Tue Dec 04, 2018 11:43 pm
THE HANG GLIDER BASIC TRAINER DESIGN PROJECT:
This open source project was run on another hang gliding forum and is now in its final stages of preparing to build a full scale prototype. I thought it was time to present it on this forum for an additional audience.
THE HISTORY:
Thousands of hang glider pilots taught themselves to fly on what has become known as the “standard Rogallo”. They just ran down a hill and flew. The glider was easy to ground handle, and the control was pretty much intuitive. It was light weight (about 30 lbs) so carrying back up the hill was not very difficult.
However, this glider design had some shortcomings. In launching there was a narrow window of angle of attack to successfully launch and when in turns it tended to lose a lot of altitude. The glide angle was poor ( about 3:1 or 4:1) so a steep training hill was required just to get airborne. If flown at higher altitudes it could be put into a non-recoverable dive, when the sail went into full luff condition. But, all things considered, this simple glider was responsible for many people entering this new sport even with the lack of flight schools at that time.
Beginning hang glider students at present are taught on general purpose hang gliders capable of long distance flights. These gliders are designed for performance rather than ease of use for someone who has never flown one before. The only hang glider, that I know of, that was designed specifically for beginning instruction, is the Wills Wing Condor 330, which is no longer in production. It was still based on the common plan form of the single surface gliders flying today but had a very large area (330 sq ft) and a high lift, soft stalling, high camber airfoil. This was a good trainer but was still a long span, hard to ground handle, glider. The structural tubing was reduced and the sail thickness was reduced in order to reduce the weight of this monster hang glider but it still weighs in at 55 lbs. The glider is not certified for anything and WW says not to fly it in any heavy conditions (or higher than you care to fall). Unless short packed, it would be a problem to car top on many vehicles. However, a lot of pilots began their learning on this glider and I love flying mine at the beach.
THE GOAL:
To design a basic trainer hang glider specifically for that use, disregarding any other performance goals. A glider that is under 40 lbs, has a high lift (high camber) airfoil, has a large sail area, is slow flying with a gentle stall, has a glide angle much better than the Rogallo, easy to launch and land, and easy to ground handle. A glider that avoids the aerodynamic problems of the “standard Rogallo”.
After a student gets confident with the launching, flying, and landing of this trainer they then “graduate” to a utility glider which they ultimately will fly from higher launches and in rougher conditions. THIS GLIDER IS THE “TRAINING WHEELS” EQUIVALENT OF LEARNING TO RIDE A BICYCLE. Most people riding a bicycle today are riding something that is much different than what they learned on. Such will be the case of the Basic Trainer hang glider in relation to what they will fly beyond the beginning training.
THE HG BASIC TRAINER DESIGN:
As I said, this project was started as an open source project last May (2018) on another forum. There were inputs from other people along the way, as I also developed my own design ideas. It culminated in the building and test flying of a free flight model scaled at 1/5 of the full scale design. The model’s battens are scaled from Condor 330 battens.
The model, without any external control, flew in stable flight above the low bluff at Dockweiler beach CA. The wind that day was a little gusty, especially for a beach site. Pitch recovery was good with the CG at 30.5% of MAC (mean aerodynamic chord). Directional stability was good and the model climbed in slope lift and one time it even soared the low bluff for a distance of several hundred feet on its own. When the model would turn off the wind it didn’t have any tendency to tighten the turn but made fairly flat stable turns. Because of the encouraging test results on the scale model, I’ve decided to go ahead with the full scale glider construction.
I present this design as “open source” and I have no commercial interest or claim on any products built from these ideas. All I ask is that I be given credit for any of these design ideas if utilized by other persons.
The design is a low aspect ratio, short span, high lift (high camber), large area glider. There is tip twist for pitch
stability reflexing and to stall the tips last and a "swallow tail" center that is also reflexed. It should be slow flying, with soft stall, stable but very responsive to weight shift control of pitch and roll. Some people have expressed concern about tip weight slowing roll response, because of the 6 feet long truncated tips. I point out that the 13.5 feet moment is shorter than other gliders of similar area, which will help. The complete glider weight goal is to be under 40 lbs.
The final design comes out at 27 feet span and approximately 280 sq ft. The weight will have to wait to be seen. I’ll use the lighter sail cloth also used on the Condor 330 and tubing sizes will be less than what would be used on a general purpose glider. The airfoil is the Condor 330 airfoil, and I will be using some of the actual 330 curved battens.
One area this glider might find its use beyond basic training is in soaring low beach front dunes “dune grooming”. Its short span, large area could make for good close in ridge soaring, keeping more of the glider in the better lift zone and the turns would be tighter.
All of my drawings are in AutoCAD, so I can’t attach them but I have attached a jpeg image of one drawing. I’ve also attached a photo of the model glider rising in slope lift above a hand launch.
I’m also looking for a wrecked salvage glider, preferably a WW Falcon or Alpha that I could cannibalize for fittings. Since I will not be selling this prototype glider I don’t need new fittings. I’ll be using all new tubing so I don’t care what condition the tubes are in or the sail. Please let me know if you know of one that’s available.
Frank Colver
- Basic Trainer, sail & battens design.jpg (324.29 KiB) Viewed 3320 times
- 1/5 scale model rising in slope lift.
- Soaring the bluff.jpg (248.34 KiB) Viewed 3320 times
Original at:
http://forum.hanggliding.org/viewtopic.php?t=36286