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Stealth Props?
7960 14 2015-9-9
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Rnfaust
Second Officer
Flight distance : 559642 ft
United States
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Wouldn't it be nice if Dji offered stealth props? My only complaint about the P3 is it seems awfully loud. It has to be pretty flown pretty high before it gets quiet. Others have reported the Dji carbon fiber props are quieter, but I haven't tried them yet. I wonder how much you would give up in performance and runtime with quiet props? Any interest for people flying in the suburbs and not wanting to disturb?
2015-9-9
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gregg1r
First Officer

United States
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Stealth has nothing to do with noise. Stealth is non-observable.

There are ways to quiet the props. The simplest is slowing the motors down, but small motors don't have the torque required to turn large props.

Props can be shrouded, but that adds weight and complexity.

How much do you want to spend for your next Phantom?
2015-9-9
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Rnfaust
Second Officer
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United States
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gregg1r Posted at 2015-9-9 08:55
Stealth has nothing to do with noise. Stealth is non-observable.

There are ways to quiet the props ...

Good point. I would be talking about quiet, as I've gone out of my way making it more observable. I hadn't thought about the motors as the source of the noise, but I do remember now, there being considerable while testing.
2015-9-9
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Rocket_Aus
Second Officer
Flight distance : 1526929 ft
Australia
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You would think balanced props would be quieter too?
2015-9-9
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spiderbot.sb
Second Officer
United States
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I found that three-bladed props significantly reduce the sound level on my other quads.  Flight seems smoother as well and this is all with a negligible change in flight time.  I wonder if we will ever see three-bladed props for the Phantom 3.
2015-9-9
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SpunOne69
lvl.4

United States
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The tri-blade props are a little quieter on my Blade 350QX3, but what you gain in quieter blades, you lose in battery/flight time.  Since the 350QX3 has a MAX flight time of 15 min (if you're not using the camera), giving up two or three minutes for quieter props is not a great advantage.  
2015-9-9
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liningiv
Second Officer
Flight distance : 329409 ft
United Kingdom
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I have found that if you gently use 1000 grit abrasive paper, on the leading and trailing edges of the props, to remove the razor sharp edges, that has a definite quietening effect.
Remember the tips are going much faster in mph than the hubs so concentrate on that part of the blades.
2015-9-9
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toddf.perkins
lvl.4

United States
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The carbon fiber props are definitely quieter if you want to try those
2015-9-9
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gregg1r
First Officer

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liningiv Posted at 2015-9-9 12:02
I have found that if you gently use 1000 grit abrasive paper, on the leading and trailing edges of t ...

If you take a Dremmel tool and grind scallops in the trailing edge, that will quiet down the props.

Look at the back edge of a thrust reverser on any of the newer large turbo fan engines. On the transcowl, they're called chevrons. It disrupts the airflow changing the resonance, good for about 3dB sound reduction.

Acoustics is one of my expertise's, but more so underwater acoustics.
2015-9-9
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HunterBrooks
Second Officer

United States
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Interestingly, I actually use the noisiness of the P3 as a way to explain why drones are NOT the tool of choice for peeping Tom's and perverts.  Those guys absolutely rely on secrecy to do what they do.  The last thing one of those guys wants to do is telegraph that they're video taping someone sunbathing by flying in a drone that can be heard coming from four houses down.

Yes, it might still be annoying, but we are not pervs ... just geeks.  : )  
2015-9-9
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liningiv
Second Officer
Flight distance : 329409 ft
United Kingdom
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I am suggesting taking the sharp edges off, not re-shaping the blades.
I think that you will destroy the balance of each blade if anyone does as you suggest.

But in answer to your suggestion, the props are rotating, the cowls are not, so an entirely different scenario.

The cowls are cut away on the Dreamliner to smooth the transition between the fan air and the ambient.  This will reduce the noise, agreed, but the P3 is fitted with props, they are not not cowled fans.
2015-9-9
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Hotwire
lvl.2
Flight distance : 10719 ft
Australia
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You can now get miniquad props with swept back tips. These are very much quieter than the bull-nose blades like the Phantom uses.
2017-11-16
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RedHotPoker
Captain
Flight distance : 165105 ft
Canada
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Hotwire Posted at 2017-11-16 17:04
You can now get miniquad props with swept back tips. These are very much quieter than the bull-nose blades like the Phantom uses.

How far back in the forum were you, when that thought struck? Haha


Please stay current, or start a new thread. Awesome.

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RedHotPoker
2017-11-16
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fansb09cc8d8
lvl.1
United States
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Stealth | Define Stealth at Dictionary.com Dictionary.com › browse › stealth a U.S. Air Force project involving a range of technologies, with the purpose of developing aircraft that are difficult to detect by sight, sound, radar, and infrared energy. 5. surreptitious; secret; not openly acknowledged: a stealth hiring of the competitor's CEO; the stealth issue of the presidential race.
2017-12-17
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fans417abfbd
Second Officer
Flight distance : 434590 ft
Thailand
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gregg1r Posted at 2015-9-9 06:55
Stealth has nothing to do with noise. Stealth is non-observable.

There are ways to quiet the props. The simplest is slowing the motors down, but small motors don't have the torque required to turn large props.

I think you are mistaken there https://dictionary.cambridge.org/dictionary/english/stealth
Do you suppose recon teams rely totally on camouflage and don’t give a thought to silence?
2017-12-17
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