Posted: February 1, 2012
Here’s how to replace waterlogged plywood that’s ruining the Formica.Older boats sometimes need a little extra TLC — not just tender loving care but touch, look and check. My 1987 34-foot Silverton was getting soft in the beloved “Silverton Triangle” areas. That’s the shape of the area perpendicular to the aft-door bulkhead. The plywood innards are sandwiched between an outside fiberglass skin and a Formica laminate on the inside.
Thanks to water intrusion and plywood’s wicking effect, the plywood was severely rotted and getting mushy. I could tell because it was causing the Formica to crack and look wavy. It wasn’t a structural issue; it was more about the aesthetics. Plus, the outside grabrail mounts through this area.
1. The trick to replacing the ruined plywood was that it was a continuous piece that ran fore into the cabin, up to the side windows. In my case, only the lower half of the plywood was rotted, but the rot extended into the cabin. With saw in hand, I cut off the bottom half, removing all of the rot and exposing the back of the fiberglass skin. Wanting a clean and sure bonding surface, I replaced the border strips and added new plywood filler. Then, I slid the cover 3/4-inch plywood in, butted it up to the existing wood and screwed it in place.
2. Before I bonded everything in place with 3M 5200, I coated the pieces of plywood with Marine-Tex for a couple of reasons: to help seal them from further water intrusion and to adhere them to the fiberglass and prevent anything from moving around inside. I also find it easier and cleaner to use than resin. Use clamps to keep the pieces in place while the adhesive dries.
3. Once the plywood was back together, it was time to replace the Formica sheeting, which I found in the same color at a local Home Depot. To get the size just right, I used a cardboard template, and I cut the Formica with a sharp razor for a clean cut. To be thorough, I coated the wood with Marine-Tex again and applied the new Formica skin. At this point, it was imperative to make sure the laminate stayed flat, so I held a piece of wood (wrapped in a rag to prevent it from scratching the new Formica) against the laminate to keep it flat. After a little light caulking, I replaced the teak trim and the job was finished.
I’ve heard that Starboard is not the best product for a project like this, as temperature changes cause it to expand and contract.