Short, fat rockets need less margin; long, slender rockets often need more, or so I'm told. Perhaps "calibers" of stability are the wrong measurement. Possibly we should be using some relationship to the overall length of the rocket instead.

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Yes, I've thought similarly. I was thinking, rather than in units of diameters (calibers), it should be in units of fractions of length. But then we'd still need to come up with a corresponding rule of thumb.

Example: The margin for a Bertha is like ~5 inches, against an overall length of ~24", for a fractional margin of stability of 5/24.

(Some can sharpen those numbers - I'm too lazy to look them up right now )

Not sure what would be a good rule of thumb, but 1/10 comes to mind.

Doug

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