Comment from a T-88 distributor web site below. You might want to consider a do-over of your parts fit-up however.
Comments about
System Three T88 Structural Adhesive:
While planning my 21 ft Dory I ran some destructive test using Pine 2x4s and 1/2" Plywood. I tried 3 different glues:
1. T-88 Epoxy
2. Gorilla Glue
3. Yellow Water Proof Wood Glue
The 1st test was with the 2 x 4 on edge with 4" of glue and held with 2 screws to the plywood. All three samples were precoated so as not to have dry joints and recoated after 5 minutes. After 24 hours the samples were broken.
1. The T-88 Epoxy Sample took wood from both the plywood and 2 x 4s. But only about 1/8" deep.
2. The Gorilla Glue also took some wood but less then the Epoxy.
3. The Yellow Wood Glue had only minor amounts of wood where broken.
The 2nd test was made only with T-88 Epoxy as it was the clear winner of test #1. With this 2nd test I once again made samples using 2 x 4s and 1/2" plywood.
1. Tight joint as in Test #1 with T-88.
2. Loose joint with one end touching and the other end 1/8" loose but fully filled with glue.
3. The 3rd sample was also loose in the same way but I added some 1/32" chopped fiberglass to the epoxy. ( 3 TBS for ¼ cup of epoxy) Sorry for the cooking measurements.
4. The 4th sample was also made with the glass filled epoxy, but the joint was tight.
After 24 hours I broke the parts.
1. The tight joint with T-88 took a small amount of wood and was about the same as the first test results.
2. The 2nd sample took a little more wood.
3. The 3rd sample took wood about 1" deep in the 2 x 4 and ripped the plywood.
4. The 4th sample also took wood but about ½ as much as sample #3.
OK, so the clear winner was a loose joint with glass filled T-88. (So much for wood class and making a good tight glue joint. Lol)
My boat plans called for face to face gluing of 2 x 4s and so I glued some samples using 18" long boards glued at one end forming a 90 deg part. I made 2 samples of each.
1. Sample #1 was glued using glass filled T-88 and held with two 3" deck screws.
2. Sample #2 was the same except I drilled a hole 3/8" diameter 1/4" inch deep at each screw. (Glue Faces) I filled these holes with glass filled epoxy and reclamped with the screws.
After 24 hours I removed the screws and broke the samples using a hyd press. All 4 samples were very strong but the samples with the filled 3/8" holes took a lot more force to break. Also these 2 samples failed by breaking deep into the board.
After getting these results I have started my boat and made all of my joints with glass filled T-88. I now have it ready to apply the plywood.
Bottom line is, I trust T-88 Epoxy. No I don't work for System Three.
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