wing tips!
 

hello. I know that the edges on the flat end of wing is bad. but why most of 3D planes don't have it? I mean this rounded edges.

RE: wing tips!
 

Not all 3d planes wingtips are like that. There are many 3D planes that i know that they are just flat.

LeBlanc

RE: wing tips!
 

For medium to high speed cruise, wingtip shape is very important, as the loss of lift can be substantial.

I think on small (RC) sized airplanes ( other than sailplanes and even then the significance is minimal I bet ), the amount of lift lost to the wingtip vortice is small and simplicity in design wins vs the tradeoff in aerodynamic performance.

Anyone want to make that more technical?

Chip

RE: wing tips!
 

I mean this: does flat edges help plane at knife edge? I think a little yeas

RE: wing tips!
 

A flat edge wing tip won't help the knife edge, but a flat plate will. The tip plates will help increase efficiency of the wing, and will help in knife edge to the extent that they increase side area. As for 3D flying and wing tips, it's pretty simple. Wing loading on these models is so low that anything fancy on the wing tip adds absolutely nothing to performance. The only benefit to a contoured or even a t/2 wing tip shape is purely aesthetic, which for some, may be reason enough to spend the time. I was actually considering adding some shaped blocks to the funtana 90 to make it look more like a scale airplane. The resulting performance differences would be marginal, and would go both ways. I would get a slightly better glide, due to the increased span, (2.5" ), but the roll rate may suffer for the same reason.

That's all I got to say about that.

RE: wing tips!
 

I know that flat wing tips help mitigate wingrock in some cases with elevators and harrier maneuvers.

RE: wing tips!
 

Are you saying that because you know first hand? Or are you making your statement based on what someone else said? If it's true, then I will definitely leave my wings alone, because they already rock too much. Also, it would then make more sense why the 3d models have flat tips more often than not, not just for economic reasons.

RE: wing tips!
 

Yes. Flat tips do no tipstall as easily as rounded tips. As a matter of fact quite a few people have been known to remove the wingtips off of their U CAN DOs and other similar planes to make them 3D better. I did not do it to mine, but I did not keep my U CAN DOs for long before I sold or gave them away.

Notice all the Edges, Extras, Yaks, etc... they all have blunt wingtips.

RE: wing tips!
 

Several years ago I ran some tests on wing tips with a friend of mine. He had built a makeshift wind tunnel and we used a wing with replaceable tips, We had thread CA'ed to the wing to check for out flow which would indicate the size of the vortex. The results agreed with my flying experience.

A big Round wing tip like on many pre-WW II planes was the worst. The Stick style was next. A rounded block was better. End plates were the best with flat wing ends coming in second best. Other than an end plate, the more you put out there, the worse it gets. Leave them square and flat. End plates will increase your roll rate and decrease your stall and landing speed.

RE: wing tips!
 

It rolls much faster without wingtips.

RE: wing tips!
 

How does your experimental data in a wind tunnel relate to wing planform? It is a known fact that the elliptical wing planform, as on a spitfire, gives the best spanwise lift distribution, and thus, the most efficient wing design as relating to overall lift and drag performance. I will agree with you about wing tip vortices, but flat wing tips are draggy compared to a sculpted aerodynamic shape. A simple tuft test will show you relative airflow, and that's all. Unless your models were mounted to a balance that was able to read minute differences in lift and drag, your assumption may be a little premature. I will qualify my statements by saying that while all airplanes fly, comaring models to full scale aircraft is like the apples and oranges thing again. It all has to do with reynolds numbers and things that I can't explain in a short reply. I can see how the lack of a wing tip may help in wing rock during harriers and such. It's just a matter of getting dirty tubulent flow on the wing tips earlier, and being able to maintain that condition throughout the maneuver. A more efficient wing tip won't want to give up quite as easily, and may be more prone to the effects of sideslip and other anomalies of the air that we don't normally think about.

RE: wing tips!
 

You are speaking of the world famous YNOT wing tip mod.

I don't know a dam thing about wind tunnels or calculating lift, however I know 3D.

The tips are great for stability and you don't want the plane more stable for 3D.

On the thick wing type planes, 3D/fun fly/profile, the tips make a huge difference. With them removed, the plane does not couple so much in knife edge and rolls faster.. (Hype, Flip, UCD, Harrier, Madness, Prozac, MOJO, Hovering Cobra, Switch Blade, Kat's, ect)

On the scale aerobatic planes it does not seem to make a difference either way. (Extra, Edge, Cap, Funtana, Vision. etc)

I figured it out on a Madness and on every other thick wing 3D plane I have owned since, I have removed the wing tips and found the exact same thing. On a couple of Flips, I left the ailerons the same and just removed the wing tip, so the aileron extended past the wing tip, funny looking, stupid roll rate.

Here are a couple of links that this is talked about. One is 4 years old.

http://www.rcuniverse.com/forum/fb.a...3&key=wingtips

http://www.rcuniverse.com/forum/fb.a...7&key=wingtips

http://www.rcuniverse.com/forum/fb.a...8&key=wingtips

Some pics of 3D friendly wing tip pics.

RE: wing tips!
 

so we can say so:

P.S. wingtips for pattern and no wingtips for 3D yeap?

wingtips more stabile and more speed, but less roll rate, and less knife edge performance.
so i'm not going to install wintips on my giles 202. it's 1600mm wingspan and airfoil thikness is 18%.


if mixed up something, plz tell me.

RE: wing tips!
 

In the second half of WWII, UK Spitfire pilots used to cut off about 18" off each wingtip, and gave the Spitfire a flat edge to each wing tip. They did this to improve roll rate.

As the war progressed, and especially after the Normandy invasions, the role of the Spitfire changed from Air to Air Fighter, to Ground Attack. They wanted the increased roll rate for low level flying, and were willing to accept a lower ceiling that followed from the lower efficiency from the wing.

RE: wing tips!
 

Hey,

Right now my Funtana 40 rocks wing pretty bad during harrier. I am thinking about installing a end plate on each wing tip, like the good old Hots. From what I gathered, the wing tip plate help reduce the wing tip trailing vortices by reducing the higher pressure air below the wing from migrating to the lower pressure air above the wing. Would it help reduce wing rock? Chip Hyde points out that wing rock is caused by wing tip stalling and regaing lift incessantly.

It's said above that it decreases stall speed. Care to explain?

I think before committing my plane to this config, I will try to attach the plates using screws instead of glue. Just how big should I make this endplate? 1/2" all the way around?

RE: wing tips!
 

I think 5 cm will go. dunno nothing about other.

RE: wing tips!
 

5 cm?!!! That's how thick the wing is. Man, 5 cm all around will be some serious looking tips.

RE: wing tips!
 

As I recall, the elliptical wing planform is not the whole answer. This is off the top of my head without any research.

The Spitfire, to my recollation also had an elliptical cross section such that the pressure distribution reduced or stopped the outflow. the problem with this is the great difficulty of construction with all the compound curves in the wing.

What I am saying is that you just can't use an elliptical plan form, you must also have an elliptical spar for the full effect. Try covering this with aluminum. This is one reason why this type wing wasn't extensively used.

An improved version of the same basic airframe design was the Spiteful which had a straight tapered, laminar flow wing.

RE: wing tips!
 

I don't think I'd put end plates on a 3d model. They would make the transition more difficult into stalled flight, rather than going thru it and staying there. Talking with Kyle, He feels that wing rock is more a function of cg than anything else. I would tend to agree with him, based on my own flight tests. A nose heavy ship is hard to force into a stall, whereas a tail heavy one wants to stall all the time. In a harrier, you want to be stalled completely, thus not leaning on the lift of the wing to hold the model up. Sure, there is still some lifting effect from the stalled wing, but the flow over the wing should be completely tubulent, and staying that way. For those interested in trying the tip plates, just be sure to change only one variable at a time, and test all flight conditions before and after mods to get a good comparison. My guess is that they will be like wheel fairings, they may help some things, maybe look cool, but not really worth the trouble.

RE: wing tips!
 

To add a little more to this discussion, I talked to several peole about the Funtana 40 and the consensus was the very wide, constant chord ailerons were the culprits. The feeling was that any small movement would greately affect the tip lift and had they been tapered, you wouldn't have the rock in harriers.

Here's another thought, from what I have seen in same size planes, .46-.61, the lower aspect ratio wings tend to harrier easier. The Pizza Box plane, PBF, and the Coroplast SPA3D will pop up into a harrier in a heartbeat. The PBF at 24x24 had an aspect ratio of 1:1 and the SPA3D has a 2:1, as I recall. The very low aspect ratio should have a very strong tip vortex. In addition, a large portion of the wing is covered with the prop blast compared to a high aspect ratio wing.

Finally, most 3D planes use a Vortec or similar airfoil with a straight line from the high point to the trailing edge instead of the usual curve. This is probably similar to, or a simplified version of, the double reflex airfoil which tries to break the laminar airflow into turbulent at the high point, increasing the lift and lowering the drag. The dimples on golf balls do the same thing.

RE: wing tips!
 

If what you are saying is true, then why does the Harrier 3D not rock the wings in a harrier? It has huge barn door ailerons and tapered wing tips. The only difference I can see is the aspect ratio is way low. Yes, the airfoil is different too from the Funtana, but this plane has been optimized for harriers, so why then does it have tapered wing tips? I flew a Harrier once, and didn't really like it, so I got the Funtana 90. Now that I have flown the Funtana, I wish I bought the Harrier. Maybe I'll get one next, but I need to destroy the Funtana first.

RE: wing tips!
 

Hmmm, I have a Harrier 90 sitting in a box that I thought about returning for a Funtana 90. Are you saying that the Harrier 90 does not wing rock at harrier? I was skeptical at first because of the rounded wing tip and the constant chord. I even thought about cutting off the wing tip right from the get go.

But now that you point it out, it does have very low aspect ratio. Each wing half looks practically square. I mean the box that contains each wing half looks square to me. So does it absolutely does not wing rock? Or only at a certain setting?

RE: wing tips!
 

Umm, regarding the Funtana 40...

It tip stalls during low speed pull-ups, to the right always, I might add. I feel that the wing rock is caused by the same mechanism that causes this tip stall. The manner it stalls sure looks grossly analogous to me[X(]. And I have tried a whole range of CG on my Funtana 40, from 5.75" to 6.25". Wing rocks @ harrier no matter where the CG is at on mine.

Therefore, I will try the tip plate. If it eliminates the tip stall as well as wing rock @ harrier, then perhaps we will find the true cause of this wing rock.

RE: wing tips!
 

I have a total of 5 minutes on the sticks with a friend's Harrier. It was way out of trim and a bear to fly. He has since set it up properly and now he loves it. My comment on the wing rock issue is not based on first hand experience, but rather what others have said on here about the plane. As for why I didn't get one, there were two big ones. I don't like the transparent covering, with the upper and lower being the same color. I was hard pressed to tell what's what on his. And the other is that I prefer side mounted 2 stroke engines. That plane asks for an inverted engine, which I just don't like. I will fly his some more this year to get a better comparison, but for now, I'm really happy with the Funtana. I may slap some tip plates on her to see if it does anything at all. If it does, I'll surely post the results.

RE: wing tips!
 

I recently converted the wing of my TWIST to tapered wing tips, similar to the UCD. I also fly a Seagull Razzle and she does Harriers much better than the TWIST. Also the TWIST won't do KE at all. I am hoping
that this will cure some of its shortcomings[img][/img]