Michael Thompson Walkalong Glider Interview
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If YouTube is blocked at your school, try this SchoolTube version http://www.schooltube.com/video/326a04c7673388c0158f/Mike-Thompson-Interview
This video is an interview with one of the major innovators of surfing objects on waves or air, but first an introduction. Michael Thompson is a college student finishing up an engineering degree in Wisconsin. He has developed very thin, and very slow-flying foam gliders, which is a whole new branch of walkalong gliding. He does extraordinary feats like one glider towing another. And he has a sense of humor. He painted one of his famous jagwings with faux blood stains—the thin foam it’s made from couldn’t hurt a mosquito.
I owe a huge debt to Mike for many things. First, I was able to design a paper walkalong glider, but only after using one of Mike’s early designs as a starting point. Throughout the process I showered him with questions about flight theory and how flying wings maintain flight stability. He patiently explained in ways even I could understand. In 2010 I was invited to demonstrate walkalong gliders at the St. Louis Science Center. I realized that the only way I could quickly show museum visitors how to make and fly them was with the foam gliders that Mike had developed. I asked him to come help me and the Science Center was happy to host him. So finally I was able to meet him at the museum, where he got lots of people flying, from kids to adults. I interviewed him right outside the front door of the St. Louis Science Center.
I saw a TV show on Discovery Channel called Next Step and during one segment I saw somebody flying a paper airplane around in circles. I later learned the guy was John Collins (The Paper Airplane Guy). He was flying a paper airplane around with a piece of cardboard under it. I wanted to do that so I started practicing. I’d learned how to make Styrofoam airplanes around 2001. I was making Styrofoam gliders with balsa wood fuselages, wings and tail of foam. I could not get them to fly right over cardboard. They would fly great and slow with a free glide from a hand launch, but when I put them over cardboard they would nose-dive to the ground.
I threw one of my gliders hard and the tail broke off. I decided I would try to fly it again, just as a flying wing. It actually flew that way—upside down, mind you—I bent the wing tips up the other way to compensate, and I was flying around this upside down broken glider with a piece of cardboard under it. I could only go a few feet at a time but it was starting to work. So that was my introduction to walkalong gliders around 2001.
(in answer to a question about how he got started with thin foam gliders) I got into thin Styrofoam gliders around the same time. My interest was driven by my desire to make extremely lightweight, elegant, slow-flying gliders that would stay in the air as long as possible. My dad had a bandsaw down in his basement so I figured I’d try slicing Styrofoam on this bandsaw. I looked for a big block of wood to set up a barrier, a jig so to speak. I tried a few cuts and it was pretty good, less than an eighth of an inch. I knew I could do better, and I found he had a nice ninety degree metal plate that you could fit into the guide slot of the bandsaw table. I ended up using that. I could adjust it very precisely, to a sixteenth of an inch or less. That’s pretty much the magic thickness for a very slow, easy to fly glider of any sort; whether for hand launch, or as a walkalong (which is what it’s best suited for).
Styrofoam has advantages and disadvantages. It’s very light; anything made from it will go extremely slowly. However it has lots of holes and the surface is pretty rough from the bandsaw cuts. The lift to drag ratio of foam cut that way is fairly low. People are developing ways to get around that by methods like hot-wire cutting. An idea that was suggested by a an employee of Hawker Beechcraft [Mike was an intern there] is to try a deli meat slicer. I’ve not tried it yet, but it’s going to be the next experiment when I have the time.
(in answer to a question about how he developed the jagwing design) I had learned about how certain kinds of real aircraft get lift. Most people have heard the explanation about how a typical wing redirects the airflow downward to get its lift. There’s a related, yet different principle that’s involved with a “delta wing” aircraft like the Concord or a French Mirage fighter jet. Those have a delta wing, a very sharp triangle, with the angle in the middle no more than about sixty degrees. That’s about the maximum you can go. So it’s like having a wingtip and a wingtip right together with no wing in the middle. The wingtips on a normal airplane can get vortices, those little swirling tornados at the wingtips that you sometimes see in good photographs. On a delta wing aircraft, those are the dominant mode for lift when it’s going at slow speed and high angle of attack. The air spills around that pointed leading edge and you get the tornados on top which have low pressure and that’s where you get your lift. I figured, “Maybe I should try something like this.”
I had already come up with Styrofoam “plank” wing gliders. They flew well enough: turned well, fairly stable, but they weren’t quite as slow as I wanted. I had one that was particularly good. It was one of the earliest I’d made and all the subsequent ones flew faster. I could not get something to fly as slow as that first lucky glider. It even had some camber which helped form the airfoil. But I could not get any more to fly as slow. So, on a hunch, I decided, “I’m going to take advantage of this vortex lift.” In my experience any successful walkalong glider has to have a long overall wing span and a short width so it stays within the narrow zone of lift over the cardboard.
To combine the two ideas, I cannot have one big delta wing. It would either be too long; it would stick too far forward and the aircraft would nosedive due to the difference in lift. Or, if I swept it out so the angle was a lot wider it would not get the vortex lift. It would simply be like a swept-back wing, which would not work. So to combine the two I figured, “All right, I’ll have lots of points. I’ll have two or three or four.” So I tried three on the first little glider on a hunch. I tried it out and I was amazed at how mushy and easy it flew. The stall was incredibly gentle and it was very slow even with the extra weight on the nose.
I’ve taken the idea further. I first took my plank flying wings and cut serrations on the leading edge—about one fourth of the overall cord depth. That gave it much-improved low-speed handling, stability and stall resistance. It was just about win-win all the way around. The only disadvantage was a slightly worse lift to drag ratio, but I can handle that. The important thing was getting good slow-speed handling and having something that can take turbulence well. That’s what the jagwing concept allows. The final refinement to it was an overall taper, making the wingtip points shorter. This improves handling because there’s less weight out at the tips to steer and control when maneuvering it. Most of the weight’s in the middle, so there’s a low moment of inertia is critical to any sort of airplane, model or otherwise.