Hey, that's great. Hopefully you will summarize the results for us when you are finished. I'm sure a lot of us would like to know more. Especially of interest is the type of glass and type of resin used for the test samples.

The goal of your impact test is to use just enough force so that there is an obvious difference between samples. Since your rod is twice as long as mine, it might completely demolish the glass layer in every case if dropped from 40 inches. So I suggest you start off from a lower height and work up if you need to. Also, in my case the rod was unconstrained by the tube once it was near the test sample. This allowed the second bounce to land in a different spot on the sample. The rod will bounce every time. Not having tried it your way, I don't know if it will make a difference.

What I lookded for was depth of dent, amount of whitening of the glass fibers, and whether the fibers were cut thus allowing water to leak into the wood. None of my samples cut all the way through using the rod, only when using the large screw driver. Perhas if I had dropped my rod from higher up it would have shown some fiber cutting.

Hope this helps,
Ted

: I am paying a professional builder to build a kayak for my wife. I e-mailed
: him this thread and asked him how his layup would perform.

: Today I got in the mail a 3' long 5/16" steel rod, a 4' long piece of
: steel tubing, a cinder block, a bunch of test pieces, and directions. The
: builder wants me to put a test piece on top of the cinder block, set the
: tubing on top of the test piece, and drop the rod through the tubing.

: Then he wants mee to tell him which test piece he should use for the kayak.

: What should I look for?