> I have two cracks in the plexiglass main hatch cover (sliding) that start on
> the aft corners and go for about two inches. They are bad enough that water
> is starting to seep in when it rains. I am concerned that they will get
> larger. Is there any product that can fix this without replacing the hatch.
> I am thinking some type of liquid epoxy that I flow into the cracks. Any
> suggestions are appreciated.
There are two different issues here, stopping the crack and repairing
RE: Repairing the crack. Here I would refer you to the other people who
have posted replies with various acrylic solvents or epoxy formulations.
RE: Stopping the crack. A crack in acrylic is similar to a crack in
many other materials. The external forces create a distributed stress.
If that distributed stress is large enough, it will propegate into a
failure at a point, the beginning of a crack. As soon as that crack is
created, it forms a stress concentration and will rapidly develop into a
longer and longer crack. The distributed stress suddenly becomes a
concentrated stress and will easily move through the material. If you
don't believe this, just try pulling along the edge on opposite ends of
a piece of paper, then repeat the pull after having put a 1/8" cut into
the edge of the paper. Not only will a tear always occur at the 1/8"
cut, but the force required to begin a tear is a tiny fraction of what
it takes if the tear is not present. The solution is pretty simple. If
you drill a hole slightly in front of the current end of the crack, as
the crack opens further, it will open into the hole. The hole will turn
the stress concentration of the crack into a distributed force, shared
over the diameter of the hole. Note: this will not work if the hole you
drill is rough or chipped. A rough hole will have microscopic cracks
along its edge that are likely to restart the crack. The best solution
is to drill a smooth hole, and then rub the hole with some acrylic
solvent. The solvent will smooth the surface of the hole to a
microscopic level and greatly reduce the potential for the crack getting