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Old 03-11-2020, 05:38 PM   #511 (permalink)
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Prandtl-D

I GOOGLED it and found the NASA site.Aircraft are ruled by skin friction.If they can lose the rear architecture of the plane,they can shave a lot of skin friction off the plane.They've already failed at a vectored-thrust jet,chasing the same goal.McDonnel Douglas/Hughes Aircraft chased the same with a tail-rotorless MD 500 variant helicopter.None of this is germane to automobiles.

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Old 03-11-2020, 07:22 PM   #512 (permalink)
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https://en.wikipedia.org/wiki/Prandtl-D
Quote:
The first two vehicles of the program showed twist of the airfoil in providing an bell shaped lift distribution instead of the elliptical distribution. This feature gave an efficiency boost and reduced strain on the wings.

In March 2016, Bowers published a technical paper entitled, “On Wings of the Minimum Induced Drag: Spanload Implications for Aircraft and Birds,” NASA/TP – 2016-219072. Detailing the aerodynamic properties and mathematics associated with the project, Bowers discusses in depth the science behind altering the spanload distribution on aircraft wings and the data gathered from experiments that demonstrated validation of its critical principles.[3][7]
Thinking about it more, I guess it's resisting spanwise airflow with washout at the tips so they don't offer lift; maintaining the 2D nature of the flow.

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Originally Posted by Xist
I think the front wing is supposed to move air over the tire.
You'd think a monoplane wing would do that. There must be some countervailing factor. Lots of interference drag.

Did you notice the tuft grids behind the tires?
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Old 03-12-2020, 11:19 AM   #513 (permalink)
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Wasn't wheel tufting so much as pitot tubes

I believe Aerohead is mostly correct, but I was under the impression that they were only looking to see if a rudderless craft could be stable. What I understood, is their experiment said rudders are unnecessary on a flying wing planform without drag augmentation, and current elliptical theory of spanwise distribution might be wrong.

In other words, the B2 would be better with washout instead of split ailerons on the tips.

Being I worked there, the NOTAR was primarily a noise reducing stealth enhancement with the added function of fewer annoying high maintenance spinning parts. I don't know what it devolved into.
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Old 03-14-2020, 01:45 PM   #514 (permalink)
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NOTAR

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Originally Posted by Piotrsko View Post
Wasn't wheel tufting so much as pitot tubes

I believe Aerohead is mostly correct, but I was under the impression that they were only looking to see if a rudderless craft could be stable. What I understood, is their experiment said rudders are unnecessary on a flying wing planform without drag augmentation, and current elliptical theory of spanwise distribution might be wrong.

In other words, the B2 would be better with washout instead of split ailerons on the tips.

Being I worked there, the NOTAR was primarily a noise reducing stealth enhancement with the added function of fewer annoying high maintenance spinning parts. I don't know what it devolved into.
In a power-off emergency auto-rotation,the loss of vectored turbine thrust would be an analogue to the absence of a mechanically-linked tail rotor with the main rotor;effectively giving zero counter-torque,directional stability and a very nice crash.
On the B2,the computer will not allow the plane to stall,so technically,any consideration of washout would be moot.And if the wing has zero-twist,the entire section will stall simultaneously,as, if you've lost the tip,you've also lost the root.
The canard on the race car is so porous,I wouldn't even want to know its drag coefficient.From what Abbott and Von Doenhoff have published on slotted wings,you wouldn't be able to print a chart tall enough to encompass its drag-to-lift ratio.
And as to the pitot array,no tube can reliably register accurate flow beyond 12-degrees incidence,and some of them might experience a local angle of attack beyond that limit.It's hard to visualize.
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Old 03-15-2020, 12:04 PM   #515 (permalink)
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If you're autorotating, you're not producing torque and are more worried about a place to land. I believe there is a work around the lack of rudder control or it wouldn't have been certified.
The HU1 had a procedure for landing with the tail rotor shot off.

The B2 is noted to have a periodic yaw wobble which the prandtl does not have. It also can only use guided weapons for this reason. So what if it cant stall, it still wobbles computer controlled or not. Read the whole treatment.
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Old 03-15-2020, 02:59 PM   #516 (permalink)
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You still have rudder control in an auto-rotation... because you're trading altitude for spinning the main rotor, which is mechanically connected to the tail rotor.

I saw a video where a kid with an RC auto-rotated upside down, then flipped it around and landed, all unpowered.
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Old 03-16-2020, 11:57 AM   #517 (permalink)
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Quote:
Originally Posted by redpoint5 View Post
You still have rudder control in an auto-rotation... because you're trading altitude for spinning the main rotor, which is mechanically connected to the tail rotor.

I saw a video where a kid with an RC auto-rotated upside down, then flipped it around and landed, all unpowered.
The point in question was a Hughes / MACDAC/Boeing NOTAR which is a turbine powered vectoring thruster that stops functioning when the turbine fails. It does not have a tail rotor.
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Old 03-16-2020, 01:35 PM   #518 (permalink)
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Ah, missed that.

It still seems it would run the internal turbine to force air out the tail under auto-rotation.



I like this design more:



Looks like a good commuter though:

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Old 03-18-2020, 03:45 PM   #519 (permalink)
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read the whole

Quote:
Originally Posted by Piotrsko View Post
If you're autorotating, you're not producing torque and are more worried about a place to land. I believe there is a work around the lack of rudder control or it wouldn't have been certified.
The HU1 had a procedure for landing with the tail rotor shot off.

The B2 is noted to have a periodic yaw wobble which the prandtl does not have. It also can only use guided weapons for this reason. So what if it cant stall, it still wobbles computer controlled or not. Read the whole treatment.
I will in my next life.I can't see any connection to road vehicle aerodynamics,and I cringe every time someone brings up things aeronautical.I cringe every time people bring up racing cars.
Washout was mentioned.Wing twist is important to that issue.I've never associated wing twist with the B2.Without twist,what happened at the wingtip would be happening at the wing root.If the computer prevents stall,its not an issue for a B2.If the Prandtl wing has twist,then tip washout would still leave the rest of the wing flying.A fixed Prandtl canard on an F-1 or Indycar would be incapable of washout or stall.Washout would not be germane.If a Prandtl canard on a race car is in yaw,you're in understeer or oversteer and have exceeded the performance envelope of the car.
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Old 03-19-2020, 10:51 AM   #520 (permalink)
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Popular misconceptions about aerodynamics of flying things. Not to worry because I cant argue your vehicle aero.

Vehicle aero and aircraft aero are related but not exactly similar

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