RocketGliders have been using motor CG shift since at least the late 60's.....in model rocketry. SO no, it's not a bad idea. It's just a really old idea. Nice design.I'm thinking about a glider design where the GC shifts by having the motor move back, like in an Astron Scout:
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It seems like it ought to work, but I've never seen anyone actually do this before, which makes me nervous because it seems pretty simple and obvious.
Is this actually a really bad idea?
It's actually a great (and workable) idea. Mine uses a burn string but I can't get it to release reliably (except once; about 10 feet above the ground. Glided fine for all of 9 seconds). So it's been a work in progress for 5 years. (I've since shortened the boom and replaced the basewood with carbon fiber).I'm thinking about a glider design where the GC shifts by having the motor move back, like in an Astron Scout:
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It seems like it ought to work, but I've never seen anyone actually do this before, which makes me nervous because it seems pretty simple and obvious.
Is this actually a really bad idea?
Cool!
How much distance does your motor move?
I'm thinking about something really simple, the ejection charge forces the engine backwards, and it gets caught by a long retaining hook. Basically identical to the way the old Scouts do CG shift for tumble recovery.
My two concerns are that the engine won't move properly or stay in the proper position during glide, or that the GC shift isn't big enough. I've only got about an inch (2.4cm) of CG change between boost and glide.
I have a scratch tumbler with shifting cg, there is near zero issue of having motors slide around on you after ejection. I would also be concerned about having enough cg shift, though it probably doesn't take much.Cool!
How much distance does your motor move?
I'm thinking about something really simple, the ejection charge forces the engine backwards, and it gets caught by a long retaining hook. Basically identical to the way the old Scouts do CG shift for tumble recovery.
My two concerns are that the engine won't move properly or stay in the proper position during glide, or that the GC shift isn't big enough. I've only got about an inch (2.4cm) of CG change between boost and glide.
Looks cool. But no dihedral in the wings for lateral roll stability?Well, here it is. A quick toss in the front yard with an expended engine suggests it will glide, so we'll see how it does on a real launch. It built as light as I can make it, so it's pretty fragile and I figure at least a 50:50 chance of significant damage. But the more weight and strength I add the less the CG moves on engine shift. If this boosts straight but dies on landing I might build another one heavier.
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There's a little bit, the wing tips are about even with the top of the body tube, so about 1cm of dihedral.Looks cool. But no dihedral in the wings for lateral roll stability?
Love the twin boom with the box tail. Great and relatively light way to avoid singed tail feathers and provide great boost stability!Well, here it is. A quick toss in the front yard with an expended engine suggests it will glide, so we'll see how it does on a real launch. It built as light as I can make it, so it's pretty fragile and I figure at least a 50:50 chance of significant damage. But the more weight and strength I add the less the CG moves on engine shift. If this boosts straight but dies on landing I might build another one heavier.
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Gotcha, I see it now. Looking forward to the flight!There's a little bit, the wing tips are about even with the top of the body tube, so about 1cm of dihedral.
I'm thinking about a glider design where the GC shifts by having the motor move back, like in an Astron Scout:
It seems like it ought to work, but I've never seen anyone actually do this before, which makes me nervous because it seems pretty simple and obvious.
Is this actually a really bad idea?
I flew it earlier this summer.Hey Jeff, were you able to get this maidened yet? So curious to know how your design worked out.
It's repairable, but I think I need to do some static firings to find out what really works for the retaining hook before I fix it and tries to fire again.
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