Rehd is correct i n all aspect. I just want to elaborate a liitle more.
1) Store bought 'epoxy Glue' is already thicken, it does not soak into wood as much
2) epoxy glue works by filling the gap. Therefore, too much squeeze out will stave the joint. In fact epoxy does not need much clamping. Clamps work only to stablize the joint while cure.
3) fast set epoxy forms shorter molecular chain -- weaker strength.
4) high temperature softens epoxy -- joint may fail under tension / twist.
All these work against you.

Chip's recommendation is the optimium process. Thin (unthicken) epxoy soaks into wood fiber and strengthen the wood. 'Peanut butter' to fill up the gap.
Light in clamping to avoid squeeze out. Slow cure for stronger bond.

: Hi Kirk

: I also had one joint fail on my Walrus and I know the feeling. I went back
: and scarfed all the joints with a 3/16" x 3/4" piece about the
: length of the joint. In the process of twisting the stringers and Chines,
: I heard two pops as well as the failure. I was using regular yellow glue.
: I went back and glued the sistered pieces with epoxy ( glass/resin W/wood
: filler ) and no problems, Don't worry about them showing as none of them
: should. The top gunwales will be covered by the skin and the Chine joints
: will be hidden by the floorboards when finished. I feel very confident in
: my joints now. The only thing that I didn't like was working the trestles
: where they met the sisters. Just had to trim them a little more..... No
: biggie!!!

: I believe the general consensus is that the store bought tubes of epoxy are
: not strong enough for use here and I can't remember the theory behind it,
: but could probably be found in the archives. When we/they epoxy joints it
: is usually with a small batch of fiberglass resin ( epoxy ) and sawdust or
: some other filler, mixed to a paste or peanut butter consistancy.

: Wet both pieces with a little, leaving about a 1/16" thick patch and
: then put the pieces together, align, and clamp lightly and don't squeeze
: all the mix out. Epoxy doesn't adhere the same as yellow glue. What little
: squeeae out I do get I wipe off with a paper towl to keep the joint
: looking clean.

: The heat in the garage is probably a big contributing factor as well. Epoxy,
: as I have heard, will soften up with heat. What with the tension you were
: putting on those joints from the twisting, it probably didn't take much to
: pop a softened joint.

: Were you just trying to twist the strips or using some sort of steam or other
: heat source? I used some wet towels microwaved to get them hot enough to
: burn the hands and wrapped the stringers in the area to be bent and
: twisted. I applied force be clamping a couple of pipe clamps on and
: letting them hand out int he breeze and the wood just bent around without
: any effort on my part. When the towels cooled, I took them off 1 at a time
: and reheated them and rewrapped. In no time, O.K., around 15 minutes or
: so, the wood would twist into the position you wanted and then a little
: past. That allowed for springback and the joints were all lined up for
: glueing and clamping.

: On your split piece, try to sand or scrape off all the epoxy glue and cleam
: the joint parts. Then give it another try. If you don't have any resin (
: since you are doing a skin boat ) then just use yellow glue. It will hold
: better than the wood itself. BUT!! You will HAVE to cleam every little bit
: of the old epoxy off the joint or it won't stick. AND, you will be sealing
: the wood anyway, so the glue will be safe from getting wet. If you left
: the stringers a bit long, then recut the joint about a 1/16" fromt he
: old joint to get fresh wood. That's a must!!

: Good luck with the reglue and go ahead and sister all the joints you have.
: Nobody will see them when the boat is done, unless the crawl inside and
: inspect it. ????

: Rehd