Interesting. I'd like to see sample weights that indicate how much epoxy was absorbed by the wood.

Regarding sample restraint, as long as each test uses the same restraint, the particular conditions aren't critical since this type of testing is used to compare panels rather than obtain properties that can be used in calculations. Yeah, some of the clamps were not as secure in some of the tests, but...

Regarding the Epoxyworks article, the West System folks do good technical stuff. I would be interested to know the panel stiffness of each layup prior to damage, not just the difference between before and after. Since their work infers residual strength from change in stiffness (a good assumption) it would be nice to know the undamaged stiffness. I also think it's good to keep in mind the function of the overall structure. Hydromat testing approximates uniform loading on panels similar to the water loads applied to surfaces on large vessels. These types of loads are very small on kayaks. For kayaks, one could argue that a more important measure of damage tolerance would be resistance to tension or compression loads aligned with the length of the boat after damage since, in waves, kayaks can be modeled as beams and the panel loads ignored. However, I think the fiber orientation in kayaks has very little real effect on performance except in the most extreme cases imaginable. Luckily, most of us can use the orientation that makes building easiest. Lastly, keep in mind that the fiber orientation changes significantly with location on the boat due to cloth drape, as does the wood grain due to strip pattern.

Sam