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Oct 14, 2014, 08:46 AM
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It seems to me that there is no major thread concerning propellers (for planes, multicopters ... not rotors for helicopters, that are very specific).
Subjects are
1) Static thrust versus rpm and power absorbed versus rpm
2) Dynamic behaviour, in-flight unloading, propulsion efficiency. Zero thrust air velocity. Zero power air velocity.
3) Data for several brands (APC, GWS, Aeronaut, Graupner, MAS, Mejzlyk, Biela, Xoar, Falcon, T-Motor , EMP, Vess, Gemfan ... and certainly a lot more)
4) Generic formulaes, influence of diameter, pitch, rpm, chord, blade area ...
5) Freeware and software for propellers data
So I try to launch a new thread. To be updated regularly.
If you(admin) think that there is a good existing thread I could join it.
Maybe a thread "Propellers data and software" could become "sticky" ?

I was asked to embed in Scorpion Calc (with a propeller little menu) to have some Falcon props in the library.
So I received some Falcon CF to test.
I attach here my first data. There are deduced from practical testings on my little bench.
("L shaped", similar to Dr Kiwi, limited to 4000 gf of static thrust, not dynamometric, no wind tunnel, Power Supply, Medusa PowerAnalyzer Pro, PC linked).
Absorbed power(Power Out) is computed from Power In minus computed power losses (iron losses, copper losses and estimated ESC losses).
Parallelly to that I am reading a lot of informations coming from different sources.
APC propellers tables, Scorpion, Cobra ... charts, UIUC documents, RCG tables (Dr Kiwi), Martyn Mc Kinney, Yomgui ... messages and replies. Propellers freewares ..
I try to consolidate different results to get coherent data and generic formulaes.
I am open to discuss and compare. I hope feedbacks.

Here attached are some graphs concerning my first Falcon CF testings
(four Falcon CF -E props, other to follow .. up to my bench limit)
Last edited by Fourdan; May 10, 2016 at 04:12 AM.
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Oct 14, 2014, 10:18 AM
cmdl's Avatar
this would be nice. i'd like to learn more about props. recommended for sticky.
Oct 14, 2014, 10:39 AM
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Links to propellers

Useful links:
1) General and theory
Mark DRELA :
2) How to calculate thrust, given RPM, prop pitch and prop diameter?
3) Calculators (some have a propeller chapter)
Ron compilation
Prop Calc v3 by Helmut Schenk (
Propeller (Schulz), very simple :
Dr. Martin Hepperle's prop tools : Javaprop
Gabriel STAPLES (EXCEL Thrust calc)
eCalc (PropCalc)
Static Thrust Calculator Version 9.3 - Developed by Szabolcs Füzesi (Hungary)

4) APC tables and reports
In french ... look on the right "Tests d'hélices" (by 'Yomgui' ) edited 2014-11-09
EXCEL file (zipped) on APC props
5) Data from bench testings (a lot by Dr Kiwi) (B.Koenig) (test data, some motors + some props by Bruce Abbott)
6) Charts
Cobra (Lucien by Innov8tiveDesigns) (one prop chart in each Cobra motor specs)
Scorpion, Dualsky, T-Motors have some prop charts
Aeronaut (folding)
TFPP (Hobbico)
7) Props library (by Robert Goble)
8) Contra rotative props
9) Benches-Stands (compilation)
04/15/2006|Power Systems|Discussion|Dr Kiwi|Thrust stand reconfiguration - the Dr Kiwi Mk III Pusher version
10) Miscellaneous
http://www.rc-airplanes-simplified.c...ropellers.html tandem of propellers (Peterangus)
11) Papers
Propeller Performance Data at Low Reynolds Numbers by John B. Brandt
One Useful Propeller Mathematical Model for MAV by S.V.Serokhvostov .....
Last edited by Fourdan; Sep 03, 2019 at 12:18 PM. Reason: rcaeronotes added
Oct 14, 2014, 02:27 PM
yank and bank!!
Great sticky, thank you.
Oct 14, 2014, 03:21 PM
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Propellers formulations and considerations

1) Given a prop (brand, reference DxP , material CF, nylon, wood, qualificatives E, gas, SF, W(ide), N(arrow) ....
Static behaviour is given-predicted (my favourites)
** by formulaes :
Static thrust = Ct (rpm/1000)^(Texponent)
Power (absorbed) = Cp (rpm/1000)^(Pexponent)
** by charts
Dynamic behaviour is considering Ct and Cp as function of air velocity (advance ratio J = V/nD)
One consider a "propulsion efficiency" with a maximum value for some J
2) Generic formulaes
There are tentatives to find Ct and Cp as a function of diameter D, nominal pitch P
and aspect ratio (max chord/radius)
3) Related speeds
** Nominal pitch speed
** tip speed
** optimum speed
** zero-thrust air velocity
** zero-power air velocity
4) Benches, stands ..
** static
** with wind tunnel or without
** dynamometric
5) Propellers data could be considered intrinsically (dependent of rpm .. but not of the motor itself)
6) Mechanical interface with the shaft, mount, adapter are important

This thread is opened to all these subjects
Last edited by Fourdan; Oct 15, 2014 at 02:38 PM.
Oct 15, 2014, 03:32 AM
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Prop appellations: Right, Left, CW, CCW, Tractor, Pusher, F, SF,W, N, E,Gas,

Right / Left = rotating sense when viewed back, observer in the air wake (from pilot view in case of front tractor prop)
Air is always pushed behind the plane axis (prop. reverse pitch is very exceptional .. for acro !)
CW/CCW = same
Usually classical props are "Right" (default appellation)
Tractor = when the prop is front of fuse or the wing nacelle
Pusher = when the prop is back the fuse or the wing nacelle or the pylon
Caution 1 : "R" could be "Left" (same for "P") !!
Caution 2 : pusher mounting could be Right or Left !!
F = "folding"
SF = Slow Fly (also RS by GWS)
W = wide (bigger chord)
N = narrow (small chord)
E (Thin E, E-1 ..) = for Electric power train
Gas = for ICE
MR = special for multicopters
DD = Direct Drive (GWS)
3B = three blades
4B = four blades
Last edited by Fourdan; Oct 19, 2014 at 02:11 PM.
Oct 15, 2014, 03:33 AM
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Prop mounting /motor/plane

There are a lot of ways for prop mounting
1) Tractor
** Motor front of the fire-wall (FW)
** Motor back of the fire-wall (FW)
** With an extra long shaft for a glider small ogive
2) Pusher
3) Folding props
4) Prop savers (o-ring or Thera band)
5) Prop adapters (with collet, set screw or bolt on rotor)
6) Prop mounting in MR (multicopters)
7) Retractable (pylon, in-line ..)
8) Vectorial thrust
9) Ducted fans
I will try to place some pictures
Last edited by Fourdan; Oct 12, 2017 at 10:57 AM.
Oct 15, 2014, 03:34 AM
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Props : generic formulaes vs D, P, rpm

1) UIUC data base with Ct and Cp, SI unit system (Brandt's paper)
Static thrust (newton N) = rho Ct (D^4) (n^2)
or Static thrust (gf) = rho x102 xCt (D^4) (n^2)
Power (watt W) = rho Cp (D^5) (n^3)
J = V/(nD)
rho (1.225 kg/m^3), could depend of altitude, temperature, humidity ..
n (rps) .. rev per second or cycle per s or Hz (= rpm/60)
V = air velocity (m/s)
D = prop diameter (m)
Ct could be around 0.1
Cp could be around 0.05

2) Other formulations
Murat Vural (IIT) is using F =rho Kt (D/P)^0.7 P D^3 n^2
with other units and Kt value

3) NASA report n°640 (year 1938 !!)
The Aerodynamic Characteristics of Full-Scale Propellers Having 2, 3, and 4 Blades of Clark Y and R.A.F. 6 Airfoil Sections

It is important to take into account the air density (function of altitude ASL , temperature and humidity)
Last edited by Fourdan; Aug 18, 2019 at 03:40 PM. Reason: formula for gf unit, NASA report
Oct 15, 2014, 11:36 AM
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Thrust stand, benches, wind tunnels

Some pictures
1) Dr Kiwi
2) Louis's bench (2014)
Power Analyzer Pro, weight scale, LETON servo tester, prop is (here) a Falcon CF 13x5 W E-1
PC linked
3) ....
Oct 17, 2014, 12:46 PM
cmdl's Avatar
didn't see this link on post #3:

very useful to me (specially in multiblade equivalence). was referred to it by slipstick. offering it as a suggestion if you're interested in adding it.
Oct 17, 2014, 05:17 PM
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Hi cmdl
Link added.
Thanks. That thread is open (and to be updated like a wiki)
Last edited by Fourdan; Oct 17, 2014 at 05:22 PM.
Oct 18, 2014, 10:06 AM
Zarapa's pilot !
Oscar Jr.'s Avatar
Hi Louis, great job, nice initiative ! A lot to learn !

In addition to this thread, it would be good to have a brushless motor ranking, made ​​by experts, scholars, owners, etc. .. I think will help people chose better and save money !

Oct 18, 2014, 11:13 PM
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you may be looking for
Oct 19, 2014, 03:15 AM
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Here is a comparison
Several motors on the same job (same load)
"Propeller MAS 10x6 at 8000 rpm"
Motors of the class "stators 2814, 2815, 3014 .."
Last edited by Fourdan; Oct 19, 2014 at 03:24 AM.
Oct 22, 2014, 12:47 PM
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APC 7x5E

Typical compilation about the APC 7x5 E prop, as a first example
** cloud of points Static thrust versus rpm (Dr Kiwi + Cobra + Louis)
note : my personal results (concerning static thrust gf) are a little lower than the best fit (around 5-10%)
So I have to re-check my bench and my weight scale
** best fit curves (Flybrushless ...)
** Aerotrash (nothing on APC 7x5E)
** UIUC (nothing on APC 7x5E)
** APC perfs (n.a , in construction)
To be done
** In flight data and relation with advance ratio J (from APC perfs)
new picture
For now I adopt : Static thrust (gf) = 3.35 (rpm/1000)^2.12
Last edited by Fourdan; Nov 09, 2014 at 09:42 AM. Reason: New text and new picture

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