Boat Peel
October 1, 2004
When I arrived at the marina Gary and his son Dan Mack where already hard at work peeling my boat bottom. They had two gel strippers going one working on the back of the boat and one forward.
The Gel Strip machine at work, it uses a long flat blade on a roller turning at a high speed. The Gel Stripper about to cut through a blister
The idea behind removal of gelcoat and fiberglass laminate is to get the damaged laminate off the boat and open it up to air so it can dry out. Of coarse I will have to replace the peeled fiberglass next year with about 1/4 inch of new biaxial fiberglass.
The hull peeled, fiberglass dust after vacuum peeling, Gary and Dan Mack with Gel Strip, Inc.
The entire job took about a full day. Gary and Dan where able to peel the entire hull in one pass.
Some options as to how to get the gel coat and laminate off your boat are:
-
Grind it off with a 8 inch grinder a very messy way that leaves an uneven hull surface behind.
-
Sandblast it off, most boat yards will require that you completely enclose the boat in a plastic tent before sandblasting.
-
Peel it off, Peeling is a very clean method that leaves a nice even cut on the hull. Peeling the hull is a bit expensive costing around $30.00 per foot but the money you might save grinding off the laminate on the hull yourself will probably go towards chiropractor fees later.
Fiberglass laminate, Osmosis and Hydrolysis
The hull was built around 34 years ago and I assume has been sitting in the water for most of that time. When manufactures build production boats they start off with a mold or an exact replica of the hull or deck. The builder waxed the inside of the mold so the polyester resins and gel coat would not stick to it. The builder than sprays a gelcoat finish in first to a specific thickness, probably between .014 and .020 of an inch. After the gelcoat cures the builder will start laying in fiberglass materials. The laminate or layering of fiberglass sheets can be anywhere from 4 to 20 layers. Each layer is wetted out with either polyester resin or epoxy resin or now vinylester resin and rolled out smooth to conform to the shape of the mold. In building some production boats in the high numbers chopper guns are used. Roving fiberglass is fed into the gun and sprayed out as chopped fiberglass. Resin and catalyst are injected separately and mixed in the gun and sprayed out from the nozzle.
Osmosis occurs when water molecules move from an area of greater concentration to a area of less concentration into the voids between the laminated fiberglass. As the water molecules move into the laminate they start to dissolve the solutes (excess glycols, acids, metals and salts trapped in the voids). This solution is called a blister fluid and as more water moves into these voids blisters push out caused by hydraulic pressure. The solution that is produced from the mixture of water with organic acids, catalyst and metallic accelerators forms an acid that can breakdown the ester linkages that bond the polyester polymers that hold the laminated fiberglass together, this is called hydrolysis. This break down allows more water to pass into the laminate resulting in even more delamination, the process feeds on itself.
I have been told by the expert redoing my peeled hull
that she will be laying up 2 layers of 1208 biaxial cloth with a final layer of
finishing cloth over my hull using vinylester resin. Everything I have read
tells me that this is the right way to go.
I have completed the lay-up of the bottom see application of new bottom and used System Three epoxy and 1 layer of 1708 with a layer finishing cloth on top.