sliding wings?

Hi, I don't think they built seven of those FS 29.



"The "Akademische Fliegergruppe Stuttgart" (in short "Akaflieg") is a
scientific aeronautical association at the University of Stuttgart. Its aims
is to develop new methods in aircraft construction and to put them into
practice. The main focus is sailplane development"



Their aim is normally not making any sailplane production...

You can take a look on http://www.uni-stuttgart.de/akaflieg/e-home.htm

(Text in German).


KH

schrieb im Newsbeitrag
oups.com...

karl-heinz: thank you. interesting russian designs. alas, they do
not tell us what the speeds and engine performances were. the IS-1
actually flew, so this would have been interesting.

I tried the aviafrance website, but cannot read french. fortunately, I
can read German, and on a google search found yet another one---and
this one from 1976 (i.e., not WW-2). it was for Akaflieg Stuttgart eV,
which apparently tried a telescoping wing plane called fs-29.
searching for airplane by name, I find indexes to "P. Lert, translator,
The FS-29, a telescoplng-wing sailplane [Aerodynamics; Lee Waves;
Sailplanes\FS-29], page 21" in Soaring Mag. more info is at
http://www.sailplanedirectory.com/stutgar.htm, which says they built 7
of these. [oops, just saw bill's post mentioning them, too.]

smitty---having internal strengtheners slide by one another should not
be too tough to accomplish, either.


What is the drag contribution of the wings in cruise flight? Is it
high? If so, this would make sense. Otherwise, not. Would it be
feasible to build an airplane that is a 60mph/150mph (stall/cruise) in
wing-extended config, and an 80mph/200mph airplane in non-wing-extended
config (i.e., not deadly if the wing extension mechanism fails at
landing time)? presumably, it would also save fuel.

in the realm of tough technology, extending wings does not seem too
difficult or error prone (e.g., compared to lowering wheels), whether
it is telescoping, or covering two successive wings, or raising up a
wing to become a biplane. the transition airflow might be tricky with
the latter two, but apparently the Russians thought it would work in
WW-2. also, if the wing does not extend, it wouldn't be so bad.


richard---it was my misunderstanding that I thought they primarily
change the angle of attack. but compared to more wing, they seem
somewhat "limited."

/iaw

At the time the FS-29 was built, carbon fiber construction was in its
infancy. Today, a monococque wing of carbon fiber sandwitch skins can be
constructed. This means the sliding outer wing panel can be made to slide
easily over a fixed inner panel.

Since you would want ailerons on the outer panel that would be the major
complexity. For an airplane, you can tolerate some less than perfect wing
aerodynamics with the wngspan extended since you are going to be flying 99%
of the time in cruise mode. Wing extended flight need only be stressed for
approach and landing airspeeds. Presumably with the wings retracted, the
strength would be more than adequate.

At high speed cruise, long wings are a liability and cruise speeds can be
increased with short wings. You'd want the cruise configuration short
enough that the wing flies at the best L/D AoA.

Think of a RV-8 like aircraft with a span variable between 30 feet and 18
feet. The sliding outer panels could cover retracted gear like gear doors.

Bill Daniels

wrote in message
oups.com...

karl-heinz: thank you. interesting russian designs. alas, they do
not tell us what the speeds and engine performances were. the IS-1
actually flew, so this would have been interesting.

I tried the aviafrance website, but cannot read french. fortunately, I
can read German, and on a google search found yet another one---and
this one from 1976 (i.e., not WW-2). it was for Akaflieg Stuttgart eV,
which apparently tried a telescoping wing plane called fs-29.
searching for airplane by name, I find indexes to "P. Lert, translator,
The FS-29, a telescoplng-wing sailplane [Aerodynamics; Lee Waves;
Sailplanes\FS-29], page 21" in Soaring Mag. more info is at
http://www.sailplanedirectory.com/stutgar.htm, which says they built 7
of these. [oops, just saw bill's post mentioning them, too.]

smitty---having internal strengtheners slide by one another should not
be too tough to accomplish, either.


What is the drag contribution of the wings in cruise flight? Is it
high? If so, this would make sense. Otherwise, not. Would it be
feasible to build an airplane that is a 60mph/150mph (stall/cruise) in
wing-extended config, and an 80mph/200mph airplane in non-wing-extended
config (i.e., not deadly if the wing extension mechanism fails at
landing time)? presumably, it would also save fuel.

in the realm of tough technology, extending wings does not seem too
difficult or error prone (e.g., compared to lowering wheels), whether
it is telescoping, or covering two successive wings, or raising up a
wing to become a biplane. the transition airflow might be tricky with
the latter two, but apparently the Russians thought it would work in
WW-2. also, if the wing does not extend, it wouldn't be so bad.


richard---it was my misunderstanding that I thought they primarily
change the angle of attack. but compared to more wing, they seem
somewhat "limited."

/iaw

The point I had hoped to make with the rib reference is that, I don't
quite see how the ribs in the extension will slide past the ribs in the

main wing.

Just do away with conventional ribs. A double skinned cored curve
might be made with only a slight weight penalty, and construction would
be very simple. After all they would be used for just slightly more
than a 1"G" climb, or flare, and are at the tips of the existing wing
where bending loads are small. While your at it might incorporate
leading edge slats in the extendable section.
=====================
Leon McAtee
thinking exoskeleton

hmm...what would happen if the ailerons were mid-wing, rather than
end-of-wing? an outer-wing stall would occur before buffeting (ok),
then it would hit mid-wing (for how long?), then it would hit full
stall.

the real benefit might be a plane that would be much faster than an
ordinary RV-8 (if there is a big drag penalty to a big wing in fast
flight), and still land the same. getting the landing speed from 60mph
to 40mph is nice, but rarely important---ok, I am not flying STOL.

/iaw

"Bill Daniels" bildan@comcast-dot-net wrote in message ...
snip

Since you would want ailerons on the outer panel that would be the major complexity. For an airplane, you can
tolerate some less than perfect wing aerodynamics with the wngspan extended since you are going to be flying 99% of
the time in cruise mode. Wing extended flight need only be stressed for approach and landing airspeeds.
Presumably with the wings retracted, the strength would be more than adequate.
snip

Why not leave the ailerons where they are and extend the wings individually and differentially side to side to
initiate turns and to counter act the reduced aileron effectiveness? Or why not eliminate them entirely to further
reduce complexity and use differential wing extension as the sole control means?

Think of a RV-8 like aircraft with a span variable between 30 feet and 18 feet. The sliding outer panels could
cover retracted gear like gear doors.

Would it really be necessary to make that large a span difference? Would just 3 or 4 feet be sufficient?
snip

Obviously questions from an non aerodynamics educated individual.

Joe Schneider
8437R



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"JJS" jschneider@remove socks cebridge.net wrote in message
...

Why not leave the ailerons where they are and extend the wings
individually and differentially side to side to initiate turns and to
counter act the reduced aileron effectiveness? Or why not eliminate them
entirely to further reduce complexity and use differential wing extension
as the sole control means?
-------------

Hmmm.. Interesting thought - differential variable span for roll control.
I doubt that idea has ever been proposed before. I could work but it would
need a lot of testing - start with an RC model.

-------------
Think of a RV-8 like aircraft with a span variable between 30 feet and 18
feet. The sliding outer panels could cover retracted gear like gear
doors.

------------

Would it really be necessary to make that large a span difference? Would
just 3 or 4 feet be sufficient?

4 feet on each semi-span would make a lot of difference and be relatively
easy to construct.

Bill Daniels

wrote in message
oups.com...

when I look at my eyeglass case, I see two closely overlapping
wing-type shapes that are being pulled apart for opening.

why would it not be worthwhile to extend wings this way for landing and
departure?

This is a solution in search of a problem.

Rich S.

"Rich S." wrote in message
...
wrote in message
oups.com...

when I look at my eyeglass case, I see two closely overlapping
wing-type shapes that are being pulled apart for opening.

why would it not be worthwhile to extend wings this way for landing and
departure?

This is a solution in search of a problem.

Rich S.
Isn't that pretty much how the B-2 is controlled?

Harold
KD5SAK

From a book about the Horton Flying Wings

"... The Horton H VII had a new type of rudder installed. It consisted of
"tongues" that slid spanwise along the spar, and protuded from the tip for
additional wing tip drag. They worked very well, nevertheless the 20 H VII's
in production at Peschke at the end of the war, had conventional drag
rudders..."

around 1944

KH

"JJS" jschneider@remove socks cebridge.net wrote

Why not leave the ailerons where they are and extend the wings
individually and differentially side to side to
initiate turns and to counter act the reduced aileron effectiveness? Or
why not eliminate them entirely to further
reduce complexity and use differential wing extension as the sole control
means?

Seems like there would be a very large adverse turning drag problem. You
want to turn left, so you extend the right panel. That increased the drag
on the right, and that is not what we want to happen.

Also, the panel would have to be very quick, or the response would be very
slow and sloppy.
--
Jim in NC