How long of a runway do you need for an effective / safe winch and/or auto
tow launch environment?

Mike Schumann

"Bill Daniels" wrote in message
...
Well, there's cheap and effective and there's just plain cheap. The
difference is critical. US winch launching has suffered a great deal from
the "lets just do it as cheaply as we can" attitude. The result is a lot
of
rusting "200HP weed eaters" welded together from junk car parts that
understandably scared the hell out of people and gave winch launch a very
bad name.

I've spent a lot of time looking at the best winches in the world and
examining the cost justification for each feature. I came to appreciate
that winch design is a complex art with profound consequences if you get
it
wrong. Nobody is building new single drums winches. Two is the minimum.

My conclusion is that the up front costs, even though they are high, can
be
easily justified if the utilization is high enough. If the utilization is
low, you can't justify anything. It's also easy to see that doing it
right
the first time is far cheaper in the long run.

Much of the cost of multiple drum winches is in the high-tech cable. A
club
can build a multiple drum winch but delay purchase of the cable for all
the
drums until the demand is evident.

Multiple drums and high HP results in fast, high launches. There are two
benefits to multiple drums. One is higher utilization and the other is
fast
queue's. If you are 6th in line for a launch while the Cu's are popping,
the winch cycle time can't be fast enough.

High HP is both a safety feature and a performance feature. Getting the
glider to a safe climb airspeed quickly reduces the exposure to two types
of
accidents - ground loop and stall on the wire. It's much easier to stall
a
glider on the wire or let a wing drop with an underpowered winch. Of
course, the glider acceleration must not be so high that the pilot can't
control pitch up.

Higher launches allow more time to search for a thermal. Even a small
increase in release height is a big payoff. If the release height is
barely
at pattern entry altitude there is little time to find a thermal. Adding
a
few hundred feet to the release height means that a much higher percentage
of launches will contact soarable lift. Given reasonable runway length,
launches above 2000 feet AGL are easy. Much higher launches are possible
with still longer runways.

Auto tow is a very cheap way to go if the room is available. The problem
is
that a long rope takes up most of the runway leaving little room for
acceleration and braking of the tow vehicle. For a typical runway, a
winch
will get you higher. A winch with multiple drums will launch far faster
than auto tow.

Bill Daniels

The whole idea of winch launch is to reduce launch costs
"Steve Leonard" wrote in message
...
I am a bit disappointed to see this thread going the
way the Yahoo Winch design group did. I still watch
there and am interested in what comes of it. It started
off (Or so I thought) with the notion of designing
a simple but reliable winch that a small group of people
could afford to build so a small club could fly. It
rapidly evolved into a multi drum, hundreds of horsepower
machine that would make the small club capable of doing
120+ launches of fully loaded ASH-25s and Duo Discuses
a day. Does a small club really need that much power
and more than one on a drum winch?

Let me say, you DO NOT have to use a big engined pickup.
We have towed with a sick V-8 in a donated old Pontiac
Grand Prix, a 6 cylinder Chrysler minivan, a Full size
Chevy Van with a 350, and a Suburban with, I believe,
a 454. And you know what? The altitude gained was
virtually the same for each tow vehicle! A FAR bigger
variable was Pilot Technique. And right behind that,
believe it or not, is CG positioin on the towed glider
(in our case, a 2-33 using the nose hook. Why the
nose hook, you ask? With our 2-33, the CG hook would
hit the ground with the nose skid on the ground and
the right wing down.)

I do agree with the comment about not using a chute
for straight auto towing using rope. It will just
take the end farther from the runway! I have been
able to buy 2000 feet of 3/8th hollow braid Poly for
$200 (plus sales tax). If well taken care of on our
very abraisive paved runway, we can expect to get at
most 100 tows from this. We drive only about 15 to
20 MPH on the return trip, and try to lay the rope
in a grass strip along the runway when we bring it
back. If you can attach an arm to the side of the
towing vehicle to drag the rope back i the grass along
the side of the runway, it will last even longer.

One of our members built up a complete system he installs
in the receiver hitch on his vehicle. It has a 3.5
HP Brigss and Straton motor, the rope reel, hand operated
level wind, throttle and brake for the reel, and a
tow release. Not sure why everyone thinks you need
to use a Tost release for this. The Schweizer releases
we are using work just fine. Whole thing is installed
on swivels, so it always pulls straight on the tow
release. Oh, and since this releas is not on an airplane,
you can make your own that acts like one of the others.
But, you can probably pick up a used Schweizer release
for less than it will cost you to make one of your
own. There aren't many airplanes pulling banners anymore,
so they might be happy to get $100 for that thing on
their tail. He is able to reel in the rope in just
over one minute, then drive quickly back to the launch
end and then star slowly paying ot the rope for the
nex launch. But, even this is probably more than you
are wanting right away.

You don't need a high dollar towplane, you don't need
a high dollar winch, and you don't need a high dollar
tow vehicle in order to get in the air. If you are
not trying to launch an ASH-25 at a 10,000 foot density
altitude, you don't need to size your launching equipment
to do that! What are you looking at launching down
there in Laredo?

Just like the comments about flaps. Well intentioned
auto towing advice, even from people that know what
they are talking about, sometimes gets slanted to their
needs, not yours.

Feel free to contact me directly if you would like
a bit more information about the auto towing we have
done here in Kansas.

Steve Leonard

Sometimes auto tow driver and pilot
1200 plus hours in flaped ships and have never ONCE
had the thing try to float the entire length of the
airport on me so I don't know why the heck you would
ever want to RETRACT the flaps and REDUCE the drag
that is there to slow you down.