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Noise requirement feasibility concern


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Flapping Flight Dec. 8, 2017, 11:38 p.m. PST
@Ken Burner
Yes, it's flying wing , the most efficient plane scheme, inspired by HO229 which look even more naturaly since it isn't stelt !
Horten braders have been exceptional engeniers .
We still have a lot to learn from the nature .
http://secrets-of-wwii.blogspot.com/2010/01/gotha-go-229-horten-ho-229.html

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Ken Burner Dec. 8, 2017, 10:06 p.m. PST
@Flapping Flight
Yes, very much so. I often think how the B-2 Spirit looks almost "organic," like a sting ray fish.

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Flapping Flight Dec. 5, 2017, 7:08 a.m. PST
Thanks for the link!
I'm not sure but probably they been driven by similar reasons ,noise reduction and increasing efficiency. BTW since the noise is mechanical wave in order to create it you put some energy in so generally more silent meen more efficient - but only generally:)

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AirKnight Dec. 5, 2017, 6:33 a.m. PST
@Flapping Flight
Very interesting. I think that is one of the reasons behing the shape of the google's zee aero flying car propellers:
https://www.theregister.co.uk/2013/11/21/zee_aero_flying_car/

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Flapping Flight Dec. 5, 2017, 5:58 a.m. PST
Another noise reduction blade tip
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Flapping Flight Dec. 4, 2017, 8:16 a.m. PST
And here one which engine drive a compressor and the compressed air driving the rotor blades by tip jets so it's torque less but noisy and probably not efficient at all.
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Flapping Flight Dec. 4, 2017, 7:43 a.m. PST
Tip Jet powered rotor blades just for reference of sound levels
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Flapping Flight Dec. 4, 2017, 7:40 a.m. PST
Here one more innovative concept where avoiding the rotor torque is achieved by self propelling rotor blades ( the blades are flapping as on ornithopter or bird wings but rotate at the same time)
The potential of lowering the noise is that no need of contra rotating rotor is needed ( which usually increase noise levels) or tip powered jet blades where tip rockets are very noisy as well
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PAV X Dec. 4, 2017, 3:40 a.m. PST
@AirKnight
Or this may be of interest....depending upon your ideas of course....
http://journals.sagepub.com/doi/pdf/10.1177/1756829316681868

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PAV X Dec. 4, 2017, 3:39 a.m. PST
@AirKnight
Not sure how much help this will be...!!
Noise Levels of Multi-Rotor Unmanned Aerial Vehicles with Implications for Potential Underwater Impacts on Marine Mammals
https://www.frontiersin.org/articles/10.3389/fmars.2016.00277/full

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Flapping Flight Dec. 2, 2017, 10 p.m. PST
@Lazer
You are welkome , I will be happy if the info is of someone's help in generating some new ideas.
Since I spent one good portion of my life investigating bird's and insect's flight and this blade tips looks like gull wings I probably ( suppous) know how they work:) If they work as I suppouse they not only reduce the noise but also the induced drag which increase the efficiency as well. Probably this blade tips do not produce any lift but thrust because of the so called "Bell shaped lift distribution" ( instead of eleptical one as usually )where good part of the energy of the wing tip vortices is converted in thrust as on winglets on some modern planes wings. Planes with such twisted and bent wings ( to active bell shaped lift distribution) benefit also of proverse yaw effect ( instead of adverse yaw on the wings with eleptical lift distribution)so they no needs of verticall tail stabilizer/ rudder when you roll the plane it yaw naturally in the direction of rolling (not opposite as usually) that is why birds do not need any vertical tail surfaces as well.
The absence of vertical tail decrease the overal dragg and the weight of the plane so respectively increase efficiency .
Here is NASA research on the theme for who is interested in.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160003578.pdf
Briefly if you have such a blades tips you no need of duct !

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Lazer Dec. 2, 2017, 4:40 p.m. PST
@Flapping Flight
Thanks for sharing all the information and videos. Really interesting stuff! Maybe you or another team will build ducted fan or ducted prop propulsion units with noise reducing blade tips. That would be cool.

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Flapping Flight Dec. 2, 2017, 1:52 p.m. PST
One more innovation from eurocopter which make rotor blades close to birds wings - elastic trailing edges
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Flapping Flight Dec. 2, 2017, 1:29 p.m. PST
By the way the noise suppressing eurocopter blade tips somehow remind on gull wings
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Flapping Flight Dec. 2, 2017, 1:19 p.m. PST
In the nature
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Flapping Flight Dec. 2, 2017, 1:12 p.m. PST
Or maybe active noise cancelation
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Flapping Flight Dec. 2, 2017, 1:05 p.m. PST
Noise suppressing rotor blades tips
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Flapping Flight Dec. 2, 2017, 6:45 a.m. PST
@Flapping Flight
Ha,ha Hirobo already built it :
electric
100km/h
30 min flight endurance
375K
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