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General control line discussion => Open Forum => Topic started by: Motorman on December 19, 2013, 09:24:54 PM
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It should be just fine. If you do anything to compensate, just make the wing a little longer.
Note that the guy on the right won the trophy in the front.
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You'll have no problem with that approach Motorman. As an example take a look at the Sig "Twister", no tips and it's a great flying design.
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Forerunner flies great with flat wing tips.
Joe
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Big Jim once said "wing tips don't fly"....they may, but it has always seemed to me that there was more opportunity to screw up the trim than any advantage we see....
Have fun!
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Do the wing tips help a stunter? I'm trying to design a plane that's very simple to build and wondering if I'll lose anything if the wing tip is just the last rib.
Or you could go for poorman's wintips: cut the last rib out of 3/4 sheet of balsa :)!
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Sneakers or hiking boots work better for flying for me than wingtips any day :),
So No wing tips for me either.
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Or you could go for poorman's wintips: cut the last rib out of 3/4 sheet of balsa :)!
Everybody's' copying me, that's pretty much exactly what you see in the picture above.
Brett
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Bob Hunt's Crossfire is another excellent flyer with essentially squared off tips, as is the ARF Score.
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Building Flite Streaks for combat we used the fuselage wing knockout for one slab wing tip and the made the other from 1/2" sheet.
Joe
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Al Rabe's profile Mustant has no wing tips.
Jim Hayes
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My old Sterling Mustang was 'sorta-scaled' to look like 'Jeannie', (previous life of the late 'Gallopin' Ghost')
I was 'up in the air' about tips, then got ahold of the 'Mike Hoerner' wing tip design as was on the real ship.
They had a concave lower airfoil, easily duplicated with 3/4" balsa...Nice finishing touch!
Didn't make a dit-of-a-shifference flying, though...Maybe it was the 'scale speed factor'. LOL
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How about an end plate style wing tip fence? You can claim that it attempts to reduce tip vortices and parasitic drag. It sure makes a KISS installation for adjustable leadouts.
Paul
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Well, let's play a little bit with words...
Where the wing ends, out from the fuselage, or whatever, is the wing tip.
The 'plan view' (from above) shape of the tip is what we're really talking about, right?
Theoretically, a Hoerner, or Flite Streak type of outward form, ending in more or less a small point at the TE, leads the wingtip vortex outboard a bit. The vortex forms from air flowing outward from "under" and wrapping around to the "over" surface because the wing is producing lift. Pressure "above" is less than pressure "under." The outward flow is only a fraction of the flow in the direction of flight...
A square-cut tip rib, or a pretty rounded elliptical tip,or a Hoerner-type don't seem to make a large difference for our models. Just do what you like to do for reasons of prettiness or easy building or whatever. Tip vortices ARE there, and spoil a bit of the lifting ability of the wing's area. Some worse, some less.
Tip plates large enough to prevent this rollover vortex, so I once heard, would need to be way large. Some even claimed they should be something like a disc with a diameter the same as the wingtip. NOT pretty! ...or practical...
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Or you could go for poorman's wintips: cut the last rib out of 3/4 sheet of balsa :)!
The Sig Twister gets by with 1/4" or 3/16" (I can't recall which -- I have some 15lb 3/16" that I'm trying to use up -- I used that).
It works fine. You do need some structural strength there so the covering doesn't bow it in -- just a regular wing rib won't hold up.
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perfect wood for the outboard wing tip ... not sure about the inboard.
Joe
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Tip plates large enough to prevent this rollover vortex, so I once heard, would need to be way large. Some even claimed they should be something like a disc with a diameter the same as the wingtip. NOT pretty! ...or practical...
We've learned more about this in recent years. Here's a summary:
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Wingtips produce drag, so we should choose a wingtip that reduces this. Or should we? I assume with the latest move to very large engines, drag may even be beneficial. Helps stop the speeding up when the nose points down.
Seriously, would someone chime in with some real aerodynamics here? If I were building a glider, I would go for a low drag wingtip. However for an F2b stunt design, WHAT is the drag requirement?
Andrew.
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Seriously, would someone chime in with some real aerodynamics here?
Stunt planes have evolved to have about the right amount of "induced" drag. If they need more, the easiest way to do it is to increase the span loading, the weight divided by wingspan. If they need less, decrease the span loading. Wingtip shape has a small effect, and the shapes that have the least drag have other deleterious aerodynamic effects. We aren't trying to minimize drag anyhow, so just pick a tip shape and adjust span loading to have the drag you want.
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Generally we do want to minimize penalties to climb though, don't we. I mean, we'd like not to lose speed when pitching up and climbing. Doesn't that indicate that reduction in induced drag is a good thing?
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What goes up must come down. A wing that speeds you up in the going-uphill part of a loop will speed you up in the coming-downhill part. As for wingovers and hourglasses, there's no induced drag to speak of going uphill after the first corner. We have controls on engines and motors now that vary power as needed. It's easier than varying induced drag as needed with moving winglets or something. The main problem with too little drag comes when wind adds energy to the airplane. Consecutive loops get pretty difficult at high Mach numbers. Maybe the optimal plan would be to have a lower aspect ratio wing for windy days.
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I do see that. Why not though encourage wing effectiveness pusuant to the stunter's task of efficient change of direction and speed maintenance uphill, and rely on ample parasite drag and thrust adjustment to control the downhill side of things? Lower A/R with taper for those days.
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Maybe the optimal plan would be to have a lower aspect ratio wing for windy days.
Or removable wing tips that lower the induced drag when on -- then on windy days you could take 'em off.
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Recheck my post #14...
If I understand it, a "pure" Hoerner-type tip is intended only for right-side-up conditions. The partial "scroll" towards the rear of the tip trailing edge opposes the roll-over from the higher pressure physical bottom surface to the lower pressure physical top surface. It does not work equally for inverted flight or 'outside' lift conditions.
The Flite Streak-type tips do what they can equally (or similarly) for both upright and inverted conditions. Clearly, if the model never met an outside-lifting condition, the effectiveness could be improved, at least theoretically.
And, as Howard mentioned, the effects don't seem to be very significant - there's so much else involved...