Volts, Current & Watts with 9x5 3-blade and 11x4.7 2-blade props.

Superimposed volt/current graphs - 9x5 3-blade in red and 11x4.7 2-blade in blue


Further to my informal testing of 3S and 4S batteries with the same prop I did a test with 9x5 3-blade props (http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=...) and 11x4.7 2-blade props (APC SF 11x4.7).

Test procedure: using freshly charged batteries I took off and hovered at ~2m for 60 secs and then landed.

Quad specs:


KDA20-22L motors from Hobbyking

2 x Super Simple 25-30A ESC's from Hobbyking

2 x Hexfet 25A ESC's from Hobbyking (2 of 4 were DOA)

3S 3000mAh Turnigy 25C

X525 frame

Average values:


Va - 11.75V, Pa - 161.6W, Aa - 13.8A


Va - 11.89V, Pa - 150.2W, Aa - 12.7A

11x4.7 uses ~11W less power and ~1.1A less current on average for the 60 second flight than the 9x5

Full graphs below: 9x5 first.


Views: 919

Comment by Jonathan M on March 7, 2012 at 2:04pm

Cool!  I have done similar with my eagletree.  What's the weight of your quad.  You may be interested in this data.. CP and CT curves for the APC 11x4.7 SF from a windtunnel  http://www.ae.illinois.edu/m-selig/props/propDB.html.  I have been meaning to do more testing, but my thrust stand needs fixing and so does the v2.4.1 firmware :)

Comment by Graham Dyer on March 7, 2012 at 10:35pm

Quad weighs 1.3kg, flying v2.5 Alpha, what is CP and CT on those graphs?

Comment by Jonathan M on March 7, 2012 at 11:04pm

1.3kg Nice! right around my weight, I will have to do some more flights with my eagletree for comparison. I am also flying 11x4.7 props.

CT and CP are non-dimensional coefficiecnts for thrust and power (similiar to CL and CD).  It's generally how you gauge the performance of props. http://www.mh-aerotools.de/airfoils/propuls3.htm is a better explanation

Did you grab v2.5alpha from GIT or is there a zip floating around? 

Comment by Marco Robustini on March 8, 2012 at 3:57am

Graham, i've same triblade props but i tried and have poor trust, i use now 10x4.5 EPP on my X525.

Comment by Graham Dyer on March 8, 2012 at 4:09am

The 3 blade props have been fine for me (once balanced) but have had two in-flight breakages with 10x4.5's from GoodLuckBuy so advise to avoid those at all costs. The APC SF props are good as are the E-flite SF props.

Comment by Marco Robustini on March 8, 2012 at 4:47am

Nice, i use 10x4.5 Mikrokopter EPP or GAUI.


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