Dec 09, 2007, 10:52 AM
Question

# Conversion factor2 to 3 blade prop

Hi all, need to know how to convert 2 bladed prop to 3 or 4 blades. Landing gear to short for bigger prop. Need to use a 3 or 4 blade prop. Need to know what the conversion factor is. Thanks In Advance, Rich
 Dec 09, 2007, 11:06 AM Certified Balsa Breaker Here on this forum the Good Dr. Kiwi has tested some of the new GWS HD three-bladers. All the info you would ever need is most likely there. or here... https://www.rcgroups.com/forums/showthread.php?t=781035 Last edited by 56S; Dec 09, 2007 at 12:28 PM. Reason: can't spell!
 Dec 09, 2007, 11:25 AM Registered User I haven't yet accumulated enough data to determine what 2-blade prop is the exact equivalent (thrust/pitch speed) to a 3-blade prop. .... but I'm working on it!
 Dec 09, 2007, 07:29 PM Registered User Propeller design theory says: 2 to 3 blades, reduce diameter by 10%, 2 to 4 blades reduce diameter by 15%, pitch stays the same in both cases. Steve
 Dec 11, 2007, 09:05 AM Registered User Go down 1 in. diameter with the same pitch will put you in the ball park. Gord.
 Mar 31, 2008, 03:57 AM <- Balsa flies better -> CTRL C Thanks Lucien Peter
 Mar 31, 2008, 10:14 AM Registered User There cheap enough at www.gwsprops.com to try them out in all the sizes. The Direct drive GWS shaped 3 blades are quite a bit differant in comparison amp draws than the SLO fly series 3 blades. Something you must consider. I generally just drop down by 1" in the dia of the 2 blade as a starting point. I am running more 3 blades than 2 now days as the torq effects for same thrust ratings are reduced. I preffer only the Direct drive profile however.
 May 22, 2016, 02:57 PM Suspended Account Really appreciate the posts here guys learned alot!
May 31, 2016, 07:09 PM
Registered User
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 The more complete formula, which takes the number of prop blades into account is D x D x D x P x Square root (N-1), where N = the number of prop blades. For a 2 bladed prop, the square root of (2-1) is the square root of 1 which is 1, so the term just drops out of the equation.
Interesting equation in it being simple, but something is not quite correct, as it implies a single blade has zero load factor..?
 Sep 01, 2016, 03:58 PM Registered User sorry wrong thread
Mar 24, 2017, 10:50 PM
Registered User

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