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Old Oct 27, 2009, 09:48 AM
the answer 42 is
Switzerland, AG, Lenzburg
Joined Jan 2006
1,890 Posts
Question
Smaller Propellers more Speed????

Hello

Im just a newby on this electric world , Im wondering why F5D planes use such small propellers (4x4.5)??

Besides I have a kind of F5D entry plane, now I have a 8x4.5 propeller it flys nicely and has some speed. I was wondering what would be the effect of just changing the propeller for something smaller, lets say a 6x4?? will this be enough to propell the plane?? will it go any faster than now?? or what will happend then ???

thanks a lo for your imput

EZ
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Old Oct 27, 2009, 09:52 AM
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rdbell's Avatar
USA, TN, Nashville
Joined Oct 2009
903 Posts
Well I'm not an expert but the motor probably wouldn't be able to spin it fast enough because of its kV rating. Lower kV ratings are meant to turn bigger props at a slower speed and higher Kv ratings are meant to turn a smaller prop at a faster rpm. Something like a 2200 rating would be just about perfect for a 6x4.
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Old Oct 27, 2009, 10:46 AM
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Verenigd Koninkrijk, Fareham
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Add a cell.
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Old Oct 27, 2009, 11:22 AM
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Detroit, MI
Joined Dec 2007
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For a given motor and cell count, a bigger prop will basically always be faster. If you went with a 6x4 your power would go way down, and you wouldnt have the available thrust if the 8" prop.

I would suggest if you want more speed
1) go with an 8x8 or similar
2) add a cell and prop down (6x6 or similar)
3) get a higher kv motor with a smaller prop (something around 3000-3200kv with a 5" prop)
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Old Oct 27, 2009, 12:56 PM
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Columbia SC
Joined Feb 2005
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It's all about pitch and RPM. Right now you have a 4.5 pitch prop. To go faster you either need to turn faster or increase the pitch and keep the RPM the same. If you were to go with a shorter prop, like a 6x4.5, it is possible that the motor might be able to turn it faster and your top end speed could be higher. That depends on whether the motor is capable of turning faster with less of a load on it. However, by going to a shorter prop you are giving up thrust to increase velocity so the plane will not accelerate from low speed as well as it did with a larger prop.

The next option is to add voltage to increase RPM of existing prop. Be careful because as you add voltage to the same prop/motor combo you will increase AMPs. You need to make sure your ESC can handle it.

Lastly you could just put a prop with more pitch on it. Diameter could stay the same or go smaller. The higher pitch will reduce the motor's RPM possibly so reducing the diameter and increasing the pitch may be optimal. It all depends on how the motor is handling the load of the current prop.

I'm sure you would get a much more precise answer if you gave us the make and model of the motor.
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Old Oct 27, 2009, 01:11 PM
the answer 42 is
Switzerland, AG, Lenzburg
Joined Jan 2006
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Hey woowo thanks a lot for all th information, the specs of the motor are:

Model : D2627-1200
KV (rpm/v) : 1200
Voltage (v) : 11.1
No Load Current (A): 0.7
No Load Speed (rpm) : 13550
Load Current (A) : 9.5
Load Speed (rpm) : 5800
Pull (g) : 550
G/A : 47.3
Weight : 40g (5g)

I used it before with a 9x6 propeller for a 1m glider I had and it can pull it very well.

so what would be your advise?? go back to a larger prop?? or a smaller one??

Regards

EZ
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