Corkscrew in Takeoff

Jan 31, 2005 2 Replies

Hi, I am new to building rockets from scratch. I built a 18 inch rocket out of Phenolic Tubing fins out of Carbon fiber. The fins were on straight as an arrow. I designed it in Rocksim and it was stable by all methods. However when I shot it off I get a bad corkscrew type motion. It was first launched on E-9 motors the second Time Aerotech F-39 motors.



any Help



Brian


Difficult to guess at without seeing the design.

I've corrected corkscrews which seemed (was a process of elimination) to have been caused by:

Flexing fins - stiffened with a laminate.

Flexing airframe - abandoned super-rocs

Asymmetrical airflow(?) - had a hi-perf model corkscrew years ago until someone here, IIRC, suggested ANOTHER set of launch lugs 180 degrees from the existing set. (I didn't have a tower back then.) It worked. That model had small fins, minimal stability margins, and long lugs.

What's the stability margin and weight of the model? Is it a "traditional" shape? Are the fins symmetric in shape and location? NC symmetric?

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