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Resurrected an old BAR project back from when I was a newbie: a swing-wing, my very first scratch-built glider. If ignorance is bliss, then it’s true I really didn’t know what I was in for. I just jumped right into the build enthusiastically without much more than a sketch and a mind sim.
The one major class of variable geometry glider I’ve always wanted to scratch build is a swing-wing. At the time, building a glider that required moving parts might have been an overly ambitious goal, since I'd never tackled the mechanics of it despite its relative simplicity. So I built one, and there was no problem with it gliding nicely in hand tosses. No, the problem was the squirrely launch where it did two wide, 360° corkscrews on the way up. Then there was the problem with the burn strings not completely releasing the wings no matter how strong the elastic was.
So now with a few years more experience and improved building skills, I decided to resurrect my former shelf-queen and dissect what went wrong.
1) Because there was a minute amount of play between the wings and the wing holder panels, it may have contributed to the less-than-straight launch trajectory.
2) Also the angle of attack of both wing holder panels was slightly different on each, about a quarter degree negative on one and the other maybe a half degree positive. Didn’t notice it at the time, and I think it happened when I sanded in the dihedral. Guess some or all of those things may have something to do with the less-than-stellar launch behavior.
So this time around I decided to really simplify things.
Sketch of what I’m planning:
The one major class of variable geometry glider I’ve always wanted to scratch build is a swing-wing. At the time, building a glider that required moving parts might have been an overly ambitious goal, since I'd never tackled the mechanics of it despite its relative simplicity. So I built one, and there was no problem with it gliding nicely in hand tosses. No, the problem was the squirrely launch where it did two wide, 360° corkscrews on the way up. Then there was the problem with the burn strings not completely releasing the wings no matter how strong the elastic was.
So now with a few years more experience and improved building skills, I decided to resurrect my former shelf-queen and dissect what went wrong.
1) Because there was a minute amount of play between the wings and the wing holder panels, it may have contributed to the less-than-straight launch trajectory.
2) Also the angle of attack of both wing holder panels was slightly different on each, about a quarter degree negative on one and the other maybe a half degree positive. Didn’t notice it at the time, and I think it happened when I sanded in the dihedral. Guess some or all of those things may have something to do with the less-than-stellar launch behavior.
So this time around I decided to really simplify things.
- First, go with a dihedral-less swing-wing. Entirely workable based on recent experience with other dihedral-less scratch-built projects. Then there were the production kits like the Edmonds Aerospace Twinsee, Ecee, CiCi, etc. which were designed without dihedral to make his kits easy to build even for kids. Estes also had a line of dihedral-less swing wings like the Crusader and Tomcat, as well as their current Gryphon.
So this will necessitate a swept-wing design for this project.
- Attaching the wings and support plates flat should take a lot of the alignment problems out of the equation.
- I’m also going to mount the burn thread wing hold-backs closer to the forward end. Routing the thread near the aft end caused them to tangle and not release the wings fully or consistently.
Sketch of what I’m planning:
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