RE: Design for Windy conditions  
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All Forums >> RC Airplanes >> Aerodynamics >> RE: Design for Windy conditions
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RE: Design for Windy conditions - 7/12/2008 5:43:51 AM   
victorzamora


 

Posts: 598
Joined: 10/16/2006
From: Mt. Airy, NC, USA
Status: offline 		Exactly....AIRSPEED needs to be constant when you land. If your plane lands at 20mph with no wind, and you've got a 10mph tail wind, you'd better be landing at least 30mph relative to you. If the same plane lands with a 10mph headwind, you can land at 10mph ground speed. While it seems like the plane is landing at different speeds to YOU, the plane feels no different under either circumstance.

Aerodynamic factors to be considered boil down to density. A very dense plane will have less side-area to weight ratio than a less dense plane. All other variables being equal, the denser plane would have less side area than a less dense plane. If you have a Sig Wonder that weighs 3lbs and a Bird of Time that weighs 3lbs, the Wonder is denser and therefore will be less tossed around by the wind. Also, if you have a Wonder that weighs 1lb and one that weighs 3lbs, the wind would have the same area to influence less weight. It can be simplified as a normal transfer of momentum, and the case should hold up fairly well.

(in reply to lnewqban)
       Post #: 26

RE: Design for Windy conditions - 7/15/2008 7:57:01 PM   
franciscan


 

Posts: 70
Joined: 11/27/2002
From: Exeter, UNITED KINGDOM
Status: offline 		I have just come back from flying in a strongish wind (20mph or thereabouts), using a converted oldtimer(super 60) now using a flat semi-symetrical wing. It will cope ok with a strong wind in a constant direction, but is a handfull when the wind varies and gusts. The problem in varing winds is the plane tends to weathercock into wind at slow speeds due to its large area at the rear. Today the wind swung almost 90 deg on late finals and I ended up with a plane sliding very quickly towards me. Not very nice!!!!
Prior to this the Super 60 had a flat bottom aerofoil and dihederal and lighter wing loading and would not cope with gusting wind very well at all. It has improved dramatically using a semi symetrical wing and ailerons.
My friend flies with me and uses a patern low wing a/c with a high wing loading which just slices through the air with no apparent problem from gusts or wind direction changes. Need I say more? I cannot wait to finish my Kwik Fly Mk 111 and join him.

(in reply to subtleguru)
       Post #: 27

RE: Design for Windy conditions - 8/15/2008 9:18:29 PM   
canardlover



Posts: 257
Joined: 8/16/2002
From: Sodertalje, SWEDEN
Status: offline 		I have seen articles from Don Sobbe in RCM many years back stating that a forward swept wing will make the plane much less sensitive to cross-winds than ordinary wings. My first FSW is still in the shop so I cannot yet say from own experience....hope this helps...Cheers/Harald

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RE: Design for Windy conditions - 8/18/2008 6:56:56 PM   
chuck993


 

Posts: 347
Joined: 1/17/2007
From: Virginia Beach, VA, USA
Status: offline 		I fly an Ultra Stick 60 in windy crosswind conditions and it flys great, what explains that if not the airplane design?

(in reply to canardlover)
       Post #: 29

RE: Design for Windy conditions - 8/31/2008 10:00:04 PM   
DwightMann


 

Posts: 55
Joined: 9/14/2004
From: Mohave Valley, AZ, USA
Status: offline 		lnewqban and dick Hanson put it well.
Da Rock, the reason that a light aircraft will handle the gusts better than a blimp is the airspeed of each.
In a steady wind, the plane is flying with the air mass and when flying in coordinated flight the air is ALWAYS from straight ahead. Tie a ribbon (like for combat) to your plane and it will show the direction of the relative wind is always from the front. The plane might appear to weathervane, but that is only because the flight path is the sum of the aircraft velocity (airspeed and direction) and the wind velocity ( the higher the planes airspeed, the less affect the wind has on the equation).
If there is a crosswind on landing, the plane must head into the wind, when adding that vector to the wind, our path is parallel to the runway.
When dealing with gusts, the affect of the gust is inversely proportional the the airspeed of the plane. A 10mph change in wind will have a huge affect if the plane is only going 20mph, but will be barely noticable is the plane is going 200mph.

< Message edited by DwightMann -- 8/31/2008 10:06:14 PM >

(in reply to lnewqban)
       Post #: 30

RE: Design for Windy conditions - 9/21/2008 6:25:22 PM   
jnhiller


 

Posts: 4
Joined: 7/11/2003
From: Spokane, WA, USA
Status: offline 		Interesting discussion. In addition to flying pattern I fly a high wing scale airplane relatively slowly and agree with Dick Hanson that flying in the wind is mostly technique and pilot expectation. If the flight path needs to be relative to the ground than a light high powered airplane is most helpful.
To get a real feel for the full effect of flying in the wind I set the airplane in a shallow bank (20-30 Degrees) and fly a constant rate 360 degree turn observing the drift down wind. The flight path relative to the ground isn't even close to round and the airplane handles it fine.
The derided downwind turn after takeoff, often with a high bank angle can be a real problem with low powered, heavy and slow airplanes.
I could go on but the easiest / cheapest way to gain a full understanding of flying in the wind is with a non-powered glider.
Jim

(in reply to lnewqban)
       Post #: 31

RE: Design for Windy conditions - 9/22/2008 4:55:02 AM   
DwightMann


 

Posts: 55
Joined: 9/14/2004
From: Mohave Valley, AZ, USA
Status: offline
jnhiller is right on. My first success flying was with slope gliders. Those planes depend on the wide for power, we learn to like it. By the time I got to power planes, the wind was no problem.
Besides being inexpensive, gliders are less hassle than anything I have tried.


(in reply to jnhiller)
       Post #: 32

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