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Prop Diameter for 3D

Old 08-10-2017, 07:59 PM
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Default Prop Diameter for 3D

OK things are slow here now, so here is something to do. OK I have a "48" Extreme Flight 540 EDGE EXP have have been using 3S cells and 14 x 7 , and 13 x 6.5 E Props from APC. Happy Happy. However I just purchased a few 4S cells which requires a smaller less aggressive prop. The manual says 12 x 6 but as I run Calculations, a 13 x 4 is a better fit. Uses less power and develops more thrust than the 12 x 6.

OK I know a 13 x 4 will not the air speed a 12 x 6 pitch. Not concerned about speed. What I do not know which is better for 3D flying a larger or smaller diameter prop? My gut tells me bigger is better as it will produce a wider column of air over the control surfaces. Only down side I can see is the larger prop will have more P Factor Torque.
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Old 08-10-2017, 08:56 PM
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I enjoy 13x4 (wood) on the suggested Torque motor. Less top end but amazing pull out authority. Try it, it may suit your taste in flying. Yes, bigger is more suitable post stall. I have friends running 14x7s on the Xpwr 3910 and they love it. I just don't feel like buying another motor.
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Old 08-20-2017, 03:43 AM
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Old 08-23-2017, 09:01 AM
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Prop selection as you understand depends on results you want.

Pitch is for speed
Diameter is for thrust.

The thing to take into account is to maintain a pitch that will give speed reasonably over the stall or minimum speed needed.

I use eCalc for my motor / prop / battery selection ... and I find it is usually about 10-20% below actual field result.... in run time.

When I am setting up a 3D machine - I like to try the recc'd prop against eCalc's .... and I do not use Slow Fly's .... they lack the stiffness for good punch out in my view.

If the model shows good speed and obviously can fly a touch slower .. then I go down a step in pitch and up one in diameter ... but stopping once diameter gets to what I think is maximum model can take while standing horizontal on ground.
I like to find that vertical hover occurs at 55 - 60% throttle - which means I have more than enough to climb vertically.
The beauty of electrics of course is the versatility of throttle and ability to stop motor in flight .... unlike wet fuel. This gives a wider range of props we can use.

Sorry if I cannot advise what actual prop to use on your model - but hope the post can assist you in trialing props to get to desired.

Most of us go through this and I know not only myself - but many others have boxes of props from this ... all saved for that 'other' model etc.

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Old 08-24-2017, 06:39 PM
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The recommended 12 x 6 works fine. A 13x4 would give better static thrust which is fine if all you want to do is post stall manoeuvres and hovering but the 12x6 is better all round and for higher speed 3D like tumbling manoeuvres, pop-tops etc.
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