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Help! Moving CP Tumble recovery
Hi Folks!
I'm trying to simulate an Estes Sprite, the one with the ring tail that utilizes the ejection charge to kick the engine back about an inch. This causes the CG to move and the whole rocket becomes unstable and tumbles for recovery. It would normally be flown with the old series 3 engines but those are no loger available. That being the case, I'm trying to make an adapter so I can use 13mm engines. I know folks have used spent 18mm engine cases to do this and they have flown without problems but, to me and my OCDness, this just doesn't seem right. Hence the need for an adapter that will end up weighing the same as a Series 3 engine when I have a 13mm engine loaded in it. I've simulated the ascent with the adapter I put together and the motor in the forward position and the numbers look reasonable. My problem has been simulating the recovery phase. I've tried simulating with the motor/adapter combo in the rear position amd was surprised at how well it flew and more surprised when it augered in for a core sample without any tumbling. So how bad is my logic here and please be kind Thanks Roy |
#2
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Quote:
I think this part of the project is fairly straightforward. The bigger challenges involve securing the hook and venting the airframe. The mini motors are notorious for potent ejection charges, so you need a bit larger vent hole in the airframe. And when the hot ejections blast the motors aft, they tend to either slip the hook and come out, or wrench the hook and tear it loose. So some reinforcement is needed over the stock hook attachment. I think a piece of glass cloth and epoxy is a good modification over the original attachment method. The other trick is to make the motor slightly tight in the airframe by applying some tape to it (ala friction fitting). It needs to slide freely, but not too loose. It needs to have enough friction such that it doesn't slide aft, bounce off the hook and then slide back in (thus resulting in lawn dart recovery instead of tumble). Doug .
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#3
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I had a sprite...it always kicked the series three (s) motors and augured in with no damage
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#4
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You could approximate the proportional mass change with an ejection enabled rearward piston launcher, short throw, with a gas passage at full extension. I have not coined a name for it, but have employed it successfully.
Just Jerry EERPLSTGP. Nope. |
#5
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Rear gas passage name? FART I employ it successfully on a daily basis.
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I love sanding. |
#6
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I was talking rockets not bodily functions. But what better rocket to place on your desk?
Jerry again |
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