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Using lift to reduce hypersonic drag.
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Rand Simberg
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Joined: 02 May 2005
Posts: 18

PostPosted: Mon Jul 17, 2006 11:54 pm    Post subject: Re: Using lift to reduce hypersonic drag. Reply with quote

On 17 Jul 2006 16:50:29 -0700, in a place far, far away, "Robert
Clark" <rgregoryclark@yahoo.com> made the phosphor on my monitor glow
in such a way as to indicate that:

Quote:
If you do a google search on "winglets", "thrust", and "vortices" and
you'll see that one interpretation of how they work is that they create
additional thrust.

No.

Quote:
To be precise, these explanations note that the
direction of flow of air in vortices around the wing tips when they
flow over the winglets produces a lift force in the *forward*
direction. This is in fact how they were first invented. Now since the
winglets could not produce this force without a propulsion method
driving the vehicle forward you can also describe their effect as
reducing the overall drag.

Yes, they reduce drag. They don't, in any way, increase thrust.
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Robert Clark
science forum Guru Wannabe


Joined: 30 Apr 2005
Posts: 129

PostPosted: Tue Jul 18, 2006 12:41 am    Post subject: Re: Using lift to reduce hypersonic drag. Reply with quote

Rand Simberg wrote:
Quote:
On 17 Jul 2006 16:50:29 -0700, in a place far, far away, "Robert
Clark" <rgregoryclark@yahoo.com> made the phosphor on my monitor glow
in such a way as to indicate that:

If you do a google search on "winglets", "thrust", and "vortices" and
you'll see that one interpretation of how they work is that they create
additional thrust.

No.

To be precise, these explanations note that the
direction of flow of air in vortices around the wing tips when they
flow over the winglets produces a lift force in the *forward*
direction. This is in fact how they were first invented. Now since the
winglets could not produce this force without a propulsion method
driving the vehicle forward you can also describe their effect as
reducing the overall drag.

Yes, they reduce drag. They don't, in any way, increase thrust.

How Things Work: Winglets
"The airflow around winglets is complicated, and winglets have to be
carefully designed and tested for each aircraft. Cant, the angle to
which the winglet is bent from the vertical, and toe, the angle at
which the winglets' airfoils diverge from the relative wind direction,
determine the magnitude and orientation of the lift force generated by
the winglet itself. By adjusting these so that the lift force points
slightly forward, a designer can produce the equivalent of thrust. A
sailboat tacking sharply upwind creates a similar force with its sail
while the keel squeezes the boat forward like a pinched watermelon
seed."
http://www.airspacemag.com/ASM/Mag/Index/2001/AS/htww.html

Winglets.
"Winglets, which are airfoils operating just like a sailboat tacking
upwind, produce a forward thrust inside the circulation field of the
vortices and reduce their strength. Weaker vortices mean less drag at
the wingtips and lift is restored. Improved wing efficiency translates
to more payload, reduced fuel consumption, and a longer cruising range
that can allow an air carrier to expand routes and destinations."
http://www.nasa.gov/centers/dryden/about/Organizations/Technology/Facts/TF-2004-15-DFRC.html

Winglet
"The vortex which rotates around from below the wing strikes the angled
surface of the winglet, generating a small lift force that angles
forwards relative to the direction of flight - thus the energy in the
vortex contributes to thrust rather than drag as it normally would.
This is analogous to a sailing boat sailing very close to the wind.
This small contribution can be very worthwhile on long distance
flights."
http://en.wikipedia.org/wiki/Winglet

Reducing Parasite Drag.
Winglets
"NASA researcher Richard Whitcomb invented "Winglets."
"The winglet, like so many great inventions is obvious once someone
else has thought of it. It represents one of the few effective means of
fighting induced drag.
"Unlike the other methods mentioned above, the winglet does not strive
to reduce induced drag so much as it uses it to create an offsetting
thrust."
"In the diagram to the right we can see that the air flowing over the
winglet, due to the presence of the tip vortex, strikes the winglet at
an angle of attack.
"Like any airflow, over any wing, it produces lift. In this case the
lift ( or a component of it) is forward. Thus, the winglet produces
thrust. The stronger the vortex the more thrust it produces."
http://selair.selkirk.bc.ca/aerodynamics1/drag/page8.html



Bob Clark
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Rand Simberg
science forum beginner


Joined: 02 May 2005
Posts: 18

PostPosted: Tue Jul 18, 2006 12:46 am    Post subject: Re: Using lift to reduce hypersonic drag. Reply with quote

On 17 Jul 2006 17:41:18 -0700, in a place far, far away, "Robert
Clark" <rgregoryclark@yahoo.com> made the phosphor on my monitor glow
in such a way as to indicate that:

Quote:
Rand Simberg wrote:
On 17 Jul 2006 16:50:29 -0700, in a place far, far away, "Robert
Clark" <rgregoryclark@yahoo.com> made the phosphor on my monitor glow
in such a way as to indicate that:

If you do a google search on "winglets", "thrust", and "vortices" and
you'll see that one interpretation of how they work is that they create
additional thrust.

No.

To be precise, these explanations note that the
direction of flow of air in vortices around the wing tips when they
flow over the winglets produces a lift force in the *forward*
direction. This is in fact how they were first invented. Now since the
winglets could not produce this force without a propulsion method
driving the vehicle forward you can also describe their effect as
reducing the overall drag.

Yes, they reduce drag. They don't, in any way, increase thrust.

How Things Work: Winglets

Nothing you posted refutes my statement.
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Alan Anderson
science forum beginner


Joined: 31 Aug 2005
Posts: 3

PostPosted: Tue Jul 18, 2006 1:07 am    Post subject: Re: Using lift to reduce hypersonic drag. Reply with quote

"Robert Clark" <rgregoryclark@yahoo.com> wrote:

Quote:
Rand Simberg wrote:
On 17 Jul 2006 16:50:29 -0700, in a place far, far away, "Robert
Clark" <rgregoryclark@yahoo.com> made the phosphor on my monitor glow
in such a way as to indicate that:

If you do a google search on "winglets", "thrust", and "vortices" and
you'll see that one interpretation of how they work is that they create
additional thrust.

No.

Agreed: no. They can be interpreted as recovering thrust from the
induced drag, but they don't create any. They create *lift*, and that
lift does act partially in the direction of travel, but the lift is
taken from the motion of the tip vortex, which robbed the vehicle of
some of its thrust in the first place.

Quote:
How Things Work: Winglets
"The airflow around winglets is complicated, and winglets have to be
carefully designed and tested for each aircraft. Cant, the angle to
which the winglet is bent from the vertical, and toe, the angle at
which the winglets' airfoils diverge from the relative wind direction,
determine the magnitude and orientation of the lift force generated by
the winglet itself. By adjusting these so that the lift force points
slightly forward, a designer can produce the equivalent of thrust. A
sailboat tacking sharply upwind creates a similar force with its sail
while the keel squeezes the boat forward like a pinched watermelon
seed."
http://www.airspacemag.com/ASM/Mag/Index/2001/AS/htww.html

If you can wrap your head around that complicated airflow and follow it
from the right point of view, you can see that the apparent thrust from
a "toed" winglet is more simply understood as a targeted disruption of
the tip vortex and consequent reduced drag.

Of course, there are always people who don't want to make the effort to
see it from the point of view that simplifies things. For them, the
"forward lift = thrust" explanation is the easy way out. It adequately
describes the effect, but it completely obscures the mechanism.
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William.Mook@gmail.com
science forum addict


Joined: 06 May 2006
Posts: 50

PostPosted: Tue Jul 18, 2006 2:13 am    Post subject: Re: Using lift to reduce hypersonic drag. Reply with quote

Read the NASA paper I gave you a reference to originally. Winglets
don't operate like sails on a sail boat. They reduce wingtip vortices.
Period.

Read up on compressible flow that I gave you. It shows in detail how
compressible flow works, and why you can't produce thrust by sticking
things across shock waves (since doing so creates new shock waves!)
You *might* be able to create thrust with weird gas flows, as in
supersonic combustion - but that's not what you're talking about.

Quit talking and start listening - and maybe you'll understand.
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BlagooBlanaa
science forum beginner


Joined: 05 Mar 2006
Posts: 15

PostPosted: Tue Jul 18, 2006 2:50 am    Post subject: Re: Using lift to reduce hypersonic drag. Reply with quote

<William.Mook@gmail.com> wrote in message
news:1153188785.506261.227270@35g2000cwc.googlegroups.com...
Quote:
Read the NASA paper I gave you a reference to originally. Winglets
don't operate like sails on a sail boat. They reduce wingtip vortices.
Period.

Read up on compressible flow that I gave you. It shows in detail how
compressible flow works, and why you can't produce thrust by sticking
things across shock waves (since doing so creates new shock waves!)

what you need to do is combust *in* the shock wave interface

Quote:
You *might* be able to create thrust with weird gas flows, as in
supersonic combustion - but that's not what you're talking about.

Quit talking and start listening - and maybe you'll understand.
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William.Mook@gmail.com
science forum addict


Joined: 06 May 2006
Posts: 50

PostPosted: Tue Jul 18, 2006 3:59 am    Post subject: Re: Using lift to reduce hypersonic drag. Reply with quote

Combust in the shock wave -

Yes, that's what I'm talking about some sort of air/fuel mix. Another
possibility is to wave the 'winglets' like flapping wings - which I
didn't think of but could work, maybe. But they the little buggers
have gotta move FAST! I'm not sure you could do it.

Another possibility is that you have a nearly supercritical fissile
material that goes critical in the shock wave - but we're talking BIG
s**t here, a control sytem for a rocket with downtown Chicago as the
payload, burning the entire inventory of nuclear weapons material every
few hours, or if you really crank up pressure and temperature, you pass
the Lawson criterion in a fusile material! lol. But I'm damned if I'd
know how to build THAT! lol. Maybe a fusion assisted fission rocket.
lol.

That last might be useful in moving STARS around if you could do it!
lol. Directing the stellar winds coming off of stars. Self
replicating starships that spread across the universe would implement a
Kardeshev V civilization! lol. They would have this little trick in
their bag of tricks.

The solar wind goes through a shock somewhere between Earth orbit and
Heliopause.

If you had solar collectors held by in place by solar wind close in to
the solar surface, modulating that wind might move the sun around.
Folks back in the 70s and 80s talked about 'starlifting' - which might
be possible. This is might be a nuance in actually lifting stars.

Frank Tipler talked about the universal paradigm that all intelligence
has, which is to change the environment of the universe to extend life
as long as possible. This entails encompassing the entire universe and
changing the momentum of stars so that things collapse into the right
kind of shape so that we can process an infinite amount of information
over an infinite period of time. Damn you if you're wrong! lol. The
end of the universe would then be one big DOH! Which may explain the
popularity of Homer Simpson.

But if Tipler's right, then there are no Type V civlizations - and
we're the first.

Other folks think we don't see these advanced civilization. We think
their work is nature. The voids we see around us are evidence of their
existence - since they turned off the stars once they moved them, to
conserve resources for the long haul, and the bright regions are left
untouched for some cosmological reasons - and we think its natural, but
ask about the missing mass! lol.

Still others think we're already stuck in a VR model of the universe at
the end of time, a footnote in a infinitely complex program that never
stops - we're already in a matrix.

But I digress! lol.
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BlagooBlanaa
science forum beginner


Joined: 05 Mar 2006
Posts: 15

PostPosted: Tue Jul 18, 2006 6:41 am    Post subject: Re: Using lift to reduce hypersonic drag. Reply with quote

as you know critical mass is accomplished by having the right
geometric buckling for any given material buckling

you could use standing acoustic waves in the bow shock to shape
species concentrations so that a self-sustaining critical mass
was acheived

i would not want to be in the exhaust plume however
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Ian Parker
science forum Guru Wannabe


Joined: 15 Jul 2005
Posts: 100

PostPosted: Tue Jul 18, 2006 10:13 am    Post subject: Re: Using lift to reduce hypersonic drag. Reply with quote

Robert Clark wrote:
Quote:
If you do a google search on "winglets", "thrust", and "vortices" and
you'll see that one interpretation of how they work is that they create
additional thrust. To be precise, these explanations note that the
direction of flow of air in vortices around the wing tips when they
flow over the winglets produces a lift force in the *forward*
direction. This is in fact how they were first invented. Now since the
winglets could not produce this force without a propulsion method
driving the vehicle forward you can also describe their effect as
reducing the overall drag.

It is well known among sailors that the *magnitude* of the boat
velocity can exceed the *magnitude* of the wind velocity when tacking
into the wind. This is discussed in the web page I cited, "The physics
of sailing." This method of tacking into the wind also works with ice
sailing where the runners pushing sideways against the ice is what
causes a force on the boat with a forward component that allows the ice
boat to move at an angle into the wind. With ice boats the speeds can
exceed more than 70 mph when tacking into the wind, much higher than
the wind speed.

I am suggesting taking advantage of the fact that with the hypersonic
shockwave you have two fluids of very different densities moving with
respect to each other. That is what happens with a shock wave attached
to the vehicle.

It is known that placing vertical airfoils at the top and bottom of a
hypersonic vehicle can *reduce* the overall drag eventhough each of
these produces an additional shockwave. These are known as "star
bodies." This is discussed at the bottom of this page:

Waverider Design.
http://www.aerospaceweb.org/design/waverider/waverider.shtml

Here's a reference:

Performance Study of a Power Law Starbody
John W. Sabean; Mark J. Lewis; David Mee; Allan Paull
Journal of Spacecraft and Rockets 1999
0022-4650 vol.36 no.5 (646-652)
http://pdf.aiaa.org/jaPreview/JSR/1999/PVJAIMP3496.pdf [abstract]

The authors though don't appear to be suggesting that these two
vertical foils operating in concert can produce additional forward
lift.


Bob Clark



As I see it the basic Physics is the following. In general vortices

lead to drag. reducing vorticity will thereby reduce turbulent drag. If
you pump air from low pressure to high pressure you do work, where that
work goes is not clear and depends very much on circumstances. If you
pump air into a vortex it will incease the size of the vortex and
thereby create more drag. If you had an airplane with holes in the
airframe/piezoelectric material you could have reduced drag for most of
the flight and put energy into the vortices on landing giving the
effect of retro thrust.

If on the other hand you have continuous high pressure on the lower
wing anf low pressure on the upper wing (causing lift) and you pump gas
from the upper to the lower wing you will, in principle, get thrust.
Mind you have to be careful that in so doing you don't induce drag.
This in fact is the principle of swimming with flippers and the leg
movements of "crawl". You are moving your legs at right angles to the
fluid flow.

At super and hypersonic speeds one of the main characteristics is the
presence of shock waves. If you inject fuel into a shock wave it is
possible, in principle, to gain energy. There are of course a very
large number of ifs and buts. The shape of the trailing edge is
critical. In principle you could place rocket motors on the leading
edge and increase the specific impulse from what you would get in a
vacuum.

This is all however in principle, in principle. Years of research would
be needed to get any effective advantage. I think most people would
agree that a 2STO, completly recoverable was the best practical
solution at this stage.
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Robert Clark
science forum Guru Wannabe


Joined: 30 Apr 2005
Posts: 129

PostPosted: Tue Jul 18, 2006 1:21 pm    Post subject: Re: Using lift to reduce hypersonic drag. Reply with quote

Alan Anderson wrote:
Quote:
"Robert Clark" <rgregoryclark@yahoo.com> wrote:

Rand Simberg wrote:
On 17 Jul 2006 16:50:29 -0700, in a place far, far away, "Robert
Clark" <rgregoryclark@yahoo.com> made the phosphor on my monitor glow
in such a way as to indicate that:

If you do a google search on "winglets", "thrust", and "vortices" and
you'll see that one interpretation of how they work is that they create
additional thrust.

No.

Agreed: no. They can be interpreted as recovering thrust from the
induced drag, but they don't create any. They create *lift*, and that
lift does act partially in the direction of travel, but the lift is
taken from the motion of the tip vortex, which robbed the vehicle of
some of its thrust in the first place.

How Things Work: Winglets
"The airflow around winglets is complicated, and winglets have to be
carefully designed and tested for each aircraft. Cant, the angle to
which the winglet is bent from the vertical, and toe, the angle at
which the winglets' airfoils diverge from the relative wind direction,
determine the magnitude and orientation of the lift force generated by
the winglet itself. By adjusting these so that the lift force points
slightly forward, a designer can produce the equivalent of thrust. A
sailboat tacking sharply upwind creates a similar force with its sail
while the keel squeezes the boat forward like a pinched watermelon
seed."
http://www.airspacemag.com/ASM/Mag/Index/2001/AS/htww.html

If you can wrap your head around that complicated airflow and follow it
from the right point of view, you can see that the apparent thrust from
a "toed" winglet is more simply understood as a targeted disruption of
the tip vortex and consequent reduced drag.

Of course, there are always people who don't want to make the effort to
see it from the point of view that simplifies things. For them, the
"forward lift = thrust" explanation is the easy way out. It adequately
describes the effect, but it completely obscures the mechanism.

Einstein said: "Things should be made as simple as possible -- but no
simpler."

We are agreed that the drag reduction effect can occur from breaking
up the vortices, but any vertical plate could do that. But if you
ignore the lift production effect then you are ignoring an important
facet in how they operate and furthermore this could limit further
insight in how to improve them.
It would be easy to see if a forward lift force is operating and thus
validate that this is an important *part* of the explanation of their
method of operation. Attach winglets to wings in a wind tunnel, but
attach them in a way using springs that allows them to move to shift
their position somewhat under applied forces. Then connect force meters
to the winglets to detect which direction the *net* force is operating.

If the *net* force on the winglets has some component pointing forward
despite the fact that the drag from the wind tunnel air flow tends to
move them backward, then this will confirm that the forward lift force
produced is an important part of their operation.


Bob Clark
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William.Mook@gmail.com
science forum addict


Joined: 06 May 2006
Posts: 50

PostPosted: Tue Jul 18, 2006 1:43 pm    Post subject: Re: Using lift to reduce hypersonic drag. Reply with quote

BlagooBlanaa wrote:
Quote:
as you know critical mass is accomplished by having the right
geometric buckling for any given material buckling


I don't see how buckling has anything to do with it. So, I don't
understand your comment. From my worm's eye view of nuclear physics
classes I took in school, criticality is achieved when more neutrons
are generated in a given volume than are lost from the volume through
the surface. For a spherically symmetric implosion the integration is
easily performed. For other structures, as in a rocket exhaust, or
more complex structures, the integration would likely be done
numerically.

Quote:
you could use standing acoustic waves in the bow shock to shape
species concentrations so that a self-sustaining critical mass
was acheived

I don't see how this is possible.

Quote:
i would not want to be in the exhaust plume however

I agree, that would be bad.
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Robert Clark
science forum Guru Wannabe


Joined: 30 Apr 2005
Posts: 129

PostPosted: Tue Jul 18, 2006 2:00 pm    Post subject: Re: Using lift to reduce hypersonic drag. Reply with quote

William.Mook@gmail.com wrote:
Quote:
...
Frank Tipler talked about the universal paradigm that all intelligence
has, which is to change the environment of the universe to extend life
as long as possible. This entails encompassing the entire universe and
changing the momentum of stars so that things collapse into the right
kind of shape so that we can process an infinite amount of information
over an infinite period of time. Damn you if you're wrong! lol. The
end of the universe would then be one big DOH! Which may explain the
popularity of Homer Simpson.

But if Tipler's right, then there are no Type V civlizations - and
we're the first.

Other folks think we don't see these advanced civilization. We think
their work is nature. The voids we see around us are evidence of their
existence - since they turned off the stars once they moved them, to
conserve resources for the long haul, and the bright regions are left
untouched for some cosmological reasons - and we think its natural, but
ask about the missing mass! lol.

Still others think we're already stuck in a VR model of the universe at
the end of time, a footnote in a infinitely complex program that never
stops - we're already in a matrix.

But I digress! lol.


Reminds me of the famous Asimov story, "The Last Question":

The Last Question
By Isaac Asimov
http://infohost.nmt.edu/~mlindsey/asimov/question.htm


Bob Clark
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Tom Sanderson
science forum addict


Joined: 22 Dec 2005
Posts: 55

PostPosted: Tue Jul 18, 2006 2:41 pm    Post subject: Re: Using lift to reduce hypersonic drag. Reply with quote

"Robert Clark" <rgregoryclark@yahoo.com> wrote:
Quote:
We are agreed that the drag reduction effect can occur from breaking
up the vortices

Also lift reduction...if you actually broke the vortices on a real aircraft
wing, you'd have no lift.

Quote:
but any vertical plate could do that

And does. Even a straight vertical plate lowers induced drag on the wing.
They key is whether it reduces it enough to offset the weight of the plate.

Quote:
If the *net* force on the winglets has some component pointing forward
despite the fact that the drag from the wind tunnel air flow tends to
move them backward, then this will confirm that the forward lift force
produced is an important part of their operation.

No, it won't. The only thing that matters is the net force on the aircraft.

You could cook the rest of the wing such that you've got a wierd flow over
the winglet and you could get a net forward force component on the
winglet...basically, you could alter the local wind enough that the winglet
was "pulling" forward on the rest of the wing. However, in order to do so,
you'd have to be causing an opposite force on the rest of the wing. Since
no airfoil can convert airflow to lift with 100% efficiency, the amount of
force to gain from the winglet will always be less than the amount you lost
on the rest of the wing.

Tom.
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Robert Clark
science forum Guru Wannabe


Joined: 30 Apr 2005
Posts: 129

PostPosted: Tue Jul 18, 2006 4:00 pm    Post subject: Re: Using lift to reduce hypersonic drag. Reply with quote

Tom Sanderson wrote:
Quote:
"Robert Clark" <rgregoryclark@yahoo.com> wrote:
We are agreed that the drag reduction effect can occur from breaking
up the vortices

Also lift reduction...if you actually broke the vortices on a real aircraft
wing, you'd have no lift.

but any vertical plate could do that

And does. Even a straight vertical plate lowers induced drag on the wing.
They key is whether it reduces it enough to offset the weight of the plate.

If the *net* force on the winglets has some component pointing forward
despite the fact that the drag from the wind tunnel air flow tends to
move them backward, then this will confirm that the forward lift force
produced is an important part of their operation.

No, it won't. The only thing that matters is the net force on the aircraft.

You could cook the rest of the wing such that you've got a wierd flow over
the winglet and you could get a net forward force component on the
winglet...basically, you could alter the local wind enough that the winglet
was "pulling" forward on the rest of the wing. However, in order to do so,
you'd have to be causing an opposite force on the rest of the wing. Since
no airfoil can convert airflow to lift with 100% efficiency, the amount of
force to gain from the winglet will always be less than the amount you lost
on the rest of the wing.

Tom.

So what is your suggestion on what the result of this experiment would
be?
Would there be a forward component to the net force on the winglet?
I argue that the effect of this is to pull the wing forward more than
if the winglet was not there.
If a rope tugs on rock the rock is tugging back on the rope. That
doesn't change the fact that the rock moves forward.


Bob Clark
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Tom Sanderson
science forum addict


Joined: 22 Dec 2005
Posts: 55

PostPosted: Tue Jul 18, 2006 8:59 pm    Post subject: Re: Using lift to reduce hypersonic drag. Reply with quote

"Robert Clark" <rgregoryclark@yahoo.com> wrote
Quote:
You could cook the rest of the wing such that you've got a wierd flow
over
the winglet and you could get a net forward force component on the
winglet...basically, you could alter the local wind enough that the
winglet
was "pulling" forward on the rest of the wing. However, in order to do
so,
you'd have to be causing an opposite force on the rest of the wing.
Since
no airfoil can convert airflow to lift with 100% efficiency, the amount
of
force to gain from the winglet will always be less than the amount you
lost
on the rest of the wing.

So what is your suggestion on what the result of this experiment would
be?

There is no winglet you could add to a wing which would cause a net forward
force between the wing and the mount.

Quote:
Would there be a forward component to the net force on the winglet?

There can be, if you tweak the wing properly. It will be more than
counteracted by the backward force such a tweak induces on the wing.

Quote:
I argue that the effect of this is to pull the wing forward more than
if the winglet was not there.

You're treating the problem as if the wing without the winglets just loses
the force from the winglet. The presence of the winglet alters the airflow
over the entire wing...it doesn't really make sense to talk about isolated
winglet/wing forces because you can't separate them.

A good winglet will reduce drag in the overall assembly. You can screw with
the wing such that the winglet actually generates a forward force, but
you'll induce so much drag on the wing that the overall effect will be worse
than the wing with a properly done winglet (which does not contribute a
forward force). Either scenario could have less drag than a wing without
winglets.

Quote:
If a rope tugs on rock the rock is tugging back on the rope. That
doesn't change the fact that the rock moves forward.

Although true, it's not relevant to the forces on wings. Whatever's tugging
on the rock has to be tugging on something else. An aircraft has no
externally applied forces on the thust axis during level flight.

Tom.
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