Wingtip Design...Will these work??? Come on engin

Here is a pic of the Dago Red. I flat out stole this pic off another thread...thanks! I have often wondered if flared tips like these would be beneficial to the stunter. What do you all think??

I know that stablet give the elevators more power. Maybe tips like these would give the wing more lifting power at low speeds???

Doug,

I don't really know, but my modified Twister is going to have something similar on the tips in an experimental attempt to help control wake vortices. Of course it will be removable if it doesn't work or makes the vortices worse.

I'll take a WAG before the aero experts get to this one. I'm thinking the stablets on the Bear, etc, reduce spanwise flow and slightly increase the amount of air forced over the elevator as opposed to spilling off. The winglets on the P-51 there, and many modern jetliners are for reduction of the tip vortices primarily for drag reduction (although on heavy jets it probably also reduces the amount of small planes battered by wake turbulence) I'm not sure we need drag reduction for stunt, but wingtip vortices are a pain in dead air. It is possible, then, that besides looking cool they might actually have some benefit under certain conditions. Problem is they would probably just beg to be broken off getting in and out of the car....

Steve,

Not if there made out of 1/16 plywood like mine are going to be.

As my old professor at MIT said, if you are going to add surface area, put it in the wing, not tip plates. Tip plates on crop dusters are good because those planes are span - limited by the need to maneuver in tight places. Tiplets on jets work ONLY at cruise speed. They hinder performance everywhere else.

We fly at many different speeds and angles of attack. Can't tune the rascals to handle that.

For stunt, good 'ole George got it right. The Flite Streak has the most efficient tips you can get. Check Hoerner's book on drag.

I can't imagine it would help both upright and inverted flying. Still, it's a cool enough idea someone needs to do it. Quite possibly, it would have a neutral effect on most of our ships.

Larry,

Drag is not why i'm using them. An attempt to manage or change tip vortices is the object of my usage. I already know about the swept tip and drag - it does have an effect on vortices to. I'm trying to get some sort of control using (hopefully) a tiny bit simpler method.
Ummm, aren't models limited in span too?

Actually, we use far lower aspect ratios than would generate the optimum lift and minimum concentrated vortices. The problem is that stability and control are the big issues in stunt, not maximum lift! Those who have built LOTS of different designs tell us that the high aspect ratio models are really hard to trim.

As such, perhaps you do have something going for you. One other consideration is that any right angle intersection like the one between the wing and tip plate is a nasty source of additional drag. Or are you planning to do sculpted tips? If so, do they go up, down or both?

Larry,

Both top and bottom but unfortunatly not sclptured.
At least they will be removable if they are of no help or are a hinderance.

LAST EDITED ON Dec-19-03 AT 10:47 PM (CST)
 
>>Those who have built LOTS of different designs tell us that the high aspect ratio models are really hard to trim.<<

Being one of those that has built many, many high aspect ratio stunters, I'll say they are not hard to trim, just hard to keep in trim with changing conditions. And absolute death in very turbulent conditions...unless of course you really like looking at the top of your wing during square corners. <grin> Really rather nice in good conditions.

Randy Powell

Edit: wish I could spell

>For stunt, good 'ole George got it right. The Flite Streak has the most efficient tips you can
>get.

There is more than one way to manage the tip vortices. The swept tip is the simplest, but there is an optimum ratio of tip span to chord (or is it wing span?), requiring a greater tip span than the FS has. Unfortunately, I cannot remember where I found the data on this. I also wonder whether there might be an advantage in making the top and bottom of such tips concave (symmetrical 'Hoerner' tip?).

I think in most instances, it is advantageous to get the best L/D in turns, without having to go to high aspect ratios, although I like to play with high-A/R design. Wind and trimming, as mentioned below are reasons to explore ways of getting high span efficiency without actually having to increase the span. There is some neat NASA stuff out there. See also the Stanford Aircraft Aerondynamics and Design Group site:

http://aero.stanford.edu/

and follow appropriate links.

Regarding Doug's original question, the asymmetry wouldn't help, but as others have hinted, some sort of tip treatment may be advantageous. Just make sure it is biased in favor of reducing induced drag at maneuvering aoa's, rather than making the plane more efficient in level flight. FWIW.

SK

I have been thinking on this one. I dont think this tip would hurt inverted. The tip in this picture is not a lift producing device but a vortex killer. It will kill vorticies inverted or upright.

I am thinking of trying this. Mine will be molded to shape. Just adding tip plates will be more like fences and I have tried a fence on my high ar wing and it acted like a more like a bunch of tip weight and other funny things.

I find trimming the high ar wing not any harder than the low ones.

an old stunt news had a guy with some wing tips like that, they were not real big, i think it was like a banshee or a twister, i know that isnt a whole lot of help but i think it was around the 95-97 time frame when the pic was in the magazine.

sorry that isnt a ton of help but i look at them all the time even the old ones and so if i run across it maybe you can call the dude or email him or something

other than that, i may have to get into some cad myself

i took it in college along with CNC stuff but have forgotten most of it.

Doug.

That plane fly's in a circle when racing. And I ..........GEE maybe you got something.
It's just like when I made my stunter I made the Stab Shorter on the outside of the circle. I got that info from the RENO RACEING WEB SITE two years ago. Divid Fitz and I talked about it.

Scott(I like IT)Riese:)

LAST EDITED ON Dec-19-03 AT 11:01 PM (CST)
 
Doug,

What's high? My lowest High AR competition plane in recent years was 7.2 to 1. I actually built one (to fly in contests) that was 9.5 to 1. I also had a very experimental profile job that is 12 to 1 and flapless. That was, ah interesting.

These things will drive you nuts. They are like the Shoestring with the OSFP 35 I flew last summer. The engine would run great just often enough to keep me messing with it. Same for very high AR planes. They do some things so incredibly well that it makes you want to overlook the things they do really poorly. I built ten of these things trying to come up with a formula that would at least moderate the things that drove me up the wall. Seemed every time I made something better, something else got worse. Further development is on hold till I figure a couple of things out...if I ever do. Maybe I'll have an Epiphany.

Fun stuff, I'll tell ya.

>I have been thinking on this one. I dont think this tip
>would hurt inverted. The tip in this picture is not a lift
>producing device but a vortex killer. It will kill
>vorticies inverted or upright.

It'd kill vortices in one direction but not the other. Note the shape isn't symmetrical. Vortices when upright go the opposite way of vortices when inverted, since air from the high pressure underneath spills over the tip to the low pressure above. Something that kills the vortex is supposed to block or oppose this airflow, and the sculpted tip fences are designed to force the air to rotate in the opposite direction, thus cancelling out the vortex. Turn the wing upside down and you might actually be adding to the problem.

Golly, Iskandar, don't discourage Doug. Try to get him to put tabs on his flaps, too.

No Doug,

That tip is shaped to smooth the vortex from the high pressure area under the wing into a smooth drag reduced vortex as the higher pressure air rolls from under the wing into a smoother vortex. It is shaped only for upright flight. It wouldn't work inverted, in fact, it would probably have an opposite effect.

Al,

The wing in the pic is not symetrical so what you are saying holds true all the way. However we have fully symetrical wings, well alot of do... So if it were to fly good upright it should fly well inverted being that the wing is fully symetrical. The tip acts the same since the lifting properties are not changed when the wing is flipped over...????

Doug,

Probably...until you deflect the flaps.

Doug,
Unfortunately, there is high(er)pressure under the symmetrical wing at all times, upright or inverted, otherwise the model wouldn't fly - something has to support the weight, that means that the wing is flying at a tiny angle of incidence - ie leading edge further from the ground than the trailing edge. There is only one height(in level flight) where the wing flies at absolutely zero incidence.

Now if you coupled the tip configuration to the controls...that would be a different story.

Someone mentioned tip plates on ag aircraft - these are often used to modify the spray pattern, usually to increase swath width.

>Now if you coupled the tip configuration to the
>controls...that would be a different story.

Wow.. there's an idea... I'd love to see the linkage for this! Probably a pair of pushrods attached to the bellcrank arms..

Doug-

Your idea will still operate asymmetrically. Because as others have noted, symmetrical wings, like cambered sections, have air trying to round the tips from bottom (high pressure) to top (low pressure), thus producing vortices. At best, this shape might shape the vortices upright, and minimally inhibit their formation inverted. I think that the net effect would be minimal (inconsequential), but it might look nice

However, as I hinted above, there ARE other ways to manage tip vortices symmetrically. The Stanford site contains one (and other more complicated ideas that might be adaptable), and there are some interesting patented ideas on the USPTA site. I sketched a really radical design just last week using a NASA (Ames)-researched idea and thought of a couple more such tip ideas today. I think that this is a place for legitimate, potentially profitable experimentation, and I encourage you to try some things. Profitable approaches probably include those that inhibit large vortex formation, split up vortices, or re-use them to create more lift or do other useful work, like energising and re-attaching boundary layers. Unfortunately, most effective new design applications may not be judged "attractive".

What works and does not work at our Reynolds numbers, I don't even know. Heck, I can't even build my first experimental wing without a warp. You're the man! ...Well - you, Howard, Randy, and...

SK

I used to put flat tips on the combat ships- cut the tip at about a 15 degree angle, swept back, and leave 'em flat. The idea being that in maneuvers the high pressure on the flat face of the tip will help keep the higher pressure air on the bottom of the wing from spilling around the tips. The planes flew just fine. In fact the flat tip seemed to help stability in maneuvers. On the minus side, it was draggy, and the tips were easy to damage in handling. Plus, you couldn't stand a wing up on the tip without it falling over or cracking the wood.

>On the minus side, it was draggy, and the tips were easy to damage >in handling. Plus, you couldn't stand a wing up on the tip without >it falling over or cracking the wood.

Interesting, on a stunt ship a little draggy could be good, also don't know anybody that would stand a stunt ship on it's wing tip. I am thinking I have seen a stunt ship with wing tips like I think you are describing.

LAST EDITED ON Dec-20-03 AT 05:19 PM (CST)
 
"I am thinking I have seen a stunt ship with wing tips like I think you are describing."

Bob, you must be thinking of the Buccaneer. Don't you have a Buccaneer? Scott Crichton brought out a stock CL'd SIG FAZER to one of our Poker Hand Fun-Flys, and flew it with 1/2a combat streamers attached to each tip. Can you say HUGE tip vortex? Especially when the monster flaps were deployed. PW was seen observing this with some interest. Steve

Tip plates increase lift and drag. the Mustang plates are designed to separate the vortex off of the end of the wing,cleanly, so that the air doesnt roll up towards the center of the wing, bringing a lot of drag. IMHO.
A tip plated 3/1 AR plane could make the about the same lift as about a 5/1 plane without the gust or warp sensitivty.
I have done a lot of experimenting with tip plates , from full scale race cars(Trans AM, and dirt modifieds) to hand launch gliders.
Add small ( each side = to chord) triangle shape tip plates to your glider. The Cg will have to move to the rear and the dihedral will be less effective due to less loss over the tips. You also might see 2-10 sec on 1 min still air time. Business cards work well for trials:)
Your results will vary... MM

And the big idea was to REDUCE drag from the tip vortices.. so in the end one doesn't gain anything.

On the other hand, if it really does reduce induced drag in hard turns, but adds pofile drag in the straights.. that might be beneficial for Stunt..