On Friday, June 5, 2020 at 1:50:59 PM UTC-4, WB wrote:
On Friday, June 5, 2020 at 12:26:21 PM UTC-5, wrote:
Good and cheap are mutually exclusive. A good, safe machine won't be cheap.

Right, but I thought the idea of the original question was to see if sacrificing some good (higher than 300 foot tow?) might make cheap and safe possible.

Seems like a small corner case until there are lots more FES, but still fun to think about.

A light duty winch to get you to 300 feet would still require all the same components as a heavy duty winch designed to get a Duo to 2000'. Assuming you will climb at a relatively shallow angle, you could get away with somewhat less power than a typical glider winch because you won't need to climb steeply as is done in a regular winch launch. Also, because line tension will be less in the shallow climb, your winch drum can be lighter. Brakes are critical on a winch to manage inertia of the drum/line and to put some tension on the in when reeling it out. A lighter system could have correspondingly lighter brakes. Your winch line will be under less tension, and with a low launch rate, wear would not be a big issue. You could forego expensive Dyneema line and just use polypropylene (might be a false economy eventually). These would all be small increments of "lighter, smaller, cheaper". Probably not enough to justify building it. My guess is it would be better to buy/build a regular winch or go with auto launch. Hard to get cheaper and simpler than an old car, a bucket of rope, and a tow release on a trailer hitch.

You could forego expensive Dyneema line and just use polypropylene (might be a false economy eventually).

I would advise against using polypropylene line since it has a much higher elongation compared to UHMWPE lines. It would most likely lead to a very unsteady launch with a lot of surging - like hanging on a bungee cord. Spectra or Dyneema have an elongation very close to what a steel cable has but at about 1/10 of the weight. That also plays into the overall equation for accelerating the line and then stopping everything with your drum brakes.
Rather than building something on the 'Hold my beer - watch this' principle, spend the money and get the right stuff.

Uli
'AS'