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Old Sep 30, 2012, 09:34 AM
Registered User
Australia, QLD, Beaudesert
Joined Jul 2008
559 Posts
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Prop advice

Hi guys,
I have a clouds fly which I think for the money, the fact it is sold as a good tnainer/noob plane, it is damm great, flies slow easy handler, but does not like too much wind. But give some stick it can get up and go pretty good. anyway I am looking for a new motor for it, and I want a little more speed and power, but I am after an answer to a prop question, if I am running for instance a 2000kv motor on 3s and a prop of 5x5 and I get 50mph if I go to 6x5 would the speed be similar, I spose I am asking is pitch the only thing that will make a difference?
If for instance I run a 2200kv motor with a 5x5 prop and it draws 200 watts and does 60mph do I need a 5x6 for more speed or does a larger prop with with a similar pitch give me more speed?? I think I have little understanding of props!!
Neal
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Old Sep 30, 2012, 04:14 PM
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Cromer,Norfolk, UK
Joined Nov 2006
2,505 Posts
In general, a prop has two loads which it imposes, coming from a combination of pitch and diameter. If either increases, so does the load on the engine, and thus the RPM reduces.

So, generally, whilst you are correct in that increasing pitch will increase the maximum speed (assuming the airframe drag etc enables it to increase) but only if RPM is minimally altered. So, generally, a rule of thumb is that 1inch more pitch = 1in LESS diameter.

So in your scenario, to get a higher speed, you would either need a 4x6 prop, which I doubt you'll get, or a much higher Kv motor, which will turn a smaller prop at a faster speed.
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Old Sep 30, 2012, 05:48 PM
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Australia, QLD, Beaudesert
Joined Jul 2008
559 Posts
Hi and thankyou MCarlton
You have answered it well,much better than I framed it!
Thanks for the explanation, would I be correct to say that a 6x5 prop at same rpm would not offer an increase in speed? Or by my way of thinking as the prop is covering a greater area, I would see an increase in speed, if given the extra power required?
Nea
PS. Dont bother to answer, I have done more reading , and can answer that!
Going to be a few more Kv
Neall
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Last edited by neale; Sep 30, 2012 at 06:07 PM.
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Old Oct 01, 2012, 07:29 AM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
12,897 Posts
Increased speed generally means increased power will be consumed. Make sure your ESC and battery are up to it.

There is an equation somewhere that related power increase to speed increase, and it need a lot of power to increase speed noticeably.

If you really want a model that goes fast, you really need to choose a model and power train that are all matched for it.
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