With Robust Engineering they are very Heavy at 32 lbs. A USA Part 103 Aircraft 254 lbs Empty Weight and the Highest MTOW I have seen for one is 660 lbs which need 40.1hp. At 254 lbs and Avg Pilot Weight between 180-235lbs + Gas 30 lbs, at 254 lbs + 235 lbs + 30 lbs = 519 lbs! Even for most Small kit planes, the MTOW falls into the same 450 lbs to 660 lbs range. Most of these Tube & Fabric Airplanes in the last 40+ Years have used 0.058" to 0.065" Wall Tubing for up to MTOW of 660 lbs. Using Spar OD's of 2" x 2" or 2.25" x 2". My T-Bird I, uses 2" OD x 2" OD - both 0.065" wall tubes for an MTOW of 660 lbs. With over 4000 Built in the last 40+ years, I have only heard of (1) T-Bird failure (Human-caused) and that was a Bolt not tightened, not a structural Failure from Tube Size used. Spar Loads are usually 70/30 so using a Bigger Front Spar helps. I believe the CGS Hawk has one of the Highest MTOW at 800 lbs.
