Modern Sailplane Airfoil Coordinates

[superficial intelligence]

Hello,

Does anyone know a resource where i could find airfoil coordinates for
(more) modern composite gliders. I understand that many of the currently
competetive sailplane manufacturers would have very closley guarded data on
their airfoils but i may get lucky. The most modern data i can find is on
the ASW 20.

I am doing a bit of research mainly to do with airfoil advancement over the
last 30 years.

Regards,

Steven McKay

[Bob Kuykendall]

Earlier, "superficial intelligence" >
wrote:

> Does anyone know a resource where i
> could find airfoil coordinates for
> (more) modern composite gliders.

The most effective resource for coordinates are the articles
themselves. Be sure and call it "research."

A hint: always check both right and left sides of the article.
Asymetry abounds.

> I understand that many of the currently
> competetive sailplane manufacturers
> would have very closley guarded data
> on their airfoils but i may get lucky.

You might.

> The most modern data i can find is on
> the ASW 20.
>
> I am doing a bit of research mainly to
> do with airfoil advancement over the
> last 30 years.

Since you mentioned it, here's my take pundit's-eye-view of the last
30 years of airfoil development:

The biggest changes have been not in the airfoils themselves, but
rather in the degree of difficulty of developing custom airfoils for
specific applications. With airfoil development packages now available
for desktop computers (or even online), it is now practical to develop
six or eight different sections for a wing panel that optimize the
section for the constraints at that part of the wing. None of those
sections would be anything that a dedicated airfoil designer couldn't
have developed over the course of a few weeks or months in 1975.
However, the fact that you can develop each section over the course of
only a few hours or even just minutes, and have a high degree of
confidence in its effectiveness, can make a noticeable difference in
overall performance.

Beyond that, there has also been sort of a wave of realignment, in
which airfoil design has started to take more account of real-world
conditions. For example, when it comes to low drag at cruising speed
in smooth conditions, there isn't much in the sailplane realm that
beats the old FX-67 sections. However, when you add in turbulence,
construction and fabrication defects, paint chips, dust, bugs, and
rain, the FX-67 degrades rapidly; especially in the 17% thickness
common on second-generation composite gliders. Later airfoils such as
the FX-81 will tend to be more conservative, and try for less in the
way of laminar run, but lose less of their performance as surface
conditions deteriorate and so come out ahead.

Thanks, and best regards to all

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

[Chip Fitzpatrick]

I'd contact Peter Masak or Mark Maughmer. Someone at Ostiv may be able to help.

[Dan Somers]

Bob Kuykendall wrote:

> Since you mentioned it, here's my take pundit's-eye-view of the last
> 30 years of airfoil development:
>
> The biggest changes have been not in the airfoils themselves, but
> rather in the degree of difficulty of developing custom airfoils for
> specific applications. With airfoil development packages now available
> for desktop computers (or even online), it is now practical to develop
> six or eight different sections for a wing panel that optimize the
> section for the constraints at that part of the wing. None of those
> sections would be anything that a dedicated airfoil designer couldn't
> have developed over the course of a few weeks or months in 1975.
> However, the fact that you can develop each section over the course of
> only a few hours or even just minutes, and have a high degree of
> confidence in its effectiveness, can make a noticeable difference in
> overall performance.
>
> Beyond that, there has also been sort of a wave of realignment, in
> which airfoil design has started to take more account of real-world
> conditions. For example, when it comes to low drag at cruising speed
> in smooth conditions, there isn't much in the sailplane realm that
> beats the old FX-67 sections. However, when you add in turbulence,
> construction and fabrication defects, paint chips, dust, bugs, and
> rain, the FX-67 degrades rapidly; especially in the 17% thickness
> common on second-generation composite gliders. Later airfoils such as
> the FX-81 will tend to be more conservative, and try for less in the
> way of laminar run, but lose less of their performance as surface
> conditions deteriorate and so come out ahead.


How enlightening to have one's profession summarized in two, short
paragraphs. Apparently, we airfoil designers have been remiss in
explaining our work.

It seems illogical that the sailplane factories would expend so much
effort guarding their proprietary airfoils if these shapes can be
developed in minutes using publicly available software. I am often
asked by amateur aircraft designers if they should obtain an airfoil
code and design their own airfoils. My advice is "Go for it and, while
you are at it, stop by your local medical supply house and pick up a
scalpel so you can perform brain surgery on your kids." The safety
issues alone are comparable. Interestingly, almost all aircraft
manufacturers, and all the sailplane factories, employ specialists to
design airfoils for their new aircraft designs.

Indeed airfoil design continues to be an area of intense research
because airfoils are the single largest contributor to the aerodynamic
performance of almost all aircraft. For example, the wing profile drag,
which is a function of the airfoil alone, contributes approximately 60
percent of the entire drag of the sailplane at high speeds. Thus, even
small gains in airfoil performance produce significant improvements in
sailplane performance.

The theoretical methods available today are unquestionably invaluable
tools. It takes as long or longer now to design an airfoil than it did
30 years ago, however, because our understanding of aerodynamics is
deeper. Also, with these methods, we can explore many more variations
than was previously possible. Although the methods, specifically XFOIL
and the Eppler Code, are powerful, they are not perfect, requiring
experimental verification of the predicted characteristics. Wind-tunnel
testing of airfoils also takes longer today than it did in the good old
days. During World War II, NACA tested three airfoils per day (one per
eight-hour shift) in their Low-Turbulence Pressure Tunnel. They used
manometers to measure the wall and wake pressures for three Reynolds
numbers plus one roughness condition. They had a staff of about 75,
most of whom manually integrated the pressures to obtain the lift and
drag coefficients. Today, a typical single-element airfoil test takes
about two weeks, directly involving about five people. We measure
airfoil and wake pressure distributions at more angles of attack for
more Reynolds numbers and roughness conditions using precision transducers.

The past five decades have seen a dramatic shift in airfoil design
philosophy, but not necessarily toward more conservative shapes. NACA
and later F. X. Wortmann developed catalogs of airfoils for classes of
aircraft. Today, because of the ever widening range of applications and
the availability of calibrated codes, pioneered by Richard Eppler,
airfoils are tailored to specific aircraft. Thus, airfoils are designed
for the Discus 2 and different airfoils are designed for the ASW 28. In
the future, this trend will continue as airfoil/aircraft design
integration intensifies, leading to further increases in performance.
If this is not enough to dispel the myth that we have reached a plateau,
concepts such as laminar-flow-control and slotted, natural-laminar-flow
airfoils hold promise for even larger increases in performance.

We glider pilots are fortunate that the four individuals who, in my
opinion, are good low-speed airfoil designers practice their craft more
in pursuit of their passion than of money. Not surprisingly, all four
are glider pilots and good friends. So the next time you see Richard
Eppler, Karl-Heinz Horstmann, or Loek Boermans at the gliderport, offer
to pay for their launch--they have contributed much more than that to
the sailplane you are flying. (They will almost certainly graciously
decline, in any event.)

Dan Somers
Port Matilda, Pennsylvania USA

[Eric Greenwell]

Dan Somers wrote:


> We glider pilots are fortunate that the four individuals who, in my
> opinion, are good low-speed airfoil designers practice their craft more
> in pursuit of their passion than of money. Not surprisingly, all four
> are glider pilots and good friends. So the next time you see Richard
> Eppler, Karl-Heinz Horstmann, or Loek Boermans at the gliderport, offer
> to pay for their launch--they have contributed much more than that to
> the sailplane you are flying. (They will almost certainly graciously
> decline, in any event.)

Or offer to buy them lunch, and get them talking. I've had the pleasure
of this with Eppler and Boermans, but not Horstmann and the fourth
fellow ... didn't quite catch his name. The last time was with Loek B.
at the Ostiv/SHA meeting at Tehachapi, California, a couple years ago.
He discussed things like why the LS8 has curved winglets and the ASW28
doesn't, the difference between the DG 800 airfoil and the ASH 26
airfoil (even though the wing planforms are almost identical), and
curiosities in the design of the "wings" (blades) on all the wind power
generators at Tehachapi as we stood next 100' long blades lying on the
ground like beached whales.

--
-----
change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[Udo Rumpf]

"Dan Somers" > wrote in message
...
> Bob Kuykendall wrote:
>
> > Since you mentioned it, here's my take pundit's-eye-view of the last
> > 30 years of airfoil development:
> >
> > The biggest changes have been not in the airfoils themselves, but
> > rather in the degree of difficulty of developing custom airfoils for
> > specific applications. With airfoil development packages now available
> > for desktop computers (or even online), it is now practical to develop
> > six or eight different sections for a wing panel that optimize the
> > section for the constraints at that part of the wing. None of those
> > sections would be anything that a dedicated airfoil designer couldn't
> > have developed over the course of a few weeks or months in 1975.
> > However, the fact that you can develop each section over the course of
> > only a few hours or even just minutes, and have a high degree of
> > confidence in its effectiveness, can make a noticeable difference in
> > overall performance.
> >
> > Beyond that, there has also been sort of a wave of realignment, in
> > which airfoil design has started to take more account of real-world
> > conditions. For example, when it comes to low drag at cruising speed
> > in smooth conditions, there isn't much in the sailplane realm that
> > beats the old FX-67 sections. However, when you add in turbulence,
> > construction and fabrication defects, paint chips, dust, bugs, and
> > rain, the FX-67 degrades rapidly; especially in the 17% thickness
> > common on second-generation composite gliders. Later airfoils such as
> > the FX-81 will tend to be more conservative, and try for less in the
> > way of laminar run, but lose less of their performance as surface
> > conditions deteriorate and so come out ahead.
>
>
> How enlightening to have one's profession summarized in two, short
> paragraphs. Apparently, we airfoil designers have been remiss in
> explaining our work.
>
> It seems illogical that the sailplane factories would expend so much
> effort guarding their proprietary airfoils if these shapes can be
> developed in minutes using publicly available software. I am often
> asked by amateur aircraft designers if they should obtain an airfoil
> code and design their own airfoils. My advice is "Go for it and, while
> you are at it, stop by your local medical supply house and pick up a
> scalpel so you can perform brain surgery on your kids." The safety
> issues alone are comparable. Interestingly, almost all aircraft
> manufacturers, and all the sailplane factories, employ specialists to
> design airfoils for their new aircraft designs.
>
> Indeed airfoil design continues to be an area of intense research
> because airfoils are the single largest contributor to the aerodynamic
> performance of almost all aircraft. For example, the wing profile drag,
> which is a function of the airfoil alone, contributes approximately 60
> percent of the entire drag of the sailplane at high speeds. Thus, even
> small gains in airfoil performance produce significant improvements in
> sailplane performance.
>
> The theoretical methods available today are unquestionably invaluable
> tools. It takes as long or longer now to design an airfoil than it did
> 30 years ago, however, because our understanding of aerodynamics is
> deeper. Also, with these methods, we can explore many more variations
> than was previously possible. Although the methods, specifically XFOIL
> and the Eppler Code, are powerful, they are not perfect, requiring
> experimental verification of the predicted characteristics. Wind-tunnel
> testing of airfoils also takes longer today than it did in the good old
> days. During World War II, NACA tested three airfoils per day (one per
> eight-hour shift) in their Low-Turbulence Pressure Tunnel. They used
> manometers to measure the wall and wake pressures for three Reynolds
> numbers plus one roughness condition. They had a staff of about 75,
> most of whom manually integrated the pressures to obtain the lift and
> drag coefficients. Today, a typical single-element airfoil test takes
> about two weeks, directly involving about five people. We measure
> airfoil and wake pressure distributions at more angles of attack for
> more Reynolds numbers and roughness conditions using precision
transducers.
>
> The past five decades have seen a dramatic shift in airfoil design
> philosophy, but not necessarily toward more conservative shapes. NACA
> and later F. X. Wortmann developed catalogs of airfoils for classes of
> aircraft. Today, because of the ever widening range of applications and
> the availability of calibrated codes, pioneered by Richard Eppler,
> airfoils are tailored to specific aircraft. Thus, airfoils are designed
> for the Discus 2 and different airfoils are designed for the ASW 28. In
> the future, this trend will continue as airfoil/aircraft design
> integration intensifies, leading to further increases in performance.
> If this is not enough to dispel the myth that we have reached a plateau,
> concepts such as laminar-flow-control and slotted, natural-laminar-flow
> airfoils hold promise for even larger increases in performance.
>
> We glider pilots are fortunate that the four individuals who, in my
> opinion, are good low-speed airfoil designers practice their craft more
> in pursuit of their passion than of money. Not surprisingly, all four
> are glider pilots and good friends. So the next time you see Richard
> Eppler, Karl-Heinz Horstmann, or Loek Boermans at the gliderport, offer
> to pay for their launch--they have contributed much more than that to
> the sailplane you are flying. (They will almost certainly graciously
> decline, in any event.)
>
> Dan Somers
> Port Matilda, Pennsylvania USA


Since you are beating the drums for your profession and rightly so, because
I understand how much "effort and time" is involved in developing and
improving airfoils, in spite of all the aides available today.
It takes many hundreds of hours to do the analysis after the airfoil
reaches a stage, were one could say this may be a winner. I agree with in
your sentiment about the previous post, but there is room for the amateur.
To day it is possible with a narrow knowledge base, but with time and
perseverant and very good software
to be successful
There are amateurs out there that are still able to realize there dreams.
I had the good fortune to pursue this aspect of our hobby to the fullest .
I have successfully developed an airfoil for my glider, now sold.
At the moment I am in the process of building a new wing with my new
airfoil with out constrain, which I had on my previous project.
You are well come to check out my claim and compare some of my flights "head
to head" against the best equipment flying today.
http://www.soaridaho.com/Schreder/Stories/Contests/2003_Seniors/2003_Seniors.htm

Regards
Udo Rumpf