I thought there *may* have been a way to do this using Replicator --- I can't see a way to offset the extrusions where they make a spiral, however...
I needed this functionality a while back, and as it wasn't in AC3D already, I ended up getting "Spiralizer":
http://www.armanisoft.ch/webdesign/FrmDownloads.html
Scroll to the bottom section and click that Spiralizer link if you don't understand German.
It exports to DXF, which loads nicely into AC3D. Good workaround until there's a way to do this natively in AC3D...