Flash is derived from the old "instant boat" design Windsprint from Phil Bolger and Friends. I wanted a boat that would be quicker to rig and easier to single-hand than the Light Schooner, but would still have enough room for two of us and the dog. I always liked this design, but thought it was over-canvassed and a bit light of build, especially the 1/4" bottom. If I scaled it up to 125%, the bottom panel would be wider than a 4' sheet of plywood and it would become heavy and use material inefficiently. Then it occurred to me that if I scaled up only the side panels and kept the frames the same as designed, I'd get a 20-footer with the same beam as the original. Scaling up the side panels makes them wider than the originals, but this allows end decks that are about 4" below the gunwales, which doesn't spoil the sheerline. Some other modifications would be possible with the longer length - the midships mold could become a permanent frame, and the daggerboard could be moved to the centerline and weighted. The boat could use the original rig.
Here are the scaled up side panels being scarfed. I used glass tape butt scarfs, without hollowing the panels out.
The frames are simply the molds from the original design, but made permanent and given fastening frames.
The sides were then attached to the frames, forming the basic shape of the boat. In this view, the chine logs are also in place, inside the planking instead of outside as called for in the original plans.