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Thread: Delta wing airfoil

  1. #16
    Registered User Monty's Avatar
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    Re: Delta wing airfoil

    Quote Originally Posted by Himat View Post
    I can’t remember what book, but one aerodynamic book had a story from the development of the A4 Skyhawk. One of the aerodynamic engineers had done a lot of testing of different airfoils and could not decide. One of the seniors told him to cut a plywood sheet to the same outline and thickness as the wing tested. All in all, the plywood sheet did not perform that much worse.
    I have read that same book at some point....and I agree that way too much emphasis is placed on airfoils.

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    Registered User Monty's Avatar
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    Re: Delta wing airfoil

    Quote Originally Posted by Topaz View Post
    Okay, I'll bite. If you're not trying to cut airframe costs, why are you doing this, instead of a more-efficient "regular" airfoil? Perhaps I misunderstood your intent.
    Because metal does not like to bend in more than one direction.

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    Registered User Monty's Avatar
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    Re: Delta wing airfoil

    Quote Originally Posted by Vigilant1 View Post
    It would be a natural for solid-core foam construction. If the flat area could be built up to the proper thickness using off-the-shelf XPS sheets, then no hot wiring would even be required (it's not hard, but it is "another step", and it is a step where ridges and dips in the core are often introduced, which need to be addressed sooner (light) or later (heavy)). The flat surface skins could be made using infusion or vac bag against a flat smooth surface "mold" to avoid filling/sanding, though getting the excess resin out out would require some tricks. Go with a thick enough skin and no true separate spar might be required, though the front and back of the center sheet would need to be beefed up for the LE/TE attachments.

    I don't know about the aerodynamics.
    This is all true, but I am only interested in aluminum. It's recyclable, and I want to save the planet

    It's also a fuel tank, and I don't like working with composites very much. Personal preference.

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    Registered User Monty's Avatar
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    Re: Delta wing airfoil

    Quote Originally Posted by rotax618 View Post
    If you choose the planform carefully you probably wont need the drooped LE/TE to avoid sudden loss of lift at normal stall AOA, read NACA report 431.
    Thanks for the info. I knew there had to be some data somewhere....

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    Moderator Topaz's Avatar
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    Re: Delta wing airfoil

    Quote Originally Posted by Monty View Post
    Because metal does not like to bend in more than one direction.
    >squints< Most wings are flat-wrap conic projections until you get to the tip, which is the same for this delta as a "regular" wing. What am I not following here?
    "If you have built castles in the air, your work need not be lost; that is where they should be. Now put the foundations under them." - Henry David Thoreau

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    Registered User Monty's Avatar
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    Re: Delta wing airfoil

    Quote Originally Posted by Topaz View Post
    >squints< Most wings are flat-wrap conic projections until you get to the tip, which is the same for this delta as a "regular" wing. What am I not following here?
    fuselage intersection!

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    Re: Delta wing airfoil

    The Rogallo wing has a very real airfoil. If you slice a cone at an angle.......

    Take a cone, cut in half, tip to base. Lay imaginary half cones on table, edge to edge. Sliced parallel to the join are airfoil sections, varying in washout, root to tip. Pure conic projection, a half parabola.....
    https://en.m.wikipedia.org/wiki/Conic_section

    Although, I believe In real life it's a catenary curve, not the ideal parabola.

    https://en.m.wikipedia.org/wiki/Catenary

    In a real world rogallo, you cut the trailing edge in a curve ( modified catenary) to eliminate unsupported, fluttering, drag area.

    You can make the Rogallo wing from sheet aluminum, but it's generally a waste of effort to do so, since it's the foldable nature of a membrane/cloth wing that made such wings attractive, first for kites then space craft landing parachutes, the Flying jeeps..... Then hang gliders.

    The irony and humor that the most advanced NASA reentry tech technology was being flown by amateur pilots did not escape us at the time.

    I will point out the conic curves from the Rogallo wing were used as wing tip shapes on F-106 Mach 2 interceptors. Greatly improved low speed performance.

    I'm not suggesting using a Rogallo on your design, just pointing out that although the projected platform of a delta is the same, it's an apples to plums comparison.

  9. #23
    Registered User Voidhawk9's Avatar
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    Re: Delta wing airfoil

    Quote Originally Posted by Monty View Post
    I have read that same book at some point....and I agree that way too much emphasis is placed on airfoils.
    For thin sections, the airfoil shape does not have as much of an effect as on thicker sections, especially in a design like this. In general, however, the emphasis is well deserved.

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    Re: Delta wing airfoil

    Quote Originally Posted by Monty View Post
    fuselage intersection!
    Not as much of an issue with a delta as with others. The wing itself is it's own tapered root fillet.
    You can just stick it on a slab side.

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    Re: Delta wing airfoil

    Quote Originally Posted by Monty View Post
    fuselage intersection!
    >squints harder< ... That's still just a conic intersecting another shape. It doesn't distort the conic, it just dictates how the base of the conic is trimmed. If you're actually talking about the fillet, then that, like a wingtip, is another matter, one usually handled either with non-structural composites or an English Wheel.
    "If you have built castles in the air, your work need not be lost; that is where they should be. Now put the foundations under them." - Henry David Thoreau

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    Registered User Monty's Avatar
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    Re: Delta wing airfoil

    Quote Originally Posted by Topaz View Post
    >squints harder< ... That's still just a conic intersecting another shape. It doesn't distort the conic, it just dictates how the base of the conic is trimmed. If you're actually talking about the fillet, then that, like a wingtip, is another matter, one usually handled either with non-structural composites or an English Wheel.
    Keep squinting....Have you used an English wheel??

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    Registered User Monty's Avatar
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    Re: Delta wing airfoil

    Quote Originally Posted by Sockmonkey View Post
    Not as much of an issue with a delta as with others. The wing itself is it's own tapered root fillet.
    You can just stick it on a slab side.
    Slab side is not an attractive look...

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    Re: Delta wing airfoil

    Please see original post. How much difference does it make?? No one has given a number. I want a number, not a feeling.

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    Re: Delta wing airfoil

    Quote Originally Posted by Monty View Post
    Please see original post. How much difference does it make?? No one has given a number. I want a number, not a feeling.
    Reference post #2. " Would it fly, yes. How well? [There is] only one way to tell."

    If you want numbers you need to do the work or have someone else do the work for you. I appears you are looking for the second solution. So am I (and many others).
    The most elegant theory can never change reality but even a mediocre theory can predict reality most of the time.

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    Re: Delta wing airfoil

    This would be great for a supersonic wing made of unobtainium.

    I haven't read any papers showing that vortex lift has the magic lift enhancing abilities implied here. It might allow you to reach a fairly normal Cl with a low aspect ratio wing, I suppose.

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