Updated 06-11-00
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Thoughts this month
How safe is your hull? If its an older one, some inspecting should be done on a routine basis. The most important areas for checking are the stringers, the long boards running nearly the length of the boat. The next area to check would be the bottom of the hull, and transom. Finally, the upper deck structure should be tested.
A simple test that can be used to find bad spots in the hull, is the tap test. Simply put, hold a quarter edge on, and tap the hull every 3 inches or so. If there is any delamination in the fiberglass, a hollow sound will be heard. To further inspect an area where wood is covered with fiberglass, use a 1/4" drill, and drill into the wood under the fiberglass. If hard dry wood shavings come out, then its just a case of fiberglass delamination. If soft mushy wood comes out, then there is rot taking place. In either case, the area will have to be repaired.
To repair a stringer or transom with a wood core, remove the fiberglass at least two inches from where the tap test sounded solid. If there is only minor wood rot, sand away the bad wood, until only clean dry wood is exposed. Depending on where the repair is, there are different fiberglass repair procedures. Check with the manufacturer for the specific type of fiberglass you should use for the repair. If the manufacturer is no longer in business, try to approximate the materials used.
If the wood has severe damage, then replacing it is the only alternative. I've seen guys try to fill a gap in a stringer with fiberglass, and it doesn't work. the flexibility between wood and fiberglass is to different, and breakage will occur. For a stringer repair, the bad wood can be cut out, and a new piece of wood can be installed, Make sure its the same type of wood also. You can make a tongue and groove joint to fit the area where the stringer is to be repaired. Above all, make sure its a very snug, but not excessively tight fit. Use a wood glue to bond the new piece to the original stringer.
Next, sand with medium grit paper until smooth. Then the glass work can begin. when glassing the new wood, try to cover at least two inches over the original fiberglass. lightly sand between layers of glass to keep them flat. One thing to stress, is keep the area clean. Use Acetone to wipe down the surfaces before glassing starts, and between glass coats. CAUTION!!! Use only in a well ventilated space. Both acetone, and fiberglass resin give of flammable vapors, and can explode under the right conditions.
Once the last layer of glass has cured, apply a skim coat of resin. Use a disposable foam brush to apply a thin layer of resin only to the repaired area.
For areas that stress crack constantly, use an epoxy resin, instead of a polyester resin. Its much more flexible and will not crack again. Be sure to sand into the affected area at least 1/8". Use mat instead of bi weave, for better results.
To fill small holes, use polyester resin, and household fiberglass insulation. Just pluck a wad of insulation from you attic, and soak it with resin. Then put it into the hole or gap you need to fill. This works especially well where there are drain holes in the rear of the stringers that have rotted out. Simply fill the holes with house insulation and resin, and wait for it to cure. Sand it flush with the stringer, and then drill a 3/8" hole where the drain should be. Insert a brass tube into the hole and seal it with 3M 4200 adhesive.
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