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All Forums >> RC Airplanes >> Aerodynamics >> Wing tapers - Pro's/cons of different configurations of aerobatic designs?
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Wing tapers - Pro's/cons of different configurations of... - 9/1/2003 9:56:07 AM   
wigglesticks


 

Posts: 2
Joined: 8/27/2003
From: Surrey, BC, CANADA
Status: offline 		Anybody know in what ways the different wing taper configurations affect performance in aerobatic designs?

For example, how does the Giles configuration, with a tapered leading edge, compare with an Edge, with a tapered trailing edge, or an Extra with the double taper configuration?

Do any of these designs better lend themselves to perform harriers or hovers, or others better for spins/rolls, etc.?
       Post #: 1

Wing tapers - Pro's/cons of different configurations of... - 9/1/2003 8:45:53 PM   
KenLitko


 

Posts: 243
Joined: 1/3/2003
From: Crown Point, IN,
Status: offline 		wigglesticks,

I think you are confusing taper and sweep. Taper is the relation of tip chord to root chord:

Taper Ratio = Tip_Chord / Root_Chord

Wing sweep is the angle formed by the leading edge, measured positive if swept back (traditionally) and negative if swept forward.

It sounds like what you are describing is a combination of these two parameters.

Sweeping a wing improves stability, which is not necessarily a good thing for an aerobat.

Taper helps to reduce induced drag by allowing a designer to approximate an elliptical wing loading pattern... which, theoretically, has the lowest induced drag.

OTOH, a straight/untapered wing is the easiest to build.

_____________________________

Ken - http://www.litkoaero.com/
R/C Aircraft Laser Cutting and Design

(in reply to wigglesticks)
       Post #: 2

Wing tapers - Pro's/cons of different configurations of... - 9/1/2003 9:00:18 PM   
Deanoo



Posts: 90
Joined: 2/5/2003
From: Dubai, UNITED ARAB EMIRATES
Status: offline 		Hey wigglesticks,

I asked the exact same question a little while ago and here was my responces.

Click on the link below

http://www.rcuniverse.com/forum/tm.asp?m=1075759+design]

(in reply to wigglesticks)
       Post #: 3

Wing tapers - Pro's/cons of different configurations of... - 9/1/2003 10:17:42 PM   
wigglesticks


 

Posts: 2
Joined: 8/27/2003
From: Surrey, BC, CANADA
Status: offline 		KenLitko was absolutely right, I had my termilogy wrong - thanks for setting me straight.

Deanoo thanks for the link to your thread great discussion!

Perhaps some background explanation for the question. I had in the back of my mind been considering a giant scale project for some time. A fellow club member has kick started those planes when he made me such a great deal on a quadra 50 that I couldn't refuse. So now I am trying to pick a design for an aerobat.

I have been flying a 49" Giles 202 , with a 4c 65 Super Custom (or SC - a Chinese knock of of the O.S.) that I just absolutely love to fly. Here is a link to the manufacturer: http://www.cmpairplane.com/new_page_14.htm

However, discussions with some of the experts 3D flyers at the Club - http://www.rcfcbc.com/ - have resulted in recommendations for the Extra and the only real difference I could see was the wing design.

Deanoo's link suggested that the Giles had a tip stall problen - I have had no such problems - it will rock a bit - but won't snap over even if I try!

Anyway, my plans are to scratch build a plane and seeing as I already have a small plane I love, I am leaning towards just doubling the size of my current copy. I believe doubling the size will triple the wieght, which should put me in about 15 -16 lb's all in. Something the the Quadra's 4 hp should pull beautifuly.

What do you think, is it worth the effort to find plans for a large Extra or just scale up my Giles.

Thanks....

(in reply to wigglesticks)
       Post #: 4

Wing tapers - Pro's/cons of different configurations of... - 9/1/2003 10:43:20 PM   
KenLitko


 

Posts: 243
Joined: 1/3/2003
From: Crown Point, IN,
Status: offline 		Actually, doubling the size should about quadruple the weight (going with a strict length to volume relationship), but your mileage may vary.

As far as which plane... that's your call! Whichever one you can find -plans- for will be easier. If you have to scale it up yourself, there is a lot more work involved.

_____________________________

Ken - http://www.litkoaero.com/
R/C Aircraft Laser Cutting and Design

(in reply to wigglesticks)
       Post #: 5

Wing tapers - Pro's/cons of different configurations of... - 9/1/2003 11:11:52 PM   
LouW



Posts: 804
Joined: 1/1/2003
From: Moreland, GA, USA
Status: offline 		I followed Deanoo’s link to the previous discussion, and there are some good comments there regarding planform influence. It’s no accident that the vast majority of pattern airplanes use a swept back leading and straight trailing edge. Its because that configuration performs the graded maneuvers better, to gain more points. If AMA were to change the required maneuvers or the number of points awarded for the different maneuvers, the airplanes would change to provide the best performance of the revised maneuvers.

A wing design is a compromise between different criteria. For instance I doubt if the aerodynamic efficiency of a tapered planform (though real) is of any particular importance in an aerobatic airplane since it primarily effects fuel consumption. However the structural efficiency of the tapered wing is very real, especially in full scale structures. There is no one airplane that will do all maneuvers equally well. The particular maneuvers the airplane is being designed to perform will suggest the best approach to take. Though most designers are reluctant to admit it, they are also influenced to a degree by aesthetics.

As far as harriers, and hovers, There were a couple of full scale fighter designs in the 50’s that took off and landed on their tail and there might be some theoretical stuff in some old NACA reports. Since this flight regime is of no interest to full scale designers (except maybe some extreme air show pilots) there is not likely to be much in the way of actual data available. A lot of modelers are experimenting in this area and they may be able to suggest some things.

(in reply to wigglesticks)
       Post #: 6

Wing tapers - Pro's/cons of different configurations of... - 9/3/2003 3:33:14 AM   
Deanoo



Posts: 90
Joined: 2/5/2003
From: Dubai, UNITED ARAB EMIRATES
Status: offline 		Wigglesticks,

I am also in a similar situation and I have racked my head about which aircraft to build. I have heard a million (no joke) different opinions... and like Louw just said,

"There is no one airplane that will do all maneuvers equally well. The particular maneuvers the airplane is being designed to perform will suggest the best approach to take."

I have come to the conclusion that there is no real best airplane for anything. I reckon that you should build the plane that you think looks great. Keep it as light as you can and practice, practice, practice till you know your model as well as you can. If you crash it, build another one exactly the same and keep practicing. I have seen people do some amazing stuff with all different kinds of planes, but that is because they know their plan, not because everybody chooses one thing.

I personally dont like Extra's, purely because everyone I know flies them. It seems every manufacturer has an extra in thier line up. I LOVE the look of the giles 202 and because of that I am going to build one of them. Also I love fiberglass fuse aircraft because I cant cover for cr#p, but i cant find anyone that makes a giles with a fiberglass fuse. I have decided to to for a 96" model design ( http://www.modeldesign.com.au ) Extra and design a set of giles type wings to put on it. Unconventional, but I like it.

Better the devil you know.... go with the scaled up Giles... My opinion!!

(in reply to wigglesticks)
       Post #: 7

Wing tapers - Pro's/cons of different configurations of... - 9/5/2003 11:28:20 PM   
Cdallas2



Posts: 547
Joined: 2/7/2002
From: Kamloops, BC,
Status: offline 		Well here's my 2 cents regarding this subject.

In my research i've found that in an aerobatic design you have leading edge sweep to increase stability. This is done instead of dihedral so that it will act accordingly while inverted. Trailing edge sweep is incorporated to help with spin/ snap characteristics. That is why most F3A ships now use a double tapered planform since there are lots of snaps and spins in the latest schedules (and also the latest influx of biplanes).

From what I've gathered from the Giles is that the tip stall so much is because they use a very small tip chord which in turn will readily stall.

_____________________________

Help!!!! Help!!!! I'm Being Repressed!!!!

(in reply to wigglesticks)
       Post #: 8

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