Intro: Cardboard Geodesic Play Den
First of all - you have to go here and check out this amazing Instructable!
I looked at this and thought it was good enough to make but I couldn't see where I'd store it when not in use so I made a de-mountable version of it. To do this I made it in sub-assemblies and then bolted it together.
You will need, as stated in the original, lots of cardboard (we've just moved house so I had the luxury of picking a big stack of identical strong boxes), Sanley knife (box-cutter), hot glue gun, rulers, pens, etc. and then as well, lots of nuts, bolts and washers. We went through nearly 60 nuts and bolts and 120 washers.
Step 1: Making the Triangles
I followed the previous Instructable using lots of cardboard to make 30 ABB and 9 AAA triangles. I hot-glue gunned until I had 6 pentagons and a pile of triangles. This was my cunning plan as these don't take up too much room and can be stored in the garage. Then I started assembly of the pieces by lining them up and holding in place with clothes pegs. I poked holes through with a corkscrew and opened them out with a pair of scissors. Finally I bolted them together using a large washer on each side to make it less likely to tear. I measure in about 4" from each edge but I also labeled each joint so they will line up when it's reassembled.
I used 1/2" bolts with 13mm heads and nuts and a large washer on each side. Using two per join, and leaving gaps for the window and door, in total there are 29 joints, using 58 nuts and bolts and 116 washers.