Author Topic: Wing shape changes vs flaps  (Read 4453 times)

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Offline wobblywalrus

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Wing shape changes vs flaps
« on: January 22, 2016, 09:58:57 AM »
This is an interesting article.  This concept will eventually be used for land speed vehicles.  Some clever builder will apply the concept to tail and fuselage shape.www.bbc.com/future/story/20160122-the-shape-of-wings-to-come

Offline hotrod

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Re: Wing shape changes vs flaps
« Reply #1 on: January 25, 2016, 09:21:45 PM »
Interesting article. Not likely that many racers will dabble much in that arena, but it does raise an interesting question.

Have you ever noticed how much some cars hoods flap around at speed? Well that is an adaptive surface and helps encourage flow separation.
Folks who have video showing body panels moving around a lot at speed might want to spend some time stiffening them up so you have a smooth surface that does not flex as much.

In flow testing glider wings, they found for lowest possible drag you wanted a wing surface that had a very smooth and gradual shape change with no ripples.
To get that highly uniform shape with no surface ripples they go to great lengths to fair in the surface with very long sanding blocks to get a highly uniform shape.

Something to think about if you are just a few hundredths shy of a record in your class.

Offline bbarn

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Re: Wing shape changes vs flaps
« Reply #2 on: January 26, 2016, 10:13:16 AM »
Bugs on the leading edge of a wing can reduce the aero effectiveness of the wing by up to 10%. The air becomes turbulent and separation begins at the leading edge. This means that smooth airflow is critical to reduced aero drag. Anything you do to smooth or control drag is helpful, the more you do the better.

Flopping or oil-canning body panels in a random fashion is a sign of changing pressure being applied. This is likely causing an aero oscillation which would be less than efficient as well. Simply making the panels stiff would solve the oscillation BUT maybe setting one panel in a lowered position is better aerodynamically while another higher is optimal. (i. e. stiffening the hood in the "down" position and the trunk in the "up" position)

Not sure how you would measure all the effects together but since we are talking tenths in some of these examples a good study may yield positive results.
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Re: Wing shape changes vs flaps
« Reply #3 on: February 09, 2016, 02:19:58 AM »
A slotted or Fowler flap is far superior to a smooth surface "morphed" flap.  So is a plain flap that is aerodynamically balanced at 27-32 degrees flap MAC.  On the Carbinliner, we use a plain flap because the flapped L/D ratio is not important below 450 mph on a car designed to go 550.  At 500-550, the wing is designed for the required downforce with the flap fully in trail; i.e. zero degrees of deflection.  At lower speeds the flap is deflected which results in higher negative lift coefficients which match the lower dynamic pressure (the multiple of which is flat downforce from 200-550 mph).  Yes, it's not as "efficient" at lower speeds.  It doesn't matter, the speed is lower so the flat plat drag times the dynamic pressure (D/q) is lower despite the flap deflection. 

The wing design is optimized for high speed, the flap creates traction at lower speeds for acceleration.  All commercial and business aircraft are designed this way with the wing designed for high speed and the flaps designed to provide greater lift at the expense of drag at low speed where drag matters less.

Offline Rex Schimmer

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Re: Wing shape changes vs flaps
« Reply #4 on: March 01, 2016, 01:28:37 PM »
I was just re-reading this post and ran across a comment from Brandon (bbarn), he said "Flopping or oil-canning body panels in a random fashion is a sign of changing pressure being applied. This is likely causing an aero oscillation which would be less than efficient as well. Simply making the panels stiff would solve the oscillation BUT maybe setting one panel in a lowered position is better aerodynamically while another higher is optimal. (i. e. stiffening the hood in the "down" position and the trunk in the "up" position) " In regard to Brandon's comment about aero oscillation it is very interesting to look into the rear window of a present day NASCAR racer and see the very extensive trust system that they have to support the rear window and stop it from aero oscillation. Pretty sure that what they are doing is probably a direct result of wind tunnel testing and for all of the work that they have done it is apparent that it is effective.

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Offline panic

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Re: Wing shape changes vs flaps
« Reply #5 on: March 01, 2016, 03:04:29 PM »
Ah yes - the wing warping vs. movable flap argument.
One of the earliest cases of "where the Supreme Court got it wrong": they decided that those 2 methods are the same, and that Curtiss violated Wright's patent.

So when you see remarks about Roe, Kelo, and Citizens - it's not new.

There is no safety net for the Constitution, and faith in the Court to perform this function is misplaced.

Offline SPARKY

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Re: Wing shape changes vs flaps
« Reply #6 on: March 02, 2016, 11:26:23 AM »
hear ye, hear ye, hear ye--- :cheers:
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