: Hi guys, thanks for the comments. The strongback is internal and is resting
: on 4 vertical uprights. I have just slid the forms onto the SB in their
: approx location then fixed the first one no 16 half way up and centered
: across the top of the sb then sited each form against the first form in
: turn worked forward. Each form is square to the sb at its location but
: this leaves the last couple of forms fitted and in line with the previous
: form sitting tight on top of the sb. This leave a variation of approx 8mm
: height difference from the first form fitted to last, even though all the
: forms are lined up. The sb is a single peice 3, 3/4"x 1, 3/4"
: white wood beam.

assuming your strongback is straightish and your forms are aligning, what is happening is the two are not in alignment with each other to a small angle of 8mm over 16' or so. this is easy to get outa whack if you start at one end and align the next form to that etc etc - a slight deviance of .5 mm over a foot becomes 8mm by the time you reach the other end assuming a 16' foot yak/canoe.

if you can do it over, the best approach is to align about the 4foot form with about the 12 foot form with both of them evenly mounted on the (internal) strongback with the same clearance all around. that way deviance of the strongback is minimized - at a good guess. If there are any forms that won't align, then just make the form hole larger with a pruning saw while it is still on the strongback - usually you just need to make a pass on one hole edge.

in the final analysis, the strongback alignment is really not the important thing - the only important thing is that the forms align - the strongback just needs to be strong and rigid to hold them in place - it can bob and weave and twist all over the place, but as long as it's rigid, just whack out the holes larger.

mick