: I am starting to build a three section S&G take-a-part kayak.
: Where the sections separate (double bulkheads), I would like to
: have 90 degree edges.

pre lay the glass on each hull piece with about a 6" bypass of the section cut, dart the perimeter so the fold down has minimal glass overlapping, and hot glue the overlap down onto the bulkhead making sure the glass lays correctly before any resin is applied.
Work from each pce's cntre outward and only down the bypass about 2 " or so. Use a heatgun or maybe soldering gun to soften the hotglued areas if necessary to move around a bit.

If yr trying to save glass on the bypass and can only afford 2" or so, then use dabs of CA for the fold over and resin betw the dabs. Readjustment is slightly more difficult but possibly much faster(ie using spray accellerator).

Essentially the notion is to set everything up first before applying resin.

ideas anyway,
mick