Winch Launch Extreme 5200 ft

[Walter Kronester]

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

[[email protected]]

How long was the runway?

[Wojciech Scigala]

Użytkownik napisał:

> How long was the runway?
The rope was 3000m long, so I suppose they used about 3000m runway.

--
WojtuÅ›.net

[Walter Kronester]

Fuerstenfeldbruck is a discontinued NATO airbase. They have plenty of space
there.
The runway length was 2744m, but I think they used also the safety strips
close to 3000m.
regards Walter

[Bill Daniels]

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.

Karl Hoeck, the drum designer (and really nice guy), usually has a booth at
the SSA convention showing off brochures of his winch design based on a Ford
diesel pickup.

Bill Daniels


"Walter Kronester" > wrote in message
...
> 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
>

[Duster]

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

[aviationnut]

This is good news, but I have to wonder how they, or we in the US would
protect the cable from other aircraft that might stray into it at those
altitudes. Next question is how far the cable would drift on the way
down, assuming that the wind is not always right down the runway.

Mark

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.
>
>

[Eric Greenwell]

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

[Chris Rollings]

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
>

[Bert Willing]

That's a normal climb rate for winch launching. I know of no break-up on
winch launch during the last 26 years, and there are thousands of winch
launches done every weekend in Europe.

"Eric Greenwell" > wrote in message
news:AFg1h.4183$WB4.3314@trndny04...
>> 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

[Gerhard Wesp[_8_]]

> 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.

-Gerhard
--
Gerhard Wesp / Holderenweg 2 / CH-8134 Adliswil
+41 (0)76 505 1149 (mobile) / +41 (0)44 668 1878 (office)
+41 (0)44 668 1818 (fax)
http://gwesp.tx0.org/

[Martin Gregorie[_1_]]

aviationnut wrote:
> This is good news, but I have to wonder how they, or we in the US would
> protect the cable from other aircraft that might stray into it at those
> altitudes.
>
Presumably the same way we do: have your field marked as a gliding field
on the sectionals with a warning about cables to x000 feet.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Bill Daniels]

You have to clear the area of air traffic before launch. Sinch the launch
is over so quickly, that isn't too hard. The typical light plane will
travel about three miles in 90 seconds so clearing out to that distance plus
a safety margin avoids conflict. If you operate in an area with faster
traffic, you probably had a tower to coordinate with.

Bill Daniels

"aviationnut" > wrote in message
oups.com...
> This is good news, but I have to wonder how they, or we in the US would
> protect the cable from other aircraft that might stray into it at those
> altitudes. Next question is how far the cable would drift on the way
> down, assuming that the wind is not always right down the runway.
>
> Mark
>
> 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.
>>
>>
>

[Bill Daniels]

"Eric Greenwell" > wrote in message
news:AFg1h.4183$WB4.3314@trndny04...
> 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

There is a lot about modern winches and operating proceedures that will seem
counter-intuitive to US pilots trained in aero tow.so it's easy to
mis-interpret the danger signs. You can be assured that the Europeans are
at least as concerned about safety as we are and that they have carefully
worked out how to do this safely.

The glider manufacturer has carefully specified a weak link accurate to plus
or minus 5% that is the ultimate protection for the glider airframe. 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.

For the pilot it's just like a takeoff in a powerful airplane. Just pitch
up for desired climb airspeed. If the airspeed is high, just raise the nose
a bit more and the airspeed will decrease. If it's a bit low, lower the
nose a bit and the airspeed will increase.

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.

Make no mistake, this is a LOT of fun.

Bill Daniels

[Andy[_1_]]

Bill Daniels wrote:
"For the pilot it's just like a takeoff in a powerful airplane. Just
pitch
up for desired climb airspeed. If the airspeed is high, just raise the
nose
a bit more and the airspeed will decrease. If it's a bit low, lower
the
nose a bit and the airspeed will increase. "


With a traditional winch of adequate power, pitching up increases
airspeed. How do these modern winches result in the reverse effect?
Does the reversal only happen once the line tension limit has been
reached?

Andy

[Bill Daniels]

"Andy" > wrote in message
oups.com...
>
> Bill Daniels wrote:
> "For the pilot it's just like a takeoff in a powerful airplane. Just
> pitch
> up for desired climb airspeed. If the airspeed is high, just raise the
> nose
> a bit more and the airspeed will decrease. If it's a bit low, lower
> the
> nose a bit and the airspeed will increase. "
>
>
> With a traditional winch of adequate power, pitching up increases
> airspeed. How do these modern winches result in the reverse effect?
> Does the reversal only happen once the line tension limit has been
> reached?
>
> Andy
>

A "traditional winch" doesn't control tension but tries (and often fails) to
control cable speed which doesn't relate in any logical way to glider
airspeed anyway. If the tension is controlled instead, the speed will
decrease as the pilot pitches up since this adds load to the cable which the
winch senses and slightly reduces power. This happens almost instantly so
the pilot sees the airspeed behave logically as it would in a powerful
airplane. This puts airspeed control completely in the hands of the pilot
where it belongs.

Think of it like a jet with fixed thrust. Nose up increases load on the
engine so the aircraft slows - nose down decreases load so the aircraft
accelerates.

Bill Daniels

[Andreas Maurer]

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

[william]

How do they recover the line? I've used a winch with r/c gliders and if the
wind is not down the runway it can be a problem. Do they have a parachute on
the line and wind it back on the drum as it floats down? How about tangles,
does the line ever get tangled up? R/C gliders can do a zoom off the line
and gain a lot of altitude. Just before release, with the line very tight
they dive for speed, release, and climb almost straight up for a great
altitude gain. That would be a wild ride in a full size glider if the wings
stayed on.
Bill


"Bill Daniels" <bildan@comcast-dot-net> wrote in message
. ..
>
> "Andy" > wrote in message
> oups.com...
>>
>> Bill Daniels wrote:
>> "For the pilot it's just like a takeoff in a powerful airplane. Just
>> pitch
>> up for desired climb airspeed. If the airspeed is high, just raise the
>> nose
>> a bit more and the airspeed will decrease. If it's a bit low, lower
>> the
>> nose a bit and the airspeed will increase. "
>>
>>
>> With a traditional winch of adequate power, pitching up increases
>> airspeed. How do these modern winches result in the reverse effect?
>> Does the reversal only happen once the line tension limit has been
>> reached?
>>
>> Andy
>>
>
> A "traditional winch" doesn't control tension but tries (and often fails)
> to control cable speed which doesn't relate in any logical way to glider
> airspeed anyway. If the tension is controlled instead, the speed will
> decrease as the pilot pitches up since this adds load to the cable which
> the winch senses and slightly reduces power. This happens almost
> instantly so the pilot sees the airspeed behave logically as it would in a
> powerful airplane. This puts airspeed control completely in the hands of
> the pilot where it belongs.
>
> Think of it like a jet with fixed thrust. Nose up increases load on the
> engine so the aircraft slows - nose down decreases load so the aircraft
> accelerates.
>
> Bill Daniels
>

[Marc Ramsey]

Bill Daniels wrote:
> A "traditional winch" doesn't control tension but tries (and often fails) to
> control cable speed which doesn't relate in any logical way to glider
> airspeed anyway. If the tension is controlled instead, the speed will
> decrease as the pilot pitches up since this adds load to the cable which the
> winch senses and slightly reduces power. This happens almost instantly so
> the pilot sees the airspeed behave logically as it would in a powerful
> airplane. This puts airspeed control completely in the hands of the pilot
> where it belongs.

This is best considered as *theory* as very few, if any, true tension
controlled winches exist in the real world. The electric EW-2B and
hydraulic Hydrostart could theoretically operate in this fashion, but
I'd love to hear from anyone who knows how they are actually operated in
practice...

Marc

[Martin Gregorie[_1_]]

william wrote:
> How do they recover the line? I've used a winch with r/c gliders and if the
> wind is not down the runway it can be a problem. Do they have a parachute on
> the line and wind it back on the drum as it floats down?
>
Yes, except you normally run the winch faster to pull the cable down,
which minimizes drift. Once the chute is clearly about to land on the
airfield you back off and land it 30-40 m away, completing the retrieval
by pulling the remaining cable in slowly along the ground.

> How about tangles, does the line ever get tangled up?
>
Usually only if the glider releases with a LOT of tension or if there's
a cable break.

> R/C gliders can do a zoom off the line
> and gain a lot of altitude. Just before release, with the line very tight
> they dive for speed, release, and climb almost straight up for a great
> altitude gain. That would be a wild ride in a full size glider if the wings
> stayed on.
>
Its done - just not so viciously and the height gain isn't nearly as
great. Don't forget an RC glider is very strong and you're usually using
a stretchable line which can store a lot of energy if you pull all the
way up.

For a full size example, consider a Pegase, ASW-19 or ASW-20, which all
have a Vwinch of 65 kts. If there's a wind and you arrive at the top at
just under 65, you can push to reduce tension, release, and then pull up
to get another 200 feet.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[hans]

Hi Marc!

with the EW-2B it is really as easy as advertised. For the first 2/3 of
the launch you just apply the optimal constant force, in the last 1/3
you reduce the force gradually until the gilder releases. Just did 12
tows Saturday.

Hans


Marc Ramsey schrieb:
> Bill Daniels wrote:
>> A "traditional winch" doesn't control tension but tries (and often
>> fails) to control cable speed which doesn't relate in any logical way
>> to glider airspeed anyway. If the tension is controlled instead, the
>> speed will decrease as the pilot pitches up since this adds load to
>> the cable which the winch senses and slightly reduces power. This
>> happens almost instantly so the pilot sees the airspeed behave
>> logically as it would in a powerful airplane. This puts airspeed
>> control completely in the hands of the pilot where it belongs.
>
> This is best considered as *theory* as very few, if any, true tension
> controlled winches exist in the real world. The electric EW-2B and
> hydraulic Hydrostart could theoretically operate in this fashion, but
> I'd love to hear from anyone who knows how they are actually operated in
> practice...
>
> Marc

[hans]

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

[Marc Ramsey]

hans wrote:
> with the EW-2B it is really as easy as advertised. For the first 2/3 of
> the launch you just apply the optimal constant force, in the last 1/3
> you reduce the force gradually until the gilder releases. Just did 12
> tows Saturday.

By "optimal constant force", do you mean that you fly the first 2/3 of
the launch as Bill describes (pulling if the airspeed goes over target,
pushing if you get too slow), at a constant climb angle, or some other
technique?

Marc

[J. Nieuwenhuize]

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

[hans]

If its getting faster, pull more, if its getting slower release the sick
a little bit forward. When you round out in the last third, you don't
pull to get slower.


Marc Ramsey schrieb:
> hans wrote:
>> with the EW-2B it is really as easy as advertised. For the first 2/3
>> of the launch you just apply the optimal constant force, in the last
>> 1/3 you reduce the force gradually until the gilder releases. Just did
>> 12 tows Saturday.
>
> By "optimal constant force", do you mean that you fly the first 2/3 of
> the launch as Bill describes (pulling if the airspeed goes over target,
> pushing if you get too slow), at a constant climb angle, or some other
> technique?
>
> Marc

[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:
>
>
>> 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

[Eric Greenwell]

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

[Bill Daniels]

Eric, perhaps you know George Moore who lives in your area. He has written
an series of papers on the forces involved in winch launch. He would be
able to provide the exact answers.

Bill Daniels

"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

[Eric Greenwell]

Bill Daniels wrote:
> Eric, perhaps you know George Moore who lives in your area. He has written
> an series of papers on the forces involved in winch launch. He would be
> able to provide the exact answers.

I don't know him, though I think I've heard the name. I was hoping
someone had just read the tension meter on winch during one those 5000'
launches and could tell us what it said.

--
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

[Marc Ramsey]

Eric Greenwell wrote:
> Bill Daniels wrote:
>> Eric, perhaps you know George Moore who lives in your area. He has
>> written an series of papers on the forces involved in winch launch.
>> He would be able to provide the exact answers.
>
> I don't know him, though I think I've heard the name. I was hoping
> someone had just read the tension meter on winch during one those 5000'
> launches and could tell us what it said.

It's unlikely that the winch had a tension meter. In any case, the
tension can't exceed the strength of the weak link, the weak link
specified for an ASK-21, for instance, permits a max load factor
equivalent to 2.5G.

Marc

[Niels Erik Danielsen]

"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

[Marc Ramsey]

Niels Erik Danielsen wrote:
> 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.

It looks to be quite an interesting design. Does the generator drive AC
traction motors directly through the controller, or are there batteries
or some other form of buffer in the system?

There are clearly tension controlled winches in use at a number of
sites, but so far all seem to be have electric or hydraulic drive. Does
anyone know of a true tension controlled winch using an internal
combustion engine engine driving the drums through a conventional
automatic transmission or torque converter?

Marc

[Graeme Cant]

Andy wrote:

> With a traditional winch of adequate power,

There's an oxymoron. Traditional winches (new and old) pretty much
define themselves by their inadequate power.

> pitching up increases
> airspeed. How do these modern winches result in the reverse effect?
> Does the reversal only happen once the line tension limit has been
> reached?

I must have only flown off traditional winches. My experience is the
same as Bill Daniels. What over-powered monster do you fly off?

GC

> Andy
>

[MaD]

Marc Ramsey schrieb:

> Niels Erik Danielsen wrote:
> > 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.
>
> It looks to be quite an interesting design. Does the generator drive AC
> traction motors directly through the controller, or are there batteries
> or some other form of buffer in the system?
>
> There are clearly tension controlled winches in use at a number of
> sites, but so far all seem to be have electric or hydraulic drive. Does
> anyone know of a true tension controlled winch using an internal
> combustion engine engine driving the drums through a conventional
> automatic transmission or torque converter?
>
> Marc

Ours is tension controlled. The glider type information and tension
reading is processed by the winch driver who then applies the correct
power settings. Basically shouldn't be a major problem to replace the
human with a computer.

http://www.cumulus-segelflug.ch/index.php?id=14

Regards
Marcel Duenner

[Gerhard Wesp]

Eric Greenwell > wrote:
> 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

No, I don't think so. And I think the climb rate is not related to the
cable length, IOW, you get the same 3500 fpm with, say, a 3000ft cable.

-Gerhard
--
Gerhard Wesp / Holderenweg 2 / CH-8134 Adliswil
+41 (0)76 505 1149 (mobile) / +41 (0)44 668 1878 (office)
+41 (0)44 668 1818 (fax)
http://gwesp.tx0.org/

[Andreas Maurer[_1_]]

Hi Eric,

On Mon, 30 Oct 2006 22:00:06 GMT, Eric Greenwell
> wrote:


>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.

The strongest available weak link is about 2.000 lbs which is
obviously the maximum possible tension on the cable.
A single seater's maximum allowed weak link is usually in the 1.200
lbs range.

BTW: The standard climb rate in a winch launch is usually about 3.000
ft/min, independent of glider type.



Bye
Andreas

[Andy[_1_]]

Graeme Cant wrote:

> I must have only flown off traditional winches. My experience is the
> same as Bill Daniels. What over-powered monster do you fly off?

I have flown off winches at 5 UK sites and 5 US sites (9 different
winches). I don't think any of them were over-powered monsters but
most had enough power to see this effect.

Please refer to "Gliding" by Derek Piggott, which was the standard UK
text when I started flying gliders. Page 80 of fourth edition -
"Unless the winch is seriously underpowered, steepening the climb will
result in an increase in launching speed".

Andy

[Bruce Greef]

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.

[Bert Willing]

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.
>

[Niels Erik Danielsen]

"Marc Ramsey" > wrote in message
...
> Niels Erik Danielsen wrote:
>> 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.
>
> It looks to be quite an interesting design. Does the generator drive AC
> traction motors directly through the controller, or are there batteries or
> some other form of buffer in the system?

There is no buffer, all power is generated by the generator when needed.

The frame consist of a late 60' SCANIA VARBIS tractor trailer,
combined with two traction motors (used as winch motors)and generator from a
diesel DC
electric locomotive.

The engine has been replaced with a newer more powerful turbo
charged SCANIA engine. (This engine is used for both road driving, and
winch.)

The generator is mounted as a part of the drive shaft between the
gearbox and the differential.(Rotating when in gear)
The differential had two gears controlled by air pressure, one for
normal road speed and another for reduced speed.
As the pinion for the 'normal road speed' has been removed, it has
become a `neural' allowing the generator to run without driving (moving) the
winch.
When the winch is moved the generator is still rotating, but not magnetized.

The winch drums are mounted directly on the traction motors drive
shafts.

The first 'computer' was analog, and consists of a custom made
circuit board filled with operational amplifiers, and passive
components.

This computer controls:
Parking brake/Differential interlocking
Throttle actuator for engine.
Contactors for drum selection.
Contactor for wire retrieve-braking dump load.
Torque by excitation of the windings in the generator

The systems measures:
Engine RPM
Engine Actuator position
Generator speed.
Wire speed.
Torque derived from DC current, no tensiometer needed.
DC Voltage.
Wind speed.
Wind direction component.
Position of spring loaded torque/speed command handle.
Calculation of power based on Current and Voltage.

In the late 90' the analog controller was replaced with an
industrial micro controller, but the functions as seen from the
operator is essentially unchanged.
Except for the possibility of connecting a PC via. a serial cable,
and record a time track of the launch parameters.

The max speed and max force is set on two dials.
For an ASK21 the force is set at 550daN, and max speed is set to 125
km/h,

Max. force is approx the weight of the glider, and max. speed is a
speed approx. halfway between normal launch speed and max speed
allowed in winch launch for type of glider.
Then one of the drums are selected by pressing the Left or Right
push button, this starts excitation of the generator and set the
engine in high idle (ca. 1200 RPM)

The spring loaded command handle has a manual control range for
taking up the slack and at the end of launch bring down the chute.
When the handle is full forward against it's stop a 'kick-down button'
is activating the automatic sequence.

During the launch the diesel engine RPM is controlled to ensure
enough power (Max RPM used is about 1800 RPM)

The set point for the speed/torque servo is ramped up (Ramp time
approx 2 sec.) to the values given by the dials. (Power peaks at
about 160KW for a heavy two seater)

After acceleration, during the initial climb the speed set point is
automatic ramped down to
approx 70% since the glider now have a speed composant tangential to
the winch.
The decision on when to start speed ramp down is based on time
calculated from the wind composant in launch direction. (My feeling
is rampdown is done 4 to 10 secs into the launch)

Later during the launch the max force (torque) is also ramped down,
this is also based on time.

When the glider is at an angle of approx. 75° the command handle is
eased a little backward and the glider hook back releases.

[Bill Daniels]

Neils, this is really VERY, VERY clever. Actually it's elegant.

We have now heard of 300+ launches a day with one winch and launches to 5200
feet AGL with another.

Lets say your only tug is doing 4 - 5 launches an hour at $75 each and
you're #6 in the aero tow queue. The winch across the field is making a
2500 foot launch every 3 minutes for $10. (You're #6 because you failed to
notice a solo student catch a thermal off a winch launch at 10:30 so
everybody else got in front of you.) The tug will need a fuel stop every 5
or so launches but the winch will run all day on one tank. It's going to be
2PM before you get an aero tow. What do you do?

What's not to like about winches.?

Bill Daniels


"Niels Erik Danielsen" > wrote in message
...
>
> "Marc Ramsey" > wrote in message
> ...
>> Niels Erik Danielsen wrote:
>>> 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.
>>
>> It looks to be quite an interesting design. Does the generator drive AC
>> traction motors directly through the controller, or are there batteries
>> or some other form of buffer in the system?
>
> There is no buffer, all power is generated by the generator when needed.
>
> The frame consist of a late 60' SCANIA VARBIS tractor trailer,
> combined with two traction motors (used as winch motors)and generator from
> a diesel DC
> electric locomotive.
>
> The engine has been replaced with a newer more powerful turbo
> charged SCANIA engine. (This engine is used for both road driving, and
> winch.)
>
> The generator is mounted as a part of the drive shaft between the
> gearbox and the differential.(Rotating when in gear)
> The differential had two gears controlled by air pressure, one for
> normal road speed and another for reduced speed.
> As the pinion for the 'normal road speed' has been removed, it has
> become a `neural' allowing the generator to run without driving (moving)
> the
> winch.
> When the winch is moved the generator is still rotating, but not
> magnetized.
>
> The winch drums are mounted directly on the traction motors drive
> shafts.
>
> The first 'computer' was analog, and consists of a custom made
> circuit board filled with operational amplifiers, and passive
> components.
>
> This computer controls:
> Parking brake/Differential interlocking
> Throttle actuator for engine.
> Contactors for drum selection.
> Contactor for wire retrieve-braking dump load.
> Torque by excitation of the windings in the generator
>
> The systems measures:
> Engine RPM
> Engine Actuator position
> Generator speed.
> Wire speed.
> Torque derived from DC current, no tensiometer needed.
> DC Voltage.
> Wind speed.
> Wind direction component.
> Position of spring loaded torque/speed command handle.
> Calculation of power based on Current and Voltage.
>
> In the late 90' the analog controller was replaced with an
> industrial micro controller, but the functions as seen from the
> operator is essentially unchanged.
> Except for the possibility of connecting a PC via. a serial cable,
> and record a time track of the launch parameters.
>
> The max speed and max force is set on two dials.
> For an ASK21 the force is set at 550daN, and max speed is set to 125
> km/h,
>
> Max. force is approx the weight of the glider, and max. speed is a
> speed approx. halfway between normal launch speed and max speed
> allowed in winch launch for type of glider.
> Then one of the drums are selected by pressing the Left or Right
> push button, this starts excitation of the generator and set the
> engine in high idle (ca. 1200 RPM)
>
> The spring loaded command handle has a manual control range for
> taking up the slack and at the end of launch bring down the chute.
> When the handle is full forward against it's stop a 'kick-down button'
> is activating the automatic sequence.
>
> During the launch the diesel engine RPM is controlled to ensure
> enough power (Max RPM used is about 1800 RPM)
>
> The set point for the speed/torque servo is ramped up (Ramp time
> approx 2 sec.) to the values given by the dials. (Power peaks at
> about 160KW for a heavy two seater)
>
> After acceleration, during the initial climb the speed set point is
> automatic ramped down to
> approx 70% since the glider now have a speed composant tangential to
> the winch.
> The decision on when to start speed ramp down is based on time
> calculated from the wind composant in launch direction. (My feeling
> is rampdown is done 4 to 10 secs into the launch)
>
> Later during the launch the max force (torque) is also ramped down,
> this is also based on time.
>
> When the glider is at an angle of approx. 75° the command handle is
> eased a little backward and the glider hook back releases.
>

[Graeme Cant]

Andy wrote:
> Graeme Cant wrote:
>
>> I must have only flown off traditional winches. My experience is the
>> same as Bill Daniels. What over-powered monster do you fly off?
>
> I have flown off winches at 5 UK sites and 5 US sites (9 different
> winches). I don't think any of them were over-powered monsters but
> most had enough power to see this effect.
>
> Please refer to "Gliding" by Derek Piggott, which was the standard UK
> text when I started flying gliders. Page 80 of fourth edition -
> "Unless the winch is seriously underpowered, steepening the climb will
> result in an increase in launching speed".
>
> Andy

Well, I speak only from my experience, not from a book, no matter how
eminent the author, and ... it's not MY experience. Clearly it's also
not Bill Daniels' and several others. I note what you say about your
experience and I'll learn from it.

As for Derek Piggott's experience, I recommend the 7th Edition where he
has modified his teaching somewhat and simply says (p.106, K&G edition)

"Steepening the climb MAY result in an increase in launch speed..." (my
emphasis).

Earlier on that page, however, he also says

"If the launch is too fast, for example, the glider pilot pulls back
more..." He seems to have revised his views between the 4th and 7th
Editions. That's the problem with citing authorities - they change
their mind without telling you!

My experience of winches (also on two continents - Snap!) tells me that
European winches are generally more serious and powerful than the ones
I'm used to. Nobody on this continent could afford a Skylaunch for
example and nothing like it exists in my area. Not many exist in the US
either judging by the fact that, like us, they appear to find the cost
of a European winch is about the same as a brace of good Pawnees.

Perhaps that explains why I said that "traditional winch" and "adequate
power" didn't go together. I also used the words "overpowered monster"
lightheartedly... :)

GC

[Andy[_1_]]

Graeme Cant wrote:

> Well, I speak only from my experience, not from a book, no matter how
> eminent the author, and ... it's not MY experience. Clearly it's also
> not Bill Daniels' and several others. I note what you say about your
> experience and I'll learn from it.

I suspect that our experience of pitch effect on speed is not really
that different. Neither of us has defined the conditions in sufficient
detail. I think it's true to say that for any winch that is capable of
maintaining constant tow line speed, pitching the glider up will result
in an increase in airspeed. It is also true to say that continuous
pitch up will not result in a continuous increase in airspeed. Either
the winch has insufficient power to maintain line speed, or the tension
limiter reduces line speed, or the glider weak link breaks. So I
believe there is a cross over point for underpowered or tension
controlled winches. For pitch/speed below the cross over point,
increasing pitch results in increasing speed. Above the cross over
point the reverse is true. For a tension and speed controlled winch I
suspect that the cross over point is early in the launch and before the
glider has established normal climb attitude.

Thanks for the update on "Gliding". You are right, he didn't tell me
he'd changed the text ;)


Andy

[alex8735]

I personally don't think that a constant force regulation results in an
ideal winch tows. I have observed a number of tows in which the glider
was initially accelerated to quickly so that the pilot reacted by
maintaining a low climb angle. This low angle results in lower force
measured by the winch and leads to a further increase of power. In a
Ka8 nearing Vne the only possible action is to abort the tow.

At our airfield we use a system which transmits the airspeed of the
glider to the winch operator. Pared with a good winch operator and a
powerful winch, this results in very good winch tows.

[Bill Daniels]

Interesting. What sort of telemetry equipment are you using? I had
proposed this several years ago but the consensus was that it would be too
expensive to equip each glider with a telemetry transmitter. Constant
tension puts all the sensors at the winch and requires no extra equipment in
the glider.

George Moore has written a series of excellent papers on automatic control
of winch launches. George favors the constant tension approach but with
cable speed regulation in the ground roll and rotation phases to prevent
overspeeding the glider. These papers are available for download from the
files section of the Yahoo group "winchdesign".

Bill Daniels


"alex8735" > wrote in message
oups.com...
>I personally don't think that a constant force regulation results in an
> ideal winch tows. I have observed a number of tows in which the glider
> was initially accelerated to quickly so that the pilot reacted by
> maintaining a low climb angle. This low angle results in lower force
> measured by the winch and leads to a further increase of power. In a
> Ka8 nearing Vne the only possible action is to abort the tow.
>
> At our airfield we use a system which transmits the airspeed of the
> glider to the winch operator. Pared with a good winch operator and a
> powerful winch, this results in very good winch tows.
>

[Mike Schumann]

You can't just control for constant force. You also need to limit the
maximum winch speed to address this exact issue.

Mike Schumann

"alex8735" > wrote in message
oups.com...
>I personally don't think that a constant force regulation results in an
> ideal winch tows. I have observed a number of tows in which the glider
> was initially accelerated to quickly so that the pilot reacted by
> maintaining a low climb angle. This low angle results in lower force
> measured by the winch and leads to a further increase of power. In a
> Ka8 nearing Vne the only possible action is to abort the tow.
>
> At our airfield we use a system which transmits the airspeed of the
> glider to the winch operator. Pared with a good winch operator and a
> powerful winch, this results in very good winch tows.
>

[news]

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

[Eric Greenwell]

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 agree with that, but what I asked about was the rate of climb (fpm =
feet per minute):

>> Surely the cable tension must be greater to provide a 3500 fpm launch
>> instead of a 1000 fpm launch?

--
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

[Bill Daniels]

"Eric Greenwell" > wrote in message
news:ei5ch.74$R_1.4@trndny08...
> 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 agree with that, but what I asked about was the rate of climb (fpm =
> feet per minute):
>
>>> Surely the cable tension must be greater to provide a 3500 fpm launch
>>> instead of a 1000 fpm launch?
>
> --
> 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

Not surprising.

A typical launch will have the glider climbing at a 45 degree angle and 60
knots. That works out to a little over 42 knots vertical speed. Of course,
that the peak climb rate. The average on a high launch can be around 35
knots. The stresses are about the same as mild aerobatics.

There are a number of GPS logs on the web that show rates of climb about the
same as these figures.

If you want to work out the stress for yourself, the peak cable tension will
roughly equal the flying weight of the glider. The cable pull vector will
start horizontal and swing down to 70 degrees during the launch. At
approximately 70 degrees, the CG hook will automatically "back-release" the
cable.

Serious fun.

Bill Daniels

[Derek Copeland]

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
>
>
>

[Derek Copeland]

Just to confirm what Bill writes, have a look at the
following link:

http://www.youtube.com/watch?v=-VlRd9-wxQI

You will see that the vario reads a steady 1500 metres/min
up for some time during the winch launch. That is over
4500 ft/min (or 45 knots) for those who can't think
in metric units. There are also some good aerobatics
on the way down in the Fox two-seater.

Derek Copeland

At 02:48 02 December 2006, Bill Daniels wrote:
>
A typical launch will have the glider climbing at
a 45 degree angle and 60
>knots. That works out to a little over 42 knots vertical
>speed. Of course,
>that the peak climb rate. The average on a high launch
>can be around 35
>knots. The stresses are about the same as mild aerobatics.
>
>There are a number of GPS logs on the web that show
>rates of climb about the
>same as these figures.
>
>If you want to work out the stress for yourself, the
>peak cable tension will
>roughly equal the flying weight of the glider. The
>cable pull vector will
>start horizontal and swing down to 70 degrees during
>the launch. At
>approximately 70 degrees, the CG hook will automatically
>'back-release' the
>cable.
>
>Serious fun.
>
>Bill Daniels
>
>
>

[Stefan]

Derek Copeland schrieb:

> http://www.youtube.com/watch?v=-VlRd9-wxQI
>
> You will see that the vario reads a steady 1500 metres/min

Actually, it reads 15 m/s.

[Derek Copeland]

Whoops, quite right Stefan, but then I'm used to instruments
calibrated in knots and feet. In that case the climb
rate will be 900 metres/minute or just under 3000ft/minute
(30 knots).

Most UK varios stop at 10 knots or 1000ft/min, so I
only know that that I'm normally climbing faster than
that for the majority of the winch launch.

At Lasham a 1500 ft winch launch takes about 35 seconds
including the ground run, so 3000 ft/min would be about
right with a sufficiently powerful winch.

Derek Copeland


At 15:06 02 December 2006, Stefan wrote:
>Derek Copeland schrieb:
>
>> http://www.youtube.com/watch?v=-VlRd9-wxQI
>>
>> You will see that the vario reads a steady 1500 metres/min
>
>Actually, it reads 15 m/s.
>

[Stefan]

Derek Copeland schrieb:

> At Lasham a 1500 ft winch launch takes about 35 seconds
> including the ground run, so 3000 ft/min would be about
> right with a sufficiently powerful winch.

The video shows that the climb rate of 15m/s (around 3000ft/min, the
rule of thumb for the conversion is a factor 2 and a couple of zeros at
the right place) is reached only at an altitude of around 300m (=1000ft)
AGL. As the flight in the video was done with a Fox, I guess that the
climb was initiated extra carefully, but still. BTW, the Fox was flown
with a speed of around 145km/h (80 knots).

You'll find more infos here: http://www.segelkunstflug.mediacluster.de/193

[Bill Daniels]

I hear that a winch is being prepared for a release height record attempt in
the US. The drum can hold more than 5Km of 3mm UHMWPE rope. It will be up
to the builders to announce this officially.

It's interesting to speculate about the maximum release height theoretically
possible. The limit is not the weight of the rope since UHMWPE is so light
nor the winch power since really large engines are available. The limiting
factor will be the aerodynamic drag on the rope.

There are always new high strength fibers being introduced which would allow
still thinner rope diameter. Given ATC clearances, it may be possible to
eventually winch a glider into Class A airspace. Very large kites have
reached 35,000 feet.

How about an unballasted open class glider and 10 Km of winch rope operating
from a remote desert dry lake?

Bill D

"Stefan" > wrote in message
. ..
> Derek Copeland schrieb:
>
>> At Lasham a 1500 ft winch launch takes about 35 seconds
>> including the ground run, so 3000 ft/min would be about
>> right with a sufficiently powerful winch.
>
> The video shows that the climb rate of 15m/s (around 3000ft/min, the rule
> of thumb for the conversion is a factor 2 and a couple of zeros at the
> right place) is reached only at an altitude of around 300m (=1000ft) AGL.
> As the flight in the video was done with a Fox, I guess that the climb was
> initiated extra carefully, but still. BTW, the Fox was flown with a speed
> of around 145km/h (80 knots).
>
> You'll find more infos here: http://www.segelkunstflug.mediacluster.de/193

[Chris Reed[_1_]]

Stefan wrote:
> Derek Copeland schrieb:
>
>> http://www.youtube.com/watch?v=-VlRd9-wxQI
>>
>> You will see that the vario reads a steady 1500 metres/min
>
> Actually, it reads 15 m/s.

Which is approx 30 kt or 3,000 ft per minute

[Andy[_1_]]

Bill Daniels wrote:
>
> How about an unballasted open class glider and 10 Km of winch rope operating
> from a remote desert dry lake?

Why waste the rope (or is it string at that diameter) by reeling it in.
Use auto tow. A new type of record for Boneville salt flats?

Andy

[news]

while there are no special forces for the glider
there are special requirements for the winch.
The drums have to withhold bigger forces due
to the flexibility of the plastic cable.

Some explanations and photos at this site:
http://www.sagach.ch/Deutsch/Windenstart.htm
for english translate it from german
http://translate.google.com/translate?u=http%3A%2F%2Fwww.sagach.ch%2FDeutsch%2 FWindenstart.htm&langpair=de%7Cen&hl=en&ie=UTF-8&oe=UTF-8&prev=%2Flanguage_tools
have fun
Swiss Chris



"Walter Kronester" > wrote in message
...
> 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
>
>