Sailboat hull refinishing

[Christopher M]

I am refurbishing a Johnson M16 made in the early 1970s. I am patching a large hole in the hull using new core material, and a layup of fiberglass matting and fiberglass cloth. The old finish is dull gelcoat. I will need to finish the entire hull with something, and am considering polyurethane paint, the same as I used on the mast and boom. (Mast and boom are wood; hull is fiberglass with a 2-1/2" core).

Does the old gelcoat have to be completely sanded off in order for the polyurethane paint (or alternative?) to properly adhere? What are some other options? I don't have an area large enough to use a spray paint system, so I will probably have to brush paint on.

[D'ARTOIS]

No, it is not necessary to sand off the gelcoat in total, rough it up and clean it with a good industrial degreasing liquid. Preferrably MEK, aceton when there is no MEK available. MEK is pretyy nasty to work with, don't inhale it and make sure you use gloves.

[Christopher M]

Thanks for the response. Is MEKP better to use than MEK, or doesn't it make much difference? I have acetone in my garage, so maybe I'll just use that.

[D'ARTOIS]

You may use acetone; mek is better but the difference is not that important.

[tspeer]

How is the M class doing these days? I've heard it's dying out in favor of the MC. I refurbished a '60's vintage wooden Melges M when I was in college and sailed it on Choctawhatchee Bay in Florida - I often wish I had never sold it.

[Christopher M]

I'm not sure it's dying out, but on some lakes, such as Lake Beulah, there are no longer any M16s, there are the C class, the MCs and the X boats. Pewaukee Lake, I understand, still has a large number of M16 boats, most if not all made by Melges, which is about 10 miles from my home, Zenda, Wisconsin. Melges now is making an M17 that looks much like the 16, but is all state of the art, and built for racing.