Isnt this a sexy plane?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by berridos, Dec 13, 2019.

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  1. Dec 13, 2019 #1

    berridos

    berridos

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    https://www.horten-aircraft.com/en/
    Wondering the effects of those fences on a flying wing. I expect the swirl to be closer to the fuse, but maybe this plane isnt really flying like a delta.
     
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  2. Dec 13, 2019 #2

    litespeed

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  3. Dec 13, 2019 #3

    cluttonfred

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    It is odd that the fences are at the mid-span of the elevons rather than inboard of them to keep the stall from progressing to the control surfaces. Maybe the idea is that you want part of the elevons to stall to reduce the down force from them and allow the nose to pitch down more easily but still want to keep some aileron function?
     
  4. Dec 13, 2019 #4

    tspear

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    Really neat looking plane.
    Does a flying wing; without computer control; really have that much of a drag reduction?

    Tim
     
  5. Dec 13, 2019 #5

    Aerowerx

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    Here we go again! Seems like 2 or 3 times a year, for at least the last 10 years, someone brings up flying wing design. It runs its course for a month or two, then dies out.

    I know for a fact that there are (or were before the software change) many threads here with a lot of good discussion. I know, because I contributed.

    Having a computer has little to do with it. A properly designed flying wing doesn't need a computer.

    And yes, theoretically, not having a fuselage has a reduction in drag.
     
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  6. Dec 13, 2019 #6

    Vigilant1

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    By the time you make it into a flyable, stable airplane, I've seen no reliable analysis that shows a flying wing design offers a reduction in drag. In the real world, in instances where drag reduction is very important and competition is keen, we don't see flying wing designs predominating. There may be other good reasons to use one (RCS reduction, packaging advantages, etc).
     
    Last edited: Dec 13, 2019
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  7. Dec 13, 2019 #7

    Doggzilla

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    The argument “if it was a good idea it would have been done already” is rarely valid.

    German WWII flying wings had vastly lower drag, and at least one British copy was lost due to hitting the sound barrier.

    At that time engines were still very limited and nothing else came close except in a dive.
     
  8. Dec 13, 2019 #8

    Victor Bravo

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    Has anyopne noticed that this verison has large winglets or vertical fins, completely unlike all previous Horten style aircraft?

    Horten found that with enough wing twist you could do without the vertical stabilizers, and you could achieve proverse yaw using a simple two-control system. But Al Bowers did all the math and reported that this comes with a 10 or more percent increase in overall drag.

    So this Horten company may have realized that the winglets allow you to have yaw stability and reduce the excessive wing twist, reducing the drag that came with all that Horten twist ????
    (I'm asking if this explanation is likely to be factual, not telling that it is factual.)
     
  9. Dec 13, 2019 #9

    Sockmonkey

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    The twist also substitutes for the horizontal stabilizer in a non-reflexed flying wing, so you have to have some anyhow. I think the vertical fins on this one are there to reduce the span. Rule of thumb is a tip fin with a height of X lets you shorten the wing by X.
     
  10. Dec 13, 2019 #10

    Aerowerx

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    Keep in mind that this Horten com is not that Horten company from 80 years ago.

    The original Horten company died out as a result of WW2. One of the brothers did move to Brazil and continued research. I don't remember the details, but he may or may not have started the company up again, partnering with someone else.

    This Horten company may or may not have a direct business derivation from that one (in Brazil), but they are certainly using both the name and the basic design.
     
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  11. Dec 13, 2019 #11

    Aerowerx

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    Keep in mind that on a conventional tailed aircraft the horizontal stabilizer needs some negative AoA, or up elevator, to counterbalance the pitching moment of the main wing, along with the CG being ahead of the center of lift.

    Now, remove the fuselage, cut the H-stab in half, and glue to the tips of a swept wing. GREATLY simplified explanation, but that will give you an idea of what is going on. And having reflex certainly helps. With a reflexed airfoil you will not need nearly as much twist.

    As for winglets, Nickels in the "Tailless Aircraft" discusses them. His general opinion is that they are not a good idea, but he did not have Fluid Dynamics and FEA available to optimize the design. Yes, you can shorten the wing but then it can cause other problems according to Nickels.

    Commercial airliners have winglets because they cruise for long periods at constant speed, and the winglets are designed to reduce tip drag and improve efficiency. On a small craft like we are discussing here, you would have to ask the designer why.

    (This is meant for general consumption, Sockmonkey. Not just for you.)
     
    Last edited: Dec 13, 2019
  12. Dec 13, 2019 #12

    berridos

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    This company is an offspin of Extra. Serious guys.
    Is the book "Tailless Aircraft" recommendable? I just ordered the plans for the Verhees Delta and will start very soon to transpond it to CAD to CNC it.
    I have researched a bit in google and i am surprised that deltas are really a very different beast and i should understand better the basics. Any other recommendable book on the topic?
     
    Last edited: Dec 13, 2019
  13. Dec 13, 2019 #13

    Topaz

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    There's often a net reduction in parasite drag, which can result in an increase in cruise speed for a given power setting. Without neutral static stability (which would be made flyable by an average pilot using a computer), a tailless airplane will always suffer a penalty in induced drag, at any speed other than the design speed. The fact that the pitch controls are on the wing mean that trimming the airplane above or below the design speed (where they're in trail) results in a distortion of the lift distribution away from an ellipse, BSLD, or whatever distribution the designer has chosen. That distortion means an increase in induced drag, proportional to the distortion.

    This is why tailless configurations are best used for aircraft with a high power-to-weight ratio. Low- and no-powered designs, such as very light airplanes and sailplanes, are very sensitive to induced drag at low speeds. This mostly affects climb rate, or minimum sink rate for a sailplane. An airplane with a high power-to-weight ratio (a fighter jet, for example) doesn't care as much about induced drag, as it has a lot of engine power to generate a good climb rate.

    For lower-power airplanes, over the entire design mission, it does generally seem to be a wash at best. At worst, there can be a noticeable performance penalty.

    And yes, it's a sexy danged airplane. ;)
     
  14. Dec 13, 2019 #14

    BJC

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    Read the company history on their web site. Link in the OP’s post.


    BJC
     
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  15. Dec 13, 2019 #15

    Sockmonkey

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    It's cool. I should have been more explicit about the twist giving the tips the negative AOA. It's easy to forget that not everyone on here reads up on nonstandard designs.
     
  16. Dec 14, 2019 #16

    Aerowerx

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    Yes.

    Although somewhat dated, it is the only comprehensive book on tailless aircraft design that I am aware of.
     
  17. Dec 14, 2019 #17

    Topaz

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    I'll second that. Pretty much every other source, eventually, points to this book. It's the major work on the subject. This is probably the only text I've come across on the subject of tailless aircraft that actually works from valid aeronautical theory, rather than the combination of empirical "trial and error" and outright mythology that is employed by most of the material out there on tailless designs.

    Now, that does not mean that it's a well-written book, that the translation (from German) is particularly outstanding, or that it's at all easy to use to design a tailless aircraft. It's not, on all three counts. The authors specifically state at the beginning that they're not going to write this book like it's a formal proof of the mathematical theory behind tailless airplanes - and then proceed to do almost exactly that. The book is divided into two major parts, fundamental theory and pragmatic issues. To make any use of the text, you really need to read and understand both sections. Note also that I say, " pragmatic issues," not "pragmatic design." If you're looking for a book on how to design tailless aircraft, you can get that from this book, by developing your own understanding of the theory and issues involved in such designs, and developing your own design methods from that understanding. What you won't get is a "do this first, do this second" description on how to do the job. This book is not a "cook-book" on how to design a successful tailless aircraft. If that's what you want, you'll be disappointed.

    But no, I don't know of another text that I could recommend on this particular subject.
     
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  18. Dec 14, 2019 #18

    Aerowerx

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    There are other newer papers on tailless design out there, Al Bowers paper being the best known at this time. But you would have to scrounge, dig, hunt, snoop, pull your hair out (over search terms) in a search engine to find most of them. Most of them are PhD level research papers that cover only a single aspect of tailless design, and might be a hard read for some.
     
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  19. Dec 14, 2019 #19

    Sockmonkey

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    I've noticed that on most technical subjects like this, there is a large information gap between "explanation for schoolchildren" and "text for seasoned professionals" that tends to discourage people.
     
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  20. Dec 14, 2019 #20

    Doggzilla

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    It’s the Achilles heel of the peer review process. Papers will be rejected for publication if they are not sufficiently verbose. This encourages scientists to be unnecessarily verbose.

    One of the reasons that SpaceX and Tesla have surpassed their competitors is because they require all discussions to use clear vocabulary, and do not allow the use of intentionally overcomplex vocabulary or buzzwords.

    This reduces confusion and wasted effort significantly.
     

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