Per Clay's plans- On a dirt floor bolt to a wood base 3 1/2' wide with 4 1/2" bolts washers and lock nuts. The base is made of 10 pressure treat 4x4 at least 3 1/2 feet long bolted together with 1/2" all thread rod and dug into the ground.
If you subtract 72 from 180 degrees you'll get the correct angle of 108 degrees.
For Regular polygons the interior angle is 180-(360/s) where s is the number of sides.
You can download a pdf version from googlebooks here.
http://books.google.com/books?id=t_IRCzjTf08C&printsec=frontcover&dq=moxon&ei=Q0D0S4mtBaWCywTlvrjUCA&cd=1#v=onepage&q&f=false
You can use copper patina on tin/lead solder.
Like this. http://www.amazon.com/Super-Brite-Copper-Patina-Solder/dp/B000N64PDE
I've used it on stained glass work. It leaves a thin copper plating on the solder.
It was patented in the US by Stuart A. Hill. http://www.blurringlines.com/stuart.htm
Here you can find the U.S. patent for this technique. http://patimg1.uspto.gov/.piw?docid=04631797&PageNum=1&&IDKey=C00E06F76901&HomeUrl=http://pimg-piw.uspto.gov/
That sounds like an excellent idea for a headboard. Here's how to draw a 5 point star with a straightedge and compass. http://www.jimloy.com/geometry/pentagon.htm