Rope Tension Meter for Auto Tow

On Dec 24, 8:12*pm, " wrote:
On Dec 23, 6:37*am, STEVE SARGEANT wrote:



On Dec 19, 5:52*pm, " wrote:

We at the Fault Line Flyers Glider Club in Briggs Texas want to build
or buy a tension meter for our auto tow operation.

Does anyone have experience that might be helpful.

Bill Snead
6W

LCM Systems can offer various solutions, depending on what the force
range is that you want to measure.

Try this link for the sensorhttp://www.lcmsystems.com/sta-4

and for a handheld display, we would recommend:-

http://www.lcmsystems.com/TR150

You could but the complete kit, calibrated an ready to go for less
than $550

Could someone describe how you use the tension meter when auto
towing? *Once you are towing at a constant tension, does it change how
you fly the glider on tow? *What is the typical tension maintained
when towing a 2-33? *Also some pictures how the electronic load cell
is rigged with the release hitch would be helpful. *Thank for all the
good information

Bill Snead

With constant tension, the pilot controls airspeed with pitch attitude
(Nose up, slow down - nose down, speed up) just as in free flight. In
a thermal, the car will back off to maintain constant tension as the
thermal provides a fraction of the energy. In a downdraft, the tow
car will add power to maintain tension. It's a very pleasant way to
launch.

A 2-33 is a special case since the elevator is so small and the hook,
even the "compromise hook", is so far forward. The limited elevator
authority makes it difficult to control airspeed at any tension
value. Also, Schweizer didn't provide information on weak link or
best climb speed for ground launch. At any tension greater than about
75% of the gross weight, a 2-33 will accelerate even with full up
elevator. Most people find 55 MPH works as well as anything.

Note that winch or auto towing puts stress on the wing roughly equal
to a loop. (~3.5G) I seem to remember a letter from Schweizer around
1980 strongly discouraging loops due to the age of the 2-33. 30 years
on, I'm not comfortable ground launching one.

The tension load cell fits into the tow line at the tow car right at
the attach point. Usually in the rope just aft of the tow ring.
However, while a bit more complicated, it's safer for the load cell to
be part of the cars tow release mechanism. The full towing force
must pass through the load cell to get a correct reading.