How far are we from the perfect electric "homebuilt" ?

Discussion in 'Hangar Flying' started by Speedboat100, Aug 20, 2019.

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  1. Sep 18, 2019 #361

    Speedboat100

    Speedboat100

    Speedboat100

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    Is this your project ?
     
  2. Sep 18, 2019 #362

    stanislavz

    stanislavz

    stanislavz

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    I draw this. To call it a project - to early. I would not advise myself to building wings. Fuselage / pod / motor - yes. Wings is this thing, which i would like to be ordered.. Alternative to positive Rutan mould..

    As comparison to twin boom layout - it will go with smaller engine, less junction - less interference drag. But less efficient prop - or on front or on removable boom. Or on wing side - asymmetrical. And no easy place to place landing gear..

    Max scope, on not the sexiest look, but more on ok performance and easy to manufacture.
     
    Last edited: Sep 18, 2019
  3. Sep 19, 2019 #363

    stanislavz

    stanislavz

    stanislavz

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    henryk likes this.
  4. Sep 19, 2019 #364

    henryk

    henryk

    henryk

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    =moore close to auer "project"...

    http://www.reaa.ru/yabbfiles/Attachments/Reshotka_001.jpg

    http://www.reaa.ru/yabbfiles/Attachments/Bjaka_u_Genriha_001.gif
     
  5. Sep 19, 2019 #365

    Speedboat100

    Speedboat100

    Speedboat100

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  6. Sep 19, 2019 #366

    henryk

    henryk

    henryk

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    =wngtip vorticys utilisation ?

    (as NASA hybrid do...)
     
  7. Sep 19, 2019 #367

    Speedboat100

    Speedboat100

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    Comes very naturally when you have so many engines in e-planes...among other aspects.

    I just love lifting fuselage conceps.
     
  8. Sep 19, 2019 #368

    henryk

    henryk

    henryk

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    =L/D problem ...?!
     
  9. Sep 19, 2019 #369

    stanislavz

    stanislavz

    stanislavz

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    I do not have any believe in vortex or magic shape, and low a/r.

    But - do believe in cnc for diy community.

    Just made some camparision for carbon dragon glider, and as-4-115. Last one have vne of 200 km/h, and can make loops - but weights much more having less wing surface...

    Add to this aeronca c2 - and you have big X...
     
  10. Sep 19, 2019 #370

    stanislavz

    stanislavz

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  11. Sep 20, 2019 #371

    Speedboat100

    Speedboat100

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    36 KG empty....that is a lite ship indeed. It sorta says...I am gonna kill ya.
     
  12. Sep 20, 2019 #372

    henryk

    henryk

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  13. Sep 20, 2019 #373

    stanislavz

    stanislavz

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    Ok, wikipedia have mistake up here, it is 105 lbs / 47 kg or 59 kg in other source..
     
  14. Sep 20, 2019 #374

    stanislavz

    stanislavz

    stanislavz

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    I love this post, from nest of dragons :

    Theory of the forward Swept Flying Wing
    Consider the following:

    A note from Bill Daniels:
    Re: Marske Pioneer IId
    Date: Tue, 13 Nov 2001
    From: "Bill Daniels" <wdaniels@qwest.net>
    Newsgroups: rec.aviation.soaring

    During the flight tests of the Marske Pioneer 1 and 1A prototypes in the
    late 1960's I flew the glider configured with a variety of CG positions to
    determine the qualitative flight characteristics. Maybe the following will
    help folks understand the Marske flying wings and explain why there are no
    demons lurking in the stability and control characteristics of these unique
    gliders.

    At no time did these gliders ever exhibit any tendency toward stall/spin
    departure. Regardless of the CG position, the up-elevator authority is
    limited to less that required to stall the wing by the fact that the airflow
    over the inboard wing separates ahead of the elevator as the wing approaches
    the stalling angle of attack.

    At one point, there was a concern that they might "tumble" end over end, but
    this is impossible unless the CG is very near 50% MAC.

    It is correct to say that any flying wing has a more limited CG range than
    conventional gliders which is why gliders are probably the best application
    of the flying wing concept in that the CG does not change during flight and
    sailplanes are not required to carry cargo.

    However, it is worth viewing the allowable CG range in two ways. One is the
    CG range that optimizes performance and the CG range that provides
    acceptable handling characteristics.

    For safe handling, the allowable CG range is surprisingly wide.

    For optimum performance, there is no range at all. It must be perfect for
    the flight regime. This has led to a call for in-flight shiftable CG.
    There are substantial performance benefits to running at high speeds with
    the CG forward and thermaling with it aft. CG shifting serves the same
    function as performance flaps.

    If the CG is moved forward, the up elevator authority is limited so that the
    minimum airspeed is increased. This is not unsafe unless the minimum
    airspeed is so high that takeoffs and landings are difficult.

    As the CG is moved back, the elevator authority is increased and the minimum
    airspeed is decreased. The elevator forces also became lighter until, at
    some aft CG location, the glider would not trim to any particular airspeed
    and was neutrally stable in pitch. It is surprisingly easy to fly in this
    condition but it does take more attention to pitch attitude. This is the
    most aft CG location at which the glider should be flown. Moving the CG
    slightly aft of the neutral point results in static instability where the
    airspeed will tend to diverge toward a minimum or maximum depending on the
    initial conditions. The glider is still quite flyable but the pilot
    workload is high. The safe handling CG range, depending on the airfoil
    chosen, is usually something like 17 - 24% MAC.

    The above discussion addresses static pitch stability. One must also be
    concerned about dynamic pitch stability defined as any tendency of the
    glider to support oscillations in pitch. The Pioneer I and II series
    gliders would, if the CG was forward of the neutral point, exhibit undamped
    Phugoid oscillations typically at 17 a second period which is pretty typical
    of all gliders. It is worth noting that phugoid damping is mainly due to
    the overall drag of the glider and not to any "fly swatter effect" of a
    fixed stabilizer on a long tail boom. (This is easily demonstrated with any
    glider of medium to high performance by observing the phugoid behavior with
    the spoilers open and again with them closed.)

    They would also exhibit a highly damped resonance in pitch at about 2Hz.
    This resonance was sufficiently damped that PIO's were not a problem. I
    believe this high frequency resonance/damping is largely a function of the
    moment of inertia around the pitch axis. The greater the mass distribution
    around the pitch axis, the more likely this will become a problem.

    It was an important observation that, as the CG was moved aft toward the
    neutral point, the tendency toward dynamic instability decreased because the
    restoring forces that support oscillations were also decreased.

    It seems to me that most flying designers, with the notable exception of Jim
    Marske, seemed to fear the pitch characteristics and compensated by
    designing in far too much static pitch stability in the form of severe
    airfoil reflex or, in the case of swept flying wings, excessive wing twist.
    This resulted in dynamic instabilities that made these aircraft very
    uncomfortable to fly. Put another way, for best handling, the static pitch
    stability should be reduced to match the available damping. This also tends
    to be nearer the best-performance CG.

    I hope this helps.

    Bill Daniels

    ----------

    Forward sweep eliminates the need for washout

    At low speeds most gliders have tremendous induced drag necessitating long wing spans with high aspect ratios but notice the very short elevator on the tails of most gliders, it is short, narrow and at right angles to the rudder, a prime suspect in the elimination of induce and interference drag in a sailplane. Why not put the elevator on the rear part of the main wing where it adds to the reynolds numbers, eliminates the interference drag where the rudder intersects the elevator and eliminates the weight of the long tail?

    Weight is one of the determining factors when considering sink rate and airspeed. With a low sink rate of about 100 to 150 ft. per minute soaring can be done on what others consider marginal of no fly days. The ride is usually smoother and this occurs in the late afternoon and evening when most people have finished work. With a slower speed one can also turn in smaller circles.



    Note from Bill Daniels:

    The difficulty in comparing the tailless concept with the current state of
    the art is that conventional tailed gliders benefit from nearly 100 years of
    refinement and thousands of designs. On the other hand, even though the
    tailless concept began in the first decade of the 20th century, only a
    handful of tailless gliders have actually flown. No doubt if tailless
    gliders had the benefit of the development history that conventional gliders
    have, they would be far better than they are.

    This is not criticism of tailless concept, just a statement of the facts.
    Few designers want to step far beyond the current state of the art so they
    copy most details of their previous designs, or those of perceived
    competitors, adding a few design changes they hope will give their creation
    an edge. This, in my view, has led us into a trap of diminishing returns.
    In other words, the current design concept is very close to optimum. There
    are no obvious opportunities to significantly improve the current design
    paradigm.

    Jim Marske's approach may offer a way out of this trap. Looking carefully
    at the performance of the existing marske gliders one finds that they do
    perform better than anyone would expect given their low aspect ratios and
    wing loadings. To really answer the question, we need an all out,
    composite, 15 meter tailless racer, built to the best standards, not wood
    and fabric homebuilts. Contest scores will then tell the tale.

    I think we all should tip our hats to the bold few who experiment with
    flying wings. Put a brake on the criticism and enjoy the color and
    diversity these designs bring. Jim Marske and Matt Redsell aren't heretics,
    they are just experimenters having a lot of fun with their concept. I get a
    lot pleasure watching their progress.

    Bill Daniels

    Keep in mind that swept forward and swept back flying wings are very
    different craft. As different as canard and tail-aft aircraft. Swept back
    wings are good if you are going to fly in the high Mach numbers. Swept
    forward wings seem to offer some advantage for soaring flight. Each has a
    different set of advantages and problems.

    Swept forward wings with the elevator on the inboard trailing edge does
    indeed increase the elevator moment arm. Forward sweep moves the center of
    lift forward which requires the CG to be moved forward lengthening the
    distance from the elevator to the CG.

    The swept back wings of Horton, Northrop et. al. all had problems with
    spanwise flow thickening the boundary layer near the wing tip elevons
    leading to tricky handling at slow speeds unless the CG was well forward.
    The forward CG, in turn, limited performance at low speeds.

    It is true that a wing with substantial forward sweep will not permit the
    use of winglets, but the swept forward wingtip itself accomplishes some of
    the desired effect anyway. (At least one Pioneer II had winglets installed
    but I have never heard how that affected handling.)

    To summarize a previous post, flying wings of all sorts present a whole new
    set of issues that need to be sorted out. To date, the limited knowledge
    base related to these issues makes flying wing design a challenge. This
    doesn't say that, when sorted out, the flying wing sailplane might not have
    a significant advantage. Somebody just has to do the work.

    I'm very glad that Akaflieg Braunschweig, Jim Marske and others are working
    on the problem.

    All else equal, swept forward wings may pitch up at
    stall and swept back wings may pitch down. However, if the wing is tapered,
    that can cancel the pitch up with forward sweep since the narrower chord is
    likely to stall before the wider inboard section. This relates to a tailed
    aircraft whose up elevator authority can bring the wing to a stalling angle
    of attack.

    However, (again) if the elevators are part of the inboard wing, you aren't
    going to stall the main wing since, as soon as the flow separation starts on
    the inboard upper surface, the up elevator authority is suddenly limited so
    that a stalling angle of attack can't be reached anyway. Marske flying
    wings will slow down and stabilize just short of a stall with the stick all
    the way back. Trying to get one to fully stall or spin is a waste of time.

    Bill Daniels
     
  15. Sep 20, 2019 #375

    henryk

    henryk

    henryk

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  16. Sep 20, 2019 #376

    Speedboat100

    Speedboat100

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  17. Sep 20, 2019 #377

    henryk

    henryk

    henryk

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    =with laminar flow suction ever >100 !
     
  18. Sep 20, 2019 #378

    stanislavz

    stanislavz

    stanislavz

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    Please calm down :)

    I do no think, that anything in more than 20 L/D ratio is necessary. I would trade 5 L/D for better stability :) Or we are going out of homebuild area..

    Just numbers - 3kw level flight - 9-12kg of thrust and 180-240 kg of mtow@20 L/D
     
  19. Sep 20, 2019 #379

    Speedboat100

    Speedboat100

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    LS8 electric:

    Pretty cool system.
     
  20. Sep 21, 2019 #380

    stanislavz

    stanislavz

    stanislavz

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    And very cheap...

    Anyway - 1500 watt china direct drive hub motor with 204 mm case diamater is ok as source for e-motor, good for 12kw with revinding
     

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