. . .
: You don't have to take the forms apart from the strongback when it
: is internal to build the deck. . .
: internal strongback makes it possible to build the deck next to
: the hull and ensure that they line up and will be easy to join
: without having to disassemble the forms.

In a perfect world you can build the hull, sand and glass it, then slip it gently off of the forms after you've started to lay up the strips for your perfectly aligned deck. Then you can slip deck and hull back over the forms so they fit perfectly when you glass the two parts together.

Well, the world isn't quite that perfect. :)

After you've glassed the hull you'll discover that tiny amounts of glue and resin have leaked through the joints and glued the strips to the forms in dozens of tiny bonds. If you carefully covered the edges of the forms with a strip of masking tape these bonds are going to be very weak and you can dislodge the forms with a few sharp taps of your hammer.

But wait.

When you start knocking those forms around they won't still be aligned for stripping the deck.

So, you leave the hull alone for a while and start putting on the deck strips. After you get 3 or 4 on each side they will keep the forms in the right places while you loosen the hull. Of course the more strips you put into the deck the stronger and stiffer it will be as you work on getting the hull loose.

: . . . . I think the only
: downside to an internal strongback is the rigidity. Any
: thoughts?

Rigidity increases as you add strips. For initial strips you stiffen the 2x4 with added external supports. Give it a few more legs when you start. You can remove them as work progresses.

PGJ