Helix construction 2

My approach is a simplified version of Rainer's. Instead of a two-ply system, I rely on Unitrack to even out small disparities in elevation, etc. Basically, I cut the pieces out of high-quality (i.e., not Luan) 1/4th inch plywood, and glue them together using a one-part polyurethane adhesive (here, I used Nail Power's Power Urethane, available at Lowe's). To join the pieces, I place a smaller trapezoidal piece of plywood over the joint between the two larger pieces, and staple the pieces together using a staple gun and 3/8th inch staples.