mast step deck core question

Posted By: amory
Date: 3/23/08 4:08p.m.

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As if I didn't have enough problems already, I went looking for another one. I removed the mast step, since it was literally dissolving, and there was a short in one of the wires going to the mast, so that the lights didn't work. What I found was that the deck was sinking under the step, and the core seemed to be rotting where the four screws holding down the mast step were. So, I made an oval shaped cut in the outer skin inside the outline of the mast step, and started digging. I found a lot of wet, rotten plywood, and a lot of cracked old resin. I can't tell if there is a thin outer layer of plywood and a thin inner layer of plywood with a thick layer of solid resin in between, or if someone previously dug out all the wet wood and just filled the area with resin. At this point my plan is to make a circular sized cutout in the skin about 10 inches in diameter, centered at the mast step. The gelcoat on most of this area is badly cracked anyway, and I suspect the wet core extends back under it. Then I would rebuild the core and relaminate the outside. I plan to use polyester resin rather than epoxy since I don't want to repaint the whole deck, so I would rather try to (approximately) color match the gelcoat. Should I expect to eventually find a solid core of plywood that extends from outer skin the the cabin liner, or will there be two layers of plywood with resin in between? What is the best way to rebuild the core? I assume it would be to get some marine grade plywood, but the total thickness between outer core and inner liner appears to be about an inch and a half or more. As always, thanks for the help!