by GreenLake » Tue Oct 25, 2016 9:45 pm
At that location the hull shape near the center can be approximated by two flat "plates" meeting at a very shallow angle. On a DS1 (should be single hull, with wooden floor boards for that sail number) the laminate would not have any core. (If I've understood the description, seen from inside of the cockpit the damage should be smack in the middle of the area between the seats and between CB trunk and transom - the damage should be visible from there and perhaps a photo from that direction, lighted from along the floor to show deflection, would help).
With, what should look like a straight "crease" where the to sides of the hull meet, being broken in the middle, you have definite damage to the laminate - probably extending outward some considerable degree. If the damage is close enough to the centerline that it doesn't extend to the place where the seat tanks are tabbed to the hull, then the repair is "easy" in the sense that you have access to both sides of the hull. (If the damage extends under the seats you might think twice about doing a repair).
The trick in attempting the repair would be to restore the alignment so you get the original hull shape back when you are done.
The good news is that the hull should be approximately flat on each side of the center line. You might be able to pull the good laminate outside the damaged area into alignment by screwing it to some 3/4" plywood (two boards, one on each side of the centerline, extending from transom to CB trunk, or perhaps even further forward for more leverage).
First you'd cut out the area of damaged laminate, and bevel its edges with a very shallow bevel, about 2-3" wide. As you grind away the laminate, the edge should be clean and transparent, nothing that looks milky (which would be damaged laminate). Next you would cover the boards in some plastic foil, or release cloth, and place them on the inside. You'd use some smaller pieces of plywood on the outside to hold the screws or bolts, leaving clear the - don't worry about making a few holes). When you've tightened everything in place, the hull should be in alignment across the repair, and the opening should have a nice firm backing on the inside, covered with something to which epoxy doesn't stick.
At this point you'd be ready to build up the new laminate (best with boat resting on old tires, upside down). Use fiberglass cloth and epoxy - come back for details if you've not done this before. Finally, you fill all screw holes, fair, sand and paint.
After you're done, you can laminate a hollow stringer (hollow U channel, square or round, with 2" flanges). You can glue that one front-to-back across the repair from the inside (one on each side) to give some additional strength. Stringers would be placed front to back, and the reason I suggest hollow ones is that you never have to worry about trapped water (leave the ends open). You can use wood or cardboard covered in plastic or wax paper to make the shape and do the lamination on your work bench (covered). Much easier to do that and glue them in place than trying to laminate them in place. (Don't forget to sand away any interior paint where you want to glue them).
(If you are a glutton for punishment, and/or really handy with vacuum bagging, you could add a foam core on the inside of your hull after your repair instead. This is described here in the thread called "the core project". More work than most of us would want to put in, but the result would be a hull that's far stiffer and stronger than the one you started with).
~ green ~ lake ~ ~