How to design a new wing (apols if OT)
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... and of course, we all admire the fluids properties of the well buttered eel.
I accept what you say but it also has a low frontal area, albeit cluttered, with a silly bit of streaming which could be improved upon. The coefficient of drag of the Rogallo wing would be good to know.
I accept what you say but it also has a low frontal area, albeit cluttered, with a silly bit of streaming which could be improved upon. The coefficient of drag of the Rogallo wing would be good to know.
Glide ratio and best glide speed will give you Cd with a few back of envelope calcs.
Looking at my personal notes, I have data for a Quik, which is last generation but still quite high performance. That gives a glide ratio of 7.7:1 with MTOW=409kg and best glide speed of 50mph IAS. You should get something to 2ish significant figures from that.
Generation before that would be a Quantum: 8.5:1, 40mph, 390kg.
Generation before that an XL-Q: 8.7:1, 40mph, 365kg
And if you really want to go back into pre-history, Pegasus XL-R, 7.5:1, 41mph, 350kg.
That's for the whole aeroplane of course. I had data once for a few wings on a test rig, but unfortunately that's mostly buried now in a previous employers archives. Looking at the one graph I have tucked away in an old report, it really isn't good enough to tell you much. But for a wing of the same generation as the XL-Q, *indicates* Total drag below 400N in the range -10 to +20° AoA, with Total lift about 6500N at 20AoA (stall) and about 4400N at 10AoA, and zero at -5AoA (just blame the datum there). that was at 44±3kts.
G
Looking at my personal notes, I have data for a Quik, which is last generation but still quite high performance. That gives a glide ratio of 7.7:1 with MTOW=409kg and best glide speed of 50mph IAS. You should get something to 2ish significant figures from that.
Generation before that would be a Quantum: 8.5:1, 40mph, 390kg.
Generation before that an XL-Q: 8.7:1, 40mph, 365kg
And if you really want to go back into pre-history, Pegasus XL-R, 7.5:1, 41mph, 350kg.
That's for the whole aeroplane of course. I had data once for a few wings on a test rig, but unfortunately that's mostly buried now in a previous employers archives. Looking at the one graph I have tucked away in an old report, it really isn't good enough to tell you much. But for a wing of the same generation as the XL-Q, *indicates* Total drag below 400N in the range -10 to +20° AoA, with Total lift about 6500N at 20AoA (stall) and about 4400N at 10AoA, and zero at -5AoA (just blame the datum there). that was at 44±3kts.
G
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I take your point but the frontal area is low, if somewhat cluttered. The key to the Rogallo wing would be its coefficient of drag.
Yes. If you want a tailless delta that's efficient it wants to look something like a Horton or early Northrop, not a flexwing microlight.
That said, internal structural cleverness and use of fairings and simplified shapes certainly has potential to remove a lot of the easily identifiable profile drag generators in the way of cables, struts, pilots, etc... The best such at the moment is probably the P&M PulsR?...
https://www.youtube.com/watch?v=1RbDVS-0XTE
Which if nothing else, is very clever, and very pretty. Designed by the aforementioned Bill Brooks.
G
That said, internal structural cleverness and use of fairings and simplified shapes certainly has potential to remove a lot of the easily identifiable profile drag generators in the way of cables, struts, pilots, etc... The best such at the moment is probably the P&M PulsR?...
https://www.youtube.com/watch?v=1RbDVS-0XTE
Which if nothing else, is very clever, and very pretty. Designed by the aforementioned Bill Brooks.
G
Anyway, in this book he offers some rather depressing guides on just how bad strut/wing interfaces and bracing wires are from a drag perspective. Even the PulsR commits what Hoerner rgards as "cardinal sins" by having V-jointed struts against he wing underside. Hoerner suggests that aeronautical performance stagnated until the materials and structural sciences allowed cantilevered designs which finally eliminated these performqance-sapping features.
Another thought is that these flex-wings operate at much lower speeds than the longeze (et al), so they fly at much lower Re with consequent need for much more wing area. That alone will increase both form drag and skin friction in comparison.
PDR
* my copy is one of the first print run - the one which he typed and typeset, added the hand-drawn diagrams and graphs, and then self-published because no technical publisher wanted it. These 1st editions are now rather rare (and no, I'm not selling it)...
Most of the world uses microlight definitions that include Vso<=35kCAS, that is clearly a very important design driver and tends to deliver low speed aircraft. The newest designs are achieving 80-90kCAS in level flight, which impresses microlight pilots, but in real terms is still very low speed.
And being low speed, form drag is a bit less problematic than it would on a higher speed aeroplane - but clearly not trivial, and all the cables and cantilevers create very draggy airframes. Billy did a great job with the PulsR but it's still, well, a flexwing!
There have been attempts to achieve much lower drag with a similar wingform in, say, the Dyke Delta or Verhees Delta. But they are using much more conventional structures, and don't use aeroelastic deformation to achieve stability in the way a Rogallo wing does.
G
And being low speed, form drag is a bit less problematic than it would on a higher speed aeroplane - but clearly not trivial, and all the cables and cantilevers create very draggy airframes. Billy did a great job with the PulsR but it's still, well, a flexwing!
There have been attempts to achieve much lower drag with a similar wingform in, say, the Dyke Delta or Verhees Delta. But they are using much more conventional structures, and don't use aeroelastic deformation to achieve stability in the way a Rogallo wing does.
G
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Don't get me wrong, G, the wing is an incredible achievement - incorporating all control surfaces in one mathematically horrifically complex 3D shape. What i am saying is that it isn't efficient and this could be improved on ... somehow.
As a generator of low speed lift, or as a generator of lift for low structural mass, it's extremely efficient. Ditto achieving a functional wing for very few parts.
If I understand you correctly - you basically want to reduce profile drag? That means the short of exercise Bill Brooks did when he created the PulsR, *or* incorporate the basic wing structure into a conventionally controlled aeroplane - a bit like the Verhees Delta?
If you can do that, and retain the foldability for transport and storage of a current Rogallo wing, you might do something quite worthwhile.
G
If I understand you correctly - you basically want to reduce profile drag? That means the short of exercise Bill Brooks did when he created the PulsR, *or* incorporate the basic wing structure into a conventionally controlled aeroplane - a bit like the Verhees Delta?
If you can do that, and retain the foldability for transport and storage of a current Rogallo wing, you might do something quite worthwhile.
G
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As a generator of low speed lift, or as a generator of lift for low structural mass, it's extremely efficient. Ditto achieving a functional wing for very few parts.
If I understand you correctly - you basically want to reduce profile drag? That means the short of exercise Bill Brooks did when he created the PulsR, *or* incorporate the basic wing structure into a conventionally controlled aeroplane - a bit like the Verhees Delta?
If you can do that, and retain the foldability for transport and storage of a current Rogallo wing, you might do something quite worthwhile.
G
If I understand you correctly - you basically want to reduce profile drag? That means the short of exercise Bill Brooks did when he created the PulsR, *or* incorporate the basic wing structure into a conventionally controlled aeroplane - a bit like the Verhees Delta?
If you can do that, and retain the foldability for transport and storage of a current Rogallo wing, you might do something quite worthwhile.
G
If you compare the power requirements and the cruising speeds of Rogallo wing a/c and the Long EZ, there is a big discrepancy.
If you take a good look at these two, it seems obvious why - but because it "seems obvious", it doesn't follow that the conclusion is correct.
Protecting myself with the Edward Debono "Po" concept, here is a Po suggestion: rip the wings off a EZ and nail them on a microlight - quickly glossing over the fact that there are control surface issues, with a few tweaks, how much better/worse would it do?
Run the numbers, let us know 
My guess is, not as well if you leave all the struts and fittings in place. Both are designs optimised to the wing they have. But I'd be the first to read with rapt interest your proof that I'm wrong.
G
My guess is, not as well if you leave all the struts and fittings in place. Both are designs optimised to the wing they have. But I'd be the first to read with rapt interest your proof that I'm wrong.
G
Let me put it this way.
If you compare the power requirements and the cruising speeds of Rogallo wing a/c and the Long EZ, there is a big discrepancy.
If you take a good look at these two, it seems obvious why - but because it "seems obvious", it doesn't follow that the conclusion is correct.
Protecting myself with the Edward Debono "Po" concept, here is a Po suggestion: rip the wings off a EZ and nail them on a microlight - quickly glossing over the fact that there are control surface issues, with a few tweaks, how much better/worse would it do?
If you compare the power requirements and the cruising speeds of Rogallo wing a/c and the Long EZ, there is a big discrepancy.
If you take a good look at these two, it seems obvious why - but because it "seems obvious", it doesn't follow that the conclusion is correct.
Protecting myself with the Edward Debono "Po" concept, here is a Po suggestion: rip the wings off a EZ and nail them on a microlight - quickly glossing over the fact that there are control surface issues, with a few tweaks, how much better/worse would it do?
As GtE says, the low speeds can de-emphasise the drag issues to some extent (especially the form drag), but for a given AUW a lower speed means either more wing area ( => more form drag, more skin friction) or a higher lift coefficient (=> higher induced drag which increases with the square of lift coefficient) or both. You can partially mitigate the form drag increase by reducing the aspect ratio, and you can mitigate the induced drag increase by increasing the aspect ratio (by the square of the Cl difference) but clearly you can't do both.
Flying slowly without external help (vectored thrust etc) is inherently draggy - look at all aeroplanes designed to fly at low speeds and you see highly cambered surfaces, ofterm with slattery-flappery assistance and/or external bracing to improve structural efficiency to keep the weight down. So you either need a very complex variable geometry setup (multi-slotted, area increasing flappy-slatty stuff) that you can tuck away to remode for higher speeds, or you need lots of area to generate the lift at the lower speeds. Or both.
PDR
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2. Yes, this is so and also there is a wing loading problem to solve, possibly both with a larger wing area.
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It's the first edition of the same book. The original edition is called "aerodynamic drag", and the subsequent editions were called "fluid-dynamic drag".
(wiki refers)
PDR
(wiki refers)
PDR
Francis Rogallo
My father, who was the Executive Vice President of Aetna Life and Casualty, a/k/a "Mother Aetna", was a friend of Frank Rogallo. Though Dad was a Mechanical Engineer (Georgia Tech) and a Masters of Marine Architect (U.S. Naval Academy Annapolis), he was fascinated by and loved every aspect of flight. The Aetna insured the U.S. Space Program from Mercury through Apollo, and when the Gemini Program was first on the drawing board, the Rogallo "Parawing" was considered as a recovery system. Dad (and the astronauts!) were entirely in favor of the concept: a steerable vehicle with a glide ratio would preclude the danger-ridden parachute landing in the ocean. Unfortunately, the engineers could not find a weight-economic way to stow the wing during launch and orbit. Deployment on orbit prior to re-entry presented its own set of problems.
On Christmas Day 1964 I was presented with a real Rogallo-winged kite powered by an .049 engine. The trailing edge of the device, which spanned about four feet, was autographed by Mr. Rogallo and his wife, Gertrude. My father, younger brother, and I took this high-viz orange-winged beauty to a nearby elementary school's playground for a test flight. The engine started on the first try and we released the kite into a calm, severe clear azure sky. Up, up, up she went, ascending in a slow left-handed turn toward heaven. The engine's fuel tank was relatively large; the Rogallo was but a speck (~ 3,000 feet?) when, as soon as the engine was fuel-exhausted, a straight ahead course became evident. She flew for miles and miles and out of sight on an eastward course - I like to think she made England...
Fast forward to 2004. My wife was the Assistant Curator of the Outer Banks History Center in Manteo, North Carolina on Roanoke Island. (You know, the first British attempt at colonization of North America. Virginia Dare, etc.) She had archived maps and notes dating back to 1583! I was visiting one spring day when she said "Come back into (the temperature, light, and humidity controlled vault, occupying about 10,000 square feet) my parlor, she smiled and beckoned. I have something I know you will like!" Thinking I might have lucked into a little "afternoon delight", I was not disappointed. Before me lay the entire compendium of notes and drawings of Francis Rogallo. He lived in Southern Shores, North Carolina, next door to a big sand dune in a place called Kitty Hawk, where he would often fly his own man-carrying designs. He had come home to test the same winds that his heroes, the Brothers Wright, had spent the Fall and Winter of 1903 mastering powered, sustained, and controlled flight.
My wife and I lived across Roanoke Sound, a mile from the tall and imposing Wright Brothers Memorial. It features a very bright rotating beacon that cycles around every eight seconds. It serves as a warning to sailors of the treacherous coast of North Carolina and a beckoning candle to aviators. It stands where our species first took flight. My wife learned to fly there. She would return from a flying lesson, give me a hug and a kiss, and say "I just flew in the same airspace as Orv and Will!" Our Golden Retriever would join the hug with his cold nose and wagging feathered tail. He was nearly the color of my Rogallo that had flown out of sight all those years ago...
- Ed
On Christmas Day 1964 I was presented with a real Rogallo-winged kite powered by an .049 engine. The trailing edge of the device, which spanned about four feet, was autographed by Mr. Rogallo and his wife, Gertrude. My father, younger brother, and I took this high-viz orange-winged beauty to a nearby elementary school's playground for a test flight. The engine started on the first try and we released the kite into a calm, severe clear azure sky. Up, up, up she went, ascending in a slow left-handed turn toward heaven. The engine's fuel tank was relatively large; the Rogallo was but a speck (~ 3,000 feet?) when, as soon as the engine was fuel-exhausted, a straight ahead course became evident. She flew for miles and miles and out of sight on an eastward course - I like to think she made England...
Fast forward to 2004. My wife was the Assistant Curator of the Outer Banks History Center in Manteo, North Carolina on Roanoke Island. (You know, the first British attempt at colonization of North America. Virginia Dare, etc.) She had archived maps and notes dating back to 1583! I was visiting one spring day when she said "Come back into (the temperature, light, and humidity controlled vault, occupying about 10,000 square feet) my parlor, she smiled and beckoned. I have something I know you will like!" Thinking I might have lucked into a little "afternoon delight", I was not disappointed. Before me lay the entire compendium of notes and drawings of Francis Rogallo. He lived in Southern Shores, North Carolina, next door to a big sand dune in a place called Kitty Hawk, where he would often fly his own man-carrying designs. He had come home to test the same winds that his heroes, the Brothers Wright, had spent the Fall and Winter of 1903 mastering powered, sustained, and controlled flight.
My wife and I lived across Roanoke Sound, a mile from the tall and imposing Wright Brothers Memorial. It features a very bright rotating beacon that cycles around every eight seconds. It serves as a warning to sailors of the treacherous coast of North Carolina and a beckoning candle to aviators. It stands where our species first took flight. My wife learned to fly there. She would return from a flying lesson, give me a hug and a kiss, and say "I just flew in the same airspace as Orv and Will!" Our Golden Retriever would join the hug with his cold nose and wagging feathered tail. He was nearly the color of my Rogallo that had flown out of sight all those years ago...
- Ed
Last edited by cavuman1; 5th Dec 2017 at 12:52. Reason: verbiage courtesy of JOE-FBS!
Excellent story, thank you very much.
On a light-hearted note, as both a Yorkshireman and an engineer involved with buoyant flight, I might change "our species first took flight" to "our species first took powered, sustained, controlled flight". (For the avoidance of doubt, I put the Wright brothers on the highest of pedestals for that achievement and the science that they performed to reach it.)
On a light-hearted note, as both a Yorkshireman and an engineer involved with buoyant flight, I might change "our species first took flight" to "our species first took powered, sustained, controlled flight". (For the avoidance of doubt, I put the Wright brothers on the highest of pedestals for that achievement and the science that they performed to reach it.)
Dear JOE-FBS,
Your suggestions are correct, accurate, and appreciated! I have edited my story incorporating them. Thank you as well, my friend; I am glad you enjoyed my story.
- Ed
Your suggestions are correct, accurate, and appreciated! I have edited my story incorporating them. Thank you as well, my friend; I am glad you enjoyed my story.
- Ed
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It's the first edition of the same book. The original edition is called "aerodynamic drag", and the subsequent editions were called "fluid-dynamic drag".
(wiki refers)
PDR
(wiki refers)
PDR
I wonder if material was removed between the volumes on the grounds of military secrecy. A comparison of your book, which must be pretty valuable, to the available Fluid Dynamics could be intriguing.
Very interesting PD. I see that the author was treated to an extended American working holiday under Operation Paperclip, presumably in 1946, when he wrote your book which he self published in 1951. Then the other one comes out fifteen years later.
I wonder if material was removed between the volumes on the grounds of military secrecy. A comparison of your book, which must be pretty valuable, to the available Fluid Dynamics could be intriguing.
I wonder if material was removed between the volumes on the grounds of military secrecy. A comparison of your book, which must be pretty valuable, to the available Fluid Dynamics could be intriguing.
I believe the subsequent editions tidied up the layout, included better (not hand-drawn/plotted) figures and added in some data on numerical methods which became practicable as computers came into use. I don't think there was anything taken out - especially on grounds of military secrecy because even the original book was written in English and after the end of WW2. I did once read that Dr Hoerner wrote the book to establish his bona fides (and thus his employability at a senior level) as a proper aero guy, but I don't know how true that is.
He certainly set out to write down everything there was to know on the subject of drag prediction. The technical publishers he approached (for a commission) mostly declined on the basis that they felt such a book was impossible, and were duly embarrassed when he showed them to be wrong!
Hw wrote is subsequent book "Aerodynamic Lift" on request, because when someone said it was a shame that the hydrostatic aspect couldn't all be documented as he had for the dynamic he wanted to prove them wrong as well, which he did (but not as definitively, as aspects of very low Re and high supersonics were not known at the time and in some respects still aren't). Although he had offers this time this book was still "self published" (albeit with his publishing company which was a bit more of a serious concern by then). Sadly he died before it was finally published, but his widow continued the businesss and printed/sold all the books for several years.
PDR
* I'm a teetotaller, but I'm not very good at it...
cavuman - thank you, that is really interesting.
May I ask something: I've flown a few Rogallo winged aircraft, and studied them fairly extensively. What I have often wondered about is the relationship between Francis and Gertrude. To what extent where they a true working team of two engineers, and to what extent was Francis in the lead and Gertrude essentially his assistant?
History tends to assume the latter, but I've always rather believed the former. If you were around people who knew them, I'd be really interested in your views.
G
May I ask something: I've flown a few Rogallo winged aircraft, and studied them fairly extensively. What I have often wondered about is the relationship between Francis and Gertrude. To what extent where they a true working team of two engineers, and to what extent was Francis in the lead and Gertrude essentially his assistant?
History tends to assume the latter, but I've always rather believed the former. If you were around people who knew them, I'd be really interested in your views.
G