Circular wing

[gimballock]

Hi all,

 

Has anyone here had any experience with round/circular/disc-shaped wings?

 

I know that they aren't popular and there were many experimental designs towards the end of WWII like the Vought V-173 (http://en.wikipedia.org/wiki/Flying_Pancake) and the Sacks AS-6 (http://en.wikipedia.org/wiki/Sack_AS-6)

 

I've heard that this design is very unstable, but David Rowe in NSW has built an experimental version known as the "Useless Flying Object" (UFO) and there's a YouTube clip showing it flying quite happily:

 

 

Surely such a design has advantages such as low-drag and low stall speed etc?

 

Does anyone know any more on this?

 

Does anyone know David Rowe personally?

 

Cheers,

 

Gimballock

 

 

[bexrbetter]

Ironic that the "Useless Flying Object" is at a site called TWITT!! :)

 

http://www.twitt.org/baxter.html

 

 

[gimballock]

Yeah, I've seen this and its 1-line "discussion" on the aircraft.

 

Not a lot to go on, sadly.

 

Anyone else know more?

 

Thanks.

 

 

[rgmwa]

Baling out should be a piece of cake judging by the location of the door. Probably best to avoid a wheels up landing though.

 

rgmwa

 

 

[rotax618]

If you look at the RCgroups forum they have quite a bit on circular wings, experiments have shown that circular planforms are inherently stable at all angles of attack, can maintain upper surface attachment at high angles of attack irrespective of the airfoil used, but work best with a sharp leading edge which seems to create a vortex. There are several successful examples of circular wings. The aircraft industry has pretty much ignored these low aspect planforms because they look weird. Google "inverse zimmerman", "Arup aircraft" (semi circular) , "TWIT" (the wing is the thing)

 

 

[facthunter]

Easy to make strong. I can't see that with a low aspect ratio like that it would ever have a good L/D ratio. Probably handles high AoA's without stall. Any thing will fly but how well?. The pilot seems capable. Nev

 

 

[Deskpilot]

Only one thing wrong with that video. The operator. Too close to mindless chattering family/friends and non familiar with his camera. I wanted to see the take off and he/she missed it. As for the plane, it would be great if those long legs tucked up somewhere and the engine was quieter.

 

 

[gimballock]

You're certainly right about the Camera work, Deskpilot!

 

He got the roll and rotation but *just* happened to (irritatingly) shove the camera in the opposite direction during the climb out!

 

But as for the design, I read that the long legs are necessary to make use of a certain aerodynamic effect. Does anyone know anything about this?

 

Re: Rotax618's comments about "instability at all angles of attack", I am curious to know how he gets around this short of amazing airmanship, fortitude & skill!

 

I figured that someone in here might know him as he is clearly an Aussie and this aircraft is registered with RAA.

 

Is there another section in here where I may be able to track him down? (I'm in SEQ.)

 

Gimballock.

 

 

[rgmwa]

But as for the design, I read that the long legs are necessary to make use of a certain aerodynamic effect. Does anyone know anything about this?

Looks to me like it might depend somewhat on the age and flexibility of the pilot. The older the pilot, the longer the legs have to be.

 

rgmwa

 

 

[bexrbetter]

BProbably best to avoid a wheels up landing though.

... that's when you "Flintstone" it.

 

 

[cscotthendry]

Looking at the way the tail is blanketted by the wing, I think it might be unrecoverable from a spin.

 

 

[PA.]

Looking at the way the tail is blanketted by the wing, I think it might be unrecoverable from a spin.

Here is a picture of it in Spin Recovery.

 

 

[gimballock]

I've done some digging and might have a contact number for him.

 

I'll give him a call & if he's happy to oblige, ask him a few questions.

 

For all those interested, stay tuned.

 

 

[facthunter]

I was going to say if it went into a spin it would become a Frisbee. Nev

 

 

[cscotthendry]

Here is a picture of it in Spin Recovery.[ATTACH=full]28929[/ATTACH]

So, does that mean you have to repair bite marks after any spin practice?

 

 

[rotax618]

The UC has to be long because the wing does not stall at the 12deg that a conventional rectangular planform does, these low aspect ratio circular (curved) planforms can maintain boundary attachment at angles of attack at 23deg AOA so they dont stall, they just attain a high drag controlled sink. The fin and rudder is not blanketed by the wing, at high AOA large vortices form on the top surface of the wing and maintain airflow over the rudder. As you can see from the video the aircraft has exceptional performance considering the modest 503 power, is stable and controllable. I would say that if developed this type would make an ideal sports aircraft.

 

 

[gimballock]

Thanks, Rotax.

 

That's an answer that I was sort of looking for.

 

I agree. It would make for a good sports aircraft and a good experimental platform for different engine types.

 

For example, has anyone considered multiple small-sized electric motors along the leading edge? (Say, 2 per side at no mor than 10 or 15hp each ?)

 

Battery life issues aside, could this lead to any significant increase in performance?

 

(Possible near-vertical take-off/landing?)

 

Just spit-balling.

 

Gimballock.

 

 

[turboplanner]

I've only seen this design flying in RC models, and like all very short coupled aircraft (such as flying wings), they can be unsettled in pitch and hard to bring back under control. I've seen a few of them oscillating so severely that if they contained a pilot he would be hard pressed to retain control.

 

The conventional wing, with a long fuselage putting the horizontal stabilisers a long way back so they could maintain delicate pitch control evolved after many different wing configurations were evaluated by testing.

 

The non-conventional wing that seemed to have the longest life was the delta wing, but that was superseded around the 1950's.

 

 

[Guest Maj Millard]

I've only heard good things about circular winged aircraft and there have been a few over the years. The yanks had a ring-wing with a big hole in the middle that went well. Can't see any problem with them really just another form of delta really. Certainly doesn't need any flap !......just pull back on the stick and you've got all you want....I too would like to hear more about the builder. Seem to recall he took it to Natfly in the past, and there was something in the magazine about it......Love the entry/ exit hatch...I thought it was a belly board speed brake when it dropped down..............Maj....

 

 

[gimballock]

I'm sure that I'm teaching you guys to suck eggs when I tell you that tailless aircraft can be made more stable by a swept leading edge (like a delta), an anhedral form or by lowering the centre of mass (like a hang glider/trike.)

 

All accounts from those who have spoken to David Rowe are that it flies well and is quite stable. I'm guessing that his high seating position is simply so he can see over the nose!

 

I haven't been successful in getting hold of David Rowe. I've left a message.

 

 

[Guest Maj Millard]

This is a man of obvious talents, and it is great to have him as a fellow RAA member.................Maj....

 

 

[gimballock]

Yes, Maj.

 

David Rowe and Scotty Winton (May he rest in peace) are/were an inspiration to Australian Aviation.

 

We need more.

 

 

[David Isaac]

Well Scott Winton's Facet Opal had none of that and it was stable from the reports that I have.

 

 

[gimballock]

Yes, well Jim Marske is another tailless design fanatic (http://www.marskeaircraft.com) but I've heard that his designs require precise CofG calibration (i.e adjusting the seat before each flight) but they are, for the most part, "flying planks" with only a small degree of sweep in the leading edge.

 

I've read somewhere that Scott Winton's Facet Opal was, at times, quite tricky to fly but this in no way contributed to the crash that took his life.

 

 

[David Isaac]

Scott was tagically killed only a few kilometres from my home. The crash was caused by the structural failure of Facet Opal the main spar. The failure had its origin at the hole Scott had drilled in the main spar to attach his oxygen bottle when he broke the world altitude record at 30,000 '. This structural failure amplified the flapperon mixer control inputs which caused the wings to appear as though they were oscillating until the action was so extreme the wings departed from the fuselage leaving Scott tragically in a high speed torpedo tube that claimed his life. An absolute tragedy and the loss of a gifted soul.

 

This is not what the ATSB reported as the reason for the crash, but even when the ATSB were shown that spar failure was the cause and agreed they have to this date not altered the accident report.