Dumb question about gliders vs planes... maybe

Discussion in 'Hangar Talk' started by Tantalum, Jul 20, 2017.

  1. Tantalum

    Tantalum Final Approach

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    Killed some time today waiting for an SQL query to run and came upon this guy's YouTube channel (link below). It got me thinking... why don't planes have more glider-esq wings? It's well known that super high aspect ratios make for an efficient foil (modern race yachts have incredibly thin foils as well).. so when I look at something like a Cherokee, or even a newer build plane (even an Cirrus) I'm surprised how short the wings are

    I know Diamond builds goofy looking glider-esq planes... but it seems that if executed right you could build a fast flying machine with a relatively small (read: fuel efficient, good gph) powerplant.

    Is it just practicality considerations with having a 50ft wingspan... or am I missing something

    https://www.youtube.com/user/bviv
     
  2. Sac Arrow

    Sac Arrow Touchdown! Greaser! PoA Supporter

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    Bro do you even lift
    Gliders are efficient, but not fast. But yes, Diamond does pull off a good compromise.
     
  3. vontresc

    vontresc En-Route

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    As with anything in aviation things are a tradeoff. Long wings are efficient, but more difficult to design structually. Also while the induced drag is lower you usually have higher parasitic drag. Long wings are a paint on the ground as well.

    https://en.wikipedia.org/wiki/Aspect_ratio_(aeronautics)
     
  4. tinerj

    tinerj Cleared for Takeoff

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    And many hangars only take planes with a total span less than 40 feet.
     
  5. tspear

    tspear Pattern Altitude

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    Then you fold the wings the way glider's do.

    Tim
     
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  6. vontresc

    vontresc En-Route

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    We just take them off to fit into the trailer...
     
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  7. Dana

    Dana Pattern Altitude

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    I have a friend who owns a Stemme motorglider. He has to stop and fold the wings before he can fit on the taxiway to his hangar. Everything is a compromise.
     
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  8. GlennAB1

    GlennAB1 Ejection Handle Pulled

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    Which could be complicated with fuel in them.
     
  9. Clark1961

    Clark1961 Touchdown! Greaser!

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    Not much fuel in gliders...
     
  10. James331

    James331 Ejection Handle Pulled

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    PC12 has a bit of a glider wing on it
     
  11. nauga

    nauga Administrator Management Council Member PoA Supporter

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    Practicality and design issues with structure and loads. Add fuel plumbing and control continuity for folding wings. Note that Part 121 airplanes, where cruise efficiency is absolutely king, have relatively high aspect ratios (often span-limited by ground issues) and add sweep for high transonic wave drag management.

    As far as adding additional parasitic drag, maybe, just in terms of additional wetted area, but given that the coefficient of induced drag is inversely proportional to aspect ratio I'll bet you can't find a real case where increasing aspect ratio increased total drag, all other thing being equal.

    ETA: The fastest hobbyist model airplane (R/C) for years has been a fairly high aspect ratio glider. Currently 500+ mph.

    Nauga,
    who knows the best angle for a winglet is 0 deg off horizontal.
     
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  12. Hank S

    Hank S En-Route

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    My Mooney has been called a motor glider before, by a jealous owner of a gas guzzler . . . . 36' wingspan ages some hangars tight, in one I had 18" clearance on each wingtip. But the fuel efficiency is pretty good for a carbureted plane, 170 mph true on 9 gph.

    Long wings create more lift, and lift creates drag. So it's a compromise. On final, I often pull throttle to idle a few hundred feet before the numbers, but have never met a Piper owner who does that. Took one flying, and he nearly fainted when I did that, said in his plane we'd have been in the trees, "but in your plane, nothing happened!" Not exactly the truth, I landed gently a couple of stripes beyond the numbers and taxied in.
     
  13. GlennAB1

    GlennAB1 Ejection Handle Pulled

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    No sh!p, Clark, pay attention. We're talking about glider type wings on powered aircraft.
     
  14. Clark1961

    Clark1961 Touchdown! Greaser!

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    I never pay 'tention without compensation. Sorry. Pete is a glider driver...who is known to leave his fly open from time to time.
     
  15. denverpilot

    denverpilot Tied Down PoA Supporter

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  16. Clark1961

    Clark1961 Touchdown! Greaser!

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  17. nauga

    nauga Administrator Management Council Member PoA Supporter

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    NVM, not gonna get into it tonight.

    Nauga,
    and singing pigs.
     
  18. Ken Ibold

    Ken Ibold Final Approach

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    PA-46 series, the Malibu and Mirage, have relatively high aspect ratio wings, designed to enable more efficient flight at altitudes in the 20s.
     
  19. 1600vw

    1600vw Pattern Altitude

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    Most your small light aircraft have what is call a hershey bar style wing. This will give a light wing loading. This style airplane is flown in early mornings and late evenings. The light wing loading makes for a very rough ride when the thermals start. My guess would be if you built an airplane with such a wing you would get beat so bad flying it would wear you out. Not an enjoyable flight. This would be my guess as to why an airplane that is used to commute does not have a lightly loaded wing. But I could be wrong.

    Tony
     
  20. Grum.Man

    Grum.Man En-Route

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    Pipistrel has a few models with glider type high aspect ratio wings and they perform excellent. Those types of wings come into their own at altitude but are a bit slower down low. Considering most private planes spend majority of their time relatively low I'm not so sure a high aspect ratio wing is for everyone.
     
  21. asicer

    asicer Final Approach

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    Using as evidence the stubby 31ft AA5B wing and the gangly 39ft DA40 wing in addition to the fact that the two perform about the same, one could conclude that it doesn't seem to make much difference.
     
  22. Grum.Man

    Grum.Man En-Route

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    About the same is a little bit of a stretch. Despite being 2-300 lbs heavier the Diamond has a 3000 ft higher service ceiling, requires 2-300 feet less runway, 100 ft/min better climb, very similar cruise speed in a much roomier airplane.
     
  23. Hank S

    Hank S En-Route

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    And my 36' wing will outclimb and outrun both of them, on 180 hp. Haven't found the service ceiling yet.
     
  24. GlennAB1

    GlennAB1 Ejection Handle Pulled

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    Are they both the same NACA number?
    No.
    AA-5B is NACA 64-415
    DA40 Is FX 63-137
    Two totally different airfoils.
     
    Last edited: Jul 21, 2017
  25. Grum.Man

    Grum.Man En-Route

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    Which Mooney do you have? The ones I have seen have very similar performance with the exception of a 10 knot speed advantage. And again, a mooney is a considerably tighter airplane on the inside than either a Grumman or a Diamond. Not really apples to apples when comparing wing design.
     
  26. Anthony

    Anthony Touchdown! Greaser!

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    You also have retractable gear, and a constant speed prop. For what many, if not most people want in a GA airplane the Grumman's stubby wings are a good compromise.
     
  27. Tantalum

    Tantalum Final Approach

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    Thanks for all the replies. Obviously the engineers know what their doing, but I've noticed that the higher performance business gets (G5, Citation X) also appear to have enormous wings.. and not all gliders are slow, there are some "fast" ones out there. But as with everything in life I'm sure there's compromises to be had. What was really interesting in the video I posted up top the guy explains in one of them that he can adjust the flap setting, basically like adjusting the wing camber and get into some "negative" range to help go faster. I thought that was cool

    That's a good point.. and the handful of gliders I've been in have proper harness systems. I've never been tossed around but I know it's not uncommon when flying gliders to get bumped around quite a bit.

    That's true. But thinking personally, if I ever bought a plane it would be to use it to get places. When you're going on a 500nm leg a glider type wing would probably really come into its own in the 10-20K range. That's what appeals to me about Mooneys.. they may be "cramped" inside but they're an economical way to go long distances
     
  28. Grum.Man

    Grum.Man En-Route

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    The Questair Venture has a high aspect ratio wing. It really shines everywhere but especially at 10k and up. There has been a Questair that surpassed 30k feet too and still climbing.
     
  29. genna

    genna Cleared for Takeoff

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    I can tell you one thing for sure. Diamond DA-40 is a rough ride in the thermals. That long wing catches every little bump. C172(little less performance) is a lot less bumpy. So is 182(little more performance).
     
  30. PilotRPI

    PilotRPI Line Up and Wait

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    Higher aspect ratio reduces induced drag, which is a factor at lower speeds. Lower wing area reduces parasitic drag, which increases with speed. I think most gliders are soaring less than 70-80kts at their most efficient, which is where induced drag plays a factor, more so than induced drag. Induced drag is still a factor as speed increases but less so, so Diamond found a good compromise. I think wing area rather than aspect ratio plays more of a factor on comfort through turbulence. High aspect ration wings are difficult to build, especially varying chord wings. Hershey bars are a lot easier to build, but much less efficient at low speed, causing higher induced drag on final with the power pulled out, or on takeoff.
     
  31. Dana

    Dana Pattern Altitude

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    The shape of the wing ("Hershey bar" i.e. rectangular, or otherwise) has nothing to do with wing loading. A tapered wing has somewhat better efficiency (less induced drag) but the difference in practice usually isn't dramatic. Many GA aircraft (older Cherokees, Grummans, most of the classic lightplanes) have rectangular wings. Wing loading does affect speed, of course, and aircraft designed for higher speed have higher wing loadings.
     
  32. genna

    genna Cleared for Takeoff

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    That's(bold) probably correct in terms of catching the turbulence, but if the area of the wing catching an updraft is farther from the CG, you get a considerably higher lever and thus heavier jolt. Hence, I think, long wings tend to have bumpier rides.
     
  33. Grum.Man

    Grum.Man En-Route

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    I have no facts but I would think a longer wing would be smoother as it is more flexible in most cases. But I didn't stay at a Holiday Inn Express last night so what do I know.
     
  34. Pilawt

    Pilawt Final Approach

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    Early PA-28s had short, stubby, rectangular wings because they are quick and inexpensive to build, requiring fewer parts and less skilled labor. But it was not the most efficient configuration for a low-powered lightplane. The tapered wing was introduced on the Cherokee Warrior in 1974 in response to market pressure from customers who wanted a Cherokee that performed and handled more like a 172.
     
  35. vontresc

    vontresc En-Route

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    Long high aspect ratio wings, are also harder to design as a structure. As the wing gets longer and thinner, it gets more difficult to achieve proper torsional strength to over come the bending moment of the control surfaces. This was a major issue in designing the Concordia (http://soaringcafe.com/2011/01/concordia-history/). As has been mentioned earlier thick stubby wings (Pa-28 RV etc) are simple and cheap to manufacture.
     
  36. Pilawt

    Pilawt Final Approach

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    Sailplanes are a kick, but some of the handling characteristics of super-long wings (e.g. adverse yaw, overbanking tendencies) might get tiresome in your daily driver. There's a reason barn swallows don't have albatross wings.
     
  37. paflyer

    paflyer Final Approach

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    If they did that with the PA46 they would have sold a lot more of them
     
  38. asicer

    asicer Final Approach

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    Close enough. :)

    I probably should have qualified with "for the flying we do". Most of the difference in ceiling is in the oxygen levels. Those that enjoy breathing through a tube probably want 200+HP anyway.

    Some of the takeoff/climb difference can be attributed to the CS vs. FP prop.

    Some of the cabin difference is made up by the smaller DA40 baggage volume.
     
  39. GlennAB1

    GlennAB1 Ejection Handle Pulled

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    In the race for "range" you gotta put fuel somewhere.
     
  40. Clip4

    Clip4 Final Approach

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    Weight. A glider doesn't carry fuel or an engine.