In 1971, inspired by Richard Miller's Conduit Condor I designed and built my Skysail, commonly referred to as the "Colver Skysail". I started the build in November 1971 and completed it in January 1972. First time out on a hill, Jan 22, 1972.
Yes, kudos to D Boone and others who tested many new gliders from manufacturers. This is the only glider I tested but I had the additional task of teaching myself to fly on this glider, of my own design and very low cost build. It was high performance for its time (perhaps the best at that point in time) and difficult to train on. I should have learned on a Rogallo and then flown the Skysail. My son Matt, who was flying a Rogallo, was able to fly the Skysail from the start but it took me a lot more time before I was making flights and I made mods to the design as i was learning to fly it. By 1975 it was getting beat up to the point where I no longer trusted its airworthiness and I retired it to the San Diego Aerospace Museum where it was destroyed in the fire.
If one notices the small amount of tip twist it's because my airfoil changed from positive camber to negative camber at the tip. That's why the double covering in the outer part of the span. The rib at the tip is inverted.
I started out with "up-only" elevons at for roll control but that didn't work and I changed to the tip drag rudders which worked well. They were controlled by cables attached to the swing seat so movement was just like a fully weight shift controlled glider. The rudders also pivoted up when the tips touched the ground.
Many hang glider pilots have noted over the years that the plan form is similar to modern flex wing hang gliders and if I had gone with a flexible sail instead of rigid covering I would have had a glider, back in 1971, very much like what is a common design type today. The only reason I didn't was because I couldn't sew a sail and didn't have the money to pay a sail maker.
At low angles of attack the Skysail had a very fast flat glide but also had a slow mushing flight at high angles with made it easier to land.
So, now after all these years I'm building another glider of my own design, the "Basic Trainer, Puffin", and I will be testing it, but this time I already know how to fly a hang glider. However, I also have a good pilot volunteer to do testing who is much younger than my soon to be 84 years.
I've attached a photo from a Popular Science Magazine article that came out in 1974.
Frank Colver
Oops - for some reason I can't upload any photos now. sg, help!