I’d imagine you have looked at used power boats or sailboats for sale. During your inspections, walking down the port or starboard side you felt a give in the deck. Upon closer inspection, you would push your foot down on that spot and see it move. That is called a soft deck. It could be located anywhere on the boat, but usually on the deck. There are several ways you get this but the main two are water intrusion and delamination.
Delamination occurs when the fiberglass decking loses adhesion to the balsa or plywood it is laying on. This could be caused by the water intrusion, but may only be from extreme hot or cold, or both, resulting in expansion and contraction that eventually pulled loose the adhesion in that area. On a positive note, the underlying support (balsa or plywood) is not water soaked and the repair is made easier.
A soft deck that is spongy is usually water soaked balsa or plywood, underneath that portion of the deck. It could be from a piece of hardware (cleat, stantion) where the bedding came loose or fell away, allowing water to enter. Another spot would be a window area where the water has pushed through the bedding or found a way through the surrounding fiberglass. In both circumstances, we have to become detectives to find the reason for the water intrusion. It could be so simple or you may have to go on the hunt with a magnifying glass.
The Fix (water soaked underlay) 1. First we must find the source of the water going under the deck fiberglass. Again, check for loose hardware, missing caulking, weep holes in window channels clogged (pooling water in the channels to push behind the fiberglass) or as simple as a major stress crack right by or on the area. But, you must be successful on this hunt for the cause of the water intrusion. You will find it!
2. Once found, rebead or caulk the area where the hardware or window channel came loose. Now, let’s get to the soft wood underneath.
There are several ways to attack this situation. The main thing that I do is not destroy the deck and/or pattern that are already there. I don’t need to do more major work. I like it fast and easy. Sometimes it’s fast, sometimes easy. Easy, though, takes some time for drying. But, it is easy!
3. Let’s talk about one that is fast and easy. You’ve found a soft area that is small, maybe 3″ x 8″, or around that. You could have a diamond shaped pattern, non-skid gel coat or a stipple look – rough, matted look. But, either way, you would attack it by drilling holes in it. Depending how confident you are in repairing your gel coat, non-skid tells us the size drill to use – inch size drill, down to 1/8 inch. If the soft area happens to be in a smooth area, (no pattern) go there, but you will have to make a pattern of holes, ultimately drying down to the wood underneath with the hot sun, hot hair dryer or heat lamps. Make sure not to burn the gel coat non-skid with the hair dryer or heat lamps during the drying process. This may take hours to a few days. But, you want it dry between the holes. You can take a thin metal probe to go in sideways to see any traces of moisture. Also, use a moisture meter if you can get your hands on one.
4. With the underlay dry, use a syringe applicator to push resin w/catalyst, into the wood underlay. You can find these in many marine supply stores. You’re not filling the drill holes up, but getting the resin in between the holes and layers, use a thick, long metal pick to make the passage ways all around if the applicator can’t. The point is to soak the underlay with resin again, between the holes. The result is a stiff, hard underlay. Use the resin that pooled in the drill holes to fill the voids by using a thin, flat screwdriver and pulling up that resin into the holes, between the drill holes. Keep doing it because as the resin starts to harden, it will fill and stay in those small to tiny holes you made. Cover it as well as you can. This is not rocket science. Clean the surface area of any resin by using a dampened cloth with acetone. (Read all instructions). Let the sun, hair dryer or heat lamps keep it warm so the resin hardens completely.
5. In the drill holes, (after hardening) get any loose material out with a small screwdriver or pick, and clean with acetone on a clean rag. Make a thickened mixture of resin by adding micro fiber balls or strands. These additives can be found in many marine stores. You want it in a consistency of softened butter, but not quite drippy. Add this mixture to each drill hole. Use a syringe applicator or just push it in with a screwdriver. (Tape around each drill hole to cut down on any mess). In either case, push down and around with a thin screwdriver to fill any voids you might have left. Fill drill holes just below the surface and let harden.
6. If you have a diamond-shaped non-skid, you can get this pattern from the manufacturer of the boat or a marine supply store. This would go over the repair, forming the gel coat to the same pattern. You would wax the pattern first, (any liquid wax is fine) then put it over the non-skid, feeling it lock-in on your diamond-shaped pattern. Take it off after the gel coat hardens. You can tell this if you had left overs and put it in the area where the repair is. If that hardens, your repair did. You might have to touch up with a light sand and cut out the grooves in between the diamond shapes better with a hack saw bladeit works! To stipple, use a soft (dry) sponge (or other implement), and pull up on the hardening gel coat. Don’t be aggressive at first, just touch and pick up on the gel coat to match the pattern around it. If no pattern for the diamond shape (or your particular pattern) can be found from the manufacturer or Marine supply, you can put the gel coat on anyway without it, (even with or a bit higher with the surrounding area). When the gel coat hardens, use the hack saw blade to cut out the grooves, (do it slowly) to match what you have. If you do something wrong, rough the area up a bit and add additional gel coat. Let that harden and try again. This is easy and kind of fun. The more you do this, the faster and easier it will get. Plus the finished product will get better and better!