Hmmm... OK, I'll buy that. I have heard of someone snapping an untaped butt joint when moving it around during building. But that was most likely before the epoxy fully cured. I also like your theory on the lighter coloring. Pygmy's explaination is oxidation, but, especially in your case, greater absorbtion seems more likely.
: Kieth,

: I do understand what you are saying, but the epoxy that fills the joint, and
: wicks up into the end grain, is stronger than the wood. I think the bigger
: concern would be landing on a rock right at the joint, but I am not
: advocating removing the glass tape on the inside, which is where you will
: want the extra strength. If strength is still a concern, add more glass to
: the inside at the joint.

: As I have said before, my next S&G will probably have spline joints, avoiding
: the whole problem. I have also used butt blocks (1/8" plywood) on the
: inside. I have not had flat spots develop from any of these methods.

: I am not fond of the light areas at the taped joints. I built it fairly fast
: (6 weeks) in a basement, away from the windows. I believe the light areas
: are from not presanding before butt-joining the panels. The sanded plywood
: may absorb more epoxy causing a darker appearance over the rest of the
: hull leaving light spots at the tape.

: Mike