Ratio for perfect circles?

Anyone know what the ratio for a perfect circle is using the control points? What I mean is if the radius of the circle is 10 squares and I pull the control points perpendicular to the radius, how far out do I pull them to make it a perfect circle? I can never get it quite right. I figure it's around 2:1, but I'm hoping someone knows exactly. It's quite obvious when a helix isn't perfectly round.
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http://www.bolliger-mabillard.com

Just keep experimenting, and when you finally get it perfect (or as close as possible) save it as a prefab.

-Ride_Op

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OK...in case you can't tell, I'm a perfectionist. :-)
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http://www.bolliger-mabillard.com

If you do successfully make a good circle (for a helix, I'm guessing), save it and share it.... :)

I have one but I don't know how to save an element made up of more than one segment.
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1. Raging Bull(SFGAm) 2.Millenium Force(CP) 3. Deja Vu(SFGAm) 4.V2(SFGAm) 5.Cornball Express(IB)

Hold down shift and select each segment in the element, then you can save it.