THE DESIGN PROCESS
1 PICK REQUIREMENTS
2 DETERMINE PARAMETERS
3 COMPARE TO EXISTING DESIGNS
7 DID WE ACHIEVE THE REQUIREMENTS? Go to step 1 and redo.
Hello POU RENEW,
I include a drawing of a idea of me. Could you place drawing and text in your POU RENEW?
I am working half a year on ideas to create of stick controlled hangglider to prepare pilots for the more advanced stick controlled rigid wings like the SWIFT (www.aeriane.com). One of the proposals is a Mignet-configuration. I guess my idea could lead to a good thing, but I am not a airplane-designer, so I need help. Lots of help.
I based myself on data from the Lederlin 380-L, a Mignet looking French design. It has a constant chord of 1.3m (4ft 3 1/4 in) . The front wing is 7.92m (26 ft), the rear 6m (19 ft 8 1/4in) The wing area is 16 m2. I use 16 m2 because the hang glider for beginners of my weight use it a lot. But here starts the problem. I don't know what area I need to use to get a slow-flying beginners hang glider.
The idea is to make a rigid hang glider which everyone can store in his garage. If the wings would be folded in two (reducing the pieces to a length of about 4 meter. One could fix the wings above a car to the ceiling of a garage. The tubes needed to construct the very crude cockpit could be placed next to each other and placed against the same ceiling. Voila, a city boy can even have his own glider if he has a garage.
You can see in my drawing that the wings have a gap when seen from above. I use vertical tails at the wingtips of the rear wing to give the hang glider a ground clearance of 40° (pilot being 1.8m). I tried to use the classic Mignet-tail, but it restricted the ground clearance too much. I hope that the tails placed at the wingtips will create a moment large enough to turn the glider. I thought about only using the tail on the inside of the turn. The other would remain in his normal position. This normal position would be about 5° from the axis from front to rear (forgot name). This way the rudders have a stabilizing effect. I the current draw configuration I use no landing gear. I think I should add a skid to prevent hard landing (with damage) when tripping during take
off or landing. The cockpit is just a few tubes connected together with a fast connection system (missing name again). The lower one has all the control rods on it. I drew the rods for the pitch control. I still am working on the controls for the yaw. But I guess I will place them under or next to the lower tube being covered with something that can be removed to check them. The pilot has the lower tube between his legs. He is holding a kind of bicycle-steer. It controls both axis. I placed a curved handle to get better access when standing more right. The pilot has to run a bit bended forward. But that should not be a problem. Raymore Horten, the famed designer of the
German WW2 flying wing jet, also designed a hang glider. His pilot was bending too. He wrote that the pilot could run faster with the wing on his shoulders than he could without wing (source: "Nurflugel" by Reimar Horten and Peter F.Selinger). And does not bend all hang glider forward when running with their hang glider? The use of the bicycle-steer gives no problem if you are left or right-handed. I drew a few connection points for cables. Here is the needed extra info.
A is placed on the upper tube
B is placed about halfway the wings on top of the spar C is placed under B on the spar
D is placed on the lower tube
E is placed about halfway the frontwing under the spar.
2 cables from A to B's
2 cables from D to C's
2 cables from D to E's
I guess that the connection A-B should be in tube instead of cables, could anybody confirm or comment.
The wings are square to give the ease of only needed one airfoil. Anyway, I could not use the classic pointy wingtip of the Mignet, because I cannot fix the rudders to them on the rear wing. I tried to give the design as much as possible rounded curves to give it more a Mignet look (which I like). I hope the most of you will like the result. I need help to make usable plans for this one. I don't intend to start a firm making these gliders. I know I am not economical-minded enough to keep a firm running. I thing about placing the plans on the net, so all can create their own "man of the street" glider. I suggest to not use copyrights, because you should then be legally responsible for the design and the accidents it could create by people who USE a bad made
glider. I don't want to put any of the helpers into troubles. I just want to give others the change to prepare them self to the more advanced hanggliders. I still think that they are the future of hanggliders and maybe will take over a bit of the regular glider-market. I somebody wants to work on this project, but wants all the rights and the credit. I will understand.. as long as he has the copyright AND the responsibility.
What will I do with the plan. Well, I intend to let it be built in a technical school by students. I hope to get the materials from sponsors (is much easier then asking money). After it is built I will look for a university or other school who can test the glider. After testing the glider will be donated to a museum. I already have contacted a school and a museum.
Both are enthusiast about the project.
What is my goal? To show that you don't need to be 3-40-50-60-70-80-90 (I know a guy of 92 who is making a HM) to built a airplane (glider) and that you can be a owner of a glider even if you live in a city in a apartment (if you have a garage or garage box). I want to show that flying can be learned in a safe (slow) way.
Any...yes even VERY critic comment is welcome. Any help off course too.
Koen Van de Kerckhove
Jeroen Boschlaan 16
+32 (0)3 843 34 68
Don, I will work next week on a 3D-drawing of this idea. will send it you as soon as possible.
PS. I just viewed today the page of the Butterfly. I want to inform you
that it was not my source of inspiration. I even think it is dangerous. I
saw on a top view in a ULM magazine that the Butterfly has the wing lapping
over each other. Was that not one of the reasons of the critics about the
HM-14 (I have found these reasons in a book, want a copy?)? The butterfly
hang glider also uses the pilot in seated position. I prefer prone because if the pilot tumbles on the ground during take off and landing his legs
shift under him without problems. If this happened to a pilot trapping with his back against a seat-back, he could break his spine. Bad thing!!
Another reason to use it is to give the current hanggliders less conversion to
switch to this kind of hang glider.
PS 2. I will contact Guy Francois too, just to know if he could help or
to know what difficulties he had.
PS 3. I sure hope you could support this idea. I could give you copies of all the letters I receive so you can report from time to time in your
Pou Renew. Like I said ... I can make stuff to place into the Pou Renew,
but I lack the money to buy it.
PS 4. I hope that I don't offend people by using the text HM light on the rudder.
Material to continue your article about my project.
After reading some more theory pages about tandems, I soon found out that I made a major error. The CG of my idea was way out of line. I drew another sketch with the CG at 25 % of the total chord. The result can be easily seen. the pilot is more on the front and the front tube has to beredesigned. If I would still use a central single tube I would get a distance between the joint with the lower tube and the point where the cables of the frontwing attach to the lower tube.
This could lead to a bended lower tube if the forces on the front wing get near their limit. To prevent this I made a inverted U-formed tube. The head of the pilot is placed between the tubes. I am still doubting about putting the arms of the pilot outside the U-tube or inside. Outside would maybe give a movement area of the pilots head that is too small, inside would lead to wide extensions at the lower tube. The latter would be harder to fix against the ceiling of a garage.
A new thing is the added single wheel. Only to make transport on the ground easier once assembled. A wooden skid is added too. If it break or has rough handling it is easy to replace. A lower tube would be a bit too expensive too replace to allow such wear and tear of the lower tube. Ok, I added a bit of weight, but only to give the glider a longer life.
Don was so friendly to contact a few of his contacts to ask some advice. Several thought it was OK. It made my day. But on 25-03-2001 I got a phone call from Guy Francois, the inventor of the Butterfly. I knew the Butterfly as a derivative of the Mignet, but only knew the motorized version while I was making these sketches. Just a few days before the call I found out of the existence of a hangglider version. It was mentioned as being very light (28 kg !!). Just compare this with a open SWIFT light version, a advanced rigidwing hangglider, which weights 45 kg. So, ok, I got the call.
Very soon I came to know that I did underestimate the drag of the many cables I used. The more we talked the more, the more I got the idea of dropping my own sketches and using the Butterfly as my project. Guy Francois was willing to help.
40-50-60-70-80-90 (remove the 0 in front)
last chapter part 2, the more (a time too much)
sorry I didn't mention these at first.
PART 3 (1-04-2000) (translation of part from sketch-diary)
Today I saw the Butterfly! No April fool !!! The Butterflys were stored in a old farm, ...you better can say a castle. Guy Francois has there the frames of the Butterfly #02 (motorized with riveted frame), #03 (motorized with welded frame made by BN) and a two-seater. He brought the #01
(hangglider) with him and now it is stored there too. A set of wings were hanging on the ceiling. One wing was lying on the floor and missed half of its fabric. You had a good view at the inside structure. Boy, oh boy, this design is brilliant in its simplicity!! Aluminum, thermo formed PVC-ribs, a lot of rivets ans several nuts and bolts. The aluminum you better let bent by the supplier where you get it from. So you buy meters of U-shaped aluminum and cut it at home to the right size.
The spars are much easier than I anticipated. Simply a U-profile lying on its side (open end to the rear). The ribs are gliding over the spar and riveted on their place with a small L-shaped part. TALKING ABOUT EASY!!!
The leading edge is also of aluminum but formed by the builder. Guy Francois said it is easily done and he was going to explain it later, but we both forgot it. Pity.
I have seen the plans of the #02, #03 and sketches and windtunnel pictures of a recent project. This project is a Pou du Ciel with internal fan. The plans I saw of the Butterflys were very detailed. D-views for assembling mblying, parts list and so. The lot! Who ever can not construct a Butterfly using these is ... not able to fly it. He suggested me to make the first flight tests using autotow. Once the model is balanced you can go hill jumping. Oh yes, Guy warned me about being careful with your knees when going to jump it. I suggested another skid to prevent knee damage. I used the skid of the prototype but connected the front and back skids with each other and placed them on higher legs.
This way the structure is more solid and the knees will never touch the ground. To have some wheels I could connect these to the joints of the legs and the skid. Guy Francois thought it was OK, but suggested to add a rubber block at the rear to absorb the shocks. Or maybe I could use the shock absorber system of the Butterfly # 02 (own thought).
Something more about the plans. I heard that there are no longer plans
of the Butterfly #01. But Guy Francois is willing to redraw them.
This man really supports me. It is like POU RENEW said: "You will like
Guy Francois". I DO, I DO.
The plans I will get in A3-format. It will be reduced copies of the original. I asked how he would get the airfoil on such a small size. He mentioned not to draw the airfoil but place a table with the coordinates.
Oh yes, he mentioned one more thing. Namely, he did design the #01 20 years ago to his size. Now .. ... he no longer fits into it.
We talked about the possibility to place a side stick instead of the central placed stick. Side sticks are more know in the modern hanggliders controlled by stick. This will be a bit difficult due to the construction of the steering.
"You will have THE BOOK, no?" he asked. "Euh...the book of Henri Mignet? Euh
... no" I had to admit. "First get the book and read it, than we will go on", he said. I have a print-out of a translation found at www.flyingflea.org. I do hope it is the complete text. If not I will get me this almost-holy-to-Pou-du-Ciel-fans book.
I haven't taken much pictures. 4 at the most and 3 times my flash didn't work. But no problem ... I enjoyed the day and all is written (read burned) in my mind as if it is the ABC.
Guy Francois had seen my first sketch and mentioned that the CG was totally wrong. I explained that problem was already known to me. I told his that at the time of my first sketch I used the ACs of both wings and drew the AC total at the proportioned middle of the distance between both. Later I found the text of Paul Pontois and corrected my sketch. He suggested to use 24-26 % of the total chord.
He also mentioned that the Butterfly uses the airfoil 23012. When I mentioned that it was describes as obsolete by Paul Pontois, he said it will cause no problem.
I asked how the Butterfly hangglider performed in thermals. He said "The Butterfly is very light, be careful". But I think too that thermals should be avoided by absolute beginners.
BEFORE I FORGET TO MENTION IT... in part 1 I mention overlapping wings in the Butterfly. I should know better and not trust my memory. The wing don't overlap so that problem is not real. I take back my word about the Butterfly being dangerous due to this. Apologies to the designer. POU RENEW, could you place a note next to the original line in part 1 and tell "opinion changed; see remark in part 3!" Thank you.
PS. I will try to find sponsors for the materials to get this project constructed at the school during my stay at home. But I could use some help in finding the suppliers of aviation aluminum, aviation nuts and bolts and fabric. If you know any, please, contact me at my surface-address. Koen Van de Kerckhove, Jeroen Boschlaan 16, 2840 RUMST-REET, BELGIUM.
PS2. Due to a operation at my knee and the needed rest, I will be not able to read my e-mails at work. If you contact me, please, do not overload my e-mailbox and contact me by surface (or air-)mail.
to be continued ...
Keep that brain spawning wings,
April 5, 2001
I do not forget you, but I have been very busy lately. I am very interested when I follow the evolution of your thinking, starting with a new project of your own and evoluting to the well tested Butterfly. I believe than, sometimes, we have to make our own designs when we do find what we want, but, as in many cases, what we want already exists, why to reinvent the wheel? You show a real opening of mind and I am sure that every Flea enthusiast will help you with pleasure.
A link which is badly missing in the Flying Flea chain, is a real Ultra-light Pou, monoseater, 220 pounds empty weight, 20 to 25 HP, folding wings, very cheap and very fast to build. The idea is in the air and several Pou people (including the famous Grunberg) are thinking of it.