This is almost EXACTLY what I had pictured in my mind. I'm glad to hear it works so well. I even had the tapered ends idea. I figured I could cut from or add to center sectiom (of three 5ft straights and two 2ft tapered ends) to adjust for different boat lengths in the future.

> I used 1/2" ply for my box beam - 13 feet: just a hair under
> 2"x4" (I stuck it through the planer). I did it this way because
> it was far easier for me to make the strongback slightly undersized than
> to make the 2"x4" cutouts (in the forms) for the strongback
> slightly oversized. The narrow faces were 2", and the wide faces were
> 3". I used 1/4" wide 1/8" Masonite splines to hold
> everything together, and made the spline dados with the tablesaw. It
> worked out _really_ nicely, quite stiff, and very straight. I was very
> pleased.

> As you may remember I actually went through with my tapered-end insert
> idea. The inserts were made from four layers of 1/2" ply, cut to the
> appropriate tapers (for the smaller forms _and_ clearance), with a
> 1"x3"x12" long tenon that plugged into each end of the box
> beam strongback. When you plug them in, clamp the insert in place by
> pinching the walls of the strongback somewhere over the tennon (so that
> the insert doesn't move when you shim it - this would become obvious for
> anyone who takes this route), shim the inserts parallel to the strongback,
> then screw through the strongback walls into the insert's tennon and
> remove clamp. I was also very impressed with how well this arrangement
> worked out. Nice 'n clean.

> After that, just start threading on the forms onto the strongback and
> fasten them any way you choose. I used four 2"x4" - 1/2"
> ply plates to pinch each form in place: two in front of the form, left and
> right, and two behind, left and right, screwed to the strongback walls.
> This approach allows me to knock the whole assembly down into an 8"
> high stack of forms (16 of them), a 13' long 2x4, and two end-inserts
> under 3' in length, not to mention a bag full of 2"x4" plates.
> It took a couple of hours to do all 64 plates, but the forms are as
> rigidly fixed as I could expect them to be. If I had to set up the
> assembly somewhere else, I doubt it would take more than half an hour to
> put the whole thing back together, as the screw holes in the plates were
> all pre-drilled, ie. all of the fastening plates are
> identical/interchangeable.

> If I were to go into the forms making business, I wouldn't change my
> methods one bit. It may seem excessive and unnecessarily complex to some,
> however, it resulted in an extremely accurate and stable foundation on
> which to work.

> And for someone like yourself, Mark:

> I suspect that you would be attracted to this type of approach, if only
> because it's different! ;-)

> Mike Spence