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my propeller makes a droning type of sound at times

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my propeller makes a droning type of sound at times

Old 10-27-2018, 12:12 PM
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suzonka
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Default my propeller makes a droning type of sound at times

on my clipped wing supersport , with a light 9x6 propeller , and a good powerful motor E flight type and a 3S lipo power , sometimes on a fly buy when given a full throttle make a kinda of droning or flopping , or whomping sound , sound then goes aw , ad never at slow speeds what causes this ?

Last edited by suzonka; 10-27-2018 at 12:14 PM. Reason: spelling
Old 10-27-2018, 02:12 PM
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speedracerntrixie
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Did you balance your prop?
Old 10-27-2018, 04:41 PM
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Originally Posted by suzonka View Post
on my clipped wing supersport , with a light 9x6 propeller , and a good powerful motor E flight type and a 3S lipo power , sometimes on a fly buy when given a full throttle make a kinda of droning or flopping , or whomping sound , sound then goes aw , ad never at slow speeds what causes this ?
You sure it is propeller noise ?
Control surface flutter can be described as a "flopping" or "whomping" sound , and can prove just as deadly to your plane as an unbalanced prop can ....
Old 10-27-2018, 07:29 PM
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True, it could in fact be flutter as well. However most cases of flutter end up with a crashed airplane the first time you hear it. Not always though.
Old 10-27-2018, 08:31 PM
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Default prop noise

Originally Posted by speedracerntrixie View Post
Did you balance your prop?
yes i double checked the pro ad even center balance the shaft hole in the prop
Old 10-27-2018, 08:41 PM
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Default prop 9x6 tin yellow tip

Originally Posted by init4fun View Post
You sure it is propeller noise ?
Control surface flutter can be described as a "flopping" or "whomping" sound , and can prove just as deadly to your plane as an unbalanced prop can ....
e flight thin this is a very thin prop it almost seems under full power it goes out of alignment n a heavy loop for example

e flight thin
Old 10-28-2018, 07:04 AM
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Try replacing the prop with an APC brand prop.
Old 10-28-2018, 07:29 AM
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Originally Posted by speedracerntrixie View Post
Try replacing the prop with an APC brand prop.
Agree 100%

For lightly loaded casual flying the E Flight thin may be OK , but since it sounds like we're talking a "tear the skies a new one" fast plane (clipped wing & possibly overpowered E Flight motor) the APC is the right prop .
Old 10-28-2018, 09:02 AM
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Default try APC PROPELLER

Originally Posted by init4fun View Post
Agree 100%

For lightly loaded casual flying the E Flight thin may be OK , but since it sounds like we're talking a "tear the skies a new one" fast plane (clipped wing & possibly overpowered E Flight motor) the APC is the right prop .
i think your right it seems like th blades are not tracking when full power comes on with a loop
Old 10-29-2018, 11:33 AM
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Depending on how many watts worth of power you're using it may even be proper to use a glow engine prop.
Old 10-29-2018, 12:36 PM
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With the current number of available electric only sizes that APC produces I donít see the need to go with a glow prop. Even the 2,700 watt system I run has an APC electric thin blade prop.
Old 10-30-2018, 01:03 AM
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Default prop noise

Originally Posted by init4fun View Post
You sure it is propeller noise ?
Control surface flutter can be described as a "flopping" or "whomping" sound , and can prove just as deadly to your plane as an unbalanced prop can ....
yes the prop is the problem
Old 10-30-2018, 01:12 AM
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Default prop

Originally Posted by speedracerntrixie View Post
With the current number of available electric only sizes that APC produces I don’t see the need to go with a glow prop. Even the 2,700 watt system I run has an APC electric thin blade prop.
and watts Wow Wee what are you flying 2,700 Watts that's enough to take off a 13 pound airplane

Last edited by suzonka; 10-30-2018 at 06:50 AM. Reason: spelling
Old 10-30-2018, 03:48 AM
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Or fly an 11 lb pattern airplane straight up forever.
Old 10-30-2018, 06:40 AM
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Default watts watts

Originally Posted by speedracerntrixie View Post


or fly an 11 lb pattern airplane straight up forever.
wow
Old 10-30-2018, 09:06 AM
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Originally Posted by speedracerntrixie View Post
With the current number of available electric only sizes that APC produces I donít see the need to go with a glow prop. Even the 2,700 watt system I run has an APC electric thin blade prop.
FAIR ENOUGH! ! ! They do make good props, that's for sure. So let me change that to staying away from the light slow flyer props such as GWS and the very light APC if we think we might be running a strong motor.
Old 10-30-2018, 09:59 AM
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Absolutely, the slow flyer props that they make donít do well with the higher KV motors. Good point Bruce.
Old 11-04-2018, 01:03 AM
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Put simply the prop blades are probably flexing in a twisting manner where the pitch is actually changing. One could actually call it Prop Flutter to give a better perspective on what is happening. Virtually ALL plastic props will flex to some degree with the thinner ones being the worse. Wood and carbon will flex too but to a lesser degree with wood being the more stable in model size. The real problem comes when one blade flexes differently from the other. This uneven flexing is an indication of too high an rpm for the prop in use and will eventually cause a failure. Prior to that it is introducing destructive vibrations into the airframe.

I'll bet you can take your prop and holding the tip, easily twist the blades back and forth? This type of prop relies on the centrifugal forces to stiffen the blade when in use. Helicopter rotor blades take this concept to extremes. But with our models it is possible to reach an rpm where there simply is not enough force to hold the blade in proper shape. The sounds you hear is probably the twisting action being out of control. Again, think flutter here. But at 10,000 rpm.

Another possibility for the sound would be the blade tips breaking the sound barrier. But for a 9 inch prop that would require an RPM in the range of 26,500. Possible but unlikely. And BTW, you do not want that to happen.

Last edited by Appowner; 11-04-2018 at 07:47 AM.
Old 11-04-2018, 07:53 AM
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Quite an informative post and for the most part right on the money. I would however have to go on record as saying that as materials go, you will not get a more stable material then carbon fiber. Usually when talking propellers, the molds are machined from billet so they are very accurate. CF does not have heat expansion properties that wood has nor will it absorb moisture and change shape. It does absorb moisture, it just doesn't influence the dimensions. The only real issue is that you need to maintain the same resin saturation throughout but due to the use of pre preg CF fabrics that is not really an issue.

That being said, for 99% of what is being flown today, you can find a suitable APC propeller.

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