Gelcoat separation from fiberglass hull

Hello. I have the prototype Knickerbocker One Design, 1960. It was one of 20 sloops built for the KNICKERBOCKER Yacht club. My understanding is that it was built in the early days of fiberglass construction. The boat has been out of the water and covered for many years. About 10 years ago the past owner painted the hull. When I bought it, it all looked very good. Now there is an area about 6" in diameter that appeared to be cracked and lifting. It is just above the waterline, port side, near the transom. The hull is always dry, no water getting in there, no freezing water issues etc. I pulled off the gelcoat in one piece easily. The inside surface is clean, smooth, and shows no sign of ever adhearing to the fiberglass hull. Any ideas as to why? Was the gelcoat not properly cleaned before the roving was laid in? If I gently try to lift up any more of this area and find it all not adhearing then I'm in trouble. Any info, opinions, anyone can supply, will be greatly appreciated. Thanks

 

Can you post a photo? It may be paint with bad adhesion and not gelcoat.

 

photos of hull

On photo of separate piece of gelcoat, the paint is the lighter blue.

 

The gel coat looks very thick, not good. The laminate didn't bond well to the gel coat, there could be many reasons why, but to quote Hillary "What difference, at this point, does it make"

If it's peeling off you're not going to prevent it, or slow it down much, but to be fixed you need to remove it and either re-gel coat, or paint it.

 

Hello,
The average thickness of the pieces of gelcoat that came off is between 1/32" and 3/64", wihout paint. The blue paint had adhered very well; hard to lift it from the gell coat with a knife blade.
You're right, how it got to this point is spilled milk, at least no one died, and I need to look at solutions. If I continue lifting off gelcoat with a thin scraper blade and find that it is just this area, what would be the material to build back the surface before painting? Or am I dreaming....it's all gonna loosen up! Your thoughts? Thanks, MGM

 

There are some high build primers/fillers that can be used and they're easy to work with.

Sometimes only one area is affected, maybe some contamination, although it almost looks like they may have used gel coat with wax in it.

 

Why the wax, sounds counter productive?

 

Could have been a number of reasons why, it could have been flocoat, wiped with a waxing rag, spillage of some sort ? If it is widespread your best option is to rip it all off and spray with epoxy hi build at least then osmosis will be banished. If it is local sand until you get a food surface to key to, exposing some fibre would be good and then re-coat with waxed gelcoat and re-fiinsh.

 

Someone f*%&ed up !