High Tows

Barry,

In one of my favorite books, Richard Miller's "Without Visible Means
of Support", there is a tale of a Russian Glider air/winch/winch tow.
A twin engined towplane, a bunch of wire, a two place sailplane, a
bunch of wire, and a single place sailplane. Tow plane goes as high
as he can go, lets out his line. The two plane and single place
"kite" themselves up higher. Then, the two place lets out his line,
and the single place "kites" himself as high as he can get. Not
really winching in the classic sense. More like an auto tow using a
towplane and a sailplane.

On their first attempt, the towlane got to 15,000, the two place got
to about 18,000, and the single place got to 21,000. On a later
attempt, the single place got to 28,050 feet.

Fred, have you got reels in your towplanes? How much spectra do you
think it could hold? :-)

Steve

Steve:

We have a reel in our towplane, but it is driven by a rubber band and
certainly doesn't have enough power to act as a winch. In fact I have
to keep the airspeed below 80 Kts when I reel in the line or it stops
retracting. And speaking of Spectra, I'm told it requires extra
strong drums on winches because it has enough stretch that it builds
up tension on the drum, kind of like wrapping a stretched rubber band
around your finger -- the tension could eventually crush the drum of
many winches. Fred

don't need to reel it in for the winch effect..
just climb as high as you can with about 3 miles of spectra..
and hang on while the glider "kites" up behind you for a few thousand extra
feet of altitude.

either that or the glider can just "catch the wave"...

we have 30G40 down here tonight after today's frontal passage..
how much snow did you get?

BT


"Fred" wrote in message
...
Steve:

We have a reel in our towplane, but it is driven by a rubber band and
certainly doesn't have enough power to act as a winch. In fact I have
to keep the airspeed below 80 Kts when I reel in the line or it stops
retracting. And speaking of Spectra, I'm told it requires extra
strong drums on winches because it has enough stretch that it builds
up tension on the drum, kind of like wrapping a stretched rubber band
around your finger -- the tension could eventually crush the drum of
many winches. Fred

So far we've only got flurries. Temps below zero forecast for
tonight, then up to the low 40's tomorrow. Lots of snow just a little
north of us in Reno. Fred

On Dec 22, 9:13*pm, Fred wrote:
Steve:

We have a reel in our towplane, but it is driven by a rubber band and
certainly doesn't have enough power to act as a winch. *In fact I have
to keep the airspeed below 80 Kts when I reel in the line or it stops
retracting. *And speaking of Spectra, I'm told it requires extra
strong drums on winches because it has enough stretch that it builds
up tension on the drum, kind of like wrapping a stretched rubber band
around your finger -- the tension could eventually crush the drum of
many winches. *Fred

Spectra (and other UHMWPE ropes) don't stretch at all. They are fluid
like when winding on a drum and under tension the crushing force is
cumulative since there is no elasticity, there is no relief either.
Not at all like a rubber band.

1/8" Amsteel Blue has a breaking strength of 2500lbs. 7/64" is
1600lbs. You can get a lot on a reel, but I think you'd still need a
bigger reel to set records.

Frank Whiteley