Slow delta wings?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by deskpilot, Jul 21, 2009.

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  1. Jul 21, 2009 #1

    deskpilot

    deskpilot

    deskpilot

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    Hi Guys, just a note to let you know that I haven't given up on this thread. I recently got in touch with a cousin whom i haven't seen or hear from in over 35 years and it's all go catching up on family news. She is in the UK , I'm in Oz so there's a lot of photo scanning etc taking up my time. Will be back soon.
     
  2. Jan 25, 2010 #2

    deskpilot

    deskpilot

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    G'day guys,
    I recently found a rather poor photo of the Dyke Stingray and was immediately taken by it. I have a desire for 'something different' to build and this aircraft almost fits the dream. Problem is, it's landing speed. Here in Oz we have a limit of 45 knots (51.8mph) and the Stingray was reported to land at 65knots (74.9mph) My question is, is there any way to reduce the stall speed of a delta wing. I've concidered L.E./ T.E. flaps and V.G's but am not sufficiently informed on either with regard to deltas.

    If any one has photos of the Stingray, I would appreate it if you care to share. I understand it is in a musem now.

    I have already been to the DykeDelta web site. That's where I started.

    Cheers, Doug
     

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  3. Jan 25, 2010 #3

    bmcj

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    I think you might be able to slow it down more than the published landing speed, but it would be at a high angle of attack with absolutely no forward visibility. This is why the Dyke Delta is flown on in a flat attitude. Also, you would have to do some research and experimentation to find out what kind of stall break or lateral roll-off tendencies it might have.

    Does your 45 knot requirement apply to landing speed or minimum controllability speed? You might be able to demonstrate min control speed at altitude, yet land at the higher speed they call for on the Stingray.

    Bruce :)
     
  4. Jan 25, 2010 #4

    djschwartz

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    The only really practical way is to reduce the wing loading. If you had access to lots of sophisticated FE airflow modeling and were willing to attempt computer aided stability augmentation you could try to use captured vortices at very high AOA. The problem is drag goes way up under these conditions as well. Works well for an advanced fighter jet with an afterburner; not real practical for a light sport aircraft. Flaps, either LE or TE are not practical with a tailless design, whether delta winged or Northrup style flying wing. Without a tail it is almost impossible to overcome the pitching moments created by the flaps without canceling out much or all of the added lift they would generate.

    To lower the landing speed from 65 kt to 45 kt the wing loading would would need to be reduced to (45/65)^2 or .48 of the original aircraft. That means essentially doubling the lifting area of the airplane without increasing its gross weight. Thats a difficult engineering challenge even if you assume optimum use of state of the art structural materials.
     
  5. Jan 25, 2010 #5

    Lucrum

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    (I make no claim to be nearly the expert in aerodynamics some of these guys are)

    1)More wing area/lower wing loading.
    2)I've never seen a chart showing the effects of leading edge high lift devices on pitching moment. But based on personal experience I'm thinking leading edge devices don't effect pitching moment as much as trailing edge device. So for a tailess configuration that might be something to look into. Of course leading edge devices generally extend the lift slope, meaning higher stall AOA's so landing gear length can become an issue.
     
  6. Jan 25, 2010 #6

    lr27

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    I don't think a properly designed delta wing would necessarily need leading edge flaps as you could use the aforementioned vortex lift. A proven approach for an aircraft like this is, of course, the Facetmobile. Barnaby Wainfan, it's designer and pilot, has demonstrated that it's feasible to make a small delta aircraft that stalls at a slow speed and is reasonably practical.

    In a tape I obtained from TWITT (yes they have a web site), he says that if you use forward slanting surfaces near the l.e., the drag doesn't have to be all that awful. One approach to this is called conical camber, and you can see this on some of the old, '50s delta wing fighters whose wings curl over a bit right near the tip.
    http://www.aerospaceweb.org/aircraft/fighter/f102/f102_08.jpg
    Some interesting papers on it on line here and there.

    However, I like Wainfan's approach where he makes the wing pretty thick instead, and puts the pilot inside. With windows in the floor to deal with the high angle on landing. I seem to recall he called it his 1:1 scale moving map display.

    If you Google Wainfan and Facetmobile you will find a pretty interesting site.

    If I recall correctly, there's another very light delta wing from maybe the '60s or '70s in the EAA Sport Aviation archives. If you're a member, you can dig through this stuff on line.

    BTW, be aware that at least one amateur delta wing designer has died, if I understand correctly, because of a pitch up effect from the engine failing on takeoff after a fairly high speed was reached. It was a pusher, and I think a tractor engine design might not have this particular problem. Also in the EAA archives, from the 60's, I think, but I don't recall the name. Looked like a little jet fighter but had pusher piston engine.
     
  7. Jan 25, 2010 #7

    autoreply

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  8. Jan 26, 2010 #8

    deskpilot

    deskpilot

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    Thanks for your replies guys, much more helpful than my home forum at Recreational Flying

    So, it is doable re the Verhees Delta, but what a god-awfull looking aircraft. I've seen the Facetmobile mentioned a few times but will have to follow up on the designers thoughts.
    In the meantime, I've decided to build myself a small wind tunnel to experiment with a few things (long term project). What I'm seeing is a double delta (only because I like the look, much more sleeker that a single) with a fence at the intersection line and another at the wingtip. I'm not at all sure what they will do the vorticese. Also thinking of an extending/drooping L.E. for T/O and landing. Might even incorporate the down curl at the tips (thanks lr27). I'm also still concidering the flat top fuselage as per the Dyke Delta but with small strake at the sides to prevent the airflow from slipping off the side.
    I take the point re T.E. flaps and pitching so will leave that to one side for now.
    My power plant would be either the Jabiru 2.2 or the 1.8 WV. I'll be posting another thread under engines later on as I've an idea or two. By God, I'm creative lol.
     
  9. Jan 26, 2010 #9

    autoreply

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    A Blended Wing Body might also be an interesting option. The Atlantica is from my point of view an interesting design exercise though their claims are definitely way too optimistic.
    A scaled-down version of that one might be in your corner as well :)
     
  10. Jan 27, 2010 #10

    flyvulcan

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    Hi Doug,

    The aircraft you are interested in is actually called the Delta Stingray and it was designed and built by a Mr. Lowell J. Borchers. I spoke with Mr. Borchers around 1 year ago about his aircraft as I am also interested in deltas/tailless (i.e. Me163, Scotty Wintons Opal etc).
    He advised that his aircraft was initially flown without the small horizontal stab with some adverse qualities that were fixed by the addition of the stab.
    He indicated that it was quite stable in the cruise with docile handling characteristics and that it built up speed rapidly when pointed downhill.
    He eventually donated his aircraft to his local town museum where it is on display.
    He did not produce plans for it, nor does he have any drawings of it, but he did remember wing section details etc.
    He didnt seem to mind talking with me about it, so if you are really interested in talking with him, I probably still have his number somewhere. PM me if you would like it and I'll have a look.
    One thing that he did say was that it was heavy. From memory, he said that it was around 800 lbs empty. With the right construction techniques and powerplant, I suspect that you could get this down closer to 450lbs as it is a small aircraft. This will bring the stall speed down by reducing take-off weight by 25%.
    Cheers,
    Dave
     
  11. Feb 1, 2010 #11

    lr27

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    Although the curl is only visible on the tip in the photo, in the papers I read it seemed like it was a taper along the whole length of the leading edge, i.e. very minor at the tip, but linearly increasing as you went out. Whether that's the optimal configuration I don't know.

    On the wind tunnel, beware of Reynolds number effects. On anything that's rounded, the flow will probably stay attached longer as the Reynolds number goes up. If you're counting on vortex lift that could be a problem. I think that may be one reason that Wainfan stayed with sharp edges. He made several models before finalizing the Facetmobile, as I recall.

    BTW, I seem to recall that the landing (and takeoff) speeds of the Facetmobile were not limited by the aerodynamics but by the angle of attack allowed by the landing gear.
     
  12. Feb 2, 2010 #12

    deskpilot

    deskpilot

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    It's been a bit slow here at home so I 'wasted' some time(according to my wife) modelling my version of the Delta/Stingray using GoogleSketchup7.

    For ease and speed, I've done it in Flat Panels just to get an idea of what it'll look like. In reality it will, more than likely have conventional aerodynamic surfaces.

    I'm aiming at getting maximum lift at low speed to fit our 45knot stall speed (I've made the mistake previously by saying low landing speed) The existing landing speed is fine. Anyway, to this end I've lengthened the cord by about 10% (guesswork), raised the tail plane attachment to give a full length, un-obstructed lifting surface on the fuselage top, and added winglets to miniumize roll over vorticese.

    As for power, hopefully something in the 80 hp area such as the Jabiru 2.2ltr, flat 4. I want to stay with air cooled for lightness.

    So, what d'you think? If you're qualified enough to tell me I'm talking out my rear end, fine. But if you're only expounding an un-educated opinion, best you don't say anything.
     

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  13. Feb 2, 2010 #13

    bmcj

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    No, tell us how you really feel DeskPilot. :gig:
     
  14. Feb 2, 2010 #14

    deskpilot

    deskpilot

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    OK brnj, maybe I was a bit O.T.T. So let me restate, in different words. All comments gratfully received. ie 'Wow!', ' I like that',' I want one' etc etc. But, ' It won't work because I think....' sort of replies, unless from a qualified person (Orion for one), just p**s me off. (Where's your 'Sorry' smilie)

    This is definately not welcome :roll: :roll: :roll: (kidding)

    This is a great site for info sharing, putting forward idea's etc. There are old , knowledgable members, and very young, enthusiastic but raw members, covering a very wide 'type' base. Not wishing to ignore or shoot down the less knowledgable, I'm looking for information as to whether I'm on the right track or simply wasting my time as the wife says. To that end, I need guidance from experienced people, but I'll accept positive comments as well.

    Back to the design, I was taking some measurements yesterday (total wing area) and realized that in scaling down, I made the fuselage a bit too narrow for comfort. I am now widening it but retaining an approx 18ft wing span (8ft center section with 5ft removable wings for trailering) The body will be just under a meter wide (3ft) This is not only for comfort but also to present a more usable wing area.

    So, I'll try again, any comments?
     
  15. Feb 3, 2010 #15

    bmcj

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    No apologies needed... I completely understand where you are coming from. When you are talking serious design issues, you need two things here... a thick skin for those less than tactful comments and the patience to learn who on this forum has the necessary knowledge to answer your questions correctly and who (on the other side of the fence) are just talking without the background or experience to support their views. You also have to be open to the fact that even the less knowledgeable members sometimes come up with a gem of an observation that might be useful.

    Now, to your design proposal... I like it. In configuration, it is similar to the Dyke Delta and, to a slightly lesser degree, the Miller Jem. Both of these designs proved successful, so I see no reason to doubt yours. As for keeping your stall speed low, just remember that more wing area (and low wing loading) is your friend in the low speed range.

    Bruce :)
     
  16. Feb 3, 2010 #16

    Lucrum

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    I claim no expertise, but I like it. I'm always more interested in something a little different (within reason) more than just another cookie cutter design (no offense intended). It's similar enough to a couple of flying models so that, done properly, there's no reason it won't fly.
     
  17. Feb 19, 2010 #17

    deskpilot

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    Time for an update on my design.

    On close inspection of my original model, I found that it was way off reality in that the pilot would have to lie down as though on a luge to fit in it. So, taking one crash test dummy scaled to 6 ft, and a block scaled to the same dimensions as a Jabiru 2.2 engine, I started again. See attached images. I'm still not completely happy in that I feel the forward delta needs to be wider and the fin needs rescaling for the single version. Personally I like the twin better but of course, this is more complicated to design and build. I could streamline the nose more if I went rotary but then there's more of a weight penalty. Note that I have a sharp undercut on the leading delta to form a stake. I'm not too sure what effect that will do a slow speeds but I believe it will aid in keeping the AoA down somewhat. Something to do with vortex generation.(So much reading, my brain hurts ;-)

    I feel that the pilot may have to be moved back about 1ft to position the CoG but, having taken some basic measurements of the original wings, it is about right as is. My understanding is that it should be approx 10% cord in front of mean-cord. It just doesn't look right.

    Any feed back?
     

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  18. Feb 20, 2010 #18

    lr27

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    You're probably already thinking of something like this, but it seems like the airframe would be cleaner if the sides of the "fuselage" were slanted to blend in more. Also, I wonder what those tip fins are doing for you. Looks like they're not as far back as the center fin. Is there a span constraint so you can't extend the tips flat?
     
  19. Feb 20, 2010 #19

    ultralajt

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    Nose heavy...I think..would be....
     
  20. Feb 21, 2010 #20

    DaveK

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    Sounds a bit Yoda like:)

    "Nose heavy...I think..would be...."
     

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