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Thread: Airfoil experiments

  1. #1
    Randy's Avatar
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    Airfoil experiments

    I have been reading with great interest the discussions regarding the modifications to the Cub wing to make it perform better in the landing and take-off modes of operation. When the Cub was designed in the 1930's, and the U.S.A. 35B was chosen to be the airfoil for the Cub, it turned out to be a very good choice, and has stood the test of time.
    My question today is now that 60+ years have gone by and advancements in aviation technology....has anyone else developed an airfoil in recent years that would be more optimized for the flight regimes that Cubs still fly...with an emphasis on low speed performance...without added enhancments such as leading edge cuffs, slats, complex flaps, ect?
    I realize that standard category Cubs would be unable to change their wings radically...but what about those that would fly their Cubs in the experimental category. What kind of wing would we have if we could take a blank sheet of paper and design one from scratch?
    I have seen some work along this line by Chris Heinz with the Zenair 701 type wing.
    This is such a great site....Thanks to Steve and all the contributors/posters!!
    I've been interested in Cubs all my life...and have learned more about them here than anywhere else.
    Keep up the good work.
    Randy

  2. #2
    Steve Pierce's Avatar
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    Welcome Randy, good question I am curious myself.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  3. #3
    Guest
    The S1223 and S1223RTL are a little draggy, but have a very high CLmax, about 2.1-2.2 unflapped. I work on the flight mechanics of a couple of rather large late-Cretaceous azhdarchid pterodactyls, Quetzalcoatlus species (wingspan about 16 feet, weight about 44 pounds) and Quetzalcoatlus northropi (wingspan 36 feet, weight about 330 pounds). Both of these animals usually set a camber distribution somewhat like that of a thinned S1223, and both could achieve steady-state LC's of about 2.2. Could do a little better when flapping, and a little bit less during the late stages of landing while using the flutter stroke with hesitation and full momentum reversal. I think a cub wing with a similar camber distribution might be worth trying.
    JimC

  4. #4
    FlipFlop's Avatar
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    Quote Originally Posted by Anonymous
    The S1223 and S1223RTL are a little draggy, but have a very high CLmax, about 2.1-2.2 unflapped. I work on the flight mechanics of a couple of rather large late-Cretaceous azhdarchid pterodactyls, Quetzalcoatlus species (wingspan about 16 feet, weight about 44 pounds) and Quetzalcoatlus northropi (wingspan 36 feet, weight about 330 pounds). Both of these animals usually set a camber distribution somewhat like that of a thinned S1223, and both could achieve steady-state LC's of about 2.2. Could do a little better when flapping, and a little bit less during the late stages of landing while using the flutter stroke with hesitation and full momentum reversal. I think a cub wing with a similar camber distribution might be worth trying.
    JimC
    Huh??...

  5. #5
    Steve Pierce's Avatar
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    Ditto. Jim, please explain.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  6. #6
    Jerry Burr's Avatar
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    Stuff.

    Hi Randy. When you say simple. Are you sure you mean the Zenair 701? The one with the fixed leading edge slat, and the complex inverted tail, and the setoff interconnected flap/aileron? It's a heck of a lot more complicated than my Cub. And on top of that my wheels are in the right place. Jerry.

  7. #7

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    Was the pterodactyls airfoil fixed or did the airfoil change with wing warping??

  8. #8
    Clay Hammond's Avatar
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    Did we ever in our wildest dreams imagine that we would go from Cubs to flying dinosaurs on this site. I not knockin' your pterodactyls Jim, just think its kind of wild.

    ceh

  9. #9
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    Good thought about them power lines. I mentioned the pterosaurs only because they were what led me to the S1223, when I was looking for a fixed airfoil that generally approximated the average camber distribution in the azhdarchidae. Wei Shyy's UF airfoil is also a good approximation, being similar to a thinned, somewhat decambered S1223. In my opinion, a family of airfoils similar to a fattened UF or S1223, or a thickened version of my cea0405 might all show some promise on a cub airframe, particularly if flapped. They would all three probably require a somewhat enlarged tail.

    At the risk of saying more than anyone might want to hear about animal flight, pterosaurs were not dinosaurs though both were diapsid archosaurs, and they were about as close to crocodiles as to dinos. Their airfoils (both in ramphorynchs and pterodactyls) were quite sophisticated and were not fixed. Their primary flight membranes (brachiopatagia) did tend to approach variations on a theme that resembled the S1223 camber profile, but with variable location of max camber and variation of camber itself. They did use wing-warping, but not in quite the same sense or for the same purposes that the Wright brothers did. The five largest known species (including one still unpublished and unnamed) all approach the size of small aircraft with wingspans on the order of 34-36 feet. It would appear that spans on the loose order of 42 feet might be possible, but nothing greater than about 36 feet has been found yet. As an example of scale, the elbow of Quetzalcoatlus northropi is over 9" thick from top to bottom, and the first bone of the 4th finger (equivilent to the bone in our 'little' finger nearest the palm) is 5 feet long. Their steady-state CLmax was about 30% greater than the highest steady-state CL achieved by birds, and about 50% greater than that in bats, and substantially greater than that of a flapped US 35B mod. For aircraft airfoils, the S1223 probably comes closer to approximating their performance than any other fixed airfoil that I'm aware of, also sharing the rather high drag and the substantial nose-down pitching moment. The big azhdarchids operated as motor gliders and had overall weight, size, and flight performance quite similar to the SparrowHawk sailplane and L/D ratios similar to Diomedes exulans (the Wandering Albatross). Membrane aeroelastic constraints restricted pterosaur Vne to something less than that of the SparrowHawk sailplane (At high speeds, their flight membranes would go bi-stable and/or flutter). Their flight mechanics, kinematics, and biomechanics are fascinating and worth some study by anyone interested in aircraft performance. My talk at the September, 2001 conference at Toulouse, France celebrating the 200th anniversary of the discovery of pterosaurs was 'A Skeletal Mechanism With Application to Automatic Gust Load Alleviation in the Azhdarchidae'. I figured if I made the title long enough, I could shorten up the speech.

    But enough of that. I don't want to bore you with stuff irrelevant to Cub flight.

    JimC

  10. #10
    SuperCub MD's Avatar
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    Wassa usefull load on a pterodactyl?

    Seriously, it sounds like facinating study. It doesn't take to long watching the falcons and herriers that like to hunt over the runway, silently hovering and manuvering in a gusty breeze, to realize how crude all our flying machines really are. I've watched them at length, it's facinating to see how they they work the wind, and not so different than a Cub.

  11. #11
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    "Wassa usefull load on a pterodactyl? "

    Are you sure you guys want to hear this stuff?

    But.... proceeding on, depends upon the pterodactyl. More seriously, northropi weighed about 330 pounds. In today's atmosphere, he could have flown comfortably at a gross weight of about 500-550 pounds, but could not launch at the higher weight in a dead calm. At 300-350 pounds, he could launch in a calm, even in today's atmosphere. Launch was very un-birdlike. Re real-life useful load, not much because of the bauplan. northropi was a late-Cretaceous azhdarchid and very highly derived, specialised for flat-water skimming in ground effect with rather extreme proportions. The skull was about 7-8 feet long, and there was a relatively inflexible neck that was about 10 feet long. The tip of the snout was close to 18 feet in front of the shoulders, and the pelican-like throat pouch was 9-11 feet in front of the shoulders. On the other hand, the torso was only about the size of a large man's, about 24 inches from the notarium socket where the shoulder girdle mounted to the spine back to the acetabulum (the hip socket). The stomach and intestine volume was quite small, and the pouch was located about 10 feet in front of the wings, so the ability to carry a large payload was limited by baggage compartment volume and baggage compartment location. Other, earlier pterosaurs were mostly smaller, shorter necked, and had more neck flexibilty, but total volume available for payload and fuel storage was still quite limited. Even so, range was still quite respectible. Some of these animals were capable of crossing the Atlantic (which was not quite so wide then as now). northropi would have been capable of doing so, but actually lived well inland in the area of the Big Bend in west Texas. At that time, the west coastline of the Cretaceous sea was located near Austin, Texas, a couple of hundred miles away, and the east coastline was near Tupelo, Mississippi. So far, only one member of the american azhdarchidae has been found on the east side of the Cretaceous sea, and it was about 5 million years older than Q northropi and Q species with a much smaller wingspan, perhaps on the loose order of 8 feet (a rather iffy estimate on my part, since only the 4th cervical vertabra has been found so far).
    JimC

  12. #12
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    I never could spell. Vertebra, not "vertabra'.

    JimC

  13. #13
    SuperCub MD's Avatar
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    Cool, Were these creatures airborne hunters like todays raptors, or ground hunters, similar to todays shore birds?

    Nothing to do with Cubs I know, but I find anything that flies interesting.

  14. #14
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    Some of both. At the time of their demise (when the Chixulub impact whacked 'em), pterosaurs had been around as long as birds have been now, and there had been about as many different species and lifestyles. By the end of the Cretaceous, all of the small ones appear to have been gone, replaced by birds. But there were no large soaring birds, possibly because soaring birds weren't able to compete effectively with the big pterosaurs. I've seen thousands of pterosaur tracks along an old mudflat in France, where they were obviously filling shoreline niches, but most pterosaurs were marine feeders, collecting fish from the ocean and were not skimmers. So far, only Quetzalcoatlus is known to have been a fresh-water skimmer. Some others were filter feeders, and some of the small ones appear to have been insectivorus. (spelling??).
    JimC

  15. #15
    Dave Calkins's Avatar
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    What about the poor little 7AC, Mark? It flies!

    Seriously. Jim, I'm blown away. I could stand reading more about your "dinoaurs". (yeah, I know they're not actually dino).

    Dave Calkins.

  16. #16
    Guest
    Dave, see the thread on books for some sources of info on pterosaurs.
    JimC

  17. #17
    SuperCub MD's Avatar
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    Dave, It depends on your definition of "flying". A cinder block "flys" to, if you throw it hard enough....

    Seriously though, before the Chump fans send me hate mail, I have flown all in that line, some more than others. The airplane just needs more power, it really starts to shine with a 180 on it. Since this started out about airfoils, the 8KCAB with the symetrical wing is one of my favorite airplanes.

  18. #18
    Guest
    I didn't mean to subvert the original purpose of this thread. Dave, I'm hosting some of Dave Peter's work on pterosaurs on one of my websties,

    www.taiwindfairings.com

    if you'd like to see it, open my home page, and click on his name. I don't agree with Dave on a lot of things (particularly his belief that pterosaurs were bipedal -- they weren't), but wanted to help his work reach an audience.
    JimC

  19. #19
    Guest
    Oops. I misspelled tailwind. Sorry bout that.

    www.tailwindfairings.com

    JimC

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