First Layers?

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#1

What are the best first layers after the Epoxy Surface Coat? for years i have been doing twill fiberglass or just a simple 3 oz fiberglass in pieces. then CSM. but, lately i have been getting some holes on the surface coat from airbubbles =(.

i want to try and get something that i can glop on first, doesnt run. and can work with epoxy. i have tried chopping up some fiberglass and then some epoxy and it worked well. but its a long process. work great thou. then fiberglass over that, then csm. … any examples with pics out there?

#2

why cant you use regular poly gel coat? epoxy will stick to it later if you use it as the next layer of resin…

I dont know why everyone says poly sucks…I can take a part of mine and stand on it and it doesnt crack…and Im 200 pounds.

To me, if its a clear surface coat and the part gets damaged…its ruined anyways…why pay more for epoxy?

How many of us actually make something that has to support a big load?

#3

well its not so much the load, or price. its the shrinking. Poly shrinks up to 15% after time + heat. and this is after its cured! for epoxy, there is only a 5% shrink i believe. i might be wrong. any input?

#4

Each manufacturer is different. Make sure you check the data sheet for the real shrinkage to expect. 5% for epoxy would be some cheap stuff. The guy who builds our molds uses VE that shrinks 1%.

And keep in mind that most shrinkage happens on the y axis. If not all shrinkage. The X axis has cloth to hold the resin in place while curing.

#5

Have been making motorcycle fuel tanks using poly resin for several years, and must say that I have never noticed this 15% shrinkage. Guess it must make things rather difficult when building somehting like a GRP yacht, when there is plenty of secondary bonding involved, and the parts have shrunk 15%!

#6

Thinking out loud and being silly, you want to build a 100 ft boat but it ends up 85 ft due to 15% shrinkage. I have noticed minor shrinkage in width on a mold 1400mm wide but nothing to get concerned over.

Baz

#7

The hotter the PER batch / thicker the laminate, the more shrinkage with PER. I never see any shrinkage…:wink:

#8

i think im going to start using PER! =)

any sugestions on which ones to use for Gelcoat layer, then reg. per for the CSM etc?

#9

Ive only seen some minor shrinkage in the fact that the weave becomes apparent in the surface coat…If I mix too hot and try to cure it fast.

This was a source of problems for me this winter with our unusually cold winter…

I tried to keep things moving at a decent pace by making my batches a bit hotter and it ended up kicking my ass…I had to sand more of the surface coat out and use more automotive clear to make it up…

I dont do that anymore.

but as far a shrinkage? I cant say Ive seen it. I would have some pissed off customers if my parts didnt fit like they should.

#10

Its very easy to add a little extra MEKP to speed up cure time in colder weather, but knowing exactly how much extra is something that you learn from experience. Recently its been quite cold here in the UK, and my laminating has been trouble free, using 3%.