50+:1 15m sailplanes

I don't see it on their web page..

BT

"Paul T" wrote in message
...
Here's the figures on the American DuckHawk (got to
be one of the most awful names for a sailplane) from
the promo sheet.

Windward Performance LLC takes its advanced technology
to the racing class.


Specifications
Empty Weight 300 LBS
Gross Weight 900 LBS
Wing Span 49.17 FT
Wing Area 74.93 FT^2
Aspect Ratio 32.2:1
Length 20.6 FT
Horizontal Span 6.8 FT
Vertical Height 4.5 FT

Structural Limits
+11.0 / -9.0 g's
Va, Vb = 165 KTS
Vne = 200 KTS

Performance
At 500 LBS, 6.7 Lbs/FT^2
Best Glide 50:1 at 50 KTS
Min Sink 94 FPM at 40 KTS
Stall Speed 35 KTS

At 900 LBS, 12.0 Lbs/FT^2
Best Glide 52:1 at 67 KTS
Min Sink 122 FPM at 57 KTS
Stall Speed 47 KTS
(data for 900 LBS, 12 PSF)

Airfoils
Inboard 12.7 % t/c
Outboard 10.2 % t/c


The DuckHawk has the broadest wing loading range available,
the highest maneuvering and redline speeds, and the
lowest inertias for snappy handling. The lower flying
mass within the 15m span constraint gives an induced
drag advantage of 49% at 500 LBS and 33% at 900 LBS
(span loading squared) compared to the competition


Time will tell - my money is on the Diana 2 which is
a development of the SZD-56-1 Diana. (Whose cockpit
is bigger than a Ventus a!). Incedently at Leszno they
were also talking about an 18m version and 22m Open
class version.

I hope that they will give the wing a bit more AOA related to the
cockpit/fuselage.
The Dianas I have seen always had bad visibility in the landing approach and
in
high speed the tail always hang a bit low in the airstream.
One of the factory guys from Poland told me in Borlaenge, that the
performance
could be increased by fixing that problem, but these days they had no money
to do
so.
The design shows some clever features, but I heard German designers having
some
doubts if the glider really would pass all JAR requirements.
CHo



"Paul T" wrote in message
...
Here's the figures on the American DuckHawk (got to
be one of the most awful names for a sailplane) from
the promo sheet.

Windward Performance LLC takes its advanced technology
to the racing class.


Specifications
Empty Weight 300 LBS
Gross Weight 900 LBS
Wing Span 49.17 FT
Wing Area 74.93 FT^2
Aspect Ratio 32.2:1
Length 20.6 FT
Horizontal Span 6.8 FT
Vertical Height 4.5 FT

Structural Limits
+11.0 / -9.0 g's
Va, Vb = 165 KTS
Vne = 200 KTS

Performance
At 500 LBS, 6.7 Lbs/FT^2
Best Glide 50:1 at 50 KTS
Min Sink 94 FPM at 40 KTS
Stall Speed 35 KTS

At 900 LBS, 12.0 Lbs/FT^2
Best Glide 52:1 at 67 KTS
Min Sink 122 FPM at 57 KTS
Stall Speed 47 KTS
(data for 900 LBS, 12 PSF)

Airfoils
Inboard 12.7 % t/c
Outboard 10.2 % t/c


The DuckHawk has the broadest wing loading range available,
the highest maneuvering and redline speeds, and the
lowest inertias for snappy handling. The lower flying
mass within the 15m span constraint gives an induced
drag advantage of 49% at 500 LBS and 33% at 900 LBS
(span loading squared) compared to the competition


Time will tell - my money is on the Diana 2 which is
a development of the SZD-56-1 Diana. (Whose cockpit
is bigger than a Ventus a!). Incedently at Leszno they
were also talking about an 18m version and 22m Open
class version.

I seem to remember a wonderful letter in Sailplane and Gliding in which
the writer noted that, when he first started gliding in his twenties,
average glider LD ratios were around 1:20's. In his thirties, this rose
to 1;30's and, at the time of writing, in his forties, 1:40's. He was
looking forward to his 100th birthday! May be new materials, better
design will prove a substitute for span. The one thing that there will
never be a substitute for is Money. Anyone who disagrees may care to
explain the absence of K8's from the various handicapped comps.

-----Original Message-----
From: Glider Pilot Network ]
Sent: Wednesday, December 24, 2003 10:10 PM
To: Steve Hopkins
Subject: [r.a.s] 50+:1 15m sailplanes


------------------------------------------------------------
Newsgroup: rec.aviation.soaring
Subject: 50+:1 15m sailplanes
Author: Robert Danewid
Date/Time: 22:00 24 December 2003
------------------------------------------------------------
JJ, negative thinking - use the force!

Robert

JJ Sinclair wrote:
"There is a substitute for span, it's called skill, but you can buy
span"


OK, it's 7:00 PM, the sky has been completely overcast for hours, you
have
5000 feet and your looking at a 50 mile final glide. Now SKILL your
way
home.

A very mery Christmas to all my RAS buddies.
JJ Sinclair


------------------------------------------------------------

Does someby know a set of specs for the Diana 2 similar to those =
supplied for the American Duck Eagle ?

Ian Strachan wrote:
Our vaches may not be very vicious but our roads (for retrieving) are

But didn't the ``vaches folles'' (=mad cow) start out in the UK??

SCNR ;-)
-Gerhard

"Ian Strachan" wrote in message
...
In article , Bob Johnson
writes
..........
It refers to the "easiest way to increase performance" (max L/D I
suppose), contrasting the relative simplicity of adding span compared to
the complexities of adding flaps, new airfoil sections, new
configurations, etc.
........

ahhh - I like this remark Ian,
wouldn't it have been very wise if the IGC would have had this insight
before they created the 15m class.
Isn't it true that already then, several manufacturers proposed 18m wingspan
instaed of the PIKs 15m?
Or can you tell us why the racing class really got 15 instead of 18m
wingspan?
Chris

In article u, Swiftel
writes
"Ian Strachan" wrote in message
...
In article , Bob Johnson
writes
.........
It refers to the "easiest way to increase performance" (max L/D I
suppose), contrasting the relative simplicity of adding span compared to
the complexities of adding flaps, new airfoil sections, new
configurations, etc.
.......

ahhh - I like this remark Ian,
wouldn't it have been very wise if the IGC would have had this insight
before they created the 15m class.
Isn't it true that already then, several manufacturers proposed 18m wingspan
instaed of the PIKs 15m?

No, but some of the German manufacturers proposed 16 m, which was so
close to the 15m flapped ships already being built (like the Pik 15)
that IGC decided to stick with 15m.

From memory the date was 1974 or so, when I was the UK delegate to IGC.
It was actually a BGA proposal to IGC that the old standard class rules
(under which the K6 was designed) be left alone, and the new class
should only be span-limited.

It is interesting that when Gerhard Weibal lectured at the BGA weekend
about 5 years ago, he naturally concentrated on huge-span sailplanes. I
therefore asked him in the question period what he considered the most
"cost-effective span". I expected him to say about 20 or 22 metres but
his reply was 17. Pretty close to the 16m I mentioned above, and
fortunately also to 18m which is now a separate IGC class and is
particularly suited to bearing the extra weight of a motor (whereas 15m
is a tad small for a self-launcher in a weak-thermal country).

Or can you tell us why the racing class really got 15 instead of 18m
wingspan?

I have written up my perspective on this for Sailplane and Gliding and
it may be published shortly. But basically as above. 18m was never
discussed by IGC in 1974 although this span was used in older wooden
designs such as the Skylark 3 and 4, etc.

--
Ian Strachan

Bentworth Hall West
Tel: +44 1420 564 195 Bentworth, Alton
Fax: +44 1420 563 140 Hampshire GU34 5LA, ENGLAND

"Ian Strachan" wrote in message
...
In article u, Swiftel

Snip-----

It is interesting that when Gerhard Weibal lectured at the BGA weekend
about 5 years ago, he naturally concentrated on huge-span sailplanes. I
therefore asked him in the question period what he considered the most
"cost-effective span". I expected him to say about 20 or 22 metres but
his reply was 17. Pretty close to the 16m I mentioned above, and
fortunately also to 18m which is now a separate IGC class and is
particularly suited to bearing the extra weight of a motor (whereas 15m
is a tad small for a self-launcher in a weak-thermal country).

Snip-----


Ian Strachan

Bentworth Hall West
Tel: +44 1420 564 195 Bentworth, Alton
Fax: +44 1420 563 140 Hampshire GU34 5LA, ENGLAND


Interesting.

I recall a technical discussion a long time ago asking whether there was a
"natural best wingspan" imposed by the nature of soaring weather. The
question was this: "Ignoring competition classes, is there a single best
wingspan that is suited for the widest range of soaring conditions? The
answers converged around 18 meters. Larger spans were considered too slow
in strong conditions and smaller spans suffered in weak conditions. It's
interesting that the "most cost effective wingspan" is about the same.

This makes me wonder if eventually the 18 meter class will become dominant.
It also makes me wonder if the selection of 15 meters for the two most
popular classes was an error.

Bill Daniels

"Ian Strachan" wrote in message
...
No, but some of the German manufacturers proposed 16 m, which was so
close to the 15m flapped ships already being built (like the Pik 15)
that IGC decided to stick with 15m.

Just a bit of nit-picking, but it was Pik-20. Pik-15 "Hinu" is a towing
plane...

regards,

h

Never mind

It is till a good quote

(I still think it was Moffat back in the 70s)

Robert

Bob Johnson wrote:
Just to keep stuff straight, while Mr. Moffat has certainly expessed
from time to time his fondness for span, I believe "there is no
substitute for span" quote comes from Michael Bird ("Platypus") who used
to "tinsfos" us quite regularly in S & G (Brit mag) from across the pond
...

Of course I could be wrong ..

BJ


Robert Danewid wrote:

There were 2 SZD56 flying in the worlds in Sweden in 1993. They
performed nice but not astonishing. One of them even had a minor midair.

A year later or so we had one (modified) exhibited at the Annual Swedish
Cliding Conference, and as Chris writes, the cockpit were not built for
nice looking guys from the West, but supposedly for thin, starving
pilots from the eastblock...... (now that has thank God changed!)

Moffat once wrote: there is no substitute for span! If you want 50+ go
for an 18m or larger ship, if you want nice handling, easy rigging etc,
it is easy to trade in som finesse-point to achieve that in a 15m glider!

Robert
H304

Chris OCallaghan wrote:

It's been a few years, but if memory serves Gerhard said that the 27
wing could manage a Finesse (best L/D) of 100, that is, if he didn't
have to hang a fuselage off of it. However, most glider pilots like to
fly their aircraft in the first person, so he compromised and got a
Finesse around 46. The Diana, on the other hand, took the road less
travelled by and decided that pilot comfort (or in my case, presence)
were not critical marketing factors. Based on that philosophy, I
wouldn't doubt that a determined engineer could achieve a Finesse of
50+ for a 15 meter glider. However, we've learned that best L/D is a
poor means of judging sailplane performance. It is the flatness of the
drag curves on both sides of the intersection that really determine
the worth of your glider. A polar free of a low speed bucket and
relatively flat increase of sink with speed make a great glider. Might
the poles have found a new trick? A more stable high aspect ratio
airfoil that needs less tail? A better fuselage/wing transition?
Improved laminar control? Perhaps.





Paul T wrote in message ...


'DuckHawk 15m racer announced at 2003 SHA Western Workshop.
53:1glide ratio VNE 200 kts' -from Winward Performance
- anyone got anymore details?

'SZD-56-2, Diana 2: Newest 15-meter Sailplane.The technologically
advanced SZD-56-2 Diana 2 will soar on new wings next
summer. Bogumil Beres, chief design engineer of the
Diana and owner of Biuro Projektowe 'B' Bogumil Beres,
recently announced the design project of a breakthrough
Diana 2, featuring a curved wing platform with a continuously
varying airfoil and high-performance winglets. The
original Diana fuselage will be retained, but with
a lower drag fuselage-wing junction. The wing loading
range will be 6.08 - 11.7 psf. Most remarkably, the
Diana 2 will break the long-standing 15-meter glide
ratio barrier of 50/1 with room to spa forecast
performance includes a max L/D of 52/1. The prototype
Diana 2 wings will fly next August. Diana 2's will
be delivered in the Spring of 2005.'

Have the Germans got something to worry about?