52/1 Performance in a 15M ship at half the weight.

On Feb 28, 9:23*am, wrote:

Keep in mind that the polar of any glider is a continuous curve and

9B

While I don't dispute anything you say about the DuckHawk, your
statement about 1 polar curve is not correct.

As you can see from the Johnson Reports over the years, a flapped
aircraft has a different polar at each flap setting (you have a
different camber line and airfoil/wing-shape at each flap setting).

When you see a single polar curve for a flapped aircraft, you're
viewing a "composite" curve that is comprised of the "sweet spots" for
each flap setting.

--Noel
(geek/engineer)

On Feb 27, 11:55*pm, Eric Greenwell wrote:
wrote:
It would seem that the Duckhawk would have more international appeal
as a Standard class (15m no flaps) ship - wonder how it would perform
without flaps?

It sure wouldn't need that 200 knot Vne, would it? Flaps are essential
to get the wide speed range that makes the the 200 knot Vne useful. My
understanding is the airfoil is optimized for climbing and very high
speed flight.

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

* Updated! "Transponders in Sailplanes"http://tinyurl.com/y739x4
* * * New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" atwww.motorglider.org

Climb and glide scenario has been going out of favor as optimum
strategy for many years now in favor of extended glide techniques that
optomise cross country speed by minimizing circling and using long
periods of time in the mid to high range to maximize speed made good.
This requires a glider with excellent performance through the whole
speed range which likely will mean that very low speed and or very
high speed are less favored.
Optomising for really high speeds is great for ridge and wave, but not
much use other than final glide in most soaring environments.
It is good to see guys like Gred and Bob giving it a shot.
FWIW
UH

On Feb 28, 12:43*pm, wrote:
On Feb 27, 11:55*pm, Eric Greenwell wrote:



wrote:
It would seem that the Duckhawk would have more international appeal
as a Standard class (15m no flaps) ship - wonder how it would perform
without flaps?

It sure wouldn't need that 200 knot Vne, would it? Flaps are essential
to get the wide speed range that makes the the 200 knot Vne useful. My
understanding is the airfoil is optimized for climbing and very high
speed flight.

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

* Updated! "Transponders in Sailplanes"http://tinyurl.com/y739x4
* * * New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" atwww.motorglider.org

Climb and glide scenario has been going out of favor as optimum
strategy for many years now in favor of extended glide techniques that
optomise cross country speed by minimizing circling and using long
periods of time in the mid to high range to maximize speed made good.
This requires a glider with excellent performance through the whole
speed range which likely will mean that very low speed and or very
high speed are less favored.
Optomising for really high speeds is great for ridge and wave, but not
much use other than final glide in most soaring environments.
It is good to see guys like Gred and Bob giving it a shot.
FWIW
UH

Good point Hank. Cruise speeds have been coming down, though an
analogous set of principles apply. Still a lighter, smaller airframe
should be able to add a 5-10 knots in cruise speed and you'd think
they could design around that.

9B

9B

On Feb 28, 11:15*am, "noel.wade" wrote:
On Feb 28, 9:23*am, wrote:

Keep in mind that the polar of any glider is a continuous curve and

9B

While I don't dispute anything you say about the DuckHawk, your
statement about 1 polar curve is not correct.

As you can see from the Johnson Reports over the years, a flapped
aircraft has a different polar at each flap setting (you have a
different camber line and airfoil/wing-shape at each flap setting).

When you see a single polar curve for a flapped aircraft, you're
viewing a "composite" curve that is comprised of the "sweet spots" for
each flap setting.

--Noel
(geek/engineer)

Yup, that's what I meant. There is an optimal flap position/polar for
every alpha. Only the composite curve matters unless you want to fly
with the wrong flap setting.

Andy
(aerospace geek/engineer) ;-p

It is absolutely mind boggling how boring and uninformative Soaring magazine
has become. There are hardly any topics anymore on gliders (new or
old).radios, avionics, navigation programs etc...
When I read the article below, I wonder what goes through the mine of
Soaring's editor, what kind of agenda causes them to reject information
like this.No matter the name of the project, whether or not this glider can
live up to the expectation they project, this is EXACTLY the kind of topic
this magazine is lacking , and most of us are looking for! PeterK
"SF" wrote in message
...
I wrote the following article and submitted it to Soaring for
publication because it was something I was interested in and I thought
others would be too. It was rejected because the subject matter
wasn't suitable for soaring. Greg Cole is doing something
extraordinary at Windward Performance and I feel that Soaring is doing
all of us a disservice by not putting content like this in the
magazine.
******************
My Trip To Windward Performance

At the 2008 SSA convention in Albuquerque, NM I attended Greg Cole’s
presentation on the new 15M sailplane he’s building called the
DuckHawk. The presentation piqued my interest and I managed to
retain the knowledge that the DuckHawk is an American name for
Peregrine Falcon, the fastest moving creature on earth, and that Greg
Cole’s Sailplane factory is in Bend Oregon.

Other details stuck with me too, like an L/D of 52/1. Minimum Sink
is 111 fpm; empty weight is 300 Lbs, and this Hawk has an aspect ratio
of 30.0:1. The 200 Kt. VNE would make for one hot smoking final
glide.

When business took me to Portland, Oregon last Fall, I realized I’d be
fairly close to Bend. A few phone calls got me an appointment with
Greg Cole, president and creative force behind Windward Performance
Ltd, DuckHawk’s creator as well as builders of 11M span SparrowHawk.

Greg Cole has been building and flying his designs since he was a
kid. He has a BSME from the University of North Dakota, and a MSAE
from Notre Dame. He holds a US patent on propeller design. His work
experience includes the McCauley Propeller Company, Columbia Aircraft
Company (chief Engineer), Cirrus Design, Lancair, and Adam Aircraft.
He has made significant Design contributions to several different
aircraft including: the Lancair Legacy, the Lancair Evolution, The
Columbia 300, The Chanute, The A500, and of course the SparrowHawk
which is the only U.S. designed sailplane to hold a world record in 30
years. The Columbia 300 bears mentioning again as it was the first
new design certified by the FAA in 17 years, and it was a full
composite airframe from a new company.

For those of us that live in America’s South, the drive from Portland
to Bend is simply amazing. In South Carolina we drive in one green
tunnel of pine trees after another, and while we have mountains, they
don’t have snow on them in early September like Mount Hood. The drive
down through the high desert is truly beautiful - just don’t try to
pump your own gas. Oregon gas stations are required by state law to be
full service.

The modern sailplane is one truly amazing piece of machinery. They
may look simple but they’re among the most sophisticated aircraft
flying. I learned to fly in a Grob 103. My first single-place glider
was a 1968 Open Cirrus with massive fiberglass spars, fat wings, and
heavy enough to send everyone on the field running the other direction
any time you pull your trailer into the assembly area.

I moved up to a mid-80’s LS6-a, and began teaching students in a
2-33. The historical progression from the 2-33 and its flying barn
door performance, to a first generation glass ship like the Cirrus, a
second generation glass ship like the LS6-a, and a modern glider using
knife like laminar-flow wings is exciting to experience firsthand.
One of my friends sums it up saying “these new planes just do what you
want them to do so much easier, and they do it so much better”.

Improvements in modern sailplane performance have been driven by
advances in materials, a better understanding of how to design
aerodynamic structures with these materials, computer modeling, and
leaps in understanding aerodynamic principles. Most modern sailplanes,
with the exception of Windward Performance’s aircraft, are built with
a wet, room temperature cured, epoxy resin lay up using glass, carbon,
or Kevlar fiber reinforcement. The reinforcing cloth is laid into the
mold by hand and the epoxy squeegeed, or painted on. This type of
construction process was quite an advance over previous wood and metal
construction and quite a bit better than “fiberglass” or polyester
resins or even the vinyl ester resins but still imposes several
limitations on how strong aircraft parts may be made.

When the resins cure at room temperature there is fairly short
amount of “out-time” – the number of minutes workers have to craft the
part before the resin’s curing process begins. Complicated multi-
layer layups have to be done quickly. Yet fiber orientation and
wetout are important in critical aircraft applications. As a result
room-temperature resin application often means a heavier composite
structure to maintain structural safety. The room temperature curing
of resins, causes the finished part to lose structural integrity
rapidly at temperatures over 140 F, which is why modern composite
sailplanes are painted white. If they were painted black or even red
they would heat up under sunlight and loose structural integrity.

Thus Cole’s Windward Performance is the only sailplane manufacturer
I’m aware of to use sophisticated prepreg oven-cured carbon fiber
construction. Prepreg carbon fiber is produced in a factory by
sandwiching a carbon fiber cloth between two epoxy resin sheets, the
sandwich is then run this between high-pressure rollers. The high
pressure insures an even and complete epoxy coating of the fabric with
the ability to very precisely control the ratio of resin to fabric.
This allows the composite’s weight to remain low but optimized for
strength with very tight tolerances. Once the fabric is epoxy coated
it is refrigerated for storage and transport, greatly retarding the
start of the curing process.

Since the resin does not cure at room temperatures there is much more
out-time in which to lay up the prepreg material in, say, a wing-mold
while avoiding mistakes from rushing. There’ more time for forming
complicated multi-layer configurations.

In Windward’s aircraft, the prepreg layup is vacuum-bagged to ensure
all air is squeezed out of the layup and the entire assembly goes into
an oven to cure at high temperatures. The benefits of all this are
lighter, far stronger and stiffer composites with a much larger
temperature operating range than conventional wet layup composites
afford.
Given these advantages, and given Greg Cole’s expertise and obviously
high standards of craftsmanship, it became clear why Windward
Performance uses prepregs, and why they result in the Duck Hawk’s
performance advantages.

A winning 15M racing sailplane moves around the course in the least
amount of time with the highest average cross country speed. The key
to obtaining that is, naturally, minimizing the time you go slow.
Climbing well and going fast between thermals sounds easy, but
mastering this simple concept is far from easy. Most of us with
modest skills in this area could use all the help we can get from the
aircraft.

The modeling of average cross country speeds with different
atmospheric conditions allowed performance simulations of different
design iterations to be run and small improvements or losses to be
determined. The accuracy of modeling new designs was, for Cole,
validated by modeling current designs with known performance
characteristics.

Designs that can be made light with small wing areas offer improved
performance over conventional designs especially in tough conditions.
Tough conditions – small thermals, weak lift, headwinds, etc. - seem
to have a far greater negative impact on my contest results than do
the positives of favorable conditions.

Cole’s calculations show soaring with the ability to fly well with low
lift coefficients can also give the ability to go fast at relatively
low wing loadings, meaning faster average cross country speeds. The
results of the modeling process indicated an optimum with a wing area
of 80 SQFT, and a wing loading of 8.75 LBS/SQFT.

Determining the optimum airfoil also benefits from Cole’s computer
modeling process. Structural constraints start as the wing area drops
below 90 square feet, and wing volume available for ballast drops
rapidly as well. As wing area decreases, the Reynolds number goes
down and achieving low drag at high and low lift coefficients becomes
more and more difficult.

Good stalling behavior is another factor Cole considered. Amongst all
of the airfoils designed the final airfoil selected for the DuckHawk
is the CS33-18; it allows the aircraft to fly at low lift coefficients
at high speeds as well as at high lift coefficients at low speeds.
Winglets were considered but an evaluation of their negatives and
benefits indicated the DuckHawk would fly better without them when
real world soaring techniques were considered.

State of the art performance is what Cole is after here, plus safety
and relative affordability. The 30:1 aspect ratio and its razor thin
wings are an obvious clue this is not your generic modern glider.
Eighty-pound wings will be appreciated by everyone during assembly.
Eighteen-meter L/D performance with a 15-meter wing span will result
in lower drag while circling and this plane should climb like a
bandit.

The ship’s lower mass will give it an induced drag advantage of 29%
compared to today’s 15m sailplanes at equivalent wing loadings. That
means better climbing. Lower wetted area means lower parasitic drag
and improved high speed running. A wing loading range between 6.25 and
10.0 lbs./sq. Ft. will give it ability to adapt to a wide variety of
soaring conditions - a plane that will get you quickly around the
course on the tough days and fly faster than anything else out there
now on really good days.

Before my trip to Windward Performance I was unaware of the complexity
of the sailplane manufacturing process. The plugs and molds required
to produce a sailplane, fill a good sized warehouse even without
working room around them. The design and production capabilities of
this small sailplane operation were a very pleasant surprise. This is
a small operation but it possesses world class design talent and state
of the art manufacturing processes. While I love my German sailplane
and fully recognize the abilities of the established sailplane
manufacturing companies, I find myself rooting for the underdog home
team in this case.

The first DuckHawk should take to the air summer 2009, and I look
forward to seeing the finished product. In addition to the DuckHawk
Windward has a few other products currently in the works. They are
currently building the Perlan sailplane designed to take two people to
90,000 FT. The Windward Goshawk, an electric aircraft is also being
built. Advances in composites are ushering in a new era in aircraft
innovation and thanks to Greg Cole’s love of soaring we get be benefit
from his creativity, with an exciting new American sailplane.

Peter wrote:
It is absolutely mind boggling how boring and uninformative Soaring magazine
has become. There are hardly any topics anymore on gliders (new or
old).radios, avionics, navigation programs etc...
When I read the article below, I wonder what goes through the mine of
Soaring's editor, what kind of agenda causes them to reject information
like this.No matter the name of the project, whether or not this glider can
live up to the expectation they project, this is EXACTLY the kind of topic
this magazine is lacking , and most of us are looking for! PeterK

I'd like to suggest it wasn't the DuckHawk subject matter that led to
the rejection. The fact this thread has gone on so long with a number of
questions about the design of the DuckHawk indicates it the article by
"SF" is incomplete at best.

A month ago, I had a brief 15 minute discussion with Greg Cole that
covered a number of important aspects about the DuckHawk's goals and his
approach to solving them, most of which are missing from the article.
Since that wasn't our main topic, the brevity and the lack of notes
means I can't add a lot to the conversation here.

It's still a rough draft in my opinion, and I hope he got some useful
guidance from the Soaring magazine editor or contributors (like Bill
Collum) about filling in the holes. Perhaps culling the best from the
article until it's short enough to fit into the Soaring Mail or Soaring
News departments would be a good way to pass on what he learned.


"SF" wrote in message
...
I wrote the following article and submitted it to Soaring for
publication because it was something I was interested in and I thought
others would be too. It was rejected because the subject matter
wasn't suitable for soaring.

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

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

On Feb 28, 8:29*pm, Eric Greenwell wrote:
Peter wrote:
It is absolutely mind boggling how boring and uninformative Soaring magazine
has become. There are hardly any topics anymore on gliders (new or
old).radios, avionics, navigation programs etc...
When I read the article below, I wonder what goes through the mine of
Soaring's editor, what kind of agenda *causes them to reject information
like this.No matter the name of the project, whether or not this glider can
live up to the expectation they project, this is EXACTLY the kind of topic
this magazine is lacking , and most of us are looking for! PeterK

I'd like to suggest it wasn't the DuckHawk subject matter that led to
the rejection. The fact this thread has gone on so long with a number of
questions about the design of the DuckHawk indicates it the article by
"SF" is incomplete at best.

A month ago, I had a brief 15 minute discussion with Greg Cole that
covered a number of important aspects about the DuckHawk's goals and his
approach to solving them, most of which are missing from the article.
Since that wasn't our main topic, the brevity and the lack of notes
means I can't add a lot to the conversation here.

It's still a rough draft in my opinion, and I hope he got some useful
guidance from the Soaring magazine editor or contributors (like Bill
Collum) about filling in the holes. Perhaps culling the best from the
article until it's short enough to fit into the Soaring Mail or Soaring
News departments would be a good way to pass on what he learned.

"SF" wrote in message
....
I wrote the following article and submitted it to Soaring for
publication because it was something I was interested in and I thought
others would be too. *It was rejected because the subject matter
wasn't suitable for soaring.

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

* Updated! "Transponders in Sailplanes"http://tinyurl.com/y739x4
* * * New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" atwww.motorglider.org

Please note that the Soaring editor has an advisory group, which has
been under development for about a year. Currently it's listed as the
Editorial Advisory Group, but my understanding from the Chicago SSA
board meeting was that it was more properly to be a Technical Advisory
Group (and so renamed I thought), not involved in editing submissions
in any way. I don't know if all articles are reviewed by the relevant
contact. If you have any questions, this group has a chair person.
The group reports to SSA director John Dezzutti.

http://www.ssa.org/members/governanc...l.asp?group=70

HTH,

Frank Whiteley

On Feb 28, 10:54*pm, kestrel19 wrote:
On Feb 28, 8:29*pm, Eric Greenwell wrote:





Peter wrote:
It is absolutely mind boggling how boring and uninformative Soaring magazine
has become. There are hardly any topics anymore on gliders (new or
old).radios, avionics, navigation programs etc...
When I read the article below, I wonder what goes through the mine of
Soaring's editor, what kind of agenda *causes them to reject information
like this.No matter the name of the project, whether or not this glider can
live up to the expectation they project, this is EXACTLY the kind of topic
this magazine is lacking , and most of us are looking for! PeterK

I'd like to suggest it wasn't the DuckHawk subject matter that led to
the rejection. The fact this thread has gone on so long with a number of
questions about the design of the DuckHawk indicates it the article by
"SF" is incomplete at best.

A month ago, I had a brief 15 minute discussion with Greg Cole that
covered a number of important aspects about the DuckHawk's goals and his
approach to solving them, most of which are missing from the article.
Since that wasn't our main topic, the brevity and the lack of notes
means I can't add a lot to the conversation here.

It's still a rough draft in my opinion, and I hope he got some useful
guidance from the Soaring magazine editor or contributors (like Bill
Collum) about filling in the holes. Perhaps culling the best from the
article until it's short enough to fit into the Soaring Mail or Soaring
News departments would be a good way to pass on what he learned.

"SF" wrote in message
....
I wrote the following article and submitted it to Soaring for
publication because it was something I was interested in and I thought
others would be too. *It was rejected because the subject matter
wasn't suitable for soaring.

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

* Updated! "Transponders in Sailplanes"http://tinyurl.com/y739x4
* * * New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" atwww.motorglider.org

Please note that the Soaring editor has an advisory group, which has
been under development for about a year. *Currently it's listed as the
Editorial Advisory Group, but my understanding from the Chicago SSA
board meeting was that it was more properly to be a Technical Advisory
Group (and so renamed I thought), not involved in editing submissions
in any way. *I don't know if all articles are reviewed by the relevant
contact. *If you have any questions, this group has a chair person.
The group reports to SSA director John Dezzutti.

http://www.ssa.org/members/governanc...l.asp?group=70

HTH,

Frank Whiteley- Hide quoted text -

- Show quoted text -

EAG-or whatever name you wish to put on it, does serve to help the
editor to ensure that articles published in Soaring are technically
correct, be that related to FAR's, maintenance, training,
aerodynamics, whatever. Chuch recognizes that he doesn't know it all
and is striving to use his resources to produce a good product whuich
we can all enjoy and learn from. I serve in this group along with a
dozen or so people knowledgable in most aspects of the sport.
Having read what has been posted here, I would have suggested that the
author go to Greg and have Greg do some additions and clarifications
to it to ensure that the proposed article is technically correct and
get some interesting photos and illustrations to show some of the
points described.
Having done this, I am confident that Chuck and the EAG would find
this article suitable for publishing is Soaring magazine.
UH

While lurking on this elist for some years, we've been able to pick up
a few leads on items for publication in RC Soaring Digest http://
www.rcsoaringdigest.com. RCSD is a monthly ezine devoted to all
aspects of RC soaring. RCSD is distributed as a PDF at no charge and
is read by thousands of modellers around the world.

A large number of readers are involved in building and flying scale
models, whether on the slope, winch-launched over flat land, or
aerotowed. RCSD publishes walk-arounds of full size gilders for the
purpose of documentation for these modelers. Both the SparrowHawk and
the DuckHawk are attractive planforms for modeling, and this article
describes design and manufacturing processes nearly identical to that
used by the radio controlled model sailplane industry and by a growing
number of individuals.

We would very much like to publish this article in a future issue of
RCSD, augmented with illustrations and data from the Windward
Performance Ltd. web site.

The deadline for the April issue is March 15. Our contact information
can be found on the RCSD home page.