Verhees Delta brain fart

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by berridos, Sep 17, 2013.

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  1. Sep 17, 2013 #1

    berridos

    berridos

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    Hi Everybody

    cri-cri-twin-engined-airplane.jpg

    I was thinking on a Verhees delta with this engine setup For example using two AIxro XR50 wanker, sorry wankel engines.
    To make the idea even more stupid the engine support arm fairings could act as canards rotating around around a boom.
    Makes the thrustline offset the design unfeasible on a delta due to the pitching moments introduced by that offset?
    I bet the answer is yes. Otherwise the concept would have several really exciting benefits.
     
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  2. Sep 18, 2013 #2

    Head in the clouds

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    Nice concept. I'd probably not make it thrust vectoring but the idea of mounting the engines on the tips of a canard/strake is interesting. Using two engines/props might allow you to run them direct drive and still be able to get enough static thrust. And with small diameters the props' pitch could be set for the high cruise that a delta is ideal for.

    I think the configuration has merit and is worth investigation. My only reservation at this stage would be whether the prop slipstream would wipe out the high alpha l/e vortex or perhaps you'd need to have contra-rotating props and be able to use the slipstream to drive/trigger/augment the l/e vortex? Or maybe the prop-blast affected area would be sufficiently inboard only and the l/e vortex could develop outboard of that - maybe have an ogival + double-delta planform just like my avatar so that it would trigger outboard first? The 'blown' canard would have lots of authority and allow a reduced amount of up elevator/reflex and so the vortex lift might not be so necessary for low speed flight.
     
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  3. Sep 18, 2013 #3

    berridos

    berridos

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    i admit i dont follow your le vortex reasoning.

    Advanteges of the concept:
    The concept could have a tiny inline landing gear practically landing on its belly.
    The pilot would sit in the nose in a partial lexan bubble with the corresponding visibility and the sitting in the air feeling.
    Full laminar wing and fuse in composites without fuse wing interference drag
    Single radiator for both engines and redundancy.
    Best of all would be the production cost. The beast could have an amazing low part count. Huge upper and lower composite infused shells/hull+2 ribs + lexan cabin+seat, +canard or v-tail thats all.
    The weight of such a strict monocoque could be exceptional

    Otherwise you could place those little engines on the tip of a V-Tail with or without thrust vectoring whetther pusher or tractor. These 36lbs Engines nacelles would act as endplates of the v tail, reduce their size and v tails help in mixing controls of the delta
    However maybe you should have two positions of thrust incidence in order to avoid pitching effects in slow flight or drag at cruise (should be complex)

    I love deltas. The awesome aestetics would be in line with awesome functionality.
     
  4. Sep 18, 2013 #4

    Himat

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    Why a canard?

    If simplicity is the goal a pure delta is better. Placing the engines in front of a full laminar wing might not be a good idea either. I am not sure that a that common radiator is a good idea when it comes to redundancy.

    If you put the engine in the fin you are doing the same as Laddie Mikulasko did with one of his best known RC model airplane designs, the Northstar. A later incarnation, the Polaris Ultra, is shown here. Later on Laddie simplified the design and made the Arrow, a pure delta with fin mounted engine. If you want twin engines these could be mounted on overwing pods like on the Beriev Be200.

    laddie-arrow.jpg polarisultra-flight.jpg
     
  5. Sep 18, 2013 #5

    berridos

    berridos

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    Would be interseting to see those two in action at slow speed and than suddenly pushing the throttle forward. I dont like these two design because they have fuselage. As soon as i become more profficient with solidworks i will try a sketch closer to the verhees design.
     
  6. Sep 18, 2013 #6

    cluttonfred

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    Hmm, that's a great engine location for a seaplane--shields the prop from spray and allows you to stand on the hull/wing to check the engine when afloat--but perhaps less practical for a landplane. Still, it might work for a single-seater small enough for you to reach the fin-mounted engine comfortably while standing on the ground. What's the rational for the twin engines?

    On the idea of a small, delta-wing design, I have to say that I have seen the Verhees Delta up close and found it, ahem, aesthetically challenged. There was a one-off single-seat development of the Dyke Delta called the Stingray, you'll find a little info in this forum. If I were going down that road I'd get a set of Dyke Delta plans for inspiration and work conceptually from there. Personally, I'd love to see an LSA version of the Dyke Delta, which could potentially be a very safe, stable aircraft and a real attention-getter. The original has a high stall speed of 70-75 mph at 1,980 lb gross weight, but a lighter, fixed-gear version with the same proven aerodynamics at 1,320 lb LSA weight would bring the wing loading from over 11 lb/ft2 to under 8 lb/ft2 and a 100hp Rotax ought to be just about right.

    Dyke_Delta_JD2_(N71AW).jpg
     
  7. Sep 18, 2013 #7

    Himat

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    If you search the different model airplane forums you will find different flyers impressions of the handling of these airplanes. Both on RCgroups and RCuniverse there are several threads on the Northstar, Polaris, Arrow, Dragonfly and similar designs/copies in various sizes and construction materials. With glow engines or electrical motors. Pitch change with throttle setting is not uncommon, but opinions on the amount and if it is a problem differs.

    I do see your point about a fuselage, but if sizing such a design to fit a pilot it might be difficult to accommodate him entirely within the wing. All these models are flying boats and as such the fuselage is the hull. Another set of compromises must then be made. Maybe you would like the look of the Neptune UAV better?

    A re read of this thread might be of interest too: http://www.homebuiltairplanes.com/f...ics-new-technology/6806-slow-delta-wings.html

    neptuneUAV.jpg
     
    Last edited: Sep 18, 2013
  8. Sep 18, 2013 #8

    Himat

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  9. Sep 18, 2013 #9

    cluttonfred

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    By the way, since the Dyke is essentially a tailless design with a small trimming surface, it's also worth taking a look at some very similar low aspect ratio, unswept flying wings.

    Charles Fauvel and his Flying Wings

    See especially the AV-10, AV-60 and AV-61 under "Fauvel gliders and airplanes" and the Debreyer PĂ©lican and Payen AP-10/AP-12 under "Precursors and successors."
     
  10. Sep 18, 2013 #10

    berridos

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    Basically the idea was related to the aixro thread. Those engines are cheap small and extremely lightweight. However overthinking the idea, an off-axial thrustline on a delta in case off an engine out is absurd.
     
  11. Sep 18, 2013 #11

    cluttonfred

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  12. Sep 19, 2013 #12

    autoreply

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    [​IMG]
    (Bill Husa)

    Replace the engine with a cruciform tail with the engines on the stabs tips.
     
  13. Sep 19, 2013 #13

    Himat

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    If both engines where fin mounted in push - pull configuration there would be no side force in case of one engine out. If placed side by side the distance between the engines is a deciding factor. In direct drive the propellor on these Aixro engines would be small and the engines could be placed close. A side note, I have read that one engine out in a B58 Hustler was a big issue, not so with the Avro Vulcan. Look at the configurations and it does make sense.
     
  14. Sep 19, 2013 #14

    berridos

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    Cool Design. Imagine the design with the pilot sitting near the front in a transparent bubble. The problem I see with the cruciform tail with engines is that the horizontal stab and engines would be total blanketed at steep descent at low speed. Dont you think so? Or would the sucktion of the rear engines contribute to reattach the air flow? Pretty complicated to surpass Verhees reasoning.
    One of the beauties for me of the Verhees delta is the compactness of the design. I would minimize the nose.
    A Drawback of locating the pilot in the front and the engines in the back would be the inertia of the design. Could make stability unpleasant.

    Sooner or later I will need to get my hands on the plans of the design
     
  15. Sep 19, 2013 #15

    Head in the clouds

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    At high angles of attack (alpha) the leading edge vortex will have developed and the engines would have to be working with it rather than against it, so in a pusher configuration, and if the props were side by side rather than in tandem, the props would definitely need to be contra-rotating, and yes they should contribute to the generation of lift by adding energy to the l/e vortex rather than by keeping the flow attached. Deltas generate their lift at high alpha via the l/e vortex rather than by smooth flow attachment. On Orion's (Bill Husa's) design, posted by autoreply above, the dogtooth in the l/e is to trip the l/e vortex reliably for both wings at the same time and in a particular spanwise location.

    If you want to play deltas at low speed you need to consider the way that the l/e vortex generates lift at high alpha and has the effect of re-shaping the airfoil and keeping the flow controlled, even though it's not attached.

    See the images below for examples of the l/e vortex.

    DELTA WING LEADING EDGE VORTEX.gif DELTA WING VORTEX LIFT 1.jpg DELTA WING VORTEX LIFT 2.jpg DELTA WING VORTEX LIFT 3.jpg DELTA WING VORTEX LIFT 4.jpg DELTA WING VORTEX LIFT 5.jpg DELTA WING VORTEX LIFT 6.jpg

    Yes, Verhees reasoning seems to be to avoid all the complicatedness of deltas. The Verhees is a very simple delta and doesn't appear to take any real advantage, except compactness, from its being a delta. I don't think it is intended to fly in the zone where the l/e vortex is generated which means it does not have any low-speed capability. As soon as you start to explore the delta concept further, to take advantage of their great speed range they do become a bit more complicated than they appear.

    I don't follow your reasoning, as long as the CG is in the right place how does it make any difference to stability where the pilot or engine is located? The main advantage of having the pilot in the nose is for forward visibility during landing at high alpha, which is another reason why the Verhees configuration can't use high alpha for landings.
     
  16. Sep 20, 2013 #16

    henryk

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    =problem solution=see LE vortex generators= BOING X32A=carier variant...
     
  17. Sep 20, 2013 #17

    cluttonfred

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    Another way to keep a more level attitude for take-off and landing, not novel but quite practical, is, of course, flaps. In a delta or other low aspect ratio design that uses outboard elevans for pitch and roll, you can certainly have flaps on the inboard sections. Personally, I really like the idea of all-moving elevons like the Vought V-173 so that the elevons are at much lower angle of attack when the main "wing" is at high angle of attack as in the clip below (skip to 2:35). With flaps (like the one big rear flap on the V-173) the incidence for take-off and landing can be brought down to something reasonable for better visibility and shorter landing gear. The same principle could be applied to all-moving outer panels on a delta or double delta design, separated by stall fences and/or vertical fins for docile low-speed handling.

    [video=youtube_share;LfpTDOAfj7Y]http://youtu.be/LfpTDOAfj7Y?t=2m34s[/video]
     
  18. Sep 20, 2013 #18

    henryk

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    https://www.youtube.com/watch?v=MIMPXr_VgNo

    =moore comfortable and simple...\LE vortex generators-vertical plates\.
     
  19. Sep 20, 2013 #19

    cluttonfred

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    If you mean the spoilers on the forward upper wing, which presumably cause large, stable vortex flow over the inboard wing, that kind of vortex flow is harder to achieve and stabilize at low speeds and low wing loadings. Ordinary, multiple "tooth" vortex generators do work well at our light aircraft speeds and loadings, but that's to help you land slower by allowing a higher angle of attack. With very low aspect ratios, that's not the issue, the challenge is flying slowly without having the nose so high in the air. One solution, of course, would be to put the wing on top (and/or use a pusher engine, but I prefer a conventional tractor engine placement). I can see high-wing, low-aspect ratio design, delta or otherwise, being very appealing. Think of a tailless, low aspect ratio delta, Arup/Zimmerman or plank flying wing on top of a fuselage pod like the Boeing YL-15 but with the vertical control surfaces on the bottom surface of the main wing. You'd have the low-aspect ratio low-speed handling but much better visibility, including using transparent panels in the wing itself for upward vision.

    8986.jpg + 426820.jpg = ?
     
  20. Sep 20, 2013 #20

    billyvray

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    In answer to your "high wing" + "low aspect ratio" I submit this:

    Lucy1.jpg Lucy4.jpg

    Not a delta wing, but certainly thinking outside the box on low aspect ratio and visibility....

    Wonder if it ever flew. I know it got up to doing taxi tests...

    ~Bill
     

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