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General control line discussion => Open Forum => Topic started by: Motorman on December 26, 2013, 04:08:00 PM
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Yup, big difference between straight line wind and turbulance. In bad turbulance, sometimes nothing helps! I think we have all lost a model or at least pancaked one in some turbulance. When it was blowing right down the runway at the SIG contest, I could deal with that, but if it came across the hangers and buildings, I usually passed on those rounds! Anyone that had flown at Buder Park when the wind is out of the north knows what I'm talking about, and I'm sure there are other flying sites that have the same reputation. The old site in Topeka is another one that comes to mind. I saw the article but have yet to read it. Hope to do that tonight.
Type at you later,
Dan McEntee
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The Banshee should handle straight line wind OK. The big thing with straight line wind is placing the manuever correctly, and a high RPM/flat prop pitch set up helps a lot also in reducing the tendency for the airplane to whip up, or get remarkably faster in each of successive loops.
In turbulance, (and I haven't read Bob's article yet to see what he mentions on the subject,) I would want a model that is basically aerodynamicly clean as possible, and turns well in order to fly through the garbage as cleanly as possible, and to turn quickly to get you out of the trouble it may put you in. A Banshee should do as well and about any other airplane, especially with some of the moment modifications you can read about on the forums. If I were going to pick a model to fly in turbulance, I might pick one without flaps, just to eliminate the potential loss of speed in corners that you have to over come any way, and may be made worse by bubbley air. Flaps increase lift, but also increase drag and that is your enemy in turbulanace, in my opinion.
Just a thought. Like I said, I haven't read Bob's article yet.
Type at you later,
Dan McEntee
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I also haven't read Bob's article yet but would say that any profile would be at some serious disadvantage in turbulance due to potential flexability in the fuselage aft of the wing. Turbulance tends to really show up any weaknesses in stiffness of the airframe because the air is not consistent and usually has a swirling and twisting flow to it. This inconsistent flow really tests the directional stability of any airframe and that would tend to say the stiffer the better. Profiles simply are not very stiff as compared to the "box" structure of a built up fuselage. Flaps also should be as stiff as possible to increase directional stability and tracking and something like the Banshee has fairly thin flaps and lack the stiffness of thicker flaps.
My personal tests flying in turbulance with several different airplanes of significantly different designs confirmed my belief that stiffer is better. Of those several I tested my GeoXL was hands down the best I've had or flown in turbulent conditions. Relatively thin airfoil, large fuselage with large side area and 29% Stab and Elevator area. Very thick Geodetic Stab with carbon in leading and trailing edges and some ribs. Very stiff flaps with geodetic construction and carbon leading edge, and covered with 3/32 balsa and two layers of .5 oz glass cloth. Relatively large wing (730 sq in) area with relatively thin airfoil, Geodetic construction, and light all up weight at 54oz without fuel.
This airplane was powered with a Belko Long Shaft .56 which gave very good power but certainly not in the realm of a PA 65 or RO Jett 65. It did regulate very well and I think that is probably more important than just excessive power (although both is best).
This airplane was amazing to fly in turbulance. In fact it flew almost as well in turbulance as in calm air. I've had several other exceptionally good flying airplanes under normal conditions and even a couple that handled strong straight wind very well but none that flew as well in turbulent conditions as that GeoXL. None of the others could compare with the stiffness of the airframe of that one either.
I'm attempting to build a different airframe now with those same characteristics. A Whitely Shoestring, with very modified construction and areas. It will be powered with a RO Jett 67 on a pipe. It will also be light and very stiff, with a 29% Stab/ elevator area and relatively large Fuselage/Fin area.
Gotta' go read Bob's article now to see what he thinks, but I'll be surprised if he doesn't agree in principle with what I've said. If not well Dang...I'm gonna try it anyway. LL~ LL~
Randy Cuberly
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I have read Bob's article and he has a lot o f good points. No more than I fly I don't worry unless the plane comes in at me. Dan has flown at the old Topeka KS Gage park circle on the pavement. He should try the grass circle, if it was still there when the wind was from the west. Now he has flown at our new site at 21st & Urish. Yes it is on a slope but the circle is flat.
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Something Bob didn't mention...I'd think wing taper, especially more elliptical chord distributions, would be significant advantages in turbulence. Also, I'd fly faster and/or heavier. You need the momentum and upwind CF.
SK
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Even though it sounds logical I definitely do not agree with the heavy airplane theory for turbulent conditions. I've had both heavy and light airplanes in turbulent conditions that we have often here in Tucson whenever the wind blows from the North.
My 74 oz Trivial Pursuit was all but unflyable it very turbulent conditions but flew very well in straight wind and normal conditions as well as dead air. My GeoXL which as mentioned before was very light at 54 oz (730 sq in wing) but flew very well in turbulent air and tracked good even when the air caused severe buffetting.
I've flown heavy airplanes that were well trimmed but not predictable in turbulent conditions.
When the weight and momentum is moves it's just that much harder to stop!
My experience has been that light (to a point), is better!
Randy Cuberly
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I see your point, Randy. I was just thinking of the huge Nats winds a few years ago, when some upwind legs couldn't be completed without a lot of back-pedaling.
SK
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I see your point, Randy. I was just thinking of the huge Nats winds a few years ago, when some upwind legs couldn't be completed without a lot of back-pedaling.
SK
Hi Serge. I understand your position and certainly didn't mean to be disrespectful of what you stated...as I said it is a very logical assumption. I simply wanted to relate my personal experiences with my airplanes.
Hig winds that are reasonably steady are a somewhat different problem. My solution to those is usually to chicken out and not fly... LL~ LL~
Randy Cuberly
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So far, I've been too dumb to do that. Ha! I'm fixing another one.