When fiberglassing, if you bear in mind exactly why it's so strong, you can improve your results.

Fiberglassing basically works by stopping any tiny cracks that develop under stress from traveling through the whole structure and making the whole thing fail.

The joint between the glass fibers and the matrix (the glue) is weaker than the glass fiber itself, so any crack that tries to pass through it gets diverted along the length of the fiber as the material starts to delaminate, which is a different direction from the original stress, so tends to it stops the crack from developing right across the structure resulting in the whole thing breaking..

It's a bit like trying to tear a plastic film without starting it by creating a crack with your teeth!

That's why it tends to buzz before it finally breaks, and finally explodes when it fails.

Sooo, try to make sure the fibers are at 90 degrees to most likely stress direction, and concentrate more glass fiber at the high stress points.

Hope that helped a bit!

David C.