Hi. I tried the 3-point arc method before i made my last post. It doesn't work as a true spiral. Look closely at the arcs. When you rotate around the view, it looks "wobbly". The curves are all G1, but they don't have correct incline in the Z-axis. Follow this test, and see the result:

1) make the point spiral array

2) draw a 3-point arc. everything seems to be OK.

3) now draw a 3-point circle through the same points as the arc

You will see the path of 3-point arc will follow the exact path of the 3-point circle. And the path does not follow the spiral point array... now draw the curve through points, using all points in the spiral array. Zoom in and compare the 3-point arc to the drawn curve, you will see the "wobble"...

jonah