Repairing fibreglass

[Guest 000]

The Sissons Nordkapp that I recently purchased is a kevlar boat in need of a small crack repair.

Easy as.

Wash and sand the interior, wipe down with acetone, lay up a couple of bits of 10 oz cloth. When cured grind out the crack on the exterior side, fill, fair, paint.

Done it lots of times.

But, Grahame Sissons (the builder) states on his website that epoxy resins must not be used in any repair - he doesn't say why. He stipulates polyester resins only. I've always used epoxy resins on the inside of polyester hulls to repair, re-tab bulkheads etc with never a problem. My understanding is that epoxy gives a superior bond over polyester. Any advise here?

[Crazyhorse 47]

Yes, epoxy over poly is no problem, but not the other way. We got tired of having to repair our spray dodger so impregnated it with polyester then cloth polyester. Let it cure properly before epoxy. Make sure you wash wipe the surface with isopropyl alcohol prior to glassing with epoxy, removes the wax. We did this. Looks great...well a bit rough but worked now have a solid strong light hard dodger.

[Freedom GBE 27]

Core builders in Warkworth apparently use a mix of glues for the Americas cup boats, without issues. 

[Guest 000]

Yes, I agree about epoxy over poly. Grahame Sisson is the guru on glass/Kevlar kayak construction and I don't know why he should stipulate only using poly to repair poly. Once the poly substrate is fully cured then any subsequent patching with poly will rely purely on adhesion, no chemical bonding. From my experience epoxy is a better adhesive. Grahame is retired now, otherwise I'd love to ask him why not epoxy.