Robert --

I would like to learn how they do this. Our Blanik has perhaps the best
located CG hook on any sailplane I'm aware of, although some would say
the bridle is somewhat awkward to use.
On a typical tow, with the Blanik weighing about 1100 lb, the 300 hp
winch engine throttle is advanced to the forward stop in 3 seconds and
at this time the engine is already rapidly approaching redline 5000 RPM.
At this point the Blanik is already beginning its climb and the throttle
is eased.

This quick takeoff and climb performance is still not fast enough to
load the ship and its occupants to more than about 0.8 - 0.9 G
horizontal acceleration, which I think one would have do to attain any
more than the 1/3 line length releases we are attaining.

We limit our climb airspeed to 55-60 kt, which I believe is the POH
recommendation. Very little if any back stick is necessary, and the
Blanik attains the 55 kt climb pretty much on its own until the last
part of the 45 second tow, when some back stick is applied to counter
the downward (with respect to the ground) pull of the rope. Our
Spectra/Dyneema/Plasma plastic rope weighs less than its full 66 lb when
partially wound on the drum, so line weight (and its necessary
acceleration and ground contact friction) for us is practically
negligible.

If there is a better setup anywhere in the world, I would sure
appreciate a description.

Thanks for your reply,

BJ
Midland, Texas
http://www.permiansoaring.us/

Robert Ehrlich wrote:

Bob Johnson wrote:

Eggert --

Those are really good numbers for your winch.

With V8 300 HP (GMC 454 c.i., 7.4 L), and 5000 ft (1550 m) Plasma line
laid out, we are getting the rule of thumb 1/3 cable length releases of
1700 ft (525 m). This is into 10-15 kt wind. Much over that, we leave
the Blanik in the barn!

BJ
Midland, Texas



Eggert Ehmke wrote:

Bob Johnson wrote:

Mr. Ehmke --

Your ability to get 600 m releases with a winch on a 1200 m strip seems
extraordinary. Is your cable length just 1200 m also or is it greater
than your strip length?

That's 1200 m of cable laid out, with a V8 240 HP engine at the other end.
What I told is the normal range - with strong wind aligned to the runway we
had 750 m (2460 feet) agl with a double seated ASK21. I did not see this
launch, but it sounds reasonable. 650 m I have experienced myself.
Eggert

1/3 cable length seems low. There was in France an experiment showing
40% cable length without wind with cable length from 1000 to 2000 m.
See HTTP://www.gliderforum.com/thread-vi...geID=1466#1466