Bill Daniels wrote:

"wy" wrote in message
et...

...
We have not had any launches with strong headwinds in fact there has
been little or no wind at all. The steel launches we made were
700'-900' then the Plasma were 1000'-1200' I wish we could pull out
1500' more rope maybe someday.
...

I find these heights abnormally low. I expect about 40% of cable length,
this is what we used to reach in my club with steel cable and no wind,
now
the engine does no more provide its full poweer, so the height is
sligtly
reduced (350m instead of 400m with 1000m cable).

My guess is that you are out side of north america. European winch
technology is far ahead of anything we do in the states. Although we do
seem
to be experimenting more with the type of cable material a little more.
The
fact that we are even talking about it in the states is a huge change from
just ten years ago.

We have been auto towing (off and on) for several years with Dacron rope
and
are quite happy with it.

wy

I suspect release heights will get higher as pilots get more comfortable
with the new winch. I find US pilots are extremely reluctant to enter the
full climb attitude until 200 - 400 feet AGL which significantly reduces the
height achieved.

This conservatism is appropriate when a group is learning new procedures but
it does limit launch heights.

Bill Daniels


I think the time at which you enter the full climb attitude should not
be determined by your altitude but rather by your speed. The main reason
you should not go to quickly to a high nose up attitude is the risk of
stall in case of cable break. In this case, a push down to 0g causes a
ballistic recovery path with a modern glider having a near zero drag
(compared to other involved forces), i.e. the glider flies an arc of a
parabola with a nearly constant horizontal component of speed. This means
that if you start the recovery at 100km/h and 45 degrees nose up, the
horizontal component is 100*sqrt(2) ~ 70km/h and you will reach the top
of the parabola with a speed of 70 km/h, i.e. above stall speed On the
other hand, even with a lot of altitude margin, if you have a cable break
with a high nose up attitude and you don't immediately push to 0g, you
are probably going to stall. If you do it starting from a to low speed, you
will need to continue at 0g past the top of the parabola in order to recover
a speed above the stall speed, and diving toward the ground at low altitude
is a thing any pilot would be reluctant to do.


As "wy" guessed, I am in Europe, more precisely in France. Winches are very
common in Germany and some other european countries, but in France, up to
a not very long time ago, the situation was very similar to that in the US. At the
time when a lot of gliders were built in France, a lot of them had no CG hook.
My knowledge on the subject is only from hearing what older pilots are saying,
since I started only in 1995, but as far as I understand, winch launching in
these years (50 to 80) was perceived as an old fashionned launching method
superceeded by aero tow. The availability of a lot of Rallye's dropped by the
army as tow plane helped that. Now the raising cost of maintenance of these
old planes, the complaints of neighbours of airfields against their noise
and the vanishing of the financial helps from the state are causing a renewed
interest for winching. But a lot of old mentalities remains. There are several
big clubs in the vicinity of Paris (more than 100 members), but my own one is
the only one owning and using a winch. And despite the efforts of the fans
of winch (I am one of them) the winch is highly underused (lowest year 2001 with
only 3 launches).