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Quiet Rotors?

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Ok I did search this topic but it may be so crazy no self respecting operator would ask, So self respect be darned here goes.
Has anyone tried or heard of any rotor quieting devices such as lightweight shrouds, wing tipped rotors (reduce vortice noise), variable pitched blade sets, etc..?

Why you ask would I be interested in quieter operation? For the same reason I go to the fish market, for the Halibut! Ok that was bad but it honestly just seemed like a natural evolution especially for anyone operating near communities, wildlife, LE Operations. Yes some ideas will add weight however I suspect motors and batteries will become more powerful and efficient.
 
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Ok I did search this topic but it may be so crazy no self respecting operator would ask, So self respect be darned here goes.
Has anyone tried or heard of any rotor quieting devices such as lightweight shrouds, wing tipped rotors (reduce vortice noise), variable pitched blade sets, etc..?

Why you ask would I be interested in quieter operation? For the same reason I go to the fish market, for the Halibut! Ok that was bad but it honestly just seemed like a natural evolution especially for anyone operating near communities, wildlife, LE Operations. Yes some ideas will add weight however I suspect motors and batteries will become more powerful and efficient.
Some military choppers have noise dampening blades. I would think someone could come up with a similar prop configuration.
 
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Not conducted in a perfect environment under perfect conditions with a perfect microphone with perfect wind sock with perfectly repeatable results in a perfect place with perfect anything....

BUT

A little experiment I did for my own edification to try to prove/disprove the claim that carbon fiber props are quieter than DJI plastic props on the Inspire.

Up close, not much difference. At typical flight altitudes in an urban env though, they are clearly quieter.

But, no. You ain't never gonna sneak up on someone or peep in their window unnoticed if that's the idea...

ImageUploadedByTapatalk1451319730.642626.jpg
 
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are there cf t-type props out yet?
my switch to the latest attachment has quieted my bird a bit too
 

Tj_

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are there cf t-type props out yet?
my switch to the latest attachment has quieted my bird a bit too
CF props have their own mounting configuration. We probably won't see a newer style quick release for some time.

If you noticed a difference between plastic propellers it might be an unbalanced prop.

Are you balancing your props?
 
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are there cf t-type props out yet?
my switch to the latest attachment has quieted my bird a bit too
You can use standard T-Motor carbon fiber 14x4.8 props with various adapters out there.

I've been using them almost exclusively since summer and they are awesome. Expensive, but awesome. No good for close quarters flying or rock star on stage hand catches but my preferred prop otherwise.
 
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I would think that curved blades like a scimitar would help to reduce noise by reducing the pressure pulse between the blade and the supporting hardware. On the I1 the two CF tubes that connect the two left side and two right side motors are in the prop wash and as the blade rotates to be inline with the tubes a pressure pulse is generated. By curving the blade you should be able to reduce the pressure pulse. You might also do a little feathering of the trailing edge as raptor wings as.

OTH, both would likely reduce efficiency a bit.


Brian
 
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CF = Carbon Fiber blades

Variable pitch is not possible.

Stealth mode? You watch too many movies. There's stealth like approaches. Only skilled pilots can achieve!
Thanks for the edumacation () on CF, ok the word stealth is a bit much but it's only to convey the idea which everyone else seems to have gotten, just like firearm suppressors which I own several, sounds can be reduced quite a bit by various methods I wanted to generate conversation and ideas on ways to quiet that "swarm of bees", prop shrouds could in fact help redirect some of the noise with the downside of added weight and possibly deleterious effects with aerodynamics. But I totally thank you for your input. Fixed pitch props can be manufactured with various pitch angles and much of the tech we enjoy now was "impossible" in the recent past. Don't think "it can't be done" think how do I go about achieving it share your ideas with a collective and make the impossible possible.
Btw a lot of movie science fiction is now reality science fact so relax and watch a movie when the weather is too bad to buzz the neighbors kids!
 
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Tj_

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Thanks for the edumacation () on CF, ok the word stealth is a bit much but it's only to convey the idea which everyone else seems to have gotten, just like firearm suppressors which I own several, sounds can be reduced quite a bit by various methods I wanted to generate conversation and ideas on ways to quiet that "swarm of bees", prop shrouds could in fact help redirect some of the noise with the downside of added weight and possibly deleterious effects with aerodynamics. But I totally thank you for your input. Fixed pitch props can be manufactured with various pitch angles and much of the tech we enjoy now was "impossible" in the recent past. Don't think "it can't be done" think how do I go about achieving it share your ideas with a collective and make the impossible possible.
Btw a lot of movie science fiction is now reality science fact so relax and watch a movie when the weather is too bad to buzz the neighbors kids!
You've inspired me to watch Blue Thunder with it's "whisper mode"!
 
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Yeah, as I said a bit back the kinds of things you can do to reduce noise will likely reduce efficiency a bit so if 14 minutes is what we get with the X5 maybe 12 minutes is what we'd get with silent rotors on the X5. I guess it's possible it will be more efficient and it would be great if it is, but I wouldn't hold my breath.

The amount of noise reduction portrayed in the clip above seems a bit hard to believe and if it did translate to our sized copters it could go a long way to mitigating some of the issues we have with non copter types. It will still do nothing to open up National Parks but it could help in stopping further prohibitions and that would be a good thing.


Brian
 
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Yeah, as I said a bit back the kinds of things you can do to reduce noise will likely reduce efficiency a bit so if 14 minutes is what we get with the X5 maybe 12 minutes is what we'd get with silent rotors on the X5. I guess it's possible it will be more efficient and it would be great if it is, but I wouldn't hold my breath.

The amount of noise reduction portrayed in the clip above seems a bit hard to believe and if it did translate to our sized copters it could go a long way to mitigating some of the issues we have with non copter types. It will still do nothing to open up National Parks but it could help in stopping further prohibitions and that would be a good thing.

Brian
My I1 dual remote is scheduled to arrive January 5th, it's my second venture into R/C since nitro boats, I have no intention of mounting the blades until at least a week of simulator time, I do however fully expect to be able to purchase something cheaper and used to tinker with, as I will never have the skills to design rotors I will try shroud options. No it won't quiet but simply redirect the noise but that's not a bad start, yes there will be an efficiency penalty, one bite at a time first reduce the noise signature then weight, then try to improve aerodynamics. I have absolutely no doubt more efficient power sources and motors will be developed thereby increasing flight time.
Just another thought, ducted fans are an attainable future option already used in r/c. An obvious bonus to shrouded operations would be safety and rotor protection.
Thanks everyone for your input.
MacDyver
 
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I don't think there is much you can do to make the inspire 1 more quieter. There is not much difference between props you can mount. But it is possible to built a much more quiet UAS that the Inspire 1. The Yuneec Typhoon is for instans more quiet because it has big slow rotating props (relative). The motor is also "tuned" to rotate slower. If a company build a UAS like the Typhoon and maybe with 3 ore 4 balde props or could certainly be more quiet that the inspire 1.
 

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