Circular wing

[winsor68]

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.

There is plenty of room for batteries...and surely fly by wire is available to the amateur market...

 

 

[rotax618]

If you want to have any endurance using current battery technology I suggest that you aim for the highest aspect ratio that you can build within structural/weight restraints, you really need a L/D of >18. There is a place for very low aspect ratio aircraft, they can be built lighter, more compact, stall free, stol performance BUT you will not get sailplane performance.

 

 

[rotax618]

The attached sketch is probably something like what you are thinking.

 

 

 

[gimballock]

I've been keenly reading the thread on Very Low Aspect Ratio aircraft over on homebuiltairplanes.com.

 

Interesting.

 

Getting into the nitty gritty.

 

A few "TINSFOS" (There is no substitute for span") detractors are constantly arguing against them.

 

Interesting, nonetheless.

 

 

[bexrbetter]

So Gimballock (and anyome else), these lower aspect ration wings seem like a good thing, safe stall etc, not awful looking, and today with CNC equipment and better composite understanding they are actually easier to make than a "normal" plane whichs begs the question why haven't they taken off?

 

The Dyke Delta doesn't seem unreasonable for example ...

 

http://en.wikipedia.org/wiki/Dyke_Delta

 

 

[gimballock]

So Gimballock (and anyome else), these lower aspect ration wings seem like a good thing, safe stall etc, not awful looking, and today with CNC equipment and better composite understanding they are actually easier to make than a "normal" plane whichs begs the question why haven't they taken off?

Well, from reading the thread over on homebuiltairplanes.com, it's somewhat of a religious debate.

 

There are a lot of proponents, but a few detractors.

 

I am on screenful number 13 out of 26 and the debate rages on.

 

These guys are more technical than I am (I fly 'em - I don't fix 'em or build 'em!) and are dealing a lot in Reynolds numbers, Lift coefficients, torsional strengths and discussions on relative weights and performance.

 

From what I can see, and from what I've learned from talking to a bonafide owner of a one-off, self-designed low aspect ratio, circular winged aircraft, this type of aircraft can:

 

1) Fly slow

 

2) Fly stably at all speeds

 

4) Be as efficient at the correct aspect ratio (1.25) as a higher aspect ratio (6)

 

5) Land short with a parachute-like descent rate

 

6) Take off in a relatively short distance

 

6) Stall and spin resistant.

 

The main disadvantages are somewhat ugly, bad Lift-to-drag ratio and poor visibility in certain directions (depending on where the pilot sits relative to the wing.)

 

So, I personally believe that they have some good things going, but there are a couple of die-hard glider pilots who argued (to the point of being a little miffed at each other!) that their problems outweigh their benefits.

 

As for why they haven't "taken off" (pardon the pun), who knows?

 

I, for one, like them as a replacement to the autogyro (of which I am a big fan) but without the downside that goes with them.

 

Ultimately, like many fellow aviators, I look forward to a time when we're all getting around in one of these:

 

 

This is my main interest in low aspect ratio aircraft.

 

The link to the discussion is here: http://www.homebuiltairplanes.com/forums/aircraft-design-aerodynamics-new-technology/6333-very-low-aspect-ratio-planes.html

 

I continue to read.

 

 

[bexrbetter]

The main disadvantages are somewhat ugly, bad Lift-to-drag ratio and poor visibility in certain directions (depending on where the pilot sits relative to the wing.)

Looks are always subjective of course but the form of most 'normal' planes would probably triumph in most cases but remember that most of the flying wing craft we are referring too are very much amateur built by people who's talent doesn't always include aesthetic design knowlege.

 

I think the Dyke Delta looks pretty darn good and a more modern coupe cabin would bring it up to quite desireable levels - IMO.

 

The amount of dirt cheap cameras and screens available these days makes landing visibility resolvable.

 

 

[Garfly]

 

It seems like they're planning on taking this Light Sport Geobat FS-7 to market in the US:

 

[MEDIA=vimeo]90223874[/MEDIA]

 

http://www.aerobataviation.com/Light-Sport-Aircraft-FS-7

 

http://www.tested.com/tech/robots/460940-designing-new-breed-flying-disc/

 

Also, following up David's post on Scott Winton I found this interesting old video on the Facet Opal:

 

 

 

[bexrbetter]

I think the Dyke Delta looks pretty darn good and a more modern coupe cabin would bring it up to quite desireable levels - IMO.

.

Oh and then I noticed this updated Dyke impression ...

 

 

 

[gimballock]

I look around at all the roadworks and lack of proper infrastructure and I say, over and over again to my wife (and boy, is she sick of it!) "This will all be a thing of the past when someone finally invents the flying car!"

 

 

 

[Deskpilot]

Many people have taken a liking to the Dyke Delta and have bought the plans. Unfortunately, it's a very complex thing to build so many planes are unfinished. One guy took 18 years to complete his. Others have moved on and made modifications to the wing shape in the 'strake' area. It is a very good aircraft and has , as far as I know, no flying vices at all. I based my single seat delta on the DD2 but got carried away with reflex wings and other 'improvements'.

 

 

 

[gimballock]

Whenever the Delta Dyke/Low aspect ratio discussion starts up, this picture also does the rounds:

 

 

From what I understand, it was a one-off build, done 20 or 30 years ago and no longer flies.

 

Shame.

 

It looks quite cool and sexy!

 

Almost like some sci-fi spacefighter!

 

Imagine the nerdgasms you could have in that thing!

 

:P

 

 

[bexrbetter]

Whenever the Delta Dyke/Low aspect ratio discussion starts up, this picture also does the rounds:[ATTACH=full]29060[/ATTACH]

From what I understand, it was a one-off build, done 20 or 30 years ago and no longer flies.

 

Shame.

 

It looks quite cool and sexy!

 

Almost like some sci-fi spacefighter!

 

Imagine the nerdgasms you could have in that thing!

 

:P

Not a Dyke Delta apparently, I will quote RF member Flyvulcan and I'm sure he won't mind ..

 

The aircraft is actually called the Delta Stingray and it was designed and built by a Mr. Lowell J. Borchers. I spoke with Mr. Borchers around 1 year ago about his aircraft as I am also interested in deltas/tailless (i.e. Me163, Scotty Wintons Opal etc).

 

He advised that his aircraft was initially flown without the small horizontal stab with some adverse qualities that were fixed by the addition of the stab.

 

He indicated that it was quite stable in the cruise with docile handling characteristics and that it built up speed rapidly when pointed downhill.

 

He eventually donated his aircraft to his local town museum where it is on display.

 

He did not produce plans for it, nor does he have any drawings of it, but he did remember wing section details etc.

 

He didnt seem to mind talking with me about it, so if you are really interested in talking with him, I probably still have his number somewhere. PM me if you would like it and I'll have a look.

 

One thing that he did say was that it was heavy. From memory, he said that it was around 800 lbs empty. With the right construction techniques and powerplant, I suspect that you could get this down closer to 450lbs as it is a small aircraft. This will bring the stall speed down by reducing take-off weight by 25%.

 

Cheers,

 

Dave

 

 

[Deskpilot]

I spoke to John Dyke about the Stingray and he informed me that he helped L.J.B. with it's design but said it was ultimately far too heavy even though it cruised at about 150knots. JD refused to help me with my version. LJB eventually out grew the cockpit , hence it being in his local museum. I can't remember

 

what construction method he used but have a feeling it was wood.

 

 

[winsor68]

There is potentially a lot of space inside this sort of airframe...you could fit a nice bed in it...

 

 

 

[Deskpilot]

Facetmobile may well be easier to build than a DD2

 

 

 

[bexrbetter]

This one's a bit different, semi canard, semi flying wing ...

 

http://www.rmtaviation.com/index.htm

 

 

Facetmobile may well be easier to build than a DD2

For all it's supposed worth the Facetmobile is never going to win people over with it's shape and access issues IMO.

 

 

[Bob Llewellyn]

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:

 

The aspect ratio is 1. At a lift coefficient of 1.4, the induced drag coefficient will be 0.637 (times the wing area).

For a 300kg 95:10 machine, at a lift coefficient of 1.4 the induced drag will be 68.4 lbf (304N odd). This lift coefficient corresponds to 36 kts, making the induced drag power 7.6hp. By contrast, the mighty T-83 (Thruster) has an induced drag power at 36kts of 1.5hp.

 

With a streamlined bump for the pilot, the disk wing would have a (minimum) total drag of ~78lb, plus ~2lb for the engine cooling (if cowled well) and ~9lb for the U/C as shown. The power for level flight would therefore be about 10hp, on a thrust hp of perhaps 20 (prop inefficiency eats the rest), giving a max ROC of 500fpm on a rotax 503. Funnily enough, my T-83 with a single-carb, points ignition 503 also gets 500fpm...

 

 

[winsor68]

I guess the real trick is to remove all the bits that don't contribute lift.... Sailplane pilots don't seem to like them because they don't glide in circles very well...which is true from what my amateur reading of the numbers indicates...

 

 

[Guest Baron Biggles]

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:

 

First met David and his UFO at WeeWaa during 1998. He is alive and well and modest; still working with rare aircraft. Cheers Baron Biggles

 

 

[rotax618]

The aspect ratio of a circular wing is 1.27, it has been found from experimentation that wings with aspect ratios from about 1.2 - 1.4 behave like wings with aspect ratios of approx 5. Provided that the relationship between CG is kept in the 25% range Circular wings haven been found to be very stable and have some unique low speed characteristics, it is no accident that Davids UFO flies very well, is stable and controllable.

 

 

[bexrbetter]

I have found using models that an inverse zimmerman planform has a better L/D than a circle.[ATTACH]28977[/ATTACH]

I decided last night to have a quick look at your drawings in 3D, I stuffed up the way I did the wing but at least gives you an idea of your design. There is no ailerons - the basic only took a half hour or so, I love Sketchup.

 

 

 

 

 

 

 

 

[SDQDI]

I decided last night to have a quick look at your drawings in 3D, I stuffed up the way I did the wing but at least gives you an idea of your design. There is no ailerons - the basic only took a half hour or so, I love Sketchup.[ATTACH=full]32145[/ATTACH]

 

[ATTACH=full]32146[/ATTACH]

 

[ATTACH=full]32147[/ATTACH]

 

[ATTACH=full]32148[/ATTACH]

 

[ATTACH=full]32149[/ATTACH]

 

[ATTACH=full]32150[/ATTACH]

We could call it the 'Akubra' would suit it to a t

 

 

[BigBen]

BREAKING NEWS!I made contact with David Rowe!

I had a good chat with him and he was most obliging with information.

 

He said that, as you know, efficiency of a wing drops off with aspect ratio, but then, at a certain point, it sharply rises again!

 

He says that when the aspect ratio hits approximately 1.25, it is almost the same as an aspect ratio of 6.

 

The aspect ratio of a complete circle is approximately 1.27, and so, with some added aerofoil at the rear, it is approximately 1.25.

 

It doesn't actually stall, so much as it mushes.

 

He didn't recall the actual point at which this happens knotswise.

 

Power-out, it glides slightly better than a Drifter.

 

It is very stable and flies quite well.

 

It lands quite short. (He often lands it in the driveway of many farms out where he lives.)

 

It's a standard aerofoil with a reflex (as all flying wings/tailless aircraft are.)

 

The model glider he built had a Centre of Pressure at about 33% but on the full-scale model that proved unstable, so it was best placed at about 25%.

 

As mentioned here before, the high undercarriage was due to the rotation angle and the need to avoid scraping your tail on the ground.

 

Also, he said that the seating arrangement was purely due to the fact that he sits, basically, on top of the wing.

 

He said that it's actually quite uncomfortable, so flights of more than an hour are not advised in this current model.

 

I told him of the interest in low-aspect ratio aircraft on both here and homebuiltairplanes.com.

 

I urged him to get onto this site as his knowledge would be invaluable - a person with first-hand experience is worth a thousand "internet armchair experts."

 

Sadly, he doesn't frequent the internet very much, so isn't interested in getting on this site.

 

He did, however, invite me to keep in contact and said that I am welcome to call any time I have questions.

Gimballock, do you know if Mr. Rowe has an email address? I would very much like to converse with him about the design details and flight characteristics of the UFO and telephone discussions would get very costly.

 

Thanks

 

 

[BigBen]

The aspect ratio of a circular wing is 1.27, it has been found from experimentation that wings with aspect ratios from about 1.2 - 1.4 behave like wings with aspect ratios of approx 5. Provided that the relationship between CG is kept in the 25% range Circular wings haven been found to be very stable and have some unique low speed characteristics, it is no accident that Davids UFO flies very well, is stable and controllable.

Rotax618. Your model appears to be a half ellipse in planform. Have you calculated the location and length of the MAC for this planform?