: Hi there, Nick.

: So, wait for the sucker to pop, then re-glue with CA?

: I'm sticking with my heat/humidity theory for now: The problem seems to go
: away when I re-coat with even a thin coat, as long as it finally appears
: glossy when it has hardened.

: My failures have been right at the wood/thickened epoxy boundary on the
: bottom of the hooks. No wood failure was evident. Each failed hook had at
: least a small area somewhere on the endgrain surface that was not glossy.
: I take that to be an unsealed spot, even though I have no scientific
: evidence; it just seems to be acting that way. There's no way I'm getting
: anywhere close to a 250 p.s.i. tension loading with my arrangement.

: Cheers,

: Pete,
: in Snohomish

Pete,

Your observations of the failure surfaces are important, and illustrate the need to properly encapsulte bonding surfaces. But while there are several factors at work here, the common one is stress - unless folks have hooks popping off from hatches while dangling from their tethers (the hatches tethers). When considering stress, we should keep in mind that there is no single failure strength for epoxy (polymers). At constant stress, failure in polymers is dependent on time and temperature (creep). As we increase temperature or stress, the time to failure goes down. So if we increase the bond area, we decrease the stress for a given loading and increase the time-at-temperature to failure. If we increase the bond area enough, then the combination of stress and temperature that is encountered by our boats will be low enough to prevent failure (within our lifetime).

But like you point out, a good bond/encapsulation is also required.

Sam