Do winglets produce thrust?

Jon Meyer wrote in message ...
Bernhard's diagrams are spot on, but whether you call
it thrust or a reduction in drag is up to you. My Aeronautical
Engineering textbook uses both as alternative ways
of describing it. It all depends on how you choose
your frame of reference. The winglet produces a vorce
vector which consists of drag and lift, but when this
force vector is considered with the sailplane as the
frame of reference then its components could be considered
as a thrust force and a lateral force. I feel that
this is the easier way to describe the way they reduce
overall drag, but if you want to be pedantic........

If there is only drag and no thrust you'll eventually be
flying backwards, right?

Suppose you raise your glider up into the air under a balloon and
drop it. If the wings (nor anything else) generate only lift and
no thrust then you'll just move in the verticle direction only,
or hover.

If a wing can generate thrust then so can a winglet depending on
geometry, AOA etc. It will also generate drag and weight.

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FF

(cddb) wrote in message hlink.net...
Don't think so.
Gravity provides the thrust. Quite noticeably when fuselage
is pointed vertically. None at all when fuselage/wing is horizontal.


Rather obviously if this were true the glider would only move in the
vertical direction, and not at all in the horizontal.

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FF

LittleJohn wrote in message ogy.net...
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. ;)


Close. The horizontal component in the forward direction is thrust.
in a 90 degree bank the lift is also horizontal.

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FF

LittleJohn wrote in message ogy.net...
On Sat, 29 Nov 2003 11:32:36 -0800, Eric Greenwell wrote:


Sheesh! So many words and so little knowledge... Here's how it works,
guys.

For any aircraft in balanced flight, there are four forces acting on it.
All forces except gravity act only along the chord or perpendicular to it.
Gravity not only produces a force in opposition to lift,

it can also produce a force in the same direction to, or perpendicular
to lift. 'lift' is the aerodynamic force perpendicular to the direction
of motion. It is the horizontal component of lift that turns a banking
aircraft, and a vertical, downward lift that allows an aircraft to
accelerate in a dive FASTER than the acceleration due to gravity as
when the old Hurricanes inverted to keep the fuel flowing into their
engines when chasing a diving Messerschmidt. If they dove without
inverting first, they'd be chasing that M. in a glider.

Weight is the only one of the four forces that is constant in direction
is an earth-centered frame of reference. The other three forces may
be oriented in any direction though not independently as drag must be
opposite to thrust and lift perpendicular to both. Of course these
defintions are arbitrary, but other equally arbitrary defintions are
less useful.

Gravity is the
'engine' in a glider that produces thrust.

More like it is the 'fuel', the engine is the wing.

--

FF

Eric Greenwell wrote in message ...
K.P. Termaat wrote:
"soarski" schreef in bericht
om...

In my country, our gliders move forward because the wing produces
thrust, and our sailboats move over the water because the sail produces
thrust. Whether we should rule the world is causing much controversy.


In my country (Holland) students will be disqualified from their examination
when they make an "interesting" remark like this. Reducing induced drag is
what winglets do and gravity is the engine of our gliders.

And what produces the "thrust" that moves your sailboats? Gravity?

This may be a simple confusion over the word "thrust", which I used (as
did the original question) in the sense of "force in the direction of
motion". Both the glider and the sailboat are propelled in a forward
direction by lift from the wing or sail.

Not if you _define_ lift as perpendicular to the direction of motion...

--

FF

Nyal Williams wrote in message ...
Now, I'm confused! An airfoil cannot produce thrust
-- only 'lift.' But if an airfoil has a reverse counterpart,
the two are joined at the center and rotated about
an axis in a vertical plane, they are then a propeller;
this produces 'thrust.'

Well if that last statement is true then the earlier one
is false. Do propellers produce thrust?

--

FF

Fred the Red Shirt wrote:

Eric Greenwell wrote in message ...

K.P. Termaat wrote:

"soarski" schreef in bericht
e.com...

In my country, our gliders move forward because the wing produces
thrust, and our sailboats move over the water because the sail produces
thrust. Whether we should rule the world is causing much controversy.


In my country (Holland) students will be disqualified from their examination
when they make an "interesting" remark like this. Reducing induced drag is
what winglets do and gravity is the engine of our gliders.

And what produces the "thrust" that moves your sailboats? Gravity?

This may be a simple confusion over the word "thrust", which I used (as
did the original question) in the sense of "force in the direction of
motion". Both the glider and the sailboat are propelled in a forward
direction by lift from the wing or sail.


Not if you _define_ lift as perpendicular to the direction of motion...

True, which was not my intention. What I meant was "horizontal motion",
as I said later ("propelled in a forward direction"), thinking as a
pilot might as he tries to get somewhere.

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

Eric Greenwell
Washington State
USA

Fred the Red Shirt wrote:

Nyal Williams wrote in message ...

Now, I'm confused! An airfoil cannot produce thrust
-- only 'lift.' But if an airfoil has a reverse counterpart,
the two are joined at the center and rotated about
an axis in a vertical plane, they are then a propeller;
this produces 'thrust.'


Well if that last statement is true then the earlier one
is false. Do propellers produce thrust?

The first poster is confusing a wing and an airfoil. It's a _wing_ that
cannot produce thrust in the aerodynamic sense, by the definitions used.
A propeller can produce thrust. They both use airfoils.
--
-----
Replace "SPAM" with "charter" to email me directly

Eric Greenwell
Washington State
USA

At 18:54 05 December 2003, Todd Pattist wrote:
(Fred the Red Shirt) wrote:

Now, I'm confused! An airfoil cannot produce thrust
-- only 'lift.' But if an airfoil has a reverse counterpart,
the two are joined at the center and rotated about
an axis in a vertical plane, they are then a propeller;
this produces 'thrust.'

Well if that last statement is true then the earlier
one
is false. Do propellers produce thrust?

Back to definitions again. 'Lift' is defined perpendicular
to the path of the airfoil through the air. 'Thrust'
is
typically parallel to that path. However, when we
have a
moving airfoil on an aircraft (rotating propeller),
there
are two 'paths' that are relevant. One is the path
of the
aircraft (this path defines the AOA of the wing), and
the
other is the spiral path of the rotating airfoil (this
path
defines the AOA of the prop blades). The propeller's
airfoil produces 'lift' perpendicular to the spiral
path.
It produces 'thrust' when considered relative to the
airplane's path.

IOW, at any instant, the prop is mostly moving at 90
degrees
to the path of the airplane. If it produced both lift
and
thrust relative to the same path, then the prop would
turn
itself :-)

Todd Pattist - 'WH' Ventus C
(Remove DONTSPAMME from address to email reply.)

Okay, it promises to be a long winter; I'll take my
tongue out of my cheek!

Eric Greenwell wrote in message ...
soarski wrote:
I can't believe you are so confused about Thrust and Lift? EG?


Sometimes words have two (or more) meanings.

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FF