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

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

RPM314

Well-Known Member
Joined
Mar 27, 2015
Messages
724
Location
NY, USA
While we’re at it, where would you put the dividing line between a pot and a pan?
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:

Norman

Well-Known Member
Joined
Nov 28, 2003
Messages
2,934
Location
Grand Junction, Colorado
What's "distinct"? Where's the line? What does that line matter?
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%.
 

Norman

Well-Known Member
Joined
Nov 28, 2003
Messages
2,934
Location
Grand Junction, Colorado
It is all about the fuselage. Fuselages add directional stability. Wing being wing, only to be pure has nothing fixed sticking up or down or out help with stability
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.
 

Riggerrob

Well-Known Member
Joined
Sep 9, 2014
Messages
1,302
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.
 

Aesquire

Well-Known Member
Joined
Jul 28, 2014
Messages
2,399
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 )
 

Aesquire

Well-Known Member
Joined
Jul 28, 2014
Messages
2,399
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.
 

Aesquire

Well-Known Member
Joined
Jul 28, 2014
Messages
2,399
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. )
 
Group Builder
Top