Duck Hawk Kudos

On Feb 28, 12:27*pm, Bob Whelan wrote:
Am I the only one who remembers from the
Albuquerque convention Greg Cole's intention (then, anyway) to stress
the Duck Hawk for 'useful' dynamic soaring speeds and maneuvers (and
concomitant stresses)...as in enabling it to be capable of dynamically
soaring (say) the fringes of the jet stream?

I agree with the sentiment of the post. The effort deserves a lot of
credit.

That said, my personal feeling is that the most pilots will take
notice if the ship is able to achieve 5-10+ kts faster cruise speeds
at moderate-to-high McCready setting versus current designs. That's
what moves the market for a new high-performance glider. Performance
that you can only take advantage of in Class A airspace is
interesting, but not many of us want to go to the trouble to fly our
gliders regularly under IFR rules - not to mention the other
challenges of high-altitude flight.

I hope they beef the structure up a bit. I was a bit disturbed that
the canopy on the Sparrow Hawk had the apparent stiffness of a 1-liter
soda bottle. Maybe it's a false sense of security but I'd feel better
under the illusion that I can't push my fist through the side of my
glider. I'd like for the structure to be able to absorb a decent
amount of energy in a pinch.

9B

wrote:

That said, my personal feeling is that the most pilots will take
notice if the ship is able to achieve 5-10+ kts faster cruise speeds
at moderate-to-high McCready setting versus current designs. That's
what moves the market for a new high-performance glider. Performance
that you can only take advantage of in Class A airspace is
interesting, but not many of us want to go to the trouble to fly our
gliders regularly under IFR rules - not to mention the other
challenges of high-altitude flight.

I assume you are talking about wave flying in Class A airspace. Class A
is not necessary to take advantage of a high Vne. Class A's advantage
is altitude, making it easier to traverse gaps in the wave. High speed
flight comes from strong lift, which can be very strong at 18,000'.

I hope they beef the structure up a bit. I was a bit disturbed that
the canopy on the Sparrow Hawk had the apparent stiffness of a 1-liter
soda bottle.

The material is a polycarbonate (like Lexan), quite tough, lighter, and
relatively easy to form compared to the thicker acrylic used on larger,
heavier, and faster gliders. It's a good choice for the SparrowHawk.

Maybe it's a false sense of security but I'd feel better
under the illusion that I can't push my fist through the side of my
glider. I'd like for the structure to be able to absorb a decent
amount of energy in a pinch.

I doubt that any glider depends on the strength of the canopy plastic to
absorb energy in a pinch! Energy absorption comes from the design and
materials of the cockpit. I'm sure the canopy material will have to be
more substantial due to the DuckHawk's 200 knot Vne than the material
used on the 120 kt Vne SparrowHawk.

--
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 Mar 1, 9:10*pm, Eric Greenwell wrote:
Eric - see answers to your questions below:

I assume you are talking about wave flying in Class A airspace. Class A
* is not necessary to take advantage of a high Vne. Class A's advantage
is altitude, making it easier to traverse gaps in the wave. High speed
flight comes from strong lift, which can be very strong at 18,000'.

I was referring to the reference in the original post that stated the
DuckHawk was designed to take advantage of dynamic soaring at the
boundary of the Jetstream. Last I checked the Jetstream is typically
found in Class A. I have no idea how you'd get to the boundary of the
Jetstream on a typical summer soaring day via thermal. In the winter
you might use wave. I'm not sure why you'd cruise at 200 kts under
thermal soaring conditions, even when the lift is averaging 10+ knots,
which is quite rare. That kind of speed could be useful for XC in
wave, but that is a niche market based on my observations. I'm not
sure I'd optimize a design for that scenario if I wanted volume
production unless it didn't come at the expense of performance under
more mainstream soaring conditions.

The material is a polycarbonate (like Lexan), quite tough, lighter, and
relatively easy to form compared to the thicker acrylic used on larger,
heavier, and faster gliders. It's a good choice for the SparrowHawk.

I was referring to what they might use on the DuckHawk in contrast to
the SparrowHawk. 200 knots is pretty fast to have a coke bottle for a
canopy - at least for me.


I doubt that any glider depends on the strength of the canopy plastic to
absorb energy in a pinch!

I was talking about the fuselage which is quite thin - though I can
understand how you might have gotten confused because of the reference
to the canopy just before.

9B

This will be just the ticket for pilots flying for records in the
Andes. If it goes anything like the specs, it could set a new
world record for distance. Isn't the current record held by a
Nimbus set up by the factory for higher Vne than standard? 14
hrs @ 180 knots is a LOT of kilometers. Klaus Olman should be
first in line for one.

At 11:40 02 March 2009, wrote:
On Mar 1, 9:10=A0pm, Eric Greenwell wrote:
Eric - see answers to your questions below:

I assume you are talking about wave flying in Class A
airspace. Class A
=A0 is not necessary to take advantage of a high Vne. Class
A's
advantage
is altitude, making it easier to traverse gaps in the wave.
High speed
flight comes from strong lift, which can be very strong at
18,000'.

wrote:
I'm not sure why you'd cruise at 200 kts under
thermal soaring conditions, even when the lift is averaging 10+ knots,
which is quite rare. That kind of speed could be useful for XC in
wave, but that is a niche market based on my observations. I'm not
sure I'd optimize a design for that scenario if I wanted volume
production unless it didn't come at the expense of performance under
more mainstream soaring conditions.

The DuckHawk is not optimized for a 200 knot cruise - that's the Vne
number. Optimum cruise speeds would be a lot lower than that, but
significantly higher than current production racing class gliders, and
at a lower wing loading, so it can still have a good climb in thermals.

The material is a polycarbonate (like Lexan), quite tough, lighter, and
relatively easy to form compared to the thicker acrylic used on larger,
heavier, and faster gliders. It's a good choice for the SparrowHawk.

I was referring to what they might use on the DuckHawk in contrast to
the SparrowHawk. 200 knots is pretty fast to have a coke bottle for a
canopy - at least for me.

It sure is, and I'm sure Greg is aware that what works for a 120 knot
Vne may not be the best choice for a 200 knot Vne, and will choose
something appropriate. Still, I think you might not appreciate how tough
that canopy is, so try snapping a piece of Lexan )polycarbonate) and a
piece of Plexiglas (acrylic), and you will see why Lexan is used for
safety glasses.

I doubt that any glider depends on the strength of the canopy plastic to
absorb energy in a pinch!

I was talking about the fuselage which is quite thin - though I can
understand how you might have gotten confused because of the reference
to the canopy just before.

It's important to know he is *NOT* using a SparrowHawk fuselage for the
DuckHawk! He is using the same molds so the outside shape will be the
same, but the inside will be very, very different.

--
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 Mar 2, 8:24*am, Eric Greenwell wrote:

The DuckHawk is not optimized for a 200 knot cruise - that's the Vne
number. Optimum cruise speeds would be a lot lower than that, but
significantly higher than current production racing class gliders.

Yes, that's what I said. The point I was making is that 200 knots of
Vne wouldn't be all that useful except in unusual circumstances (wave,
jetstream dynamic soaring - if you could ever get there, maybe the
occasional run under a CuNim - if you had the guts). I also was
responding to your earlier comment that seemed to imply the opposite:
"Class A is not necessary to take advantage of a high Vne. High speed
flight comes from strong lift, which can be very strong at 18,000'." I
just don't think the racing performance of the ship will have very
much at all to do with Vne. It's how it does at 100 kts that will
matter to performance - assuming it climbs okay. I think we're agreed
on that.

I think you might not appreciate how tough
that canopy is, so try snapping a piece of Lexan )polycarbonate) and a
piece of Plexiglas (acrylic), and you will see why Lexan is used for
safety glasses.

Point taken - I remember trying to stop a SparrowHak canopy that was
blown open by the wind and having it deform a couple of inches. That
was a surprise. I'm sure a bigger, tougher, faster, heavier glider
will have a canopy to match. You wouldn't want to have it bow in on
you to much, even if it doesn't crack.

It's important to know he is *NOT* using a SparrowHawk fuselage for the
DuckHawk! He is using the same molds so the outside shape will be the
same, but the inside will be very, very different.

That was the hope many here had expressed. It certainly makes sense to
do it the way you describe - saves on tooling.

9B

Here is a nice bio for Greg Cole. Jody Culbert AC-4a

http://www.perlanproject.com/bio_cole.php