Thanks Woof,
I did see that one and although it is very popular, the double blade design kinda put me off, but I've re-read the thread and it seems many persons are making it into a single-blade prop.
I got impatient and cut my blades according to velacreations's plan, will keep posted if it does spin fast enough for the threadmill motor. I do have some leftovers, about 44 inches of 8" pipe, so i,ll get able to try your Zub-Woofer blades eventually
S.