hi Hugh, the hub is temporary-just had to get it up -- the ply disc is about 10 ply waterproof concretors constructors ply made with waterproof glue. strong as. I have some alumin. discs which I might give a go one day ,but 2 sandwiched with the timber blades between them -say ,in my case, 3 inches overall thickness.
The "art" blades do flex a lot , my thoughts are he could have made them wider at the root and run a fibre rod up the inside for 1/3 the length..
By the way , do you have an interesting site I can visit, like fieldlines, but one run by you guys in the uk?
Brucedownunder@hibis.wbs.net.au
Thanks-remember,u are the one responsible for my addiction-started some nearly 10 years ago. about when I bought your book.
Bruce