Based on idea I came up with some years ago, we started building the third ever Rubble Helix structure yesterday near Port Hope Ontario. My original concept for this spiraling double wall seemed like an impossible design to actually build but when I fooled around with dominoes and some small wooden wafer shapes I discovered the thing actually held together quite well.
We built one prototype indoors at a greenhouse during the winter of 2005 with workshop students.
Later we attempted to build a permanent one at the Canadian Rocktoberfest in 2007. That one looked great and lasted for several years even though it was subject to flooding every winter and severe heaving due to the difference the bases experienced, with the south leg freezing and thawing separately from the north one.
Anyway here we are on the new helix almost at the second wrung and just beginning to get the angle of the lean started. This helix spirals upwards in the opposite direction to the two previous structures we built. Next week we should be about half way up.