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