Prop Efficiency

[danhampson]

ive been build a fixed wing fpv platform for a few weeks, and would like to know more about the efficiency of props as this build is more about duration than all out performance (which is about all ive ever built)

The auw for this model is a little over 1kg

so here are the manufacturers specs for the motors.

Model: X2212-1400KV
KV (rpm/v): 1400
Non-load current: 10V/0.9A
Weight: 56g
Length: 30mm
Diameter: 27.5mm
Shaft Diameter(mm): 3

1400kv specs.jpg (61.69 KiB) Viewed 5571 times

the recommended prop for this build is a 7x5 apc prop but the airframe can accommodate up to a 9" prop. ive flown the 7x5 prop and its seems to be under powered, but that could just be me as ive only really flown 3d fixed wing models. From my LOS flight with really old 2200mah 3s i did some calculations and should be talking around 12min flight times.

so would a larger shallower prop be more efficient than a smaller more pitchy (if thats a real word) prop.

[Lee]

I'm no expert, but, by the looks of that list, 8040 is the most efficient.

[danhampson]

Yes I can see from the chart that the 8x4 is the most efficient on the list.
But the recommended prop for the efficient motor package on the falcon EVO site is a 7x5 I can see the performance being around the same but what if I threw on a 7x4.5x3 or a 8x3x3 (if I can find them)

[danhampson]

My thinking is from quads that I'll get around the sender efficiency with 7x4.5x3 as 7x5 but a bit more pop.

[Derek]

I've done a lot of prop testing with my planes over the years, yet i'm still not a prop-master. Generally what I do is bench test the motor with "prop 1" and then with "prop 2" with my Turnigy watt meter. If my ESC is a 40amp esc, for example, I run the biggest prop I can without hitting the 40amps at full throttle.

If the recommended prop is a 7x5, I imagine an 8x4 prop will do just fine. There are also different tolerances with different brands of props. I've found that APC props are nearly perfectly balanced right out of the package and they flex very little.

I dunno if I've been helpful at all, but it's kinda my two cents.

[danhampson]

Yeah it sort of helps. Looking at the above figures I could quite easily run a 9x6 which I've got. But I think I'm going to give the 7x4.5x3 a go first. It should sound pretty awesome too.

[Stambo]

The only problem I can see is a tri blade will always have a blade hanging in harms way during landing.

[danhampson]

The only problem I can see is a tri blade will always have a blade hanging in harms way during landing.

How had just put one on, on the bench and it was sitting on the blades so I've put the 9x6 on for some LOS testing.

[danhampson]

I ran the motor up with the 9x6 prop on this morning (in hand) and it seems to have enough power to vertical climb iut even with the old tired 2200mah I've been setting up with. I just hope it doesn't generate too much torque roll on launch. I think I'm going to have to be gentle with the throttle until it's stable in the air.

[Stambo]

If you launch with the Naze in acro it will pretty much prevent torque roll.

[danhampson]

Thanks for the tip Stambo I'll definitely try that on the next flight.