New winch height record

George Moore of Spokane, WA has developed some very convincing math that
says 50% of the initial rope length should be possible as release height
under no wind conditions.

As you go to longer ropes, the percentage used for ground roll and rotation
into the climb becomes less and as you get higher, you may encounter higher
headwinds which also adds to release height. I would expect higher
percentages simply due to longer ropes.

All this depends on several things. Using Spectra or Dyneema rope which is
10 - 12% the weight of steel cable for a given strength, using adequate
power to maintain a rope tension of 1 to 1.5 x glider weight and managing
that tension precisely with a computer.

In this case, they used an ASK-21 which specifies a black 2200 pounds-force
weak link. This allows a lot of power to be transfered to the glider.
Apparently it was flown solo which means a tension factor of ~1.5 x weight
was possible.

All very technical, of course. Where it's a game changer is training,
particularly glider aerobatic training. An aero tow to 1700 meters is way
over 100 Euro. The winch launch was probably less than 10 Euro.

I like to think of quietly lobbing an instructor with a pre-solo student up
over a vertical mile at 6AM for 40 minutes of instruction in glassy smooth
air.

Bill Daniels


"bagmaker" wrote in message
...

A typical winch launch yeilds about 1/3 of the runway/field available,
this is a fantastic result, Bill!
Perhaps we should be measuring the launch as a percentage of field
length, then there would actually be a record available for everyone to
shoot for, regardless of locality.
So...
With a runway of 3100m and a launch of 1718, the current known record
is 55.42%


Get out there and break it!!


bagger




--
bagmaker

I like to think of quietly lobbing an instructor with a pre-solo student up
over a vertical mile at 6AM for 40 minutes of instruction in glassy smooth
air.

This is slightly OT, but... is there an optimal launch height at each
stage of training? For example, a few really high launches at the very
beginning (so that the student has time to practice things like speed
control and turns), and then a lot of standard (~1500ft) launches
(circuit planning and landing)?

Bartek

"brtlmj" wrote in message
...
I like to think of quietly lobbing an instructor with a pre-solo student
up
over a vertical mile at 6AM for 40 minutes of instruction in glassy
smooth
air.

This is slightly OT, but... is there an optimal launch height at each
stage of training? For example, a few really high launches at the very
beginning (so that the student has time to practice things like speed
control and turns), and then a lot of standard (~1500ft) launches
(circuit planning and landing)?

Bartek

Of course. Early trainees gets high launches until they can fly the glider
reasonably well and then a lot of low launches for landings and launch
failure training.

For low launches, 1500 feet or less, a retrieve winch can be used to get the
rope back for another launch achiving a launch every 2 minutes or so.

It would be great to have both capabilities.

Bill D

On Nov 26, 10:37 am, "Bill Daniels" bildan@comcast-dot-net wrote:

It would be great to have both capabilities.

....and that would probably require two winches. Even though one could
release at 1500ft when being launched by a 4000ft-capable winch, it
would probably be pointless. But then, would it be possible to operate
two winches safely?

Bartek

Bartek,
Most winches have more than one drum. In Europe, one winch can have up
to 8 separate drums and lines. This enables a launch every 3 minutes
or less.
http://www.hydrostart.nl/EN/
Tom

Most winches have more than one drum. In Europe, one winch can have up
to 8 separate drums and lines. This enables a launch every 3 minutes
or less.http://www.hydrostart.nl/EN/

Oh, sure. But what if a club wanted to have one winch for high
launches, located at the far end of a runway, and another one for
circuit practice, located in the middle of the runway?

Bartek

brtlmj wrote:

Oh, sure. But what if a club wanted to have one winch for high
launches, located at the far end of a runway, and another one for
circuit practice, located in the middle of the runway?

I don't see the point. I've never felt that a winch launch was too high,
even for primary circuit training. There are always some exercises which
you can do with students. I know a couple of maneuvres which destroy
altitude pretty efficiently... And if everything else fails, you can
always practise a rope break.

"brtlmj" wrote in message
...
Most winches have more than one drum. In Europe, one winch can have up
to 8 separate drums and lines. This enables a launch every 3 minutes
or less.http://www.hydrostart.nl/EN/

Oh, sure. But what if a club wanted to have one winch for high
launches, located at the far end of a runway, and another one for
circuit practice, located in the middle of the runway?

Bartek

I think one winch would be enough. You don't need to do high launches and
low launches at the same time. It's just ascheduling. Plan some high
launches early and some landing practice late. Give the guys who want to
soar the mid-day slot. A winch can be moved around easily.

That said, many European and British clubs do use several winches at the
same time. Again, it's just a scheduling and organizational problem.

One thing a lot of US pilots seem to miss is that a winch can, and probably
will, operate from sun up to sun down. There's no noise problem. Cost is
not an issue. If you find lift, great. If not, the cost of a winch launch
is so low and it's so much fun, just glide down for a landing and do it
again.

Spending a day trying to get that glass racer down in the smallest patch
possible is huge fun. Since you have to push it back to the start line, you
have a big incentive to land short. Knowing you can land very short if need
be is a big relief on a XC. 20 or so consecutive landings will do that.

Another fun thing is to watch is the private owners who arrive at 11:00
expecting lift to start at 12:30 when the find out a solo student has been
soaring for two hours off a winch launch.

Bill Daniels

tommytoyz wrote:
Bartek,
Most winches have more than one drum. In Europe, one winch can have up
to 8 separate drums and lines. This enables a launch every 3 minutes
or less.
http://www.hydrostart.nl/EN/

I've watched them launch gliders at Lasham at that rate using a single
drum of a Tost winch and a retrieve winch. There is a price to be paid,
of course, maybe 200 feet less altitude (if that much), but a retrieve
winch is somewhat less expensive than upgrading to an 8 drum Hydrostart...

Marc

tommytoyz wrote:
Bartek,
Most winches have more than one drum. In Europe, one winch can have up
to 8 separate drums and lines. This enables a launch every 3 minutes
or less.
http://www.hydrostart.nl/EN/
Tom

A properly motivated crew and non-chatty instructors can manage 20 launches
an hour off a dual drum winch. Its probably hard to beat that no matter how
many drums you have because you start to be held up by pilots getting ready
or, depending on your field layout, landing gliders interfering with
launches.


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