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Old Jan 07, 2002, 12:43 PM
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True Flaps (is there a easy way)


I have been thinking about ways that you could make "true" flaps for moderate sized (48" WS)RC planes. When I say true I mean someting like a fowler flap set up where the surface not only comes down but also extends aft of the trailing edge producing a more cambered airfoil shape. I think I had too many beers the other night and while I was trying to get to sleep I kept thinking about my new Pond Side with alerons and flaps. I have played with flaperons but do not like how they increase the potential to tip stall and the fact that you lose authority in the roll axis. Anyone THDT before?

Cheers,
Jim
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Old Jan 07, 2002, 12:52 PM
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I know its been done (not by me). You ought to post this in the Scale forum, I'd think you'd get a good answer from some of the pros there.

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Old Jan 07, 2002, 01:34 PM
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I was just the other day browsing thru some pics of how it was engineered. The only drawback was that there were control horns showing from below, but from the top, it looked completely scale - small price to pay for linkages and pivots vs. screws and drive shafts like the real thing! Don't ask me where I saw it, it may have been a magazine, on the web, anywhere.. it has been done, however, so as suggested, the scale guys may be able to help out..
..a
Old Jan 07, 2002, 03:24 PM
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True Fowler flaps are very difficult to implement on models, especially small ones like the Pondside. The sliding fits must be precise, and of low friction.
A Youngman type, where the flap swings down and aft is a bit more practical and easier to accomplish.
Old Jan 07, 2002, 03:26 PM
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This is a basic design I drew up for a 60Ē span Cessna 180 Iím planning, it would use a small flap servo in each wing and all the linkage is hidden. I donít know if the Pondslide wing is thick enough for it though.

Gary
Old Jan 08, 2002, 12:30 AM
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be sure to seal the gap or you could be in for a pretty wild ride

Matt
Penn State Aerospace '2000
Old Jan 08, 2002, 12:40 AM
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Matt,
Maybe I'm just ignorant, but wouldn't sealing the gap eliminate the intentional slot... and thereby make it an essentially conventional flap, as opposed to a quasi-Fowler flap?

rgds,
David
Old Jan 08, 2002, 12:47 AM
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You want the gap, thats what makes it work better.
Old Jan 08, 2002, 06:13 AM
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As far as being scale the DC-9 and 10 use a hinge point below the wing for their flap. But then they are inferior Douglas products
Old Jan 08, 2002, 12:23 PM
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On Gary's flap, I'd move the control horn onto the flap itself, to give some rigidity to the extended flap.
I'm completely another Kadet with flaps, this one a Mr. Mulligan look-alike, with totally concealed operation, using the Direct Aileron Driver type of motion...A wire bent at 45 degrees in the flap that pushes the flap up and down... the inner end is a nose-wheel control horn, pushed directly by a servo..
Like the one on my ideas page on the Earthlink site.
The external hinge does a good job of simulating a Fowler flap.
Old Jan 08, 2002, 01:04 PM
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Paul,

How important do you think it would be to round the corner of the flap portion in the transition from the front face to the upper surface? It seems to me that smoothing this transition would allow the air to flow through the slot and stick to the flap better. Any thoughts?

thanks,
David
Old Jan 08, 2002, 04:16 PM
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David, flaps are for drag for the most part. Finessing the fit when they're up is more important than when they're down.
Old Jan 08, 2002, 04:30 PM
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Thanks, Paul... I follow. Makes sense, especially if the flaps are being used mainly for landing. But regardless, there's no room for flaps in my little racers so I guess I don't need to worry about it.
Old Jan 08, 2002, 08:03 PM
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"Real" Flaps


The easiest flap to tack onto an existing wing is the split flap. Slicing the lower trailing edge skin out and replacing it with a ply flap is dead easy. Hinging is by hinge tape or covering material. For something as small as the Pondside, hard balsa would suffice. Use an elevator joiner/horn for control. Tex.


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