Electric Props efficiency/ allround

[smed]

I will be testing some propellers in August in a university wind tunnel and it was mentionned to me by member BMatthews that:

"some good electric model designs would be commercially saleable immediatley to a "hungry" audience."

I have been considering testing one or two electric designs in the tunnel if I have time, and if there is enough interest I know a company that would make the props for sure.
I am not an avid electric flyer, and my question is: is efficiency (and power usage) a big issue, or is allround ability more important? The Theodorsen math program yields a propeller best suited for a specific Rpm, flight speed, diameter/aspect ratio, desired thrust, air density, etc. It usually means high pitch, high diameter, so take off might be an issue.
I would like to know a general Diameter, rpm, and flight speed typical of modern electric flyers that I could test. And maybe what I will do is send some props free to anyone interested, and
see how they fare.
It may turn out that I won't be able to injection mold to obtain enough stiffness, we'll see. Maybe aluminum propellers would be feasible?

P.S. is it ok with RCGroups regulations if I post this message in an electric forum as well as in this one?

[vintage1]

(i) try some APC electric props in the tunnel.

(ii) Something like a 10x7 turning in the 5-10k RPM range is a good middle of the road area.

Electric motors can be geared to get whatever diameter gives the best results.,.

[Dick Huang]

Adam.
I would like to see you formulate how the smallest propeller to the largest propeller unloads in terms of RPM. Test it from 0 mph
to 100 mph. Be sure to use electric motors and not IC engines.
Dick Huang:D

[KillerWatt]

Hi smed.... very interesting opportunity... i could only wish for such !!..... I've been wondering why the various blade shapes involved in E- RC model aircraft for gear drive appls.. note the so called "slo-flyer" types with rather wide, thin undercambered, rounded blades compared to the "Electric or just E types" which seem more like their gas or glow narrow type blades for the same diad/pitch size.....How about an automatic "Vari-Pitch" prop, using springs, elastic or just "smart blade flexing" that senses the diff in planes relative air-speed and changes pitch from hi to low effective pitch values for best efficy from take-off thru cruize to aerobatics type flying.... also turned up, blade tip "winglets" which eliminate power robbing tip vorticies ?? ....good luck in your wind tunnel experience...... kw

[heli frapper]

I suspect that wind tunnel reading at low speeds will not be very informative due to to many vairables

The one aera of serious interest for most modelers is the high speed areas and in this aera the guys will consider paying extra

The average user using say 9*6 or 10* 6 getting 5% effiency might bring his speed from 35mph to 37mph is not going to invest extra for that

Hovever a pylon ship going from 155mph to 165 ish would consider 5% extra well spent

The typical propeller used for these plane are
CAM 4.7inch*4.7inch
CAM 5 inch*5 inch
CAM 5 inch*4.5 inch

In the case of the CAM 4.7inch*4.7inch freqently the users apply heat to the root of blades to increase the pitch so this is a difficult vairable to establish

also any unloading affects would show up easier on high speed engines as the spread of mph would be easier to control with wind tunnel suspect very little unloading until 120mph and most unloading at 150mph

Stephen wishing I had a wind tunnel