If the hull was fair before the addition of the deckbeams, you probably stressed the hull the wrong way when you put the deckbeams in. They were either way too long or way too short. Cut out the deckbeams and install deckbeams that are exactly the right length to fit the position in an unstressed hull. Then you won't "tweak" the hull when you put them in.

Shawn

: my first attempt at kayak building has not gone well. i've been following the
: direction of chris kulczycki's book, "the kayak shop" well, the
: truth is, not following close enough. i've attemped to build a cross
: between the yare and pocomoke. i wanted the beam of the pocomoke 28 inches
: in the 16 foot yare. to add to the problem, i didn't use marine ply; i
: substituded birch 1/8 ply. i also used 3/8 by 3/4 hemlock for sheer clams.
: the hull went together well, but when i pulled it together for the deck
: things started to go wrong. with the deck beams in place the hull seems
: warped. i don't know if the sheers being the wrong size is the problem?
: i've considered adding more deck beam to straight the hull? i've also
: considered setting it ablaze and starting over. sincerely match and
: gasoline.