Do winglets produce thrust?

On Fri, 28 Nov 2003 21:36:17 +0000, cddb wrote:

Don't think so.
Gravity provides the thrust. Quite noticeably when fuselage
is pointed vertically. None at all when fuselage/wing is horizontal.

Look at it from another point of view. If all forces are balanced and
winglets are added, drag is reduced. Then velocity increases until the
thrust/drag forces are equalized. The result of increased velocity is
additional lift. The horizontal component of the lift vector is thrust,
which increases as lift increases. Ergo, winglets produce thrust. ;)

LittleJohn
Madison, AL

This has to be winter RAS debate bait, right Bob?

For those of you responding in the affirmative, park the nearest
winglet-equipped glider on the runway on a still day and measure the
"thrust" being produced by those puppies. Be careful not to stand in front
of the wing when you do it. wink

--=Curt=-

"Bob Salvo" wrote in message
...
Anyone?
Bob

In article ,
ojunk (Bob Salvo) wrote:
Anyone?
Bob

Winglets reduce induced drag by effectively making the wingspan longer.

I've never seen anyone argue convincingly that a half a meter of
vertical wingspan does anything that couldn't be done equally well with
an extra half meter of normal wingspan. On the other hand winglets are
worse than span in that they don't produce lift in a useful direction,
and they are harder to make strong and rigid than ordinary span is.

If it wasn't for class rules limiting winspan I don't think anyone would
have winglets.

-- Bruce

Bruce Hoult wrote:
In article ,
ojunk (Bob Salvo) wrote:

Anyone?
Bob


Winglets reduce induced drag by effectively making the wingspan longer.

Perhaps in the past, but maybe not anymo from page 104 of the
Fundamentals of Sailplane Design...

"Subsequently, it has been shown that good results may be obtained with
relatively small winglets. In contrast to early winglets, which were
essentially upward wing extensions, recent winglet designs are optimized
to diffuse the vortex rollup at the wingtip, thus reducing its strength.
There is also evidence that the velocity field induced by the winglets
can improve airfoil aerodynamics in the vicinity of the wing tip by
prolonging laminar flow and delaying separation."


I've never seen anyone argue convincingly that a half a meter of
vertical wingspan does anything that couldn't be done equally well with
an extra half meter of normal wingspan.

Winglets can improve roll rate, while longer tips tend to reduce it.

On the other hand winglets are
worse than span in that they don't produce lift in a useful direction,
and they are harder to make strong and rigid than ordinary span is.

The lift they produced is used to decrease drag, which is a useful
result, and the small ones used on the ASW 27, for example, look pretty
simple to make.


If it wasn't for class rules limiting winspan I don't think anyone would
have winglets.

Much less likely, for sure.

--
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Replace "SPAM" with "charter" to email me directly

Eric Greenwell
Washington State
USA

In article ,
Eric Greenwell wrote:

Winglets reduce induced drag by effectively making the wingspan longer.

Perhaps in the past, but maybe not anymo from page 104 of the
Fundamentals of Sailplane Design...

"Subsequently, it has been shown that good results may be obtained with
relatively small winglets. In contrast to early winglets, which were
essentially upward wing extensions, recent winglet designs are optimized
to diffuse the vortex rollup at the wingtip, thus reducing its strength.
There is also evidence that the velocity field induced by the winglets
can improve airfoil aerodynamics in the vicinity of the wing tip by
prolonging laminar flow and delaying separation."

But the question is, would similar-shaped horizontal extensions to the
wing have the same effect? What about multiple small span "winglets"
off the end of the wing? Birds do that. The modern winglets look a lot
like a single tip-feather.

-- Bruce

Bruce Hoult writes:

Winglets reduce induced drag by effectively making the wingspan
longer.

I've never seen anyone argue convincingly that a half a meter of
vertical wingspan does anything that couldn't be done equally well
with an extra half meter of normal wingspan. On the other hand
winglets are worse than span in that they don't produce lift in a
useful direction, and they are harder to make strong and rigid than
ordinary span is.

But the spar does not have to deal with the extra lift on a *long*
moment arm. Well not all of it anyway.

If it wasn't for class rules limiting winspan I don't think anyone
would have winglets.

I wonder what class rules the 744 design has in mind

--
Paul Repacholi 1 Crescent Rd.,
+61 (08) 9257-1001 Kalamunda.
West Australia 6076
comp.os.vms,- The Older, Grumpier Slashdot
Raw, Cooked or Well-done, it's all half baked.
EPIC, The Architecture of the future, always has been, always will be.

The winglet holder in my Cobra trailer comes with a bungee cord to
keep the winglets in place. I have noted that whenever I leave the
bungee off, the winglets wind up in all imaginable places inside the
trailer. Thus, I would conclude, that they do indeed produce thrust.

ojunk (Bob Salvo) wrote in message ...
Anyone?
Bob

Earlier, Paul Repacholi wrote:

I wonder what class rules the 744 design has in mind

It has to fit between established jetways at established airports.
That and the inboard bending moment contstraints mentioned earlier.

Bob K.

Bruce Hoult wrote:


But the question is, would similar-shaped horizontal extensions to the
wing have the same effect? What about multiple small span "winglets"
off the end of the wing? Birds do that. The modern winglets look a lot
like a single tip-feather.

Take a look at the winglet pages in the book. It doesn't sound like they
are doing the same thing they would be doing laying flat.

--
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Replace "SPAM" with "charter" to email me directly

Eric Greenwell
Washington State
USA

In article ,
Paul Repacholi wrote:

Bruce Hoult writes:

Winglets reduce induced drag by effectively making the wingspan
longer.

I've never seen anyone argue convincingly that a half a meter of
vertical wingspan does anything that couldn't be done equally well
with an extra half meter of normal wingspan. On the other hand
winglets are worse than span in that they don't produce lift in a
useful direction, and they are harder to make strong and rigid than
ordinary span is.

But the spar does not have to deal with the extra lift on a *long*
moment arm. Well not all of it anyway.

Hmm ... well a deliberately non-lifting horizontal section at the tip
would reduce induced drag as well.


If it wasn't for class rules limiting winspan I don't think anyone
would have winglets.

I wonder what class rules the 744 design has in mind

Terminal gates.

I don't know what excuse bizjets or small turboprops such as the Beech
1900 have. Possibly fashion.

-- Bruce