Epoxy / Fiberglass Glass Marine Ply sheathing help

[delcrest]

Originally Posted by s/v Jedi

I always do a dry layup, i.e. put the fiberglass cloth on the plywood, then pour the mixed epoxy resin + hardener on the center and use a plastic spreader to work the resin further out towards the sides. The fiberglass should turn transparant very quickly while doing this. Here are some pictures:

the moment we pour the mixed epoxy in the center:


finished spreading it out:

That's exactly how I have been apply the epoxy and glass except adding a layer of peel ply to get a good Finnish. For minimum
Of sanding on finish coat...ie no blush to worry about for next layer or painting

[atoll]

Originally Posted by delcrest

That's exactly how I have been apply the epoxy and glass except adding a layer of peel ply to get a good Finnish. For minimum
Of sanding on finish coat...ie no blush to worry about for next layer or painting

what sort of humidity do you have?

sounds like either you ply or cloth is damp.

have you tried thickening the epoxy 2-3% with colloidal silica for better adhesion?

[s/v Jedi]

Originally Posted by delcrest

That's exactly how I have been apply the epoxy and glass except adding a layer of peel ply to get a good Finnish. For minimum
Of sanding on finish coat...ie no blush to worry about for next layer or painting

With this single layer of cloth, when I grab the overhang with piers and start pulling, I tear off pieces of wood from the Bruynzeel marine ply so the bond is stronger than the wood.

I would try a little test piece without the peel-ply and a dry layup. Make sure everything is clean, I vacuum the plywood, and then either put it in the sun for a bit or heat it with a heat gun. This will later draw the epoxy further into the wood fibers as it cools, plus it prevents bubbles from exothermic heat.

I have used all the wrong kinds of fiberglass with West System and MAS epoxies and even then not a problem. What brands of epoxy did you try? I have used a local brand once and got weird things much like you describe.

[jimbunyard]

Certainly sounds like a sizing/resin compatablity issue. Apparently there are many, many different sizings for the many, many different variables of the manufacturing processes available.


Sizing Up Fiber Sizings : CompositesWorld


It's not unknown for material to get mislabeled or misboxed, so even if the box or roll you have says it's one thing, it may not be necessarily so...


When you peel up the cloth, is there epoxy adhering to the underside of the cloth?

[nimblemotors]

My guess is also the plywood has moisture in it.

[Nicholson58]

My only epoxy for all builds & repairs is US Composites 635 THIN resin. Lower cost; no amine blush; very long pot life and superior wet-out. They also are a good source for glass, Microballoons, carbon fiber etc. Fiberglass , Epoxy , Composites, Carbon Fiber - U.S. Composites, Inc.

I use no other epoxy.

[delcrest]

Originally Posted by jimbunyard

Certainly sounds like a sizing/resin compatablity issue. Apparently there are many, many different sizings for the many, many different variables of the manufacturing processes available.


Sizing Up Fiber Sizings : CompositesWorld


It's not unknown for material to get mislabeled or misboxed, so even if the box or roll you have says it's one thing, it may not be necessarily so...


When you peel up the cloth, is there epoxy adhering to the underside of the cloth?

NO the epoxy is left on the ply wood with the impression of the cloth on the epoxy, the same epoxy has been used for all the construction to date and has worked VERY well
All destructive test done between wood / plywood have been excellent , joints breaking and pulling the wood/ply layers apart excellent results!!
While waiting for the independent laboratory test I have located other epoxy suppliers and will do some more testing.....in the meantime the manufacturers / suppliers can't give me an answer
By the way I live in South Africa not to much humidity or cold weather

[delcrest]

Originally Posted by delcrest

NO the epoxy is left on the ply wood with the impression of the cloth on the epoxy, the same epoxy has been used for all the construction to date and has worked VERY well
All destructive test done between wood / plywood have been excellent , joints breaking and pulling the wood/ply layers apart excellent results!!
While waiting for the independent laboratory test I have located other epoxy suppliers and will do some more testing.....in the meantime the manufacturers / suppliers can't give me an answer
By the way I live in South Africa not to much humidity or cold weather

Sizing Up Fiber Sizings : CompositesWorld

I believe this incompatibility between glass and epoxy as described in the article above is the problem, thank you for your excellent post