flatlets

[CV]

Another aerodynamic bone to toss around and chew on:

Instead of carefully crafted, expensive winglets, wouldn't
straightforward flat end plates serve nearly as well in
reducing wingtip vortices and improve performance.

Have they ever been tried, and with what results ?
CV

[Bill Daniels]

"CV" > wrote in message
...
>
> Another aerodynamic bone to toss around and chew on:
>
> Instead of carefully crafted, expensive winglets, wouldn't
> straightforward flat end plates serve nearly as well in
> reducing wingtip vortices and improve performance.
>
> Have they ever been tried, and with what results ?
> CV
>
>

Wing end plates were a big fad in the early 1950's. It was found that the
same or better improvement could be obtained by simply adding the same area
to the wingtip as additional wingspan.

Messing with wingtips has a long and somewhat eccentric history. They have
been bent up and down, swept forward and back, made wider and narrower,
sliced off at an angle or square, slots added and removed. Until Whitcomb
developed winglets, everything else people tried had a huge drag penalty.
Airflow around the wingtip is complicated. You really have to understand it
to extract any gain.

Winglets produce a real gain especially if the glider must remain within a
span-limited competition class. They have the advantage of increasing the
lift inboard of the winglet without increasing the bending force on the wing
as much as additional span would. They also convert some of the energy in
the wingtip vortex into thrust which is seen as a general drag reduction in
the wingtip area. Think of the winglet as a sailboat sail that catches some
of the inward flow on the upper surface and converts it into thrust.

Bill Daniels

[Wayne Paul]

Here is an article about the successful addition of wing tip stall fences:
http://www.soaridaho.com/Schreder/HP-14/Wing_Fences.html

Wayne
http://www.soaridaho.com/


"CV" > wrote in message
...
>
> Another aerodynamic bone to toss around and chew on:
>
> Instead of carefully crafted, expensive winglets, wouldn't
> straightforward flat end plates serve nearly as well in
> reducing wingtip vortices and improve performance.
>
> Have they ever been tried, and with what results ?
> CV
>
>

[Bob Kuykendall]

Earlier, Cv wrote:

>...Instead of carefully crafted, expensive
> winglets, wouldn't straightforward flat end
> plates serve nearly as well in reducing
> wingtip vortices and improve performance.
>
> Have they ever been tried, and with what
> results ?

Dick Schreder tried some fairly simple endplate type
winglets on the HP-18. They didn't work very well.

Winglets must be carefully designed and executed, otherwise
they are more likely to reduce performance than improve
it. The flows in the tip vortex call for carefully
optimized planform and twist distribution.

Based on the winglet design that Steve Smith did for
my HP-24 wing, I think that it is generally possible
to develop winglets that are fairly simple in geometry
and construction, and that are not very expensive in
terms of materials. However, they would still have
to be carefully made, and that's usually where the
money goes.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24

[Bob Salvo]

Has anyone tried this? http://www.minix.fr/

Bob Salvo

"Bill Daniels" > wrote in message
news:zTPfd.321990$3l3.156113@attbi_s03...
>
> "CV" > wrote in message
> ...
> >
> > Another aerodynamic bone to toss around and chew on:
> >
> > Instead of carefully crafted, expensive winglets, wouldn't
> > straightforward flat end plates serve nearly as well in
> > reducing wingtip vortices and improve performance.
> >
> > Have they ever been tried, and with what results ?
> > CV
> >
> >
>
> Wing end plates were a big fad in the early 1950's. It was found that the
> same or better improvement could be obtained by simply adding the same
area
> to the wingtip as additional wingspan.
>
> Messing with wingtips has a long and somewhat eccentric history. They
have
> been bent up and down, swept forward and back, made wider and narrower,
> sliced off at an angle or square, slots added and removed. Until Whitcomb
> developed winglets, everything else people tried had a huge drag penalty.
> Airflow around the wingtip is complicated. You really have to understand
it
> to extract any gain.
>
> Winglets produce a real gain especially if the glider must remain within a
> span-limited competition class. They have the advantage of increasing the
> lift inboard of the winglet without increasing the bending force on the
wing
> as much as additional span would. They also convert some of the energy in
> the wingtip vortex into thrust which is seen as a general drag reduction
in
> the wingtip area. Think of the winglet as a sailboat sail that catches
some
> of the inward flow on the upper surface and converts it into thrust.
>
> Bill Daniels
>

[Bill Daniels]

Like I said, wingtips are a magnet for eccentric aerodynamics (and
aerodynamisysts).

One I particularly liked was a ram air turbine that popped out of the
wingtip when needed. It spun like a pinwheel in the tip vortex. The
inventor claimed it generated electricity from energy that would have been
wasted.

At about the same time as the red smoke photo shown on the minix site was
taken, I was working on a similar project to get some good air velocity
measurements in a wingtip vortex. Our idea was to fly an airplane through a
cloud of small helium balloons and track their 3D motion with an array of
35mm film cameras known as cine-theodolites.

As expected, the balloons became entrained within the vortex flow. What we
didn't expect was that the balloons spiraled inward to the vortex center in
a plane at right angles to the vortex axis. (The lighter than air balloons
were moving up the air density gradient.) When they reached the vortex
core, they raced away after the airplane in two parallel streams. The
balloons were moving at more than half the speed of the airplane. It was
fascinating to watch and we got some good data.

Bill Daniels


"Bob Salvo" > wrote in message
...
> Has anyone tried this? http://www.minix.fr/
>
> Bob Salvo
>
> "Bill Daniels" > wrote in message
> news:zTPfd.321990$3l3.156113@attbi_s03...
> >
> > "CV" > wrote in message
> > ...
> > >
> > > Another aerodynamic bone to toss around and chew on:
> > >
> > > Instead of carefully crafted, expensive winglets, wouldn't
> > > straightforward flat end plates serve nearly as well in
> > > reducing wingtip vortices and improve performance.
> > >
> > > Have they ever been tried, and with what results ?
> > > CV
> > >
> > >
> >
> > Wing end plates were a big fad in the early 1950's. It was found that
the
> > same or better improvement could be obtained by simply adding the same
> area
> > to the wingtip as additional wingspan.
> >
> > Messing with wingtips has a long and somewhat eccentric history. They
> have
> > been bent up and down, swept forward and back, made wider and narrower,
> > sliced off at an angle or square, slots added and removed. Until
Whitcomb
> > developed winglets, everything else people tried had a huge drag
penalty.
> > Airflow around the wingtip is complicated. You really have to
understand
> it
> > to extract any gain.
> >
> > Winglets produce a real gain especially if the glider must remain within
a
> > span-limited competition class. They have the advantage of increasing
the
> > lift inboard of the winglet without increasing the bending force on the
> wing
> > as much as additional span would. They also convert some of the energy
in
> > the wingtip vortex into thrust which is seen as a general drag reduction
> in
> > the wingtip area. Think of the winglet as a sailboat sail that catches
> some
> > of the inward flow on the upper surface and converts it into thrust.
> >
> > Bill Daniels
> >
>
>

[Stewart Kissel]

I have seen a couple of versions of those things kicking
around the web...if us colonials can get over the 'freedom
fries' syndrome and overcome the lack of sexiness with
them...they apparently will do the same thing as winglets.



At 00:54 28 October 2004, Bob Salvo wrote:
>Has anyone tried this? http://www.minix.fr/
>
>Bob Salvo
>
>'Bill Daniels' wrote in message
>news:zTPfd.321990$3l3.156113@attbi_s03...
>>
>> 'CV' wrote in message
>> ...
>> >
>> > Another aerodynamic bone to toss around and chew
>>>on:
>> >
>> > Instead of carefully crafted, expensive winglets,
>>>wouldn't
>> > straightforward flat end plates serve nearly as well
>>>in
>> > reducing wingtip vortices and improve performance.
>> >
>> > Have they ever been tried, and with what results
>>>?
>> > CV
>> >
>> >
>>
>> Wing end plates were a big fad in the early 1950's.
>> It was found that the
>> same or better improvement could be obtained by simply
>>adding the same
>area
>> to the wingtip as additional wingspan.
>>
>> Messing with wingtips has a long and somewhat eccentric
>>history. They
>have
>> been bent up and down, swept forward and back, made
>>wider and narrower,
>> sliced off at an angle or square, slots added and
>>removed. Until Whitcomb
>> developed winglets, everything else people tried had
>>a huge drag penalty.
>> Airflow around the wingtip is complicated. You really
>>have to understand
>it
>> to extract any gain.
>>
>> Winglets produce a real gain especially if the glider
>>must remain within a
>> span-limited competition class. They have the advantage
>>of increasing the
>> lift inboard of the winglet without increasing the
>>bending force on the
>wing
>> as much as additional span would. They also convert
>>some of the energy in
>> the wingtip vortex into thrust which is seen as a
>>general drag reduction
>in
>> the wingtip area. Think of the winglet as a sailboat
>>sail that catches
>some
>> of the inward flow on the upper surface and converts
>>it into thrust.
>>
>> Bill Daniels
>>
>
>
>

[CV]

Bob Salvo wrote:

> Has anyone tried this? http://www.minix.fr/

Yes, all I can see is the following text:

Cet espace de 20mo a été acheté sur ovh.com

Ce fichier s'appelle index.html

CV

[Robert Ehrlich]

Stewart Kissel wrote:
>
> I have seen a couple of versions of those things kicking
> around the web...if us colonials can get over the 'freedom
> fries' syndrome and overcome the lack of sexiness with
> them...they apparently will do the same thing as winglets.
>

I don't think so. On the web site they are shown applied only
on airplanes with low aspect ratio, where anything would anyway
provide a higher improvement than on a high aspect ratio
wing as on a glider. And glider have to otimize both climb and
cruise. The minix doesn't seem to be well suited to the wide
range of angles of attack implied by this. An improvement for
climb, where induced drag is the most important, will probably
payed by an increased drag in cruise. And I am not biased by
the 'freedom fries' syndrome!