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Wing Extensions



 
 
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  #1  
Old July 18th 03, 07:39 PM
Jay
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Default Wing Extensions

Seems like it might be useful to have removable wing extensions for an
experimental. There are times when you want a fast airplane for cross
country and you can stand a long runway for the high TO/landing speeds
and then there are other times you want the low speed handling for
short field, etc. Flaps do this to some degree depending on how
exotic you want to get and have the advantage of being adjustable in
flight but the wing extensions would appear to extend the flight
envelope (on separate flights) beyond what can be done with typical
flap configurations.

A solid composite structure, perhaps 2 feet on each side that plugs
into the main spar(s) would do nicely to allow you to have both a high
speed clipped wing plane (when removed) and a long wing high lift
plane, of course not at the same time. The further out you go on the
wing the less the loads are so these wouldn't have to be built up as
strong as other parts.

They could be made with no control surfaces or other moving parts.
You could even select a different airfoil for that section if you
wanted. No problem plugging composite extensions into an aluminum
main wing. Of course the main short wing would have to be built to
allow access to the main spar(s). A hollow rectangular cross section
spar could accept an insert to mate with removable extensions.

I guess you'd need some sort of plastic overlay for the airspeed
indicator to remind you of the new critial speeds.

Anyone seen anything like this?
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  #2  
Old July 18th 03, 08:50 PM
DJFawcett26
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Default

Anyone seen anything like this?

A kitplane under design has a cruise and loiter wing.

Go to www.vulcanaero.com/index.html to see it.

Best Regards
  #3  
Old July 18th 03, 08:56 PM
Rick Pellicciotti
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Default


"Jay" wrote in message
m...
Seems like it might be useful to have removable wing extensions for an
experimental. There are times when you want a fast airplane for cross
country and you can stand a long runway for the high TO/landing speeds
and then there are other times you want the low speed handling for
short field, etc. Flaps do this to some degree depending on how
exotic you want to get and have the advantage of being adjustable in
flight but the wing extensions would appear to extend the flight
envelope (on separate flights) beyond what can be done with typical
flap configurations.

A solid composite structure, perhaps 2 feet on each side that plugs
into the main spar(s) would do nicely to allow you to have both a high
speed clipped wing plane (when removed) and a long wing high lift
plane, of course not at the same time. The further out you go on the
wing the less the loads are so these wouldn't have to be built up as
strong as other parts.

They could be made with no control surfaces or other moving parts.
You could even select a different airfoil for that section if you
wanted. No problem plugging composite extensions into an aluminum
main wing. Of course the main short wing would have to be built to
allow access to the main spar(s). A hollow rectangular cross section
spar could accept an insert to mate with removable extensions.

I guess you'd need some sort of plastic overlay for the airspeed
indicator to remind you of the new critial speeds.

Anyone seen anything like this?


Glasairs have optional wingtip extensions. They add about 5 ft to the
wingspan of the airplane.

http://www.newglasair.com/glasairSIIspecs.html

Rick Pellicciotti


  #4  
Old July 18th 03, 10:37 PM
Ernest Christley
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Default

Rick Pellicciotti wrote:

Glasairs have optional wingtip extensions. They add about 5 ft to the
wingspan of the airplane.

http://www.newglasair.com/glasairSIIspecs.html

Rick Pellicciotti



Granted that this would have been taken into account by the designer,
but wouldn't this play hell with the center of lift and by extension
throw off the CG? That is, it wouldn't modify the CG, just change where
it SHOULD be.

I'm thinking that it isn't a good idea in just any old plane.

--
----Because I can----
http://www.ernest.isa-geek.org/
------------------------

  #6  
Old July 19th 03, 07:17 AM
Jay
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Default

Chopping the wing will effect the center of lift for swept wing
aircraft, but most homebuilts (e.g RV) have a wing that just goes
straight out, chopping wing just chops lift (and drag). And I'd have
to agree, it ain't a good idea on just any old plane. First of all,
you make the basic wing on the short side for your highest speed
operation, then you have to expose the load bearing elements of the
wing structure for your extensions to be able to couple. The
structure must be able to handle the extra load from whatever longer
wing extension you attach. But in the end, you have a plane with a
wide operating envelope.

The idea dawned on me after looking at the regular structure of an
RV-8A wing I was watching being built up and comparing an aquintances
shaved wing EZ that he says he needs to come over the fence at 100kts
minimum but it goes real fast on a small HP motor.

Ernest Christley wrote in message
Granted that this would have been taken into account by the designer,
but wouldn't this play hell with the center of lift and by extension
throw off the CG? That is, it wouldn't modify the CG, just change where
it SHOULD be.

I'm thinking that it isn't a good idea in just any old plane.

  #7  
Old July 20th 03, 12:16 AM
Roger Halstead
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Default

On 18 Jul 2003 11:39:27 -0700, (Jay) wrote:

Seems like it might be useful to have removable wing extensions for an
experimental. There are times when you want a fast airplane for cross
country and you can stand a long runway for the high TO/landing speeds
and then there are other times you want the low speed handling for
short field, etc. Flaps do this to some degree depending on how
exotic you want to get and have the advantage of being adjustable in
flight but the wing extensions would appear to extend the flight
envelope (on separate flights) beyond what can be done with typical
flap configurations.

A solid composite structure, perhaps 2 feet on each side that plugs
into the main spar(s) would do nicely to allow you to have both a high
speed clipped wing plane (when removed) and a long wing high lift
plane, of course not at the same time. The further out you go on the
wing the less the loads are so these wouldn't have to be built up as
strong as other parts.


You are describing the Glasair II, Super II, and Glasair III wings.
There is a set of 2 foot extensions available from the factory, and
others of different lengths from other sources.

Down low the short wing loading in nigh onto 30# per square foot..
With tip extensions it's just a tad of 27# ft^2

The aspect ratio is 6.67 and 7.64 with the factory extensions.


They could be made with no control surfaces or other moving parts.
You could even select a different airfoil for that section if you
wanted. No problem plugging composite extensions into an aluminum
main wing. Of course the main short wing would have to be built to
allow access to the main spar(s). A hollow rectangular cross section
spar could accept an insert to mate with removable extensions.

I guess you'd need some sort of plastic overlay for the airspeed
indicator to remind you of the new critial speeds.


They don't change all that much. You leave them set for the shorter
wing. There are no real critical speeds...at least in the G-III. Vne
is listed at 335. They are routinely flown at 350 (mph) doing
aerobatics.

Maneuvering speed, (Va) is listed at 201. I've flown aerobatics at
Vne.
Vno is listed at 280 while 75% gives a POH figure of 282.
I've done letdowns at Vne. and have absolutely no worry about flying
that fast.

The wing tips will hold 5 1/2 gallons each, main tanks 53, and the
header 8...unless you have brake cylinders on the right and that
probably drops it to about 5. Many have additional wing bays turned
into tanks as well.

The Glasair (New Glasair) company recommends using the extensions
until the pilot is thoroughly familiar with the plane and during the
early phases of the flight test program.

With a turbo at high altitude you are looking at a cruise that is well
in excess of the book figure for Vne,

The plane is way over engineered. Book figures are +6, -4 Gs, but
again the plane has been tested wayyyy beyond that.


Roger Halstead (K8RI EN73 & ARRL Life Member)
www.rogerhalstead.com
N833R World's oldest Debonair? (S# CD-2)
Anyone seen anything like this?


  #8  
Old July 21st 03, 08:09 PM
Jay
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Default

I think the poster meant that for that particular case the numbers
didn't change much. But in general, there aren't many parts of the
plane that effect performance more than the wing does. Produces
effectively all the lift and most of the drag.

Dave Hyde wrote in message ...
Roger Halstead wrote:

I guess you'd need some sort of plastic overlay for the airspeed
indicator to remind you of the new critial speeds.


They don't change all that much. You leave them set for the shorter
wing. ...


I think someone else said this too, and I find it confusing. If they
don't change that much, why have the extensions? Just for more fuel?

The airpseed indicator could certainly be marked that way
and inspectors may approve it, but it seems like the long-wing version
would be more critical for safety numbers. Vne would likely be lower
for the long wing(*), and maneuvering speed will be lower as well,
assuming the extensions add any lift at all. Stall speed for *both*
wings is important.

(*) Assuming it's flutter that sets Vne, which is a
big assumption.

Dave 'corner speed' Hyde

  #9  
Old July 22nd 03, 02:45 AM
Peter Dohm
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Default

Jay wrote:

I think the poster meant that for that particular case the numbers
didn't change much. But in general, there aren't many parts of the
plane that effect performance more than the wing does. Produces
effectively all the lift and most of the drag.


I really had planned to stay out of this; but ...

The wing certainly produces most of the lift on a typical (not Rutan)
airplane, although the fuselage, in many common designs, contributes
significant lift as well; especially at low speed and high angle of
attack.

However, the wing does not contribute most of the drag. Typical wings
have L/D of around 100/1 for laminar and ... aarrrgh! ... I can't
find my Dover Edition of "Theory of Wing Sections", but even the
"rough" condition gives more than 30/1 for cruise and is still good
enough to contribute less than half of the total drag at climb speed.

The fuselage and engine cooling are usually the biggest contributors;
with enpenage, undercarriage, antennas, and other "stuff" that sticks
out of the airplane contributing lesser amounts of drag.

Therefore, the probable contribution of wing extensions on most powered
aircraft should be reduced climb and approach speeds and the opportunity
to reduce fuel consumption in a reduced speed cruise. Assuming that the
aircraft was correctly rigged for its cruising speed; then it should be
than the shorter winged slower at its cruising speed version due to the
nose down attitude of the fuselage as well as the related increased trim
drag of the empenage. The increased drag of the larger wing should make
a lesser contribution to the greater drag.

Peter


Dave Hyde wrote in message ...
Roger Halstead wrote:

I guess you'd need some sort of plastic overlay for the airspeed
indicator to remind you of the new critial speeds.

They don't change all that much. You leave them set for the shorter
wing. ...


I think someone else said this too, and I find it confusing. If they
don't change that much, why have the extensions? Just for more fuel?

The airpseed indicator could certainly be marked that way
and inspectors may approve it, but it seems like the long-wing version
would be more critical for safety numbers. Vne would likely be lower
for the long wing(*), and maneuvering speed will be lower as well,
assuming the extensions add any lift at all. Stall speed for *both*
wings is important.

(*) Assuming it's flutter that sets Vne, which is a
big assumption.

Dave 'corner speed' Hyde

  #10  
Old July 22nd 03, 05:21 PM
Jay
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Default

So if the aircraft is built with particularly short permanent wings
with facilities toi accept extensions from the start, you have the
choice of an aircraft with higher cruise speed but accelerated
takeoff/landing speeds, or as you mentioned in your posting, an
aircraft with reduced speed on takeoff/landing, and a higher
efficiency, albeit slower cruise. And of course with intermediate
size extensions, you could have something in the middle, like most GA
aircraft have these days- not too fast, not too slow.

At a specific speed those L/D numbers may be right, but I doubt they
hold for the entire range that aircraft operate in. Drag- One of the
reasons I say the wing is one of the largest contributers is because
similararly powered side-by-side and tandem 2 seaters have top speeds
in the same range, but the frontal area of the fuselage is quite
different. Gear fairing adds a couple kts.
 




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