Well I have been doing some experiments with props. Initially I started with Rev up 12 x 7 props. I pitched them to a true 6 pitch which is what the apc e 12x6 prop measures. Except at the root where it is slightly less than that, 5.7 or 5.8 pitch. I have the numbers. starting from the tip moving in toward the root, the numbers as measured on my prather pitch gauge are, 6, 6, 6, 6.,5.8,5.7,5.7,5.7,5.7. there appears to be a very small amount of Phillips entry on the blade leading edge, and towards the root there is some under camber, mostly at the root.
the props i modified basically mimic the pitch of the apc. I prepped three. I used different blade profiles based on past experiments with wet engines. Basic premise, develop the pitch desired, then thin the blades to where they feel "right" for flex at the tips. normally this ends up being about .090 thick at the tips, and about .120 at the third blade area. They are finished with two coats of epoxy, it is brushed on, and I rub them in while wearing latex gloves then wipe the excess off, letting it cure between coats.
Prop A this blade shape is similar to the scimitar shape of a standard apc prop, at least with proportion towards the tip. Normally I start with a prop an inch or so bigger than the desired finished size then I can more accurately replicate the sweep of the leading edge
Prop B basically a standard shape from the Rev up after re pitching.
Prop C this prop has a slightly steeper pitch, it is 6.7, the root is about the same, this prop also has a slight amount of undercamber.
I went flying Saturday and compared these three props with the APC in flight. I did use the eagle tree data recorder but based on the results in flight I haven't really explored the data as it basically was of minor important. I will follow up later with the flight data, suffice it to say, I was not impressed, my lap times were about .4 to .6 sec a lap slower. After talking to Pat Johnston at length, we concluded that perhaps the Phillips entry might be what was throwing the results off. Also Todd Ryan and I talked since he was there for the testing as well. His opinion was that my leading edge was to sharp.
I have posted the graphs from today's static tests without having really digested the data yet. My procedure was to run 30 sec runs at 9200 rpm while the airframe was restrained.
the first run was just as I flew it
second run, I softened the leading edge and formed a small radius
third run, I sanded a small phillips entry area into the leading edge. This is slightly less than 1/8 inch wide, and sweeps towards the top or face of the blade about 3/32" This is about as close to the apc entry angle that I could replicate.
so here are the graphs,,
The next step will be to take them out and fly them to get a feel how the variations in current draw correlate to actuall flight power.