Screws through glass skin?

[petrolhead]

Hi guys, I'm building a stretched Glen-L Squirt and I need to attach an oak keel strip and some spray guards, this will mean drilling pilot holes and screwing through the waterproof glass/epoxy skin (it's epoxy encapsulated ply construction). Should I inject some sort of sealant into the holes before putting the screws in to stop water seeping into the wood? I was thinking wax or silicon sealant, something like that? I don't want to use resin, although that might seem the obvious solution, as it may make it difficult to remove the screws later on if it needs repairs, and for the same reason I don't want to attach these parts permanently by glueing/glassing them on.

 

[snapperbait]

Re: Screws through glass skin?

Petrolhead, 3M 5200 adhesive/sealant.. Comes in caulk tubes, perfect for your application.. Comes in a coulpe colors. (white, black, and?)<br /><br />Use denatured alcohol or mineral spirits to clean up any excess sealant..

 

[petrolhead]

Re: Screws through glass skin?

That's the kind of stuff I was thinking of using to seal the wood strip to the hull surface, you think I should squirt it in the pilot holes too?

 

[JasonJ]

Re: Screws through glass skin?

Yes, put it in the holes, and be generous with it. Better to wipe off excess than wonder if it was enough..

 

[Columbia]

Re: Screws through glass skin?

It's a tricky call on what your application is for screwing a keel strip on. If you use 5200 be advised, from my experience, that it will be difficult to remove that strip later on. 5200 is a powerful adhesive. The times I've had to remove wood having used 5200 it required breaking off the wood and in your case might pull damage the subsurface...hard to tell. What I would do in your case, and have done, is to over bore your fastener holes, say 3/32" or even 1/8" all around, fill with epoxy, drill pilot holes, and then caulk your strip with a less adhesive caulk and caulk the holes and apply. I've done this with both machine screws tapped into epoxy with high a density filler, and with panheads (always use SS fasteners) or flatheads simply screwed in. This way your boat is protected from rot, your strip can be removed more easily, etc. Other ways are available when using epoxy including bonding in fasteners coated for removal later on but these have worked for me.

 

[petrolhead]

Re: Screws through glass skin?

Now that's a solution I REALLY like! Easy to do too.<br />I did a search on 3M products but couldn't find a UK supplier listing the one suggested, I did find Sikaflex 291 though which seems to be a similar product and more easily available here, I wonder if it too might be too adhesive though? <br />If I'm going to do the epoxy plug thing to seal the holes, I guess I could use pretty much any flexible marine sealant for bedding the parts down, like a deck caulking compound for instance.

 

[Rhadley]

Re: Screws through glass skin?

My boat repair book states that epoxy softens at 150F, so you can epoxy screws in and if they are difficult to remove you heat them above 150F. To direct the heat, you can push a screwdriver into the screw drive and heat the screwdriver. I haven't tried this, however.

 

[moganman]

Re: Screws through glass skin?

Hummm? Never tried it? Book? Hummmm?