[Translation of the original French comment]
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" was going to college in Arkansas. That was when I met Mark Stump. He was still flying a Fledge and I was flying a Comet 2. Mark was a die hard rigid wing fan and was allways bugging me to redesign his fledge but get rid of all those cables! I had allways wanted to design rigid wing but never had the money or the time to take it seriously. I spent many summer days cranking up with Mark and his Fledge. The fledge appeared to be a good flying glider with performance comparable to the Comet 2 I was flying. It wouldn't be untill eight years later that I would get serious and start designing my first glider. This started after a phone call from Mark. He agreed to sew the sail for a rigid wing glider if I would make the structure. We decided to keep it simple and copy a Fledge. It would be a composite airframe the same platform as a fledge. the airfoil was a 2412. It is a nearly symetrical with a low pitching moment. The first step was to make the D-tube and load test it. The first D-tube was completed a few weeks later and weighed 25 lbs. I had some questions about the load test and through a friend of a friend I was put in touch with a sailplane designer, Jim Marske. Jim gave me the info I needed and the D-tube was successfully loaded to +7 g's -4g's. Jim also invited me to visit him and check out his latest design the Genesis.
The Genesis is a standard class sailplane using a pitch stable wing. This eliminates the need for a long tail and makes for a more efficient sailplane. I was offered a job helping with the composite work on the prototype Genesis. This was an offer I couldn't refuse. The Genesis was based on Jim's Pioneer sailplane develpment, a flying wing sailplane but his other sailplane that really caught my attention was the Monarch.
The Monarch is a flying wing ultralight sailplane. It is a plank wing with slight forward sweep. I kept looking at the Monarch and thinking it has a nice low speed and gets a 19 to1 glide. It would make a great hang glider. The only problem was to get the center of gravity right, the hook in point would be close to the leading edge. This means you would be hanging out in front of the wing. Therefore I was going to have to add some sweep.
I decided to run this idea by Jim and get his reaction. He was very encouraging and just kept saying it will fly great. So the original rigid wing design was scrapped. A new design was started . It was named the Raptor. The Raptor would use the same pitch stable airfoil that's on the Monarch. A new set of D-tubes were completed. These were made of foam and fiberglass with a carbon fiber spar. They weighed 25 lbs each and were load tested to verify the strength.
Now it was Mark's turn. He got the airframe and started working on the sail. While waiting for mark to complete the sail I decided to build a hard wing version of the Raptor. I wanted to investigate the aerodynamics of this platform without the added complexity of the collapsible airframe. Jim offered use of his Monarch molds for the D-tubes. The D-tubes were made to Monarch specs with the addition of some twist. The D-tubes weighed 32 lbs apiece. Since they were built to monarch strength they were stronger than necessary for a hang glider. The ribs were made of fiberglass and spruce. There was also a spruce trailing edge. The airframe was covered with heat shrinkable Mylar. The empty weight was 140 lbs.
The wing was essentially a monarch wing swept back with tip rudders. It has a standard control bar with struts and no top rigging . The pilot uses weight shift for pitch. For roll control sliders are used just like on the later Fledge hang gliders. Now's where it gets interesting. It was time to take the new glider out and fly it. Fortunately I am part owner of a trike and only live 20 minutes from our towing site. The plan was to aerotow the Raptor and make short hops and feel it out. I was familar with aerotowing having made several hundred of them but I had never flown a glider with slider controls or drag rudders . I calculated the hang point according to info supplied by Jim.
The first flights were made in spring of 1994. I would pop the tow release after clearing the launch dolly. The 10' of altitude resulted in a long flat glide . The hang point was very close. The drag rudders were responsive and predictable. After many hops with the highest being 100' it was decided to tow to 5000' and feel it out. The climb up to 5000' was uneventful. After release the first thing to find out pitch stability. I slowly pulled in on the bar. The bar pressure built up steadily. There was very little bar movement bar but substantial bar pressure. Next thing to find out was the stall speed. I watched my airspeed indicator and eased the bar out. I kept pushing out harder and harder waiting for it to break. I watched the speed drop below 15 mph indicated. It felt mushy but wouldn't break or fall off to one side. When the sink alarm started going off I figured out what was happening. The glider never stalled and broke it just goes into a low speed mush with a high sink rate. Direction control is still there because the drag rudders are still working. The slider controls worked well but it was clear I didn't have enough mechanical advantage on the rudders. When the glider was banked it would tend to tighten up and turn higher unless high side rudder was used. All in all it was a sucessful flight The Raptor felt stable and controlable. The handling wasn't as great as I wanted but it was acceptable for a first flight.
Matt Kollman flying the RaptorPicture by James Linscome.
I spent the next couple months reworking the rudder cables and playing with different dihedral settings. Finally I got the handling just right. The Raptor was now roll neutral. That means it stays banked at what ever angle it is set at. Deploying a rudder makes the glider roll in that direction. Once the desired bank angle is achieved the rudder is released. The Raptor will continue to turn at that bank angle. To return to level flight the opposite rudder is applied. This was just like weight shifting.
I was used to pulling my body weight in the direction I wanted to turn. The transition to the sliders was easy for me. The only big difference I noticed is was a lot less work. I was flying an HP2 before the Raptor. To get it to turn required a lot of muscle. The slider control only required a pound or two of pulling . I could go up and get several hour flights and my arms wouldn't even get tired. During that first summer of tweaking and flying I got to compare the Raptor's performance against several hang gliders. It was clear there was a performance advantage. One of the first thing I noticed was the Raptor's ability to turn tight and climb in thermals. I had no trouble climbing with other hang gliders and could climb through most if I really worked at it. The glide was pure fun. To see a nice looking cloud 2 or 3 miles away and go after it knowing you got glide to spare.
First collapsable glider!
Mark with help from James Linscome completed the first collapsible glider and wanted to get a flight on this new super ship I been telling him about . Mark has been flying hang gliders for over 20 years but had allways been running them off the side of mountains. So we first gave him a crash course in aerotowing. That consists of hooking him to tow line while we offer tons of free advice like keep your eye on the trike. Hitting the throttle and seeing what happens. After he completed a few of these and got to a few thousand feet we strapped him into this 140 lb Raptor prototype and sent him on his way. The look on his face before launch was less than thrilled. I have to admit his tow on the Raptor did look better than his tows on the Fledge. By the time he landed allmost an hour later he was grinning from ear to ear. One of the first questions out of his mouth was when do I get mine?
James Linscome had also become interested in the Raptor and took the same crash course in aerotowing. He flew the Raptor and had no problems making the transition to slider controls. He also wanted to buy one.
So I decided to set up a production run of three gliders.(one for me) 6 D-tubes and hardware needed that wasn't available off the shelf. James and Mark both wanted collapsible gliders and they wanted smaller gliders. The collapsible was going to be a challenge. Our first collapsible glider took allmost an hour to put together and it wasn't easy. It also weighed over 130lbs. Mark and James persisted and finally I caved in. I would make the D-tubes and Rib material and they would put the gliders together. Their gliders would be collaspible and smaller size. They would have to be truck tested before flying. Mark would sew the sails. We put our heads together and came up with a folding rib system that looked like it would work. To get the smaller size wing and still use the same molds I modified the airfoil. These gliders were complete and truck tested about 3 years ago. The pitch curves were well in excess of what the H.G.M.A. required. Mark then did the test flying on them. We discovered by changing the size and modifying the aerfoil the dihedral setting was going to need change. Mark also found out that this wing was a lot more sensitive to dihedral settings. At settings below the exremes I had flown the prototype in Marks wing got downright squirly. After finally getting the dihedral set right Mark was able to compare it with the other hang gliders. What he found was the sink rate seemed similar but the glide was definitely better than other hang gliders. However his wing doesn't seem to be able to generate lift as well at lower speeds.
This is a result of the modification to the airfoil. Mark did all the test flying on the protoype Collapsible Raptors. Taking what he has learned through repeated set ups and break downs we have been able to modify the design. The main design goals are to make it more durable and lighter. He was the one to explore the foot launch and landing qualities of the Raptor. The first prototype I flew was allways towed off a launch dolly and landed on wheels. He reports the Raptor to have very good launching and landing qualities after you get over the additional weight. Mark seemed pretty happy with the Raptor until the Exxtacy showed up. It became clear if he couldn't sink with it nobody could. Using what Mark learned I completed the next collapsible Raptor. It was lighter 105 lbs. It set up faster and easier. Sail was made by Dick Cheney. I test flew this glider earlier this year. It used the original airfoil with less area than the first prototype. This glider flew great from the first flight. The performance seemed even better than the first glider.
I decided to take this new Raptor to Arkansas to let Mark fly it against the Exxtacy. How else would I know if we can compete with them. This was a scary idea for me. Especially since the Raptor was still in a pretty rough state. It had been temperarily painted with the cheapest cans of spray paint I could find. The gap cover was made of duct tape. Mark's first flight would set my mind at ease. It took place at mount Nebo. It was spotty lift that wasn't consistant . The Exxtacy had allready launched and was soaring the ridge and working light thermals. Other gliders had launched and sank out. Mark launched the Raptor and made a run for the ridge. He found his first thermal and started cranking. He cranked his way right up through the Exxtacy. The Raptor topped about 200' above the Exxtacy. Mark was able to stay above the Exxtacy for the next 30 minutes. They then traded back and forth for the next half hour,occasionally making runs out front to check the glide.
The next two days were pretty much the same. Midday temperatures were 105 to110 degrees. There was a 100% chance of BIG thunderstorms. The trick was to get off early and avoid them. Mark launched mount Magazine early and thermaled up and left. He didn't get a chance to fly with the Exxtacy too much. Everyone had there own opinion which way to go. He did get a chance to fly in some 1600'/min lift. He did managed to get 25 miles before the sky got too scary.
Mark stump twenty five miles from Mount Magazine talking with the local farmer. Note the on coming thunderclouds!
What did we learn through all this? That we got a state of the art rigid wing. It sets up as fast as the Exxtacy. Gets the same performance. Wieghs about the same. The only negative to report is bar pressure. I hook in at 250 lbs. I have no problem getting the Raptor to go Fast . Mark hooks in about 170lbs. the days he flew the Raptor the idea was to get high and go as fast as possible. He discovered flying above 45 mph was very difficult because of too much bar pressure.
Otherwise There wasn't any noticable difference in glide performance between the Exxtacy and the Raptor.
This brings us up to date on the Raptor Story. The latest glider has been repainted shipped to C.A. to a customer.
There have been a total of 2 hardwings and 5 collapsible gliders built to date (Sept 99). All of the gliders have been load tested and passed. The different D-tubes I made were all constructed using different techniques. The lightest one to date is 19 lbs.
Marc stump launching the raptor at mount nebo in arkansas.
Where am I headed? Here's the plan of attack. I have allready redesigned the Raptor to be 15 lbs lighter. Couple this with the 20 lb D-tubes and you get a weight of 75lbs. The amount of twist is reduced by 2 degrees, also reflex has been reduced on the airfoil to lessen bar pressure.
All raptors to date have been load tested and passed and have demonstrated the pitch and roll stability required. Roll rate is in excess of HGMA requirements.
The Raptor is now flown by weight shift. The wing is built to cantilever strength with a shifting control bar that is connect to the. the rudders. When you shift your weight the control bar shifts deploying the rudders. This is the same system used on other rigid wings except thier cables are connected to spoilers. The beauty of this system is a hang glider pilot gets on it and it flies just like a weight shift glider.
I attended the November 1998 workshop by Jim Marske, a refresher course in wing structures. I then reworked all my numbers before starting on the new design. I met Mat Redsell. Mat is a hang glider/ sailplane pilot who has discovered Jim's designs. Mat put together a team to build Monarch and Pioneer kits. I was offered a Job making the composite pieces required for the Kits. Another offer I couldn't refuse. "
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