Boating and Sailing.pdf - Moja ladja

Chapter 21: Keeping Your Boat Shipshape
1. Grind away the broken glass, leaving a smooth hole that tapers inward all around at
least 1 /8 inch. (You don’t want any sharp edges because the patch can’t be sanded in
smoothly with the surrounding surfaces.) The inside of the hole is also tapered
slightly to give the patch a better grip.
2. Wet the patch—glass mat rather than woven roving—with resin and put it into place.
Allow the patch to harden, then back it with a thin layer of putty for waterproofing,
and then several more layers of glass mat, to the thickness of the original bottom.
3. The first piece of fiberglass cloth should
be at least two inches larger than the hole
all around to allow for a good grip. Make
each succeeding layer a little bigger, to
tap into the strength of the surrounding
glass. Don’t sand the inside part—it won’t
show and you’d be taking away strength.
In a large boat that’s used offshore, it’s common
to back a couple layers of mat with a
layer or two of woven roving, which is
stronger but less waterproof.
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Boater-ese
The two most common
types of fiberglass cloth are flat,
thin mats of random-direction
fibers or threads, and woven roving,
which has thicker threads of
glass fibers woven like a wool
scarf into a heavy fabric.
A fiberglass patching kit like
this one from Ad-Tech
includes resin, hardener, and
fiberglass cloth. These are the
same materials used in making
fiberglass hulls originally.
(Photo credit: Ad-Tech Corp.)
4. Add the resin putty filler on the outside, sand it smooth with progressively smaller
grits from 00 working down to 600-grit paper, and finish it with sprayed gel-coat
resin. Polish it with rubbing compound.
That may be more than you ever wanted to know about patching a boat. Sounds like a lot
of work, doesn’t it? It is.