Circular wing

[rotax618]

Low aspect ratio has a lot of advantages for a small sports plane, the planform has been shown to be stall and spin proof, due to their low wing loading have STOL characteristics. The can have a higher power off sink rate which means they can land in smaller clearings. The dont take up much hangar space.

 

They can be built much lighter because of the short span and deep spars, have a low parts count, and can have low drag at cruise, (see performance of UFO on 50HP 503)

 

You will never thermal an LA aircraft, but if you want a small safe STOL aircraft don't disregard them.

 

 

[red750]

Here's a guy who thinks outside the box:

 

 

 

[Old Koreelah]

Hi,I know this is an old thread, but I'm all for recycling, so here goes.

On another forum, one of the guys has just posted this little beauty. It's a bit cartoonish, but the general idea is there. Here's what he said about it: I think he may be on to something...

 

Large rudder and all-flying elevators.

 

Beefy balloon tires.

 

It would handle pretty much like a gyrocopter, only safer since the disk wing is both more compact and less likely to break if it hits a tree branch or something.

 

Two-axis controls. Weight, inertia, and aerodynamic forces will keep the free-moving wing disk aligned properly. All you have to worry about is up and down. It's spin-proof and stall-proof.

 

Can probably do STOL.

 

A twelve foot disk gives us about 120 sq feet of wing area which is plenty for a plane this size.

 

Now here's my favorite bit.

 

Make the wing disk a tube and fabric structure that can fold up like an umbrella.

 

Bundle it into a canvas tube, strap it to the roof of your car and stick a trailer hitch the tail of the fuselage for towing.

 

The way this thing would handle, combined with the way it's built, means you could pull off stuff that would be too dangerous in a conventional plane.

 

Now this thing would never be all that fast, but it would be easy to fly and friendly to newbies.

 

I know a bloke who has built models similar to this to test his theories. Main difference seems to be that his disc spins- like a frisbee.

 

 

[facthunter]

Stability is a two edged sword. I question whether it makes a plane more pleasant to fly. I prefer Neutral . Control responses are all you use, whereyour input (control position) affect the result. Pendulum effect needs gravity. but other accelerations affect it as well. that is turning and acceleration/decelerating in the normal sense If the plane stays where you put it it's preferable to it swinging back to some concept of level again, which is subject to dynamic considerations. Ie if you are turning the pendulum is working to retain bank.. Excess stability produces things like dutch roll or uncoordinated roll/yaw oscillations or tendency to spiral. Sweepback, dihedral and low centre of gravity are all used to achieve a yaw roll relationship without control input. They exert an effect that you must overcome to get the plane to do other than fly straight and coordinated. Excess stability equals slower response to control input, and less control effectiveness. Not what you always need in a small plane. Nev

 

 

[rotax618]

It is much more pleasant and a lot safer to have positive stability so that it is possible to fly hands off for a period without the slightest gust sending the aircraft into a spiral dive, it is a CofA requirement that an aircraft should return to level flight in "X" number of oscillations following a control input. Combat and aerobatic aircraft are an exception. An aircraft that is neutrally stable in any plane is demanding and tiresome fo fly any distance.

 

Aircraft are subject to all sorts of external forces, neutral stability means the pilot must compensate immediately to maintain to counteract these disturbances.

 

 

[facthunter]

That's the conventional thought. If you fly leaving it to the planes stability you will fly a funny path. I' m not in any way suggesting a plane should be unstable, as it's dangerous. Control stick forces should always apply in the return to neutral sense and be stronger at higher speeds. That's accepted as basic.. The safest U/L has the most control authority, especially at lower speeds. Lots of natural stability equals less control authority. Nev

 

 

[rotax618]

I agree that you should have control authority especially at low speed, usually large enough control surfaces will give that authority without having to interfere with the stability margin.

 

 

[facthunter]

Large control surfaces have their own problems at low speed. IF you rely on a plane's stability on an approach to get you where you want to go, you will be way behind it, and not fly it accurately near the ground. Stability is good in theory, and is fine for free flight models where there's nothing else. You have to be proactive on a gusty approach or the plane is flying you. Nev

 

 

[bexrbetter]

Anything will fly if it has enough power. What efficiencies are available with a low aspect wing like that? Nev

A low aspect wing gets worse and worse in efficiency until it reaches about 2:1 when it turns around and improves dramatically. A flying body is quite efficient.

 

Of course it may come as a shock to some that people don't actually care if it's more efficient or not. I see way too much of that nonsense at the other forum.

 

 

[rotax618]

From the Nurflugel site:

 

NACA paper by Zimmerman on the subject (1929), where he presents wind tunnel force measurements for a series of low aspect ratio wings. Each wing model was composed of a straight and rectangular center section, to which two kinds of wingtips could be attached: with "square" or with semicircular planforms. Zimmerman progressively reduced the span of the center section, until it reached zero. Obviously, in that condition only the wingtips remained, directly attached to each other and forming a circular planform wing in the case of "round" wingtips. Apparently "by accident", he noticed that the circular wing developed a maximum lift much higher than that for other aspect ratios, either with round or square tips. I may not remember the exact numbers (I don't have the paper here right now), but I think CLmaxpeaked from a bit more than1.0 for the other AR's to almost 2.0 for the circular wing, that is, maximum lift almost doubled. We're talking about Clark Y airfoils, under low Reynolds conditions in 1929."

 

 

[bexrbetter]

From the Nurflugel site:NACA paper by Zimmerman on the subject (1929),

Yup, 1929.

 

There are better foil shapes, cuff and wing tip knowledge now that make the differences less than then.

 

I lost my bookmarks recently, when I get back from the factory I will link you to a similar but more recent study.

 

 

[djpacro]

...it is a CofA requirement .... aerobatic aircraft are an exception..

CofA reqt only via airworthiness design requirements, if applicable ... eg FAR 23 and aerobatic aircraft are not exempt.

[rotax618]

Yes I didn't explain myself correctly , all aircraft have to exhibit positive stability.

 

Some military aircraft are so unstable that they can only be flown because of artificial stability in their fly by wire systems.

 

As Facthunter (Nev) pointed out too much dihederal can have the unintended consequence of causing "Dutch Roll", and some designers have limited control surface deflection in an attempt to provide stall and spin proofing - not very good at low speed.

 

 

[Bruce Tuncks]

I put too much dihedral on a model glider. Before I modified the wings, there was almost no dihedral and the turn was done with ailerons. My problem was that due to lack of skill, it was too hard for me to maintain constant speed in a thermal .

 

With the dihedral, the ailerons became so ineffective they were useless. I could only turn now with the rudder.

 

I reckon a full-size like this would be awful.

 

 

[bexrbetter]

With the dihedral, the ailerons became so ineffective they were useless. I could only turn now with the rudder.

I reckon a full-size like this would be awful.

That's basically how a Flying Flea works and they fly fine.

 

 

[facthunter]

They don't handle a crosswind unless equipped with spoilers etc. Nev

 

 

[kasper]

They don't handle a crosswind unless equipped with spoilers etc. Nev

but they land and stop so short angle across any standard runway is fine ... if you can wheels down to full stop in under 200ft you can put a lot of angle into any landing on a 'normal' runway ;-) BUT I will admit dialling in wing down on a spoiler on the HM290FB did give it up to around 10knts direct cross wind ... but I never flew it as a must fly aircraft and if it was really crossed up and gusting it was as much of a day out to sit and drink coffee and talk flying $hit with all the other pilots

 

 

[Lancaster]

Hi all,

 

Does anyone know how to contact David Rowe the designer/builder of the UFO circular wing homebuilt aircraft ?

 

This one. . . thank you. . .  W. . .  Pacific Northwest, USA

 

 

 

 

[Old Koreelah]

I just spoke to David for you, Lancaster. He is now flying his fifth UFO.

 

He works for the Old Aeroplane Company at Tyabb, and I'll send his contact details in a personal message.

 

In case you missed this bit here is another link to his plane:

 

http://atsconsultancy.com.au/demo/Aeropidia_info/rowe-ufo/

 

 

[bexrbetter]

I just spoke to David for you, Lancaster. He is now flying his fifth UFO.

 

 

 

Wow, that's awesome!

 

 

[Lancaster]

Yes, that is great !

 

Thank you !

 

Will contact him in due course !

 

Blue skies and happy landings !

 

 

[facthunter]

. Have to be one really low aspect ratio wing if you ever wanted one. I've seen one flying at Narromine a long time ago.  Nev