Got some intelligence here. Yeah, you're right. And I didn't say the elliptical was continuous, just radial. There would definitely be an infinite number of radii. I think what the manufacturers mean by 3 or 4 radii is that they're looking for a specific radius in a specific spot. This also confused me with being different from the tri radial, which is probably 3 radii contected by a tangent line, which would be different than quadratic.
From what I've read, I'm almost positive the tri radial and quadratic are different. The quadratic and elliptical should be different in that the change in radius in an elliptical sidecut is much more gradual, allowing you to make those long smooth carves.
As I said before, there are a lot of quadratic equations for making different curves, and I'll admit I'm no mathematician. If you look up Palmer Project, they use Klothoid (really clothoid) sidecut derived from the cornu spiral which is like quadratic but in reverse. So, like you said, it would be comparable to an elliptical sidecut. Anyhow, they show how different spots have larger or smaller circles. They got the idea from Kessler, who is a snowboard geometry genius.
Last edited by willmetallica; 08-20-2009 at 01:03 PM.