Bill Daniels wrote:

"Mark James Boyd" wrote in message

I'd love to see a winch design that uses a 100hp or less engine,
can be easily bolted on the back of an old pickup, and has engine
and parts that are low maintenance and (especially engine) easy
to acquire (either locally or via shipping).

Alternately, how about a "spare tire" that is really a winch drum.
a stable sturdy "jack" and some way to route the cable
to ensure it winds up nice.

Might not work (thoughts of side loads tipping my car
over come to mind!), but it sure is fun to play with the
thuoght!
--

Mark, unfortunately, the physics of a winch launch says that it takes about
1 kWh or 3,600,000 Joules to launch a glider. The peak power demand places

Hmmm...so all gliders are alike? A Gapa or Russia REQUIRES the
same HP as a ballasted LAK-12 or Nimbus 4? Something 400 pounds
vs. 1600 pounds? I know this isn't what you meant...

I read the Marske site and saw the (wt lbs) x (wing loading lbs) x .03 = hp
and it looked like these mini gliders "needed" about 100 hp.

yet another constraint on the minimum HP that must be available. Those
numbers point to a 400 to 500 HP engine to be able to provide launch service
to any glider in the existing fleet. Although the initial cost of a well
engineered winch is high (nearly as much as a tow plane) the long term costs
are only a few percent as much a tug.

A coupla points: well engineered, is limited in how high you
can get, and very hard to move around are winch disadvantages.
The height is tough to get with any winch (8000 ft sightseeing
sled rides ain't gonna happen). But if we assume we'll only fly
500 gross wt. with 6# wing loading, how does this ease the
engineering and building costs, and how mobile is this
new mini-winch?

If we can build four of these things for the price and energy
of a 400hp version, is the launch weight limitation less of a
disadvantage? How about if we can build eight of these for the
same price? How about if we can build 16?

Obviously if you fly 1600 lbs of glider, this does you no good.
And sure, there are non-recurring engineering costs to
making 2, 4, 8, 16 of these. I guess what I'm saying
is I'm not gonna see a big winch that launches 1600 lbs
at MY gliderport in the next 5 years, but I'm gonna bet
I'll see a small, portable, back of the truck winch at
Tehachapi at the Vintage Sailplane Rally in about a month...

I've also seen pictures and know there are dozens (maybe hundreds)
of hugely capable, overengineered (IMHO) winch designs (they seem
to all be custom homebuilts).
For novelty, I'd like to see the juxtaposed minimalist approach.
I've been very impressed by the lighter, smaller gliders
I've seen recently. I'm excited about the idea
of towing them with a 75 hp towplane. I'd like
to see a 100 hp winch, even if it was underpowered, just to
see HOW underpowered...


The good news is that the total energy consumed for one launch (About 1
liter of diesel fuel equivalent) is tiny compared to any other launch method
except bungee launch. (Excluding, of course, the beer you have to provide
the bungee crew.)

Auto tow's about the same, but without the construction costs,
from what I gather. The huge downside (I'm finding out) is that
auto-tow takes a HUGE amount of room/runway...

A glider winch is a highly specialized piece of machinery that needs the
kind of engineering Ulrich is asking for. Please avoid the temptation to
cobble some junk together to make a barely workable winch. That sort of
thing has given winch launch a bad name in the USA.

There's that word "needs" again. ;P Keep in mind you are sharing this
thread with ME, an avid experimenter and no stranger to failure...

A well run winch operation is very attractive to newcomers to the sport. It
shows a lot of ground activity that is visible to the onlookers and the
rides are a real thrill. Lets get winching!

The only winch I know of on the west coast USA that one can
schedule use of is Northwest Soaring an hour east of Seattle.
I called them and it's a May-Oct operation at Cle Elum. Fortunately
the flights out of San Fran area are $130 round trip, so it'll
be cheap to visit there this summer )) .
--

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Mark Boyd
Avenal, California, USA