Install a strain gauge internal to the fuselage right up against the hook
mount. Get Peter Masak to design a simple circuit that trips an electronic
relay when the strain exceeds a certain amount. Knowing Peter, it should take
him less than an hour.

Jim Vincent

I've been thinking about how to measure strain on the
rope during auto-tow, but this time from the auto side, not the
glider side.

I'm planning to tow using a 50# spring scale, and never exceed
40#, and see how long (far) it takes to accelerate to rotation
speed. For 500#, I seem to get calculations near to 1000ft or so.
I'd like to see if a 40# thrust AMT turbine would accelerate
a 500# glider to rotation in a reasonable runway length
(say 2000 ft or less).

As a second issue, I'm wondering if anyone has measurements of
the typical strain on a winch or auto tow rope. I'm
guessing .5 to .9 times the glider weight (probably near the
highest altitude right before release, right?).

Spring-type weight measuring devices for up to around hundreds of
pounds are in the $200 range. In the 500#+ range, though, things
get pricey...



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Mark Boyd
Avenal, California, USA