Where to draw the line - Deltas versus Flying wings - And why does it matter?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by nerobro, May 2, 2019.

Help Support HomeBuiltAirplanes Forum by donating:

  1. May 3, 2019 #21

    RPM314

    RPM314

    RPM314

    Well-Known Member

    Joined:
    Mar 27, 2015
    Messages:
    722
    Likes Received:
    300
    Location:
    the wrong side of the clouds
    Easy, a pan can't have any purely vertical surfaces affixed to its edges. It can have pan-tip extensions that go out of plane, but clearly that is a different matter from the sharp transition to vertical walls typically seen on pots.
     
    Last edited: May 3, 2019
  2. May 3, 2019 #22

    Hephaestus

    Hephaestus

    Hephaestus

    Well-Known Member

    Joined:
    Jun 25, 2014
    Messages:
    763
    Likes Received:
    155
    Location:
    YMM
    Ok so where does a wok fit in there then? :confused:
     
    RPM314 likes this.
  3. May 3, 2019 #23

    Norman

    Norman

    Norman

    Well-Known Member

    Joined:
    Nov 29, 2003
    Messages:
    2,877
    Likes Received:
    902
    Location:
    Grand Junction, Colorado
    Google for "wetted aspect ratio" and you'll understand why it's important to minimize the fuselage. Unfortunately an adult human and an engine just won't fit inside an airfoil unless the chord is 13 feet long and the thickness is 20%.
     
    RPM314 likes this.
  4. May 3, 2019 #24

    Norman

    Norman

    Norman

    Well-Known Member

    Joined:
    Nov 29, 2003
    Messages:
    2,877
    Likes Received:
    902
    Location:
    Grand Junction, Colorado
    Fuselages detract from stability. An empennage affixed to the aft end of a fuselage adds to stability. Both fuselages and empennages add parasite drag (40 to 60% of total non-induced drag). The goal of a flying wing is to eliminate that drag and get adequate stability about all 3 axes using just wing shape. Not an easy goal.
     
  5. May 3, 2019 #25

    Victor Bravo

    Victor Bravo

    Victor Bravo

    Well-Known Member

    Joined:
    Jul 30, 2014
    Messages:
    5,740
    Likes Received:
    4,618
    Location:
    KWHP, Los Angeles CA, USA
    It's simple. A pot is something that you have to jump out of to get into the fire. A pan is something that you can just be a flash in (and not have to leave).
     
    RPM314 likes this.
  6. May 3, 2019 #26

    Riggerrob

    Riggerrob

    Riggerrob

    Well-Known Member

    Joined:
    Sep 9, 2014
    Messages:
    1,123
    Likes Received:
    309
    Location:
    Canada
    Adding to my earlier definition ......
    Flying wings are any tail-less configuration. Specifically, no separate horizontal tail surfaces. Flying wing purists also discount any airplane with vertical tail surfaces.

    Vought’s V-173 does not count as a pure flying wing because it has both horizontal and vertical tail surfaces attached near the “rear “corners” of its circular wing.

    Delta wings have sharply-swept leading edges with straight trailing edges (e.g. Mirage IIIM). Delta wings also have low aspect ratios and pointy wing tips. Not all delta wings are flying wings. For example, the Mig-21 fighter has a delta wing, plus conventional tail surfaces.
    Verhees Delta, Delta Kitten and Rohr 2-175 count as delta flying wings.

    Saab Draken, Concorde, Dyke Delta and F-16 are cranked deltas.
    Saab Draken is a double-delta, flying-wing.
    Concorde was a complex delta flying-wing with S curved leading edges and a straight trailing edge
    Despite the name, Dyke Delta is not a classic delta wing because its trailing edge has considerable forward-sweep.
    F-16 is also a double delta because of its large leading edge strakes, but it’s main wing is even less of a delta because it has a medium aspect ratio and squared wing tips.

    Mitchel’s B-10 and U-2 still count as flying wings even though their horizontal control surfaces are separate. Mitchel’s Junkers type control surfaces are only separated by narrow gaps, meaning that they still count as part of the main wing.

    Withold Kasper’s BKB-1 sailplane was not a delta. It was a flying wing with both leading and trailing edge sweep. It had a central vertical stabilizer with rudders on each wing tip. The outboard trailing edges were swept even more to incorporate large horizontal control surfaces (elevons). It could tumble when the centre of gravity was well aft of normal. Most other aircraft tumble when their c.of g. is too far aft, but they tend to enter unrecoverable tumbles or flat-spins. BKB-1 was rare in that it could be predictably tumbled and predictably recovered.
     
  7. May 3, 2019 #27

    bmcj

    bmcj

    bmcj

    Well-Known Member HBA Supporter

    Joined:
    Apr 10, 2007
    Messages:
    12,557
    Likes Received:
    4,580
    Location:
    Fresno, California
    They’re all the same. They only add labels to generate debate and confusion on HBA.
     
    Tiger Tim, akwrencher, BJC and 2 others like this.
  8. May 4, 2019 #28

    Aesquire

    Aesquire

    Aesquire

    Well-Known Member

    Joined:
    Jul 29, 2014
    Messages:
    2,239
    Likes Received:
    883
    Location:
    Rochester, NY, USA
    Riggerrob has it right.

    Delta wings and modified deltas and the lovely wine glass Concorde are kin, but not the same. The Concorde is a Ogival / Ogee/ gothic arch modification of the "slender delta" modification of a "regular delta". The F-16XL is a cranked arrow delta.

    They can be tailed, Mig-21, or not, Mirage 5.

    Clipped Deltas, trapezoids, I'll let you define where one blends into another.

    is a Concorde a flying wing? Yes imho.

    flying wing is defined, I think, by lack of additional pitch control surfaces, other than on the wing, and not fuselage shape. The Snark was a flying wing with large tubular fuselage and tall vertical tall & rudder. The XB-35 was a flying wing with very little vestigial fuselage, mostly to hold a "stinger" gun & 4th landing gear to keep it from tipping back on the ground.

    Northrop wanted a "Pure" flying wing, with no fuselage drag, no excess fins of any kind. The idea was minimum drag. Later that "Pure" shape became desirable for Stealth.

    As Norman points out, the Fuselage is a destabilizing thing, and an unfortunate necessity to carry anything on wings too small to fit everything inside... or much smaller than a XB-35. The Horten HO-229 isn't big enough. :)

    Then you can argue blended body, etc.

    The need to put things in neat boxes is a 18th-19th century notion. Useful, but not always best.

    My personal experience with flying wings is mostly with no tail, for launch reasons, and little to no vertical fins. The best flying wings from hang glider to ultralight, BKB-1, seem to have tip verticals, despite the B-2 Bomber example. I have

    Most of the Canards in the home built Rutan inspired designs with high aspect ratio cranked delta rear mounted wings have tip verticals & rudders. ( although the Quickie variations do not, they are more like a canard Snark! And the many fighters with canards don't either )
     
  9. May 4, 2019 #29

    Aesquire

    Aesquire

    Aesquire

    Well-Known Member

    Joined:
    Jul 29, 2014
    Messages:
    2,239
    Likes Received:
    883
    Location:
    Rochester, NY, USA
    Is the Vought V-173 a flying wing? I'm going to say yes. The vertical bits are not the issue, it's are those all flying elevons part of the wing?
    On a UFO, with elevons inset, yes.
    On the Arup S-2? https://en.wikipedia.org/wiki/Arup_S-2 ( Yes, flying wing )
    On the Arup S-4? https://en.wikipedia.org/wiki/Arup_S-4 ( uh. maybe? )
    The Hoffman? https://en.wikipedia.org/wiki/Raoul_Hoffman ( Yes, flying wing )

    You can argue either way on the Arup S-4 or V-173.

    Ultimately I'm going with practical over purity and declaring the V-173 as my bet for optimum solution.
     
  10. May 4, 2019 #30

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    11,405
    Likes Received:
    2,092
    Location:
    Port Townsend WA
    Last edited: May 4, 2019
  11. May 5, 2019 #31

    Aesquire

    Aesquire

    Aesquire

    Well-Known Member

    Joined:
    Jul 29, 2014
    Messages:
    2,239
    Likes Received:
    883
    Location:
    Rochester, NY, USA
    Is a Snark then a "tailless"?

    by your definition a V-173 is a flying wing.

    I'm fine with that. However the Slow Blog (Wikipedia) states that the SWIFT is not a flying wing. ? That means the hang glider in the garage isn't a flying wing?

    I'm used to being wrong, but I've then spent decades using the "wrong" science to understand the "flying wing with suspended pod" things I have hundreds of hours soaring with.

    Thus I cynically think the Wikipedia definition wrong. ( Wikipedia is wrong a lot. Right, a lot, too. Caveat Emptor. )
     
    nerobro likes this.
  12. May 5, 2019 #32

    MadRocketScientist

    MadRocketScientist

    MadRocketScientist

    Well-Known Member

    Joined:
    May 17, 2009
    Messages:
    1,405
    Likes Received:
    853
    Location:
    Canterbury, New Zealand, Earth, Milky Way Galaxy.
    and the dancing banana...
     
  13. May 5, 2019 #33

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    11,405
    Likes Received:
    2,092
    Location:
    Port Townsend WA
    The V-173 is called " all wing" here: https://en.m.wikipedia.org/wiki/Vought_V-173
    But it has some vertical surfaces and other extensions. So none are strictly pure wing, that I know of.
    The B2 is close with no vertical surface, but still has a bulged cockpit.
    So there is no absolute line drawn.
     
    nerobro likes this.

Share This Page

arrow_white