Hello All:

       Has anybody taken two 2 bladed props and converted them into one 4 bladed prop?  I was thinking that it would be a good idea for a scale project and a way to gain a bit of ground clearance to avoid having to use large diameter props.

       Perhaps a cross lap joint on each prop that is pinned and secured with a good adhesive would be adequate.  The joint could be made on a milling machine and the holes for the pins made on a drill press.  Once the machines and jigs were set up, many props could be rapidly fabricated.

       I think that with the talent available on this site, this could be possible. There are many facets of engineering to consider in this quest but it can be done.

        Thoughts and/or suggestions?

                                                                                                                  Best for 16,

                                                                                                                  Frank McCune

Something that adds strength both top and bottom, like Laurie's CF rings, please my mechanical intuition better than just taking a couple of props with honkin' big groves in them and gluing them together.

I suspect you could just use CF disks, sunk into appropriate rabbits, rather than a ring.  But I haven't fabricated any props myself, so I can't say.

Frank,

I have used dural rings, steel rings, titanium rings and also filled the groove with epoxy-wetted carbon or kevlar rowing, all works well. It was sheer luck that I found the ready carbon rings, they are the nicest so far.
I copied this construction from Sandor Havran (HUN), he uses steel rings.
I also have a ST.60 prop somewhere given by a chinese sportsman, it has just one apr. 1/16" aluminium plate at centerline of the hub, and then 2 metal pins/blade to keep them in place.
My point is that often people over-engineer these things. L

for a 4 blade prop you  could stack one prop on top of another.   I tried that bench running a ST90 and it seems to work.  Wonder what would happen if you used two different pitches and or diameters?   What angle would be the best?  traditional 90degrees, or how about 0 degrees, a biplane prop.  Or even have the second prop follow in the slipstream of the first prop?