Thin Airfoil and Climb Performance

sisu1a wrote:

If structure does not change the aerodynamics of
a wing, then why are modern hot ships still made of wood, or metal?

When the shift from wood and metal to fiberglass occurred, a huge factor
was cost: it was much cheaper to build a glider to the tolerances
required in molded fiberglass than the other materials, and it retained
the shape better. At that time, you could build a lighter aluminum
glider of the same performance, but it was a constant effort to keep the
airfoil correct. I don't know if this is still true for carbon fiber
versus aluminum; regardless, I think the cost would still favor the
molded construction.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
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Paul -

I don't argue that there isn't room for improvement and that the newer
materials have benefits.

But the bottom line is that the increases in L/D and *aerodynamic
performance* aren't likely to change by large amonths. And the new
materials have little or no effect on the aerodynamic performance or
the shape of the wings.

With all due respect (I'm not trying to be antagonistic), please read
Fred Thomas' "Fundamentals of Sailplane Design" book or go study
aerodynamics before trying to lecture about the subject.

--Noel

When the shift from wood and metal to fiberglass occurred, a huge factor
was cost: it was much cheaper to build a glider to the tolerances
required in molded fiberglass than the other materials, and it retained
the shape better. At that time, you could build a lighter aluminum
glider of the same performance, but it was a constant effort to keep the
airfoil correct. I don't know if this is still true for carbon fiber
versus aluminum; regardless, I think the cost would still favor the
molded construction.

No arguments here! Still a case for material advances improving
sailplanes (by making laminar capable wings affordable and
maintainable), but still a poor point for me to have tried to use to
advance my hypothisis for current improvements...you got me.

But the bottom line is that the increases in L/D and *aerodynamic
performance* aren't likely to change by large amonths.

I don't think I quantified the amount, just stated that many have said
"it wont get better than X amount" and have been proven wrong as
aerodynamics AND materials improve.

And the new materials have little or no effect on the aerodynamic performance or
the shape of the wings.

Now we really part ways. I was only citing that even currently
available materials offer more room for improvement, but I'm certainly
not limiting my thoughts on this to prepreg carbon. Do you not think
that once OTHER materials are advanced enough to have a super-smooth
uber-laminar wing that can change in airfoil/incidence/planform/etc
while in flight (like a bird's wing. but much slicker) will not yield
significant performance improvements? We do not yet have the materials
to construct such a thing, but when (if?) the "Unobtanium" to
construct such a wing comes about I think there will be a major leap
in performance capabilities, but perhaps you do not see it this way.

With all due respect (I'm not trying to be antagonistic), please read
Fred Thomas' "Fundamentals of Sailplane Design" book or go study
aerodynamics before trying to lecture about the subject.

Lecturing? Hardly. (not feeling antagonized ; ) I simply felt the need
to counterpoint some things from my post you clearly misinterpreted
(equating strength/weight ratio of construction with wing loading for
example). I appreciate your endorsement of Fred Thomas' book, and I
will continue to read my copy. I do not profess to be an
aerodynamicist and my opinions are mostly based on intuition, which
leaves much room for learning I am open to. My original point was
actually that the "this is all we have to look forward to" type
statement are words that thankfully have been eaten many times over,
and I think (hope?) they will have to be eaten again (also pointing
out that they can 'possibly' eaten sooner than thought using current
materials, but not that it would be practical to do...).

Is this discussion group not for the exchange of ideas and a place to
learn? I have no problem being wrong, as I all too often am. I however
do not discourage anyone from posting about things they are truly
interested in, whether they have a degree in that subject or not.
Counter to that school of thought and historically speaking, many very
important discoveries were made by people that luckily were ignorant
to the "facts" that something was impossible so they dared to leap.

Paul Hanson

But the bottom line is that the increases in L/D and *aerodynamic
performance* aren't likely to change by large amonths. And the new
materials have little or no effect on the aerodynamic performance or
the shape of the wings.

Nasa doesn't seem to agree with you either: http://www.gizmag.com/go/2242/picture/3073/
(there are links to the rest Aero Elastic Wing article along with more
pics)
Perhaps they should read Fred Thomas' book and get over
themselves! ; )

In Jest,
Paul

On May 5, 3:28*pm, sisu1a wrote:
But the bottom line is that the increases in L/D and *aerodynamic
performance* aren't likely to change by large amonths. *And the new
materials have little or no effect on the aerodynamic performance or
the shape of the wings.

Nasa doesn't seem to agree with you either:http://www.gizmag.com/go/2242/picture/3073/
(there are links to the rest Aero Elastic Wing article along with more
pics)
Perhaps they should read Fred Thomas' book and get over
themselves! *; )

In Jest,
Paul

Just for the 'what if' pile..... What if a new material becomes
available that would allow a true variable airfoil / camber wing to be
built. (like the Aero Elastic Wing on steroids) Not just the last 10%
or so of the chord, but truly changing the airfoil in flight to
whatever is best suited to the immediate circumstances? Yes, this is
JUST a fantasy, but so was aviation in general 105 years ago.

On May 5, 5:04 pm, wrote:
On May 5, 3:28 pm, sisu1a wrote:

But the bottom line is that the increases in L/D and *aerodynamic
performance* aren't likely to change by large amonths. And the new
materials have little or no effect on the aerodynamic performance or
the shape of the wings.

Nasa doesn't seem to agree with you either:http://www.gizmag.com/go/2242/picture/3073/
(there are links to the rest Aero Elastic Wing article along with more
pics)
Perhaps they should read Fred Thomas' book and get over
themselves! ; )

In Jest,
Paul

Just for the 'what if' pile..... What if a new material becomes
available that would allow a true variable airfoil / camber wing to be
built. (like the Aero Elastic Wing on steroids) Not just the last 10%
or so of the chord, but truly changing the airfoil in flight to
whatever is best suited to the immediate circumstances? Yes, this is
JUST a fantasy, but so was aviation in general 105 years ago.

How about a passive nano-unobtanium surface that smoothed and
roughened at different speeds/loadings to prevent flow separation,
along with the airfoil elasticity?

Frank W

On May 5, 4:09*pm, Frank Whiteley wrote:
On May 5, 5:04 pm, wrote:





On May 5, 3:28 pm, sisu1a wrote:

But the bottom line is that the increases in L/D and *aerodynamic
performance* aren't likely to change by large amonths. *And the new
materials have little or no effect on the aerodynamic performance or
the shape of the wings.

Nasa doesn't seem to agree with you either:http://www.gizmag.com/go/2242/picture/3073/
(there are links to the rest Aero Elastic Wing article along with more
pics)
Perhaps they should read Fred Thomas' book and get over
themselves! *; )

In Jest,
Paul

Just for the 'what if' pile..... * What if a new material becomes
available that would allow a true variable airfoil / camber wing to be
built. (like the Aero Elastic Wing on steroids) Not just the last 10%
or so of the chord, but truly changing the airfoil in flight to
whatever is best suited to the immediate circumstances? *Yes, this is
JUST a fantasy, but so was aviation in general 105 years ago.

How about a passive nano-unobtanium surface that smoothed and
roughened at different speeds/loadings to prevent flow separation,
along with the airfoil elasticity?

Frank W- Hide quoted text -

- Show quoted text -

YES! I'll buy one as soon as I'm not the weak link in my Speed
Astir's performance! Oh... never mind.

How about a passive nano-unobtanium surface that smoothed and
roughened at different speeds/loadings to prevent flow separation,
along with the airfoil elasticity?

Hey hey, I *did* say "passive boundary layer control"!! ;-)

Lemme try to be clearer, and not as abrasive as perhaps I came across
earlier:

Aerodynamicists have gotten really good at figuring out optimum static
shapes of airfoils and 3d wings for a desired "mission" or set of
aerodynamic circumstances.

Airfoil effectivness and pressure distributions are affected by the
precision and smoothness of the external shape - and newer materials
don't bring anything to the table that fiberglass doesn't already
provide.

Weight, in and of itself, doesn't play a part in the actual efficiency
of a wing to extract energy / lift from the stream of air flowing
around it; and weight savings are what things like pre-preg are
generally good for right now (you might say "stiffness" - but you can
usually get an equally stiff part with a much heavier layup of
traditional fiberglass with a good core material; so in the end it
goes back to being a weight issue).

Elastic / flexible materials have already made an appearance before,
at least as coverings over hinges to improve airflow (Speed Astir
flaps, anyone?)... But to get a marked increase in glide efficiency
over an entire flight, things like this are going to have to be able
to react and adapt quite quickly to a wide variety of aerodynamic
situations. Look at the Sinha "De-Turbulator" tape: At very specific
speeds with very specific airflows it is able to momentarily provide a
large boost to the glide ratio/efficiency of a wing. But it doesn't
(yet) appear to be capable of adapting to different airflows and
different flight regimes - so in the end if may not provide a huge
performance boost to an overall flight. Additionally, it has not been
proven that the boosted performance is a sustainable / stable flight
condition - it might just be a momentary / transitionary gain that
cannot be maintained for long enough to make a meaningful difference
during a flight.

When it comes to physics, we have pretty much mathematically solved
the equations to provide the most efficient wing shape for any single
flight condition. We can minimize drag or maximize lift or pick a
middle-point that best matches our desires at that precise moment. An
adaptable wing doesn't help in a static situation (i.e. constant
airspeed, constant angle of attack, no-wind, calm-air, straight-line
best-glide. That's theoretically what we mean when we talk about
"Best L/D"). You can only get as good as you can get with the optimal
wing-shape for that one situation.

Furthermore, there's no getting around the fact that an actual
aircraft flight is a chaotic and ever-changing blend of different
conditions. For an aircraft to fly well overall, it needs to be a
compromise that can work reasonably under all of the disparate
conditions. And with current technology and materials (no matter how
exotic), there's no way to make a wing that can dynamically optimize
its shape in-flight and in reaction to all of the various conditions.
I look forward to the day when such technology exists; but I might
well be dead by that point (and I'm only 30 right now - but even as an
optimistic technology professional I just don't see it being a near-
term possibility).

Take care,

--Noel

noel.wade wrote:

snip


Furthermore, there's no getting around the fact that an actual
aircraft flight is a chaotic and ever-changing blend of different
conditions. For an aircraft to fly well overall, it needs to be a
compromise that can work reasonably under all of the disparate
conditions. And with current technology and materials (no matter how
exotic), there's no way to make a wing that can dynamically optimize
its shape in-flight and in reaction to all of the various conditions.
I look forward to the day when such technology exists; but I might
well be dead by that point (and I'm only 30 right now - but even as an
optimistic technology professional I just don't see it being a near-
term possibility).

Take care,

Makes me think of adaptive optics used to correct for atmospheric
turbulence degrading the image generated by large telescopes. The
medium the telescope is adapting to is the same, so I imagine the time
scale is similar to what an adaptive surface of a sailplane would need.
Could be kinda heavy equipping the wing with all those actuators though.
:-o

Shawn

Maybe the time scale doesn't have to be *that* fast. Simply scale up "eagle cam"'s aerial
virtuosity

http://animal.discovery.com/converge...29.15073148073

to NASA's
http://www.nasa.gov/centers/dryden/n...-061-DFRC.html

It would be interesting to hear if this idea went any further. And fun to imagine it's use
in soaring.

--Sarah


Shawn wrote:
snip

Makes me think of adaptive optics used to correct for atmospheric
turbulence degrading the image generated by large telescopes. The
medium the telescope is adapting to is the same, so I imagine the time
scale is similar to what an adaptive surface of a sailplane would need.
Could be kinda heavy equipping the wing with all those actuators though.
:-o

Shawn