Brett Buck, LUNAR #763

Since so many people asked me about it, the Ecee Thunder boost glider can be had from Discount Rocketry - http://www.discountrocketry.com/ - for about $34. They go out of stock quickly, so get em while they're hot. And no, I don't get a kickback. Yet.

It's relatively easy to build - I don't think much of the "skill level" idea, but if pressed I would say it's a 2 or 3. It should fly fine with no or minimal finish, and with no sanding, as long as you put it together reasonably straight. Building it straight is pretty easy, as the parts are all laser-cut. While it wasn't perfectly done in my kit, all the critical parts are easy to line up. It is a lot more wood work than the average modern kit, but it's hard to screw up. Compared to the average boost-glider, it's much easier. It doesn't say anything in the instruction about an airfoil, but I think it's clear that you SHOULD NOT put a lifting airfoil on the wing or the canard, to avoid looping on boost. Yu might get it to work with some trial and error, but 6 oz gliders looping into crowds is a pretty tough test. My airfoil is a flat plate with the edges radiused.

It obviously flies well. It won't win any D R/G duration contests unless everybody else wrecks or DQ's, but it's fine for a sport rocket. The fixed part of the canard is set at 0-0, and the movable part just floats during the boost. This means the movable part has little or no effect on the way up, which is probably mandatory for stability. When the engine ejection charge goes off, the pressure forces a balsa piston forward until it uncovers a pressure relief hole. At the same time, the piston forces a control horn on the elevator into a stop, and holds it in place. This provides the necessary decalage for a stable glide. Mine has a very slight tendency to curve "up" on boost, but it's so slight you could ignore it.

It could be made to fly with R/C, and others have reportedly done it successfully. I think there would be some problems to solve - CG, is it required to have the elevator "float", or can you attach it directly to the servo and still have enough stability to get it to boost, how do you keep the weight down, etc.?

The wood in my model was mediocre - I would guess 10-12 lb, and very hard and a little crooked. Weight could easily be saved with contest wood, or built-up wings. This would help the CG, too, as mine needed about 3/8-1/2 oz of nose weight, and most of the weight saving would be behind the CG. I presume it would also greatly improve the performance, but it still wouldn't be prone to thermalling out.

Mine was only partially finished, to see if it worked before spending a bunch of time on the paint job. The wood was heavily sanded, and the edges all knocked off. It only took about an hour to shape. The orange is Peck-Polymers Japanese tissue, stuck down with Brodak clear dope. This is a classic free-flight finish, and it add a lot of stiffness to the airframe with very minimal weight gain. It's added about 3 grams so far. I used this same combination on the balsa-tube 1/4A PD and SD models from the first contest last year, and they were extraordinarily light - 2.2 grams w/o recovery system - about 2/3 the weight of a vellum model! That's why they boosted 75-100 feet higher than the others.

The recommended engines were unspecified, but it's obviously meant to use a D12. The three-second delay was on the short side for mine, but it's probably lighter and cleaner from the extensive sanding that it would have been with square-edged parts. It would be safe enough on the boost with an E15, and really get on up there, but I wonder if the macho ejection charge would blow up the piston tube, or just knock the front end off the glider! There's a weak point where the clearance for the elevator is cut out of the fuse, that's right next to the joint in the fuse, which is right in line with the cutout in the bottom for the piston exhaust. That's where mine broke on the first flight (the one that was stalling) that happened to hit the only 20 square feet of concrete in the 10 acres of soccer fields.