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Building Tips and technical articles. => 1/2 A building. => Topic started by: Motorman on May 06, 2013, 07:53:25 PM
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Check out the plane called White Lightning.
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My Kwikee Skyfire is 250 sq.in. with an APC Wasp. Plenty od performance, but wing flutter problems if there is a breeze blowing (1/8" sheet wing).
Antone Kephart built a Baby Magician with 230 sq.in. Wing aNd it is too heavy for that engine. I plan to put on a .09 engine.
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I went to about 250 squares using 1/8" on a flapped model, but I'd be inclined to fit a vertical carbon spar in between the planks if I were to do it again.
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...There has to be a point of diminishing returns on lift v weight or carving the airfoil v cutting ribs. What's the optimum thickness and size for a balsa sheet stunt wing for a Cox TD .049 on 42' lines?
Thanks,
MM
Dick Sarpolis did a bunch of 1/8" sheet wing planes for Flying Models in the 24"-26" wingspan range mostly powered by a TD .049.
George
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Hi there all,
This is not 1/2a, but shows what can be done with a simple flat sheet wing. This is my 50" span inspired by "Imitation" flat plate stunter. These sorts of designs originated in South Australia many years ago, started by Frank Coombes, starting at 40" span and larger. Wing is from 6lb 1/4' sheet with two 1/4' x 1/2" spruce spars. Front spar extends to LG mounting area, rear spar is about 2/3rds as long. Centre section area over spars then has light glass cloth top and bottom. The wing does flex notably in flight but is no problem, is common for this type of model. They fly very well. The trick is light weight. This weighs 35oz with OS35S. A carved airfoil section is not required. I hope this may inspire you and others.
Gary
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I like it. #^
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You just described a Stuntman 23 from Goldberg.
Except the 3/16" wing.
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Gary-
That's really nice! By "fly very well", do you mean that they are good for flying all maneuvers in the pattern? Also, would you compare their quality or characteristics of performance to such a model with sectioned (built up) wings? I'm favorably surprised that this structure and thichness stands up at this size.
SK
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Running a TD on a tank like a wedge is a pain in the #@@. It never works correctly, at least not for me. It always has it's shortcomings and the constant fiddling to get it to work correctly is just wasted unused flying time. I would highly suggest to run it on bladder for beautiful consistent runs. A small tank can be made from a fluorescent T-8 light tube guard and balsa end caps. At this stage, the tank isn't relevant to height and can be placed anywhere. TD's on suction just aren't very happy. I've made various styles of tanks, however seeing that you have a lot of experience with speed engines and the likes of, your knowledge would be most helpful to running one with a hard tank. You need a narrow tank with the rear end pinched down to hold the fuel in that rear corner just like a coffin tank on a speed job. This not only keeps the fuel load at the pickup, it keeps the pickup inline with the fuel inlet of the TD spraybar. Moving the tank pickup outboard which is just what a wedge tank does has the fuel traveling outboard then inboard to the engine putting it in a automatic lean condition. If the tank could be designed to sit within the fuse and directly behind the engine, I feel it would give you far better results. Don't center the tank from side to side but favor the outboard side with your pickup. If not, design a narrow tank like I mentioned with the rear corner pinched in and try that. For as simple as a bladder tank is, it works extremely well . You always have the balloon slack tank which also works well. Ken
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Hi all,
in further regard to my sheet wing "imitation", here is some more information. Tom Dixon has plans in his modern section for "Classic Yardstick", by Leon Baird who was a member of our cl club in South Australia. To quote from his plans page "48 inch span sheet wing simple stunter stunter. excellent performer despite simplicity. A great practice/training model. Use a .20-.25 engine. (he was using an Enya 21cx with diesel conversion) Placed 4th at 1992 Aussie Nats in F2b. I saw this model fly in 1994 and was Amazed!"
Yes they can fly the full pattern (not by me as yet). I saw Leon fly his model and i was amazed as well. Some further tips: wing is also covered in polyspan. To avoid warping sheet wing do not use a shrinking dope! Wood is sealed and polyspan applied using nitro-cellulose lacquer thin 50/50 with lacquer thinners. fuselage is 3/8 core hollow in rear with 1/64" ply sides.
Here are a couple of photos of my first sheet wing stunter. It is made to the outlines of TF tutor (original kit size), OS25la power. Was a bit heavy but very easy to fly.
Hope this helps
Regards Gary
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Thanks much, Gary, for the comments. Real food for thought here. With your permission, I'd like to include a picture or two in our club newsletter.
SK
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Hi Serge,
Thanks for your kind comments. Please feel free to use any of the pictures in your newsletter.
Cheers Gary
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Sheet wing models can fly a clean full stunt pattern. The key is to get a low wing loading and lots of power so you can run long lines.
Dick Sarpolus has published a fleet of very capable models when you add .061 power and longer lines. I have his Corsair and it is a delight.
The Knights of the Round circle even has an event for such models, called Kwikee Stunt. It does require flying all the maneuvers. It has been thoroughly described in this forum, so you can get all the details with a search. (It may be Quikee, not the current spelling).
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When building a sheet wing model for 1/8" stock, is it a good idea to cover the wing with either fiberglass cloth or carbon veil?
Mike
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Carbon veil would be an excellent idea!
I had serious bending and flutter issues with the Skyfire. Had to add carbon strips top and bottom, then weights ahead ofthe wingtips.
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You are correct, but for several years, .049s were out of production, so we upped the size a smidgen and just run 1cc contests. We don't call them 1/2A.
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Here's a photo of my White Lightning from Bruce Feaver's design. It's my first all balsa 1/2A and has a TD 051, 3/4 oz tank, rattle can paint-which accounts for the 10.05 oz weight. Hope it flies. I like your solid wing planes Gary, particularly since learning to hate covering!
Steve Thornton
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That is a very nice looking plane. Good luck with the flying!
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Back in the fifties 'Red' Rhinehart built a flat plate stunter powered by an Atwood Wasp at 30" span. He called it his "experiment in variable dihedral"! No spars, no carbon, no silk. I followed his explicit directions using light but stiff pieces of C-Grain balsa. 20 years old, no warp! Jim Lee had one at VSC a while back from my FM plans.
W.