Winch Launch Extreme 5200 ft

Hi Bill,

On Mon, 30 Oct 2006 06:48:05 -0700, "Bill Daniels"
bildan@comcast-dot-net wrote:


In
addition, modern winches are constant tension with computer controlls that
prevents the winch from applying enough force to break the weak link. The
tension is set at about 70% of the weak link strength for the main part of
the climb.

If the glider hits a thermal or gust, the winch senses increasing tension
and cuts power just enough to maintain the selected tension. This pretty
much guarantees a perfect launch every time.

Interesting facts - does such a winch actually exist?
I have to admit that I haven't seen any winch with such a computer
control yet.



Bye
Andreas

Hi Andreas!

I would call the control boards in our winch computer.

Best Regards

Hans



Andreas Maurer schrieb:
Hi Bill,

On Mon, 30 Oct 2006 06:48:05 -0700, "Bill Daniels"
bildan@comcast-dot-net wrote:


In
addition, modern winches are constant tension with computer controlls that
prevents the winch from applying enough force to break the weak link. The
tension is set at about 70% of the weak link strength for the main part of
the climb.

If the glider hits a thermal or gust, the winch senses increasing tension
and cuts power just enough to maintain the selected tension. This pretty
much guarantees a perfect launch every time.

Interesting facts - does such a winch actually exist?
I have to admit that I haven't seen any winch with such a computer
control yet.



Bye
Andreas

Andreas Maurer schreef:

Interesting facts - does such a winch actually exist?
I have to admit that I haven't seen any winch with such a computer
control yet.



Bye
Andreas

They are quite common actually.

The Hydrostart is a Dutch Winch, completely electrically controlled=
http://www.hydrostart.nl/EN/index.htm

In France there are some clubs flying with hydraulically controlled
winches (pressure) This works perfectly and `everyone` can winch
without making corrections for headwind...

http://assoc.orange.fr/acvv/treuil/treuil.htm

"Andreas Maurer" wrote in message
...
Hi Bill,

On Mon, 30 Oct 2006 06:48:05 -0700, "Bill Daniels"
bildan@comcast-dot-net wrote:


In
addition, modern winches are constant tension with computer controlls that
prevents the winch from applying enough force to break the weak link. The
tension is set at about 70% of the weak link strength for the main part of
the climb.

If the glider hits a thermal or gust, the winch senses increasing tension
and cuts power just enough to maintain the selected tension. This pretty
much guarantees a perfect launch every time.

Interesting facts - does such a winch actually exist?
I have to admit that I haven't seen any winch with such a computer
control yet.



Bye
Andreas

Yes, they do exist.

The Dutch Hydrostart diesel winch and the German ESW-2B electric winch do
exactly this.

Bill Daniels

"Andreas Maurer" wrote in message
...
Hi Bill,

On Mon, 30 Oct 2006 06:48:05 -0700, "Bill Daniels"
bildan@comcast-dot-net wrote:
addition, modern winches are constant tension with computer controlls that
prevents the winch from applying enough force to break the weak link.

Interesting facts - does such a winch actually exist?
I have to admit that I haven't seen any winch with such a computer
control yet.
Bye Andreas


In our Club in Herning Denmark we have a 25 year old Diesel Electrical
winch, controled by an industrial controller.

http://www.herningsvaeveflyveklub.dk/jordmateriel.shtml



Prior to launch the maximum wire tension is preset according to aircraft
type, and the rest of the launch is basically automatic.

The Pilots controls the airspeed via. pitch.



I would assume the winch has accumulated something like 100000 starts.



Niels Erik Danielsen

Eric Greenwell wrote:
Bill Daniels wrote:

Good show!

Dyneema/Spectra winch cable allows for launches to approximately 50%
of the original cable length. Calculations show that there is really
no upper limit to the amount of Dyneema that can be used.

90 seconds to 5200 feet AGL on a winch beats the hell out of 20
minutes on aero tow. That's especially true when the typical cost is
$10 for the launch.


That sounds a bit frightening - 3500 fpm! What are the stresses on the
glider to get that kind of climb rate? How far away is disaster if the
pilot twitches a bit on the controls or hits some wind shear or a thermal?

Hi Eric

I would expect that the aircraft were flown within their maximum winch speeds,
which limits the lifting load on the wings to ~2G (this is with a high bending
moment at the root because there is no relief on the wing)

The limiting structural element on most airframes on winch launch is the
elevator down load.

The 3500fpm comes from flying with a very steep angle to the ground - the
aircraft maintains a 12 to 14 degree AOA, but as vertical speed builds it
rotates relative to the ground to maintain the AOA. Do the trigonometry. The
aircraft is never at extreme speed, G load or angle of attack. It is a common
misconception that normal winch launches involve dangerous loads on the
airframe. When the airspeed exceeds the design speed, it is probable that the
loads on some part of the airframe can exceed design limits. This is
particularly true on the "top" of the launch.

The wind shear part is a possible cause for concern, which is why one uses the
specified weak link.

For what it is worth my personal best is 2300" off a 2km wire solo in a low wing
loading twin seater (Bergfalke III) into a 25 - 30 km/h wind. The winch driver
was almost at idle for the top part of the launch. The key to a high launch in
these conditions is a winch driver who knows to keep the power down once the
glider has rotated. (of course a tension controlled winch does this automatically)

A long field like this has no part of the launch where a cable / weak link break
would make it unsafe to land ahead, or execute some form of circuit. It is
generally the "no good options" window on short runways that is cause for
concern on a winch launch.

Never heard of this one...

"Bruce Greef" wrote in message news:ei7o8q$po7
The limiting structural element on most airframes on winch launch is the
elevator down load.

Amazing. If I remember correclty, my old soaring club in Michigan,
Sandhill Soaring, had a pretty impressive winch flight a few years
back. One day during winter, they launched in a pretty strong wind.
Normally they get to about 1500ft max, but at the apex of this
particular flight they simply put the winch in neutral and let the
cable play out. The glider kited to about 3000ft(?) or so. Pretty sure
it was an unofficial record for the equipment they had.

Michael Davis



Walter Kronester wrote:
Hi,
ever heared of winch launches up to 5200 ft (1590m)?
in the forum of www.segelflug.de I read the following. It might be of
interest for you
(short form translation):
During a glider acrobatic meeting in Fuerstenfeldbruck (Germany/Bavaria),
pilots from
Bavaria and Austria had the possibility to try a new launch method. Mostly
double
seaters were launched up to 5200 ft. (1590m). Acro pilots were enthusiastic
after 29
launches, because they could fly their full program out of the winch after
an only
90 seconds lasting start.
This was made possible by the winch manufacturer Tost (Assling, Germany).
They supplied a specially modified winch. Karl Hoeck from Friedberg/Germany
did the technical calculations and the design of the drum of the winch.
This drum had to withstand a pressure of 3 million lb (1400 metric tons)
from the 9842 ft
(3000m) of Dyneema rope with 0.18 inches diameter (4.5mm).
Organizing clubs were Bundeswehr Sportflieger Gemeinschaft Fürstenfeldbruck
e.V.
and Akademische Fluggruppe München. Munich control was involved.

With headwinds between aprox. 6 and 11 knots (10 - 20 km/h) following
altitudes have been reached:
ASK 21 and ASK 13 double seated: 5216 ft (1590m)
FOX double seated: 4594 ft (1400m)
Mue 28 single seated: 3937 ft (1200m)

regards
Walter

That's why they have weak links.

3,500 fpm is just the vertical component of a 45 degree
climb angle at about 50 knots.


At 06:12 30 October 2006, Eric Greenwell wrote:
Bill Daniels wrote:
Good show!

Dyneema/Spectra winch cable allows for launches to
approximately 50% of the
original cable length. Calculations show that there
is really no upper
limit to the amount of Dyneema that can be used.

90 seconds to 5200 feet AGL on a winch beats the hell
out of 20 minutes on
aero tow. That's especially true when the typical
cost is $10 for the
launch.

That sounds a bit frightening - 3500 fpm! What are
the stresses on the
glider to get that kind of climb rate? How far away
is disaster if the
pilot twitches a bit on the controls or hits some wind
shear or a thermal?

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

'Transponders in Sailplanes' on the Soaring Safety
Foundation website
www.soaringsafety.org/prevention/articles.html

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

I suspect that is not quite true, as the glider's wings
in the 5000ft winch launch have to lift a longer and
therefore heavier length of cable into the air. However
the weak link remains the same and still protects the
glider. What allowed these very high launches to be
achieved was the combination of a very long (3000 metre)
winch run and the advent of modern lightweight synthetic
UHMWPE cable.

Derek Copeland


At 02:42 01 December 2006, News wrote:
Eric,

the forces are all the same.

there is no difference in forces strengths launching
to 1000ft or to 5000ft
the applying forces just last longer thats all.

I did hundreds of take offs on the winch.
I wish we would have good winches in Australia.
Here we only have historical rubbish standing around.

Chris



'Eric Greenwell' wrote in message
news:GBu1h.4529$WB4.3254@trndny04...
Gerhard Wesp wrote:
That sounds a bit frightening - 3500 fpm! What are
the stresses on the
glider to get that kind of climb rate? How far away
is disaster if the
pilot twitches a bit on the controls or hits some
wind shear or a
thermal?

Hmmm, if they are using weak links, I don't see a
problem.

Stress (=force) is related to acceleration, not to
speed. You can go
straight up at 1000000 fpm with the same force as
at 10 fpm. Just takes
you a bit longer to reach the speed.

Of course, the net force on the glider is zero, otherwise
it would
accelerate, but the individual forces are much greater
and vary during
the launch. We've all seen the wings curve up and
stay that way as the
pilot rotates into the climb on a winch launch, indicating
much more
lift is being generated to counteract the pull of
the cable.

Surely the cable tension must be greater to provide
a 3500 fpm launch
instead of a 1000 fpm launch? I'm curious about the
amount of tension
needed to provide a 1000 pound glider that 3500 fpm
climb.

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

'Transponders in Sailplanes' on the Soaring Safety
Foundation website
www.soaringsafety.org/prevention/articles.html

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