Satellite Interceptor CP

[Rich Holmes]

I'm finishing up a Bob Harrington cardstock Satellite Interceptor. Not sure, though, how much nose weight it needs. Anyone know where the center of pressure is? Or the center of gravity (with motor) for one that flies stably? I have a sim file for the Estes original and OR puts the CP right about at the forward end of the dorsal strake... But it also shows the CG behind the CP without a motor installed, so I'm a tad suspicious.

 

[hcmbanjo]

Hi Rich,
Is this the one you have built, the Bob Harrington downscale?



The C/G is 4 1/8" from the rear with an A3-4t engine installed.
It does fine without any nose weight. My build has a plastic nose cone (I know, not the right one)
but I would bet it's stable with either a cardstock or plastic cone.

If anybody is curious, the PDF plans are available on Wayne Hill's Rocketry Blog website:
https://rocketry.wordpress.com/ultimate-paper-rocket-guide/

 

[Rich Holmes]

Yes, I meant the Bob Harrington one; I edited my post to put that in.

 

[BobH48]

I'll have to go check where it is on mine but I think I just took some clay and jammed it in the nose. It was there as much to keep the cone solid as it was to add weight.

The thing is so light that even if you add more weight than necessary, it is still going to go pretty high.

Any of my cardstock downscales that use a plastic cone uses no additional nose weight so if your cardstock cone with clay weighs as much as a Quark cone, you're good.

 

[Rich Holmes]

With no weight and an A3-4T I get a CG about 2 3/4" from the rear. That's with a card nose cone. Also I rolled the body tube from cardstock rather than wrapping a BT-5 as Chris did, which probably is part of why my CG is so much further back.

Good point about not worrying about excess weight, Bob.

I don't have a spare plastic 13 mm cone to weigh but I'd guess one would be 3 to 5 g.