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Surface prep before fibreglassing

Posted: Fri Jan 02, 2015 9:20 am
by chugalug
:D This topic probably has been touched on before:but I can't find it;Do I wash hull before fibreglassing or use damp rag after a thourough vacumming or what? I'm not quite finished with sanding fillers yet.Looked at fiberglass book but was a little vague on surface prep.just said a clean,dry,oil free surface. :roll:

Re: Surface prep before fibreglassing

Posted: Fri Jan 02, 2015 9:34 am
by Bill Edmundson
I wet the wood down/wash the wood. That will raise the grain. Then a quick light sanding with a 220 grit, hand pad. I blow that off and wipe off with a clean dry cloth.

Bill

Re: Surface prep before fibreglassing

Posted: Fri Jan 02, 2015 4:10 pm
by chugalug
:D Thanks,Bill.Sorry I didn't get right back-I had to make a run into town for supplies-we are expecting a snow event this evening and tomorrow(6to12 inches or more)I'm not worried about that as much as the -40 to -50 wind chill that's following it.

Re: Surface prep before fibreglassing

Posted: Fri Jan 02, 2015 5:07 pm
by kens
I encapsulated all the wood, and filled all screw holes, low spots, etc., etc., before glassing.
This way, the glass goes on without muss nor fuss, and is ready for the final paint prep.

Re: Surface prep before fibreglassing

Posted: Fri Jan 02, 2015 6:33 pm
by chugalug
:D Is that with CPES or precoat with regular epoxy?

Re: Surface prep before fibreglassing

Posted: Fri Jan 02, 2015 6:35 pm
by chugalug
:D I've read in the fiberglass book that for first-timers ,precoating is a waste of time since you coat cloth anyway.

Re: Surface prep before fibreglassing

Posted: Fri Jan 02, 2015 7:15 pm
by gdcarpenter
On my first and only build I essentially epoxied all the hull ply - both inside and outside - before fiber glassing - for a few reasons.

One: I was concerned that bare ply might 'absorb' too much epoxy on the first 'wet out' coat of epoxy that 'fills' the weave, possibly leaving 'ghost' weaving.

Two: I felt it might provide some better 'penetration' of the epoxy into the ply if I applied separate pre-coats of epoxy in multiple thin applications.

Three: I used scarfed 16' full length panels. It was infinitely easier to epoxy both sides of the ply with it laying flat on the workbench than mounted on the boat! :)

Re: Surface prep before fibreglassing

Posted: Mon Jan 05, 2015 12:22 pm
by chugalug
:D Was reading Woodenboat awhile ago.Mentioned a step on building kayak-pre coating hull with epoxy because surface and cloth compete for epoxy covering Also to coat when the temp in shop is falling from 80 to prevent outgassing.now the question is Cpes or regular epoxy shield? :roll:Just a thought-I've been using epoxy shield for my fillers;if I just go around my filled in spots with just the epoxy shield-shouldn't take more than a cupfull :lol: