Do winglets produce thrust?

soarski wrote:
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.



PLEASE....Readers of the World! This is not in our textbooks! Did
someone in the USA write the above???

Wings produce Lift!! A by product of lift is drag! Winglets do also
produce lift, and therefore drag. Possibly less than the wing? But
you canot call it thrust!.......

"Thrust", for the winglet question and my remarks about gliders and
sailboats, was used to mean "force in the direction of motion".
Apparently, that was an unusual use of the word for some people.

Here's an expanded expanation:

Gravity is pulling straight down, and so can not propel the glider
forward; drag is pulling the glider back, and so can not propel the
glider forward. So, what is left to counteract the drag? Lift, produced
by the wings. This forward force comes from the lift, which is not
vertical, but tipped forward a bit. Look at any diagram showing the
forces on a glider, and you will see how the lift, drag, and gravity
forces accomplish this.

It is not common to call this force moving the glider forward (without
it, drag would bring it to stop) "thrust", but the word is sometimes
used that way.

I still can't answer the original question about the winglets, though.

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Eric Greenwell
Washington State
USA

On Sat, 29 Nov 2003 11:32:36 -0800, Eric Greenwell wrote:

Here's an expanded expanation:

Gravity is pulling straight down, and so can not propel the glider
forward; drag is pulling the glider back, and so can not propel the
glider forward. So, what is left to counteract the drag? Lift, produced
by the wings. This forward force comes from the lift, which is not
vertical, but tipped forward a bit. Look at any diagram showing the
forces on a glider, and you will see how the lift, drag, and gravity
forces accomplish this.

It is not common to call this force moving the glider forward (without
it, drag would bring it to stop) "thrust", but the word is sometimes
used that way.

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, but a resultant
vector force which can be either thrust or drag, depending on the angle of
the chord in respect to earth (gravity). in other words; Gravity is the
'engine' in a glider that produces thrust.

For those that don't understand vector force components (or flunked trig),
don't worry 'bout it. Simply believe they exist.

As for the winglets, they only reduce drag. At the point where the
airfoil ends, air rolls to the other side of the wing due to the pressure
difference. The rolling air produces a vortex that kinda acts like vacuum
cleaner hoses grabbing the trailing tips of the wings. The winglets
interfere with the creation of the vortex(s) thus reducing drag. Smaller
vortex (smaller vacuum cleaner) means better L/D (slicker ship).

LittleJohn
Madison, AL

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

"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.

Karel Termaat

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.

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Eric Greenwell
Washington State
USA

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

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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Eric Greenwell
Washington State
USA

Keith W wrote:

That's against the laws of thermodynamics.

No.

Provided the thrust of the winglets is not higher than the drag of the
other part of the glider, that's not (and of course the winglet thrust
is only a few % of the glider drag)


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