lcorinth
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- Aug 5, 2014
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I'm prepping this little scratch build for launch tomorrow.
According to my OR design, it should have been 1.29 caliber stability. However, I didn't bother to weigh the parts.
When I checked the CG, it was further back than on the sim. So I did some measurements, and did a swing test.
The swing test was tricky - it was my first time doing it. First couple of swings, it got going backwards (it's windy outside today). When I tried it inside, it was fine. Then, I took it back outside, and instead of just swinging it around, I tossed it in the right direction, and it passed the swing test.
BUT, according to my measurements, the CG with wadding, chute, and an E9-6 motor has the CP at 24.3cm. The CG is at 21.9cm. That's a 2.4cm difference, and the airframe is 2.48cm - so it's just shy of one caliber stable (unless I mismeasured).
Whaddya think? Did I mismeasure? I know the swing test isn't perfect, but I've always read that a rocket which passes the swing test is stable. And a second after launch, the CG will shift forward (launching on a 1500mm micro rail). Do you think this rocket should be stable, or do I need to add a gram or two of nose weight?
Thanks!
According to my OR design, it should have been 1.29 caliber stability. However, I didn't bother to weigh the parts.
When I checked the CG, it was further back than on the sim. So I did some measurements, and did a swing test.
The swing test was tricky - it was my first time doing it. First couple of swings, it got going backwards (it's windy outside today). When I tried it inside, it was fine. Then, I took it back outside, and instead of just swinging it around, I tossed it in the right direction, and it passed the swing test.
BUT, according to my measurements, the CG with wadding, chute, and an E9-6 motor has the CP at 24.3cm. The CG is at 21.9cm. That's a 2.4cm difference, and the airframe is 2.48cm - so it's just shy of one caliber stable (unless I mismeasured).
Whaddya think? Did I mismeasure? I know the swing test isn't perfect, but I've always read that a rocket which passes the swing test is stable. And a second after launch, the CG will shift forward (launching on a 1500mm micro rail). Do you think this rocket should be stable, or do I need to add a gram or two of nose weight?
Thanks!