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 11, 2019 #261

    Topaz

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    Moderator Note: Yes, Speedboat. Please at least stay on your own topic.
     
  2. Sep 11, 2019 #262

    Speedboat100

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    I have absolutely no idea how this slipped into being a material discussion.

    Anyway here is a good electric engine (affordable)....Turnigy is favoured by some hang glider pilots at least.

    https://hobbyking.com/en_us/turnigy...pc&utm_campaign=eu&utm_term=LF&___store=en_us
     
    Last edited: Sep 11, 2019
  3. Sep 12, 2019 #263

    stanislavz

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    But please pay attention on their quality and nominal power. This stated ~2kw is like max for 10-20 seconds with huge airflow...

    I do feel wrong on my pushing into flying wind fan area. Found an perfect post : https://www.homebuiltairplanes.com/...from-the-elevons-alone.6524/page-2#post-57267

    Expanded it a little for autostable foil (like BKB-1 / Kasperwing) And classical. Sorry for both left hands.

    [​IMG]

    Red lined area are creating down force. And it being subtracted form main wing lift. So the winner is classical motorglider. Question is which one - or as close to classical as can be, but to be made with bomb-door for batter under Cg, or some more unconventional - anything from Burt rutan voyager / bumerang (batteries on on pod, passengers on other pod) and ending with BV-141 like asymmetric style.
     
  4. Sep 12, 2019 #264
  5. Sep 12, 2019 #265

    Aerowerx

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    It is not as simple as that. This has been discussed many times here on HBA.

    On a "normal" tailed motorglider the tail also produces a down force and a drag, and has weight. Also don't forget the drag and weight of the fuselage. Unless you are carrying cargo or passengers, the only purpose of the fuselage is to keep the tail from falling off.

    Eliminate the tail and fuselage and you have a flying wing. The tip sections of the flying wing produce the same forces as with a conventional tail, without the added weight. And you have eliminated the weight of the unneeded fuselage. A properly designed wing will perform just as good, or better, than an average "normal" design.
     
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  6. Sep 12, 2019 #266

    Aerowerx

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  7. Sep 12, 2019 #267

    stanislavz

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    I do have stated, what surface in red lines provide negative thrust. Which must be substracted from main lift.

    This is all as i see it.

    Plus tail allow less area for creating same momentum. Or not ?
     
  8. Sep 12, 2019 #268

    Jay Kempf

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    Then why has no one ever built a flying wing with higher L/D than a conventional sailplane? Sailplanes are the end of the optimization you are talking about and the likely set of basic references for adopting into early electric flight. Normally they have the wing area and useful load to absorb battery weight fraction. Basically sailplane people have done the optimization you allude to and a small Htail on a long thin stick ends up being less drag than no tail.
     
  9. Sep 12, 2019 #269

    Aerowerx

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    You are mixing "negative thrust" and "lift". The lift at the wing tips is not negative. It is tilted slightly forward because of the washout, but is not negative.

    And "negative thrust"??? What is that? Would that be the same as "positive drag"? As it turns out, by having the lift vector tilted slightly forward a "negative induced drag" is produced or, in other words, an induced thrust. This is a benefit. You can think of it as taking the place of the vertical tail, as it improves the lateral stability. And if properly designed can eliminate the undesirable adverse yaw.

    You can't take just one parameter to compare tailed vs tailless. You have to look at the complete design of both.

    I do not want to get any further off topic for this thread. Flying wings have been discussed many, many times. Please refer to the numerous threads here on HBA.
     
  10. Sep 12, 2019 #270

    Aerowerx

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    I do not wish to get off topic for this thread. There has been too much of that lately.

    But I suppose I could say, because no one has yet? The Horten H-IV had a glide ration of 32, and that was 45 years ago in a war-torn country. What could be done now with modern materials and techniques?
     
  11. Sep 12, 2019 #271

    Jay Kempf

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    If we can build flying wings they will be lighter meaning they can carry more batteries and they are certainly easier to build than conventional aircraft. I am all ears if it can be done. What analysis method could estimate the potential? For powered flight that could be a no brainer if true. I have always been curious about this. A flying wing vacuum bagged in hot wired or one off female molds would be about as easy as anything to build.
     
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  12. Sep 12, 2019 #272

    stanislavz

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    Sorry. Not thrust. Lift of course.

    I am not an aircraft engineer. And yes, canard configuration would have both wings green. But it have different issues - narrow flight envelope.

    Flying wings removes tail drag and weight, but adds bending moment to wing, which limits it A/R

    I will try to draw my ideas with description of choosen solutions. Strojnik untapered wing, was last piece of puzzle for me
     
  13. Sep 12, 2019 #273

    Speedboat100

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    Maybe no one has thusfar been able to create such monster L/D glider wing yet ?
     
    Last edited: Sep 12, 2019
  14. Sep 12, 2019 #274

    Speedboat100

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    I am not an aircraft engineer either...but I am spending helluva lot of time to study Laplace and Navier-Stokes etc equations in the field of fluid dynamics . Just to be sure about certain aspects concerning some aerodynamical machines.

    Lightness and lite construction are not the same...also the chosen concept plays an important role...there cannot be just one answer.
     
  15. Sep 12, 2019 #275

    Jay Kempf

    Jay Kempf

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    https://www.jetforums.net/threads/news-horten-hx-2-flying-wing-debuts.3044/

    Seems this thing at 10 meters span with Rotax 912 (100hp) and 120 liters of fuel can do 167 MPH and they are claiming 2,000 nautical mile range Probably that range number is at a lower cruise speed. But still good numbers. This is a prototype and they are looking at different power packages. Could be a great electric. Time will tell whether the thing has any weird handling. There was a tandem or single seat version of this and I can't find any info on that. I have this memory that the same group crashed an earlier prototype...?

    This one had 6 hours of test flying on it at the time of the last article I could find and has video of it flying. Certainly could be higher aspect ratio with bigger span for more efficiency.
     
  16. Sep 12, 2019 #276

    Norman

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    Yes, their engine was 12 hp but it made that power at 300 RPM and swung two 8 foot props.
     
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  17. Sep 12, 2019 #277

    stanislavz

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    Ok. My vision of as simple as possible flying thing from composite. And low risky too.. Beauty thing is it needs only three female moulds - one 3.2 metre with wing section / eileron / flap / vertical stabilizer, two with wingtips vertical stabilizator. And two tubes as male or female moulds for boom's. Boom length here is ~ 4 metres. Span and chord are visible. Wing separation on boom. Pod- i would build it from tubes as cage... Propeller diameter to bottom side of boom ~ 1.3 metre.. Wheels two on boom or on on pod.

    Another option - V tail from slightly longer wingtips.. Any hope to calculate L/D from this A/R by rule of thumb ?

    Ps. Sorry for stealing thread.

    Low risk - smaller parts, possibility to test half of airplane cheaply. And not ruing a budged if any parts molded with defects.

    [​IMG]
     
  18. Sep 12, 2019 #278

    Speedboat100

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    Don't show this to Peter Sripol or the Flite Test guys...they'd build it in an instant.
     
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  19. Sep 12, 2019 #279

    Speedboat100

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    Yes Norman I notissed it rotated the props pretty darn slow.

    ---

    Is it possible that we are nowhere close to the adequate propeller type in electric flying ?
     
    Last edited: Sep 12, 2019
  20. Sep 12, 2019 #280

    stanislavz

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    That is ok. Hopefully, they will mention me as some guy on forum in video :) It is nothing new here in this design from any point.

    Try to draw same as flying wing - it will need much bigger molds, and molds for all parts And it will not achieve same A/R with strong structure.
     

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