The 'daydreamers' thread...post your craziest designs and concepts here

Discussion in 'Hangar Flying' started by Floydr92, Apr 12, 2016.

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  1. Jan 15, 2020 at 7:56 AM #221

    rotax618

    rotax618

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    David Rowe reported that his UFO (AR 1.27, 12foot span) has an engine out glide similar to a Drifter, the UFO is an extreme Low Aspect Ratio aircraft. Please look at the video evidence before generalisation.
     
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  2. Jan 15, 2020 at 3:16 PM #222

    BBerson

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    I looked at the NACA reports from Zimmerman that listed Cd.
    If you refuse to look at Cd, nothing more to say.
     
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  3. Jan 15, 2020 at 8:51 PM #223

    rotax618

    rotax618

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    I have studied Zimmerman’s work and agree that lower A.R. generally has a lower L/D. There is an aberration at very low A.R., He didn’t study the effect of planform, his original experiment was with a rectangular wing with semi-circular wingtips and Clark Y airfoil. He measured the L/D as he reduced the span, when only the tips remained (a circle) the L/D Curve increased unexpectedly and the C.L. max continued to increase well past the normal stall break. Obviously as the C.L. increased so did the C.D.
    The UFO and Arup types are able to fly pretty well in spite of their very low A.R. because they have a very low wing loading and because of the aberration measured by Zimmerman at angles of attack necessary for cruise the L/D is similar to that of a more conventional planform. With an LAR you can use that high alpha C.D. for very short landings.
    There are no free lunches aircraft are designed for a mission there is no ideal aspect ratio and if your aim is to build a light, compact, safe single seat STOL sport plane don’t overlook LAR.
     
  4. Jan 15, 2020 at 9:50 PM #224

    BBerson

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    It isn't overlooking low aspect ratio if someone can design an AR-3 aircraft that climbs steeper than an AR-1.
    Landing short is useless if you can't takeoff again from that confined area.
     
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  5. Jan 15, 2020 at 10:00 PM #225

    Himat

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    Just remember, with fixed span the higher the aspect ratio the wing have the worse the climb.;)
     
  6. Jan 15, 2020 at 10:01 PM #226

    pictsidhe

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    LAR tends to have a better span efficiency than more conventional AR. But you will still increase induced drag as you lower AR. It just isn't quite as bad as you'd expect with constant e.
     
  7. Jan 15, 2020 at 10:01 PM #227

    pictsidhe

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    Huh?
     
  8. Jan 15, 2020 at 10:39 PM #228

    Himat

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    Usually when discussing wing aspect ratio, the wing area is held constant. The result is that different span loadings are compared at a fixed area loading. Keeping the wing span constant, different wing loadings are compared at fixed span loading.

    What physical size is varied with aspect ratio and what physical size is held constant when comparing different wing aspect ratios make a difference. Aspect ratio is dimensionless, but a change in aspect ratio changes either wing loading or span loading.
     
  9. Jan 15, 2020 at 10:52 PM #229

    pictsidhe

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    But the dominant factors for climb rate are span and power loading. Wing loading is a far smaller effect.
     
  10. Jan 16, 2020 at 5:52 AM #230

    rotax618

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    What you say is theoretically correct, but please look at the video evidence of the LAR types, the UFO can takeoff and land in an extremely short distance, and from the videos so did the Arups, both types have a very good climb considering their low power. Scientific method suggests that if the theory doesn’t fit the evidence then you don't change or ignore the evidence, you amend the theory.
     
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  11. Jan 16, 2020 at 5:50 PM #231

    Himat

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    Is it? Or is it speed?
    Climb ratio do depend on span loading, power loading and wing loading. I would add that climb ratio depend on speed too. Of two airplanes with the same best climb L/D, the fastest airplane will have the best climb ratio in height gained by time.

    Actually, I forgot that in the last posting. Comparing wing aspect ratios it is common to do it at the same speed. Now, if you rearrange the formula for how cl/cd depend on wing aspect ratio to be compared at constant span (and speed) you will see how cl/cd worsen with larger aspect ratios and higher wing loading.
     
  12. Jan 17, 2020 at 4:55 PM #232

    Speedboat100

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    I just dreamed that you shoot an airliner above the clouds with a rocket and assisted sling ( or a catapult )...and then spread the wings there...and start using ducted fans that run with solar power and batteries.
     
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  13. Jan 17, 2020 at 5:16 PM #233

    bmcj

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    Heeee’s baaaaaack!
     
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  14. Jan 17, 2020 at 5:55 PM #234

    Tiger Tim

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    Less of a daydream, more of a nightmare: the other night I had a dream I was going through a book on airplanes and within it was a few pictures of a replica “Jenny.” It was built full scale but powered by some air cooled horizontal engine and had the Super Cub-style pressure cowl to prove it. The wheels were chrome spoked motorcycle wheels with knobby dirt bike tires for good measure. Then, for whatever reason, from the trailing edge of the wing aft the fuselage and tail was scaled-down B-17 but of course fabric covered. It sure was something and even in my sleep it was a real WTF moment.

    Having said that, I’d fly it every day if I had the chance...
     

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