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PatriciaJB Administrator 
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Hello Everyone, Georges Fraise sent me these links. http://urvam.free.fr/modules/tinyd1/index.php?id=2 Flight test video, photo's and article - Yves Rousseau's ornithopter [French and English] http://urvam.free.fr/modules/tinyd1/index.php?id=3 Photo of Georges Fraise's ornithopter. [ text in French] Hello Georges, I'm very happy to hear that you are recovering from your accident. I have been thinking of you. Thankyou very much for sending me these links. Patricia |
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Flapangle Member 
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Hi, While watching the very good Yves Rousseau's video, I noticed that it was climbing on the upstroke and dropping on the downstroke. It is normal for a wing to have less lift and thrust on the upstroke, so the added lift may be due to the apparent pitching up. The confusing part is, what is causing the pitch up? The cg seems fixed and I don't see coupled elevator movement, so it might be caused by airfoil center of pressure travel. Since a typical airfoil would 'see' a lower relative wing angle during upstroke, I would expect that the center of pressure would move towards the trailing edge and would not cause a pitch up. Is it unstable? Is the tow responsible? Any ideas? George |
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Georges Member
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Hello everybody. After more than a year of stagnation I go back to work. Patricia was kind enough to present my orni on the site. All criticisms are welcome, it is always useful. To read you soon. Cordially. Georges. |
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Jon Howes Member
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"While watching the very good Yves Rousseau's video, I noticed that it was climbing on the upstroke and dropping on the downstroke. It is normal for a wing to have less lift and thrust on the upstroke, so the added lift may be due to the apparent pitching up. The confusing part is, what is causing the pitch up?" This is something I have experienced on models with simple (ie, non-articulated) wings. On these it was caused by the high thrustline as the wing descends from the top of the stroke causing a pitch-down. One of my biplane models (dragonfly style) actually had a tendency to bunt at full power due to this. The pitch up would then simply be the converse of the thrust-induced pitch-down, ie, more drag on the upstroke retarding the aircraft via a point well above the CG. This could also be pilot respnse as I think I can see some significant elevator motion. Jon. Last edited on Mon Aug 4th, 2008 03:09 pm by Jon Howes |
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Flapangle Member
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Hi Jon, Jon said: "This is something I have experienced on models with simple (ie, non-articulated) wings. On these it was caused by the high thrust line as the wing descends from the top of the stroke causing a pitch-down. One of my biplane models (dragonfly style) actually had a tendency to bunt at full power due to this. The pitch up would then simply be the converse of the thrust-induced pitch-down, ie, more drag on the upstroke retarding the aircraft via a point well above the CG. This could also be pilot response as I think I can see some significant elevator motion." I forgot about the thrust line. I should keep a long checklist Handy. The induced drag would increase as it zooms and slows, its requirement for twist to stay in a reasonable drag bucket would also increase as it slowed, but it wasn't getting more twist. The same thing happens to my model ornithopters when they fly too slow, even with active twist. Of course the models flap so much faster so watching this video was the first time I could actually see what the wing was doing during an airborne flap. George |
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PatriciaJB Administrator
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Newspaper article about the human-powered ornithopter currently being designed and built by a group of UTIAS students. It sounds like it's almost ready for testing ! http://www.allistonherald.com/allistonherald/article/111886 Last edited on Sun Aug 24th, 2008 03:44 pm by PatriciaJB |
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Jon Howes Member
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The very best of luck to them, I hope they succeed. Jon. Last edited on Sun Aug 24th, 2008 04:34 pm by Jon Howes |
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PatriciaJB Administrator
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PatriciaJB wrote: Newspaper article about the human-powered ornithopter currently being designed and built by a group of UTIAS students. It sounds like it's almost ready for testing ! Here's another article about this ornithopter with more info, photo's etc. http://www.theaerodrome.com/forum/pioneer-aviation/14678-wing-flappers-16.html |
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DDavis Member
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I’ve been reading of the latest human powered ornithopter project by the UTIAS students with interest… but finding myself critical of some aspects of its design. Particularly, the 28 metre wingspan they feel to be necessary. I could well be wrong… but I have a feeling the sheer size of this craft is going to work against it. I do like the rowing method they intend to employ, but feel it needs a little more refinement. What I am getting to here, is the frequency of the wing beats. Having watched a large Wedge Tail eagle flying ahead of my car in an effortless display of power and grace, flapping its wings through a shallow angle and perhaps less than one cycle per second, I believe it likely that an animal the size of a large pterosaur is likely to fly in a very relaxed manner indeed. But I am going purely by intuition here… because I haven’t yet noticed any calculations as to the relationship between wing span and the flapping frequency in this forum or any other discussion on ornithopter flight yet. Correct me if I am wrong… but I am feeling that this highly critical factor has never been properly analysed. If a 15 metre wingspan pterosaur were to flap its wings at the natural rate of a rowing athlete, I suggest a 28 metre wing might only require 10 or so cycles per minute to accomplish a comfortable powered flight. If so, then the rower has time to put in two or three strokes to every cycle of their wings. Obviously, if you can do this then you have the power of more than one athlete at your disposal for no extra weight but for the more complicated mechanism required. I suggest that such a mechanism might employ hydraulic actuators combined with an hydraulic accumulator, or perhaps pneumatics… (though this might prove to have greater losses) Such a transmission might prove difficult to build sufficiently lightly, but with modern materials perhaps it can be. Another approach might be electrical… perhaps combined with a flywheel to serve a similar function to an hydraulic accumulator. A lightweight flywheel spinning at high speeds will store energy more efficiently than the old-style approach of using a heavy flywheel, so perhaps this might be workable. (I read this in either New Scientist or Scientific American many years ago. It might sound counter-intuitive, but it was what the article concluded and it suggests to me that with even more modern materials might only prove truer and allow a very lightweight flywheel to be employed.) A flywheel might offer a further advantage, in that it could be employed to store energy to power a winch for an assisted takeoff… (which could be released to fall free once having done its job) It would still be human power doing the job but would allow one to build up as much energy as required at one's leisure. I see nothing wrong with winch takeoffs. After all… an albatross needs to run to takeoff from level ground, so if we do as well it can hardly be called cheating. A winch takeoff also gets us around the problems of clearing the ground with our wing tips if they were flapping… we can treat our craft as a fixed-winger for the takeoff and only begin flapping once clear of the ground. A final note… the article on this latest attempt seems to ignore the fact of Vladimir Toporov’s partial success back in the early 1990’s. While I gather this wasn’t quite so successful as Toporov might have liked… I do read that he was able to maintain 50 kph (much faster than UTIAS srudents expect to achieve) and increase his height during his short flight on the power of his flapping wings alone. I haven’t heard just how long this flight was, but perhaps it was longer than the Wright Brothers first hop… which was less than the length of the cabin of a 747. The man should be a lot more famous than he is… David. |
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DDavis Member
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A further thought on this subject... a winch takeoff also means we only need a simple undercarriage as a sailplane would use. Otherwise we have to allow plenty of height for wing clearance with a flapping takeoff, and that would also need to be sturdy to handle the bucking that would likely occur. Both of these factors inevitably means more weight. Cheers, David. |
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PatriciaJB Administrator
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DDavis wrote: A further thought on this subject... a winch takeoff also means we only need a simple undercarriage as a sailplane would use. Otherwise we have to allow plenty of height for wing clearance with a flapping takeoff, and that would also need to be sturdy to handle the bucking that would likely occur. Both of these factors inevitably means more weight. Yes, that's true and that's why many current designs incorporate winches etc.....but, if you design an ornithopter for a winch - that is precisely what you will get !! ie: an ornithopter that has to use a winch to take-off !! The design is automatically restricted to assisted take-offs [due to weight, structure etc] and can never go beyond that because the designer wasn't thinking beyond that point when he/she decided to use an assistive device. That kind of designing wouldn't easily lead to progression to unassisted take-offs anywhere. My view is that we should always be thinking of this ultimate goal when we are designing our ornithopters. BTW: re: wing span, mass vs flapping frequency - there have been many studies done - see the Journal of Experimental Biology website. http://jeb.biologists.org/contents-by-date.0.shtml click on 'search' and type in keywords to search. Cheers, Patricia |
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PatriciaJB Administrator
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PatriciaJB wrote: Newspaper article about the human-powered ornithopter currently being designed and built by a group of UTIAS students. It sounds like it's almost ready for testing ! The group now have a website which gives much more information on their ornithopter... [ including updates and photo's] http://www.hpoproject.ca/?q=content/the-project |
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DDavis Member
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EDIT: Hi David This thread is for ' Manned ornithopter updates' [of ornithopters that are actually under construction] So I've moved your message into the 'Flapping Flight - misc discussion' thread in the 'Flapping Flight - Misc' section. Cheers, Patricia Last edited on Sun Nov 30th, 2008 02:09 pm by PatriciaJB |
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Flyboy51 Member
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Hello everyone, I recently stumbled across your forum and found it brought back many memories. 30+ years ago I was competing against Paul McCready for the Kremer prize. His Gossamer Condor obviously beat me to the finish line. Where he followed fairly conventional methods, I took a more novel approach; something I'm sure you all would be interested in. I built, and flew, a foot-launched, human-powered ornithopter. This was pre-internet. Since I lost out on the prize, I never sought publicity and hung up the project to work on other endeavors. The attached photo shows me, with my two daughters, prior to one of my test flights in 1978. The aircraft, Daedalus, had a 33' wingspan and a 33 lb empty weight. After running and foot launching, I would pull back on the stick to trade a little speed for altitude. With an altitude of 10-15' I only had a second or two to swing my feet up into the pedals and start pumping. After a minute or so of pumping, I could gain about 100'. At that time I was spent and became a glider, looking for thermals. The inboard portion of the wings were fixed. The outboard 5' flapped. The natural flexing and twisting of the wings, plus the extreme light weight, were accomplished by using a Princeton Sailwing. Unfortunately, I have very limited photos and notebooks from back then. But I would be more than willing to share my experiences and knowledge with anyone interested. Attached Image (viewed 1326 times): |
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DDavis Member
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Flyboy51... your post is a revelation! It says that human-powered ornithopter flight has already been accomplished way back in 1978! You were able to climb by muscle power alone to 100 feet altitude, and then continue to fly by the use of thermals. This is a greater achievement than even that of Vladimir Toporov many years later. If you had done it today in front of the modern media and its cameras, I feel sure it would have made front page news all over the world. With modern materials and methods of design, it should be possible to do even better. I look forward to seeing where this post of yours leads... Cheers, David. |
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Flyboy51 Member
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David, Thanks for the moral support. My first post was understandably short; to see if anyone was interested. Consequently, I didn’t go into much detail. I don’t want to overstate my successes. I was definitely in the “development” mode. Most flights ended in either a structural component breaking, which planted me on the ground, or a failure of the flapping system to function as desired, which, again, planted me on the ground. Luckily, not much altitude was ever achieved in those cases, so my falls were short. Although the aircraft may have suffered, I never got more than a few scratches and bruises. I’m an aerodynamicist, structural analysis is not my strong suit. Paul McCready’s philosophy on the Gossamer Condor was, “If it hasn’t broken, it’s probably too heavy.” I mirrored that philosophy. My structural safety factors were small to start with. When I started flapping, all too frequently, the loads were greater than I’d expected and the structures responded accordingly. The control system was a single “T” joystick that hung down from the main spar. Fore-aft movement controlled pitch, side-to-side movement controlled roll, and twisting controlled yaw. That freed up my feet to pump pedals that controlled the flapping. My legs would force the wingtips down; aerodynamic forces brought them back up. During a foot launch, I’d have to simultaneously pull back on the stick, control roll and yaw, and swing my legs up into the pedals. If I missed the pedals, I was back on the ground. If I focused too much on getting my feet up, I’d miscontrol the aircraft and end up back on the ground. Although difficult, launching was just the start of takeoff problems. Wingtip travel was ±45°. To keep the tips from going to full up during launch, a pin locked the wing at small positive dihedral angle. Of course, with aerodynamic forces trying to lift the wingtip, there was a significant load on the pin. I would have to apply enough pressure with my feet to offset the aero load but not apply too much load to bind the pin in the other direction. More than one flight ended with me unable to free the pin, and therefore, unable to start flapping. The ground was always there for me. Ideally, that pin would be re-engaged after flapping to altitude to lock the wing into a soaring position. Tolerance, air loads, structural twisting, etc. made it that I never achieved re-engagement. Any post-flapping flight I achieved required me to hold the wingtips steady with my feet. So, my already tired legs had to apply a constant, steady force. If I let the tips deflect to their full 45° up, the glide ratio deteriorated, and the ground was again ready for me. The only successful flights I had were launched downhill, into an uphill wind. I really don’t know how much altitude gain was due to ridge soaring and how much was due to flapping. I’d like to think that all that effort pumping my legs wasn’t for nothing. In the end, I’d had a couple of good flights, McCready had won the Kremmer prize, and my wife had impressed upon me that the next structural failure might occur at an altitude that would be less forgiving. At most, my achievement is a small footnote in aviation; I am still in awe of what others have accomplished, maybe more so, having been there. |
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D.Bernardin Member
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Flyboy51 wroteThe inboard portion of the wings were fixed. The outboard 5' flapped. The natural flexing and twisting of the wings, plus the extreme light weight, were accomplished by using a Princeton Sailwing. Hi, Flyboy51, Very intersting results, I agree with your solution of 5' flapped . Can you tell us a little more about your realisation : blowing, airfoil(s), structure, how was obtained the flexibility of the winglets, stabilizer, spar ... ? Could you give us a 3 view drawing ? Anyway, congratulations and muxus thank yous . |
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Jon Howes Member
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Flyboy51, Fascinating stuff, we may be pointing in similar directions, see http://www.ornithopterresearchgroup.com/view_topic.php?id=115&forum_id=8&page=1 About the 8th post down. My approach is to (hopefully) use the early hydrolytic energy burst to grab some height and then to use whatever is left for glide extension and thermal hunt. If you follow the thread above you will get the general idea. I would be very interested in swapping notes as your experiments look very similar. Jon. |
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Flyboy51 Member
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D.Bernardin Unfortunately, after 30 years and numerous moves, any notebooks I had from my ornithopter project have long since disappeared. There are no 3 view drawings, or any other sketches, any more. There are, however, a few photos taken during various stages of construction. The airfoil I used was a Princeton Sailwing. A Google search should turn up some technical papers on this section. If not, I can probably find something, if you’re interested. Basically, the Princeton Sailwing has a leading edge spar (either round or “D” section), a root rib, a tip rib, a trailing edge cable, and a fabric envelope. Its maximum lift coefficient is around 1.6. A couple of hang glider designs in the early 70s were flying with this wing. I choose it because of its extreme simplicity and light weight. I used the “D” section leading edge because it offered a slightly better L/D. I also added an intermediate rib at the end of the fixed spar, to anchor the tip flapping section. Because of its variable camber and flexibility, it lent itself well to tip flapping. Roll control was through wing warping, by bending up or down the tip rib. I had no scheduled fore-aft movement or tip twist during flapping. Tip twist was just a natural outcome of the flapping load. This was not particularly efficient, aerodynamically, but it did save a lot of weight. The first photo attached shows the basic structure of the machine. It’s just an aluminum tube tailboom attached to the spar. The spar was aluminum, probably 0.025” (hard to remember exactly, but I formed it by hand over a ½” rod so it couldn’t have been too thick). The rear side of the “D” was a truss work of aluminum stringers (see second photo). Even today, it would be hard to make that structure lighter by switching to composites. The third photo shows more of the overall structural layout. This was an earlier version, when I was trying to provide a fiberglass pod for the pilot. (The wooden stand is just to hold the aircraft while I was working on it.) All cables, structural, trailing edge, power transmission, etc., were Kevlar. The Kevlar cables were as strong as steel cables but weighed only a fraction of what the steel ones would. In 1976 the company making the Kevlar cables was going out of business; I’ve never seen this product again. All of the photos I have here show the early tail. This was an all-flying tail attached to the tailboom via a universal joint. With the anhedral in the horizontal surfaces, I had to add some mixing to the rudder and elevator controls. That pretty much cancelled out the weight savings I was shooting for. Later versions used a more convention fixed horizontal with movable elevator and fixed vertical with movable rudder. All were bent tube and fabric covered. As the photos show, I did most of my work in my backyard and my garage. Flight testing was done at a nearby park. To put the aircraft away, and to transport it, it had to fold up. The simple structure allowed this. By removing a few bolts at the wing root and disconnecting some of the flight cables, the wings folded back and rested on the horizontal tail. The aircraft could be assembled or broken down in less than 15 minutes. I transported it on the roof of my car (a Pacer stationwagon!). One person could put it on the roof, but two made it a lot easier. Jon, I looked over your thread. Great minds do think alike! Early on, I decided that sustained human-powered flight just wasn’t going to happen. Better to mimic the eagle than the sparrow; get a little altitude and find a thermal. With my 33 pound aircraft, I could run into a wind on level ground and pop up 10-15’. From that height, I never could swing me legs up and start pumping before I was back to ground level. I had hoped, with more experience, to overcome that shortcoming. Launching downhill, however, offered me more time to transition from running to pumping. If I were to do it again (the benefit of hindsight), I’d probably pay the weight penalty to put a couple of lightweight bicycle wheels on the frame and never try to foot launch. I might even try to power the wheels to aid launching, by allowing greater ground speed. Strapping the pilot into one position for launch and flight just makes his/her task so much easier. Attached Image (viewed 311 times): |
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Flyboy51 Member
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Is there a way to post more than one photo per message? Here's the second photo referred to above. If you zoom in, you can see the truss work on the rear side of the spar. Attached Image (viewed 462 times): |
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Flyboy51 Member
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And the third photo. This one shows the structure, prior to adding wing coverings. Please ignor the fiberglass pod and the wooden work stand. The pod didn't survive the first launch and "landing". Attached Image (viewed 457 times): |
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robhannum Member
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Very impressive.... |
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D.Bernardin Member
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Hi, FlapBoy, Thank you for your complete description . I understand now what is a Princeton Sailwing . With your work and your knowledge, you have shown that Human Flapping Flight is possible . Bravo ! Last edited on Fri Jan 22nd, 2010 08:19 pm by D.Bernardin |
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D.Bernardin Member
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Looking for news of the HPO canadian team i have found the link of their photo-gallery . It shows the avancement of their work during 2009 summer : http://www.flikr.com/photos/hpoproject/3820643290 I remain without understanding the flapping system of the HPO, ¿bending the spar? Perhaps, ¿or is there an articulation they dont want to show? Wait and see ! And remember their page : http://www.hpoproject.ca Last edited on Fri Jan 22nd, 2010 08:54 pm by D.Bernardin |
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