Duck Hawk Kudos

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