Last I heard, while epoxy will stick to cured polyester resins such as glass fibre or gelcoat, gelcoat would not stick to epoxy.
That is false and/or incomplete information. Gelcoat will adhere just fine to correctly prepared epoxy.
Thanks Yngmar, that’s interesting to know.
Back in 2011 my boat was used for charter, but during the middle of that year a group of sixteen persons chartered two boats from the hire firm. One of the boats was mine while the other was a larger Bavaria. They went offshore and had a collision in which the bow of my boat was holed above the waterline. The chain locker remained reasonably intact, but the damage extended back as far as the aft bulkhead of the chain locker. The damage was repaired at the boatyard by a glass fibre “specialist” called in by the yard to carry out that repair. Initially I had been advised they would make a mould and lay up a new bow in the conventional manner, but that didn’t happen. Instead they made a repair using epoxy resins, and were unable to get a gel coat to stick, and I was advised of the different procedure only after the repair had been completed. The surveyor employed by the yard to oversee the repair gave me an assurance that it was a good repair, an assurance which I paid for separately, but who went on to tell me that they had been unable to get the gel coat to stick. Going online at the time of the actual repair in early 2012, the various reports I read confirmed that one would be unlikely to get a polyester gelcoat to adhere adequately to an epoxy resin repair, and more recently I have spoken to a different GRP specialist and he has not been forthcoming to suggest anything different from that of the original repairer. In consequence the bow was painted following the repair, but although time has gone by, there is still a noticeable difference in colour between the repaired area and the adjacent gel coated areas. I would love to have the bow matched in to the rest of the hull, but I don’t want to pay for having gel coat applied if it is only going to fall off after a year or two.
As for the strength of the repair, well I’d say it falls into the category of the proverbial brick built outhouse which may sound good, but with my seafaring background I am very conscious of the fact that ships years ago used to have tremendously strong bows, but after a head on collision they were written off because so much damage was transferred further aft as to make repairs financially not worthwhile. Since then ships have been built with crumple zones, much like cars.
If anyone has some definitive information on successfully applying gelcoat to an epoxy substrata, I’d appreciate seeing it.
The photos below show before and after the repair.
