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High wing vs low wing - 12/8/2003 10:10 PM   
PAINLESS


 

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From: Los Alamos, NM, USA
Status: offline 		Can some one explain the advantage (aerodynamically) a high wing has over a low wing design?
In a slower class like 424 would it make any difference, everything else being equal?
Thanks

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RE: High wing vs low wing - 12/8/2003 11:31 PM   
willflyforfood



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Status: offline 		Iv'e always heard a high wing is faster in the turns because of the weight of the fuselage being pulled around instead of pushed,like putting weight on the end of a string instead of holding the weight in your hands,the string moves around faster and with more force than if the weight were in the center. This is what I have always been led to believe.Hope it helps,

Joey

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RE: High wing vs low wing - 12/9/2003 4:42 AM   
PAINLESS


 

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From: Los Alamos, NM, USA
Status: offline 		I believe your talking about centrifical force. I could see this making a plane more stable having the vertical cg below the wing not above it, like a trainer vs a P51. I don't see how it would be faster given two planes traveling the same speed and turning the same radius corner.

The reason I ask is, a few of us want to get back into racing after a 7 plus year lay off. Back then the low wing planes where popular ie, scat cat, dodger and intimidator and the high wings were just arriving on the scene.

I personally don't like the look of a high wing plane and prefer to race a low wing, unless there is a big advantage to the high wing. Maybe form does follow function.

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RE: High wing vs low wing - 12/9/2003 2:45 PM   
Pete Bergstrom


 

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Status: offline 		With the high wing aircraft you actually have about 20 square inches more of wing area (The portion of the wing generally covered by the fuselage in a low wing installation) to contribute to the lift going around a turn. Additionally, there is a little more interference drag on a low wing vs. a high wing airframe at the joint between the wing and the fuselage. The vertical CG being below the wing does contribute to the stability and adds a dihedral effect without actually having the dihedral.

Great question!

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RE: High wing vs low wing - 12/11/2003 4:59 PM   
Stand



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Status: offline 		I agree with Pete above. There is one other factor and that is that most of the low wing designs have some dihedral. The sharper the angle where the wing joins the fuse the greater the interference drag. That is, an angle of say 85 degrees is draggier than 90 degrees. In shoulder mounted high wing you have eliminated two drag points over a mid wing.

This is also why a V-tail has less drag; when mounted at the tail shoulder it has angles of 110 on top and 125 on both sides of the bottom.

Stan D.

< Message edited by Stand -- 12/11/2003 5:02:03 PM >

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RE: High wing vs low wing - 12/12/2003 4:32 AM   
PAINLESS


 

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Status: offline 		I could be wrong, but isn't lift created by air flowing over both upper and lower surfaces? If you eliminate one or the other the remaining surface is rendered ineffective. Like the area of wing blanked out by the fuselage reguardless of whether it is on top or bottom of the fuselage.

I have heard before that a high wing generates less drag at the fuse/wing joint than a low wing, it would be interesting to know just how much.

The Dodger had the area of the fuse just behind the wing pinched together, which was said to mimic wing fillets.

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RE: High wing vs low wing - 12/12/2003 4:43 PM   
Stand



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Status: offline 		To quote from John Dreese:
quote:

Lift comes from a combined effort of the wing being sucked upwards and
the wing pushing down on air. The effects are so intrinsically linked together that we
can measure the lift force by measuring only the surface pressures on the wing.


You can read this rather well done "primer" at:
Totally Free Airfoil Primer


Stan D.

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RE: High wing vs low wing - 12/12/2003 9:10 PM   
banktoturn



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quote:

ORIGINAL: PAINLESS

I could be wrong, but isn't lift created by air flowing over both upper and lower surfaces? If you eliminate one or the other the remaining surface is rendered ineffective. Like the area of wing blanked out by the fuselage reguardless of whether it is on top or bottom of the fuselage.

I have heard before that a high wing generates less drag at the fuse/wing joint than a low wing, it would be interesting to know just how much.

The Dodger had the area of the fuse just behind the wing pinched together, which was said to mimic wing fillets.


Painless,

It's true that lift comes from the pressure difference between the top and bottom surfaces, but it does intuitively seem to me that it could matter which surface you replaced with a fuselage. I think that the bottom surface of the fuselage would be better at generating the high pressure than the top surface of the fuselage would be at generating the low pressure. The flow, and resulting pressure, on the top surface of a wing can be quite dependent on the shape of the wing. The flow on the bottom is a little less sensitive. This is not a rigorous analysis, but it does make sense to me that it would be better to preserve the top surface of the wing than the bottom.

banktoturn

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RE: High wing vs low wing - 12/13/2003 8:08 PM   
DrewTelford


 

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Status: offline 		Another element is the drag associated with the landing gear being in close proximity to the wing on a low wing. If the LG is mounted to the bottom of the wing, it will inherently cause more drag than the way the LG is mounted on most high wing Q500's today, with the gear struts extending from the corners of the fuselage.

It would be hard to measure this difference without a windtunnel, but since we're talking theory, the 'gear factor' should make the high wing design better than the low wing.

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RE: High wing vs low wing - 12/13/2003 9:35 PM   
Larry F


 

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Status: offline 		Hello,
I worked for many years in the aerospace industry in airframe design, drag reduction and sub-sonic parasitic drag reduction. Although some of what has been said here is true, there is no substantial inherent difference between high and low wing designs. Both have their strengths and weaknesses A low wing conventional tail has far less drag across the fuselage and tail surface BEHIND the wing than a high wing. The high wing has less drag in the gear and fuselage area under the wing. There have been many studies and projects over the years to back this up. The one big problem is , it all changes over a given speed range.
From my own stand point, what ever you can fly the smoothest and feel most confident with will be the fastest for you.

Happy holidays,
Larry

< Message edited by Larry F -- 12/13/2003 9:36:54 PM >

_____________________________

never fast enough

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RE: High wing vs low wing - 12/14/2003 11:04 PM   
rjones


 

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From: Bellville, TX, USA
Status: offline 		have raced both high and low wing. high wing is more stable. it grooves better. low wing seems to hunt around. in the 424 class you probably will not notice the difference. there are several high wing arfs out there .

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RE: High wing vs low wing - 12/14/2003 11:05 PM   
rjones


 

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Status: offline 		have raced both high and low wing. high wing is more stable. it grooves better. low wing seems to hunt around. in the 424 class you probably will not notice the difference. there are several high wing arfs out there .

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RE: High wing vs low wing - 1/3/2005 8:51 PM   
bigtrev@xtra.co.nz


 

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Status: offline 		I reckon the high wing viper is a real nice aircraft to fly- very smooth , quick out of the turns and with the cg at 3inch goes real sweet. don't know too much low wing versus high wing.
trevor h, nz

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