Hi Will,
The center hub is what I was speaking of -- if you make the hub, that you will be mounting your blades to -- where you intend to bolt it to a shaft or hub, if made of foam, with fibreglass cover -- you need a "hard point" to bolt to -- so you don,t crush the foam..
The ones I made, I drilled a hole in the foam, about 3/4" in diameter -- coated a wood dowel with epoxy, push it into that hole in the foam -- then glassed over it and after all was cured -- the shaft, or hub mount holes, are drilled thru the glass, and aprox center of the wood dowel -- say a 1/4" hole in the center of a 3/4" dowell-- when the bolt is tightened down with a large flat washer -- it gives you a "hard point" to bolt to, without crushing the foam hub !!
Hope that is understandable -- but if your center hub is wood, you won,t have to worry about it, just a lot heavier !!
I had built several prop sets, with, the foam and glass cover, and used a carbon fibre Arrow shaft, on several -- to act as a stiffening spar -- they worked good, but I finally went back to wood, seems like less work !!!
Looking foreward to seeing your finished product, Bill H.......