In article QIV6d.147361$D%.8795@attbi_s51,
"Bill Daniels" wrote:

"Gary Boggs" wrote in message
...
My guess as to the force on line is probably something like 300lbs? I
think
the next mod we will incorporate will be a tensiometer on the line. Right
now we use a pressure gauge on the brake line and as the disc brake heats
up, the pressure required to get the correct tension on the line goes up.
It would work much better if our winch operator was able to monitor the
actual tension on the line, instead of the pressure on the brake. If we
could find an electronic tensiometer, we could program it to operate the
brake, but this would make the winch even more complicated and expensive.
I've searched the web for available tensiometers, but found nothing
suitable,
so I think we will just build one into our system.

The tension on the line should be about the same as the gross weight of the
glider. 300 pounds will result in a poor launch. The tension on the line
is the result of cooperation between the pilot and the winch operator. No
matter how hard the winch tries to increase the line tension it won't happen
unless the glider pilot pulls up.

A better idea is to use an RC model airplane telemetry package like RCAT to
send the glider airspeed to the winch operator and let him control that.
The glider pilot can then control the line tension with the elevator.

I think it will require more power than a starter motor for that though.

Bill Daniels


This looks very similar to what we were doing last Sunday, at the 3000'
New Jerusalem airport, near Tracy, California. The payout winch we used
was manufactured by an outfit called Airtime of Lubbock (Texas), and is
known as an ATOL winch.

It has a guage mounted on the hydraulic master cylinder to show how much
force is being exerted on the disc brake, force is hand adjustable
during tow by the operator, and also has a large lever to enable an
operator to dump all tension in the event of a lock out emergency.

It also has a "level wind" feature much like a fishing reel, to feed the
line back and forth across the drum. this is connected to a rewind
motor controlled by a hand held trigger, for the operator.

The whole thing is mounted on a platform which plugs into a 2" receiver
hitch. The motor is either driven by jumper cables up to the truck
battery, or a battery mounted alongside the winch.

The operation is like this: one person drives the truck, one person sits
in back to monitor/adjust pressure and release if necessary, and we had
a second person in back to run the radio communication with the pilot
and other field traffic.

The first time we did it, the truck went to 30mph, the tension was set
for 45#, and I used 10 degress of flaps with full back stick. I got a
600 foot tow into a 10mph wind. The operator said he didn't think I was
pulling the rope off the drum very well.

The second time, the truck went to 40mph, tension was backed down to
30#, I used 20 degrees of flap, and full back stick. This time I got to
nearly 1000 feet at about 600 fpm. We used these settings for the rest
of the day.

The only functional problem we're facing is that there seems to be too
much slack in the chain between the motor and the drum, so sometimes the
chain jumps the sprockets and we have to terminate the tow early. I'm
looking at installing an idler gear with which we can adjust the chain
tension.

We're still figuring out the correct operational parameters, and anyone
with experience is welcome to give us constructive comments!

Oh, I was flying my BrightStar SWIFT, which is an ultralight composite
flying wing design. Total weight was about 300#.

Best regards,
Ken
San Jose, CA