Winch Launch Extreme 5200 ft

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

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

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

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

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

"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

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, 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

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

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