Winch Launch Extreme 5200 ft

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/

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 |

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.

"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

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

"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

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

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

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

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 |