The red plank is a Windfreak built by Bud Manning of the Greater Detroit Soaring & Hiking Club. Bud is a long time flying wing fan. Bud’s father designed and built a number of vintage free-flight gas powered flying wings. Seeing me flying my wings finally coerced Bud into building the Windfreak.
The Windfreak has a good overall performance, pretty typical for the plank type. The Windfreak is unusual, however, in that it uses an extremely thin reflex section airfoil. The large rudder is aerodynamically balanced and features a very small rudder post. This was almost the Windfreak’s undoing.
One day Bud and I were both out flying our planks at the old Greater Detroit flying field. I was flying my R42M (an elliptical plank), while Bud was flying the Windfreak. I found a thermal over a nearby housing development and Bud joined me. The light was awesome and we took turns being the highest in the thermal. When the thermal continued to drift further into the housing development and the wings were so high they were getting hard to see, I turned my R42M around and headed back toward the field.
Bud followed suit shortly afterward and put on a bit of speed to catch me up. The Windfreak, with its thinner airfoil, was much faster than the R42M. Bud had the plank going pretty fast when I heard him let out an exclamation. I looked up to see the Windfreak’s rudder fluttering down. Almost instantly, the Windfreak snapped into a high speed tumble. The Windfreak dropped several hundred feet, tumbling end over end at an incredible speed. Suddenly, it came out of the tumble by itself. Luckily it was still pointing straight at the field. With no directional control, Bud and I watched powerlessly as it flew into the tops of some tall trees at the end of the field. This was actually the best thing that could have happened, as the tree branches gently caught the sailplane and let it drop onto some lower branches. Bud was able to recover his Windfreak from the lower branches and when examined it was found that the only damage (besides the missing rudder) were a few punctures in the Monokote. Bud rebuilt the fin and the Windfreak survived to fly another day.
R42M by Dave Jones
I have since moved away from rudder/elevator planks as I find their handling extremely limited. On the other hand, they are very easy to fly, and would be a good choice for a beginning pilot. Once again, however, I think the CJ airfoils Dave developed have too much reflex which hurts performance. The elliptical wing design, although esthetically attractive, is more difficult to build than a conventional wing, and does not seem to produce any performance advantages. For anyone interested in building a plank, a better design by Dave Jones is the Blackbird 2M, that features elevons.