Sailing Zingaro) who I used to follow referring to epoxy-based adhesives like 5200 as "F..k the next guy" and I agree.

Provided I coat the exposed balsa core with a smear of epoxy before I start can anyone see a problem with installing Marlon thru hulls with 291 sealant alone or another semi flexible underwater equivalent?

Dig out 5 to 10mm of the core. Bent nail in a drill. Fill the gap with epoxy filler. When it goes off, install the fitting with a liberal dose of black mastic [Selleys type D] or one of Selleys polyurethanes.

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Ramona said..
Dig out 5 to 10mm of the core. Bent nail in a drill. Fill the gap with epoxy filler. When it goes off, install the fitting with a liberal dose of black mastic [Selleys type D] or one of Selleys polyurethanes.

Thanks. Will do. Tomorrow hopefully :)

If you insist on using a goo instead of glue I would suggest fixtec, there's a few concoctions depending on the type of substrate, and a benefit its initial grip is more than sufficient to hold a fitting in place from outboard while you get aboard and put the nut on. Ps as far as epoxy being a pain for the next guy, if the next guy has a grinder it won't be a problem

Gday Jules

Definitely go with Ramona's suggestion and core out the hole, a smear is not good enough for underwater, or a major load. It is okay if it has a little bit of glue powder mixed in when doing 3/16 bolts into ply.

I epoxy all my through hulls, hell I epoxy everything. It is cheaper, I buy 20 litre packs and it always works and my boat is epoxy. I may have to remove the seacocks one day. Maybe I will drill them out, or maybe I will do something else.

About 5 years ago, we were getting ready to go to Tassie. On the slips I put two motors on the boat instead of one and also installed a new electric anchor winch. I was a little worried about getting the old one out. I had epoxied it in really well, 5 large 5/16 bolts through 50 mm of ply deck and backing plates. I was thinking I may have to cut it out of the deck and rebuild.

But I tried something else first. I got the biggest screwdriver to fit the machine screws (it had a square shaft) and bought a medium sized butane torch at Bunnings. With the old winch apart I heated a single machine screw from on top. In about one minute the 18 year old epoxy softened. I then unscrewed the machine screw whilst the epoxy was hot with a spanner on the square shaft. Each screw came out clean and all good. I didn't even need to say any rude words to get them out. All my winch bolts are installed with epoxy and I have no issues with worrying about removing them one day.

So don't believe the bunkum about epoxy being nasty. Use its property of softening under heat (but you can only do it ONCE!) If you know how to treat it, it can be your best buddy. But why replace a plastic skin fitting anyway? What's going to go wrong with it?

(Epoxy will soften when it is heated to a higher temp than it has experienced before. This is its heat distortion temperature. Don't bugger around heating it up and then not getting the part out. If you heat it up then the epoxy will "cure" to a higher temp. So be really ready to do a good job when heat is applied. I heated up the shell of the 38ft foam tri I built. It is called post curing and we built a plastic tent, popped thermocouples all over it, hired some huge space heaters and fans from Kennards and kept it at about 60 degrees for about 6 hours. I was thankful we didn't kill anyone with the amount of nasty gases and heat around. BUt the boat had higher strength because we increased the epoxy's shear strength)

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Kankama said..
Gday Jules

Definitely go with Ramona's suggestion and core out the hole, a smear is not good enough for underwater, or a major load. It is okay if it has a little bit of glue powder mixed in when doing 3/16 bolts into ply.

I epoxy all my through hulls, hell I epoxy everything. It is cheaper, I buy 20 litre packs and it always works and my boat is epoxy. I may have to remove the seacocks one day. Maybe I will drill them out, or maybe I will do something else.

About 5 years ago, we were getting ready to go to Tassie. On the slips I put two motors on the boat instead of one and also installed a new electric anchor winch. I was a little worried about getting the old one out. I had epoxied it in really well, 5 large 5/16 bolts through 50 mm of ply deck and backing plates. I was thinking I may have to cut it out of the deck and rebuild.

But I tried something else first. I got the biggest screwdriver to fit the machine screws (it had a square shaft) and bought a medium sized butane torch at Bunnings. With the old winch apart I heated a single machine screw from on top. In about one minute the 18 year old epoxy softened. I then unscrewed the machine screw whilst the epoxy was hot with a spanner on the square shaft. Each screw came out clean and all good. I didn't even need to say any rude words to get them out. All my winch bolts are installed with epoxy and I have no issues with worrying about removing them one day.

So don't believe the bunkum about epoxy being nasty. Use its property of softening under heat (but you can only do it ONCE!) If you know how to treat it, it can be your best buddy. But why replace a plastic skin fitting anyway? What's going to go wrong with it?

(Epoxy will soften when it is heated to a higher temp than it has experienced before. This is its heat distortion temperature. Don't bugger around heating it up and then not getting the part out. If you heat it up then the epoxy will "cure" to a higher temp. So be really ready to do a good job when heat is applied. I heated up the shell of the 38ft foam tri I built. It is called post curing and we built a plastic tent, popped thermocouples all over it, hired some huge space heaters and fans from Kennards and kept it at about 60 degrees for about 6 hours. I was thankful we didn't kill anyone with the amount of nasty gases and heat around. BUt the boat had higher strength because we increased the epoxy's shear strength)

Very interesting thanks