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View Diary: The 'hero' of D-Day - the Waco CG-4A assault glider (119 comments)

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  •  I was wondering if they used a 'straw' (3+ / 0-)
    Recommended by:
    Jay C, shortfinals, RiveroftheWest

    for emergency breakaways, and what the breaking strength might be. Those gliders, fully loaded, were heavy and not anywhere close to being as aerodynamically clean as a sport/competition glider.

    Rudeness is a weak imitation of strength. - Eric Hoffer

    by Otteray Scribe on Sat Jun 08, 2013 at 05:38:13 AM PDT

    [ Parent ]

    •  Not sure what you mean by 'straw'. (2+ / 0-)
      Recommended by:
      RiveroftheWest, shortfinals

      By U.S. law for civilian flying, the breaking strength of the tow rope must be between 80% and 200% of the weight of the glider being towed. If it is not, then the rope must have weak links of that strength at each end, with the link at the tow-plane end to be no weaker than the link at the glider end. [The idea being that the rope should break before the glider or tow-plane.]

      Different clubs use different setups. Hollow-core polypropylene rope with an appropriate breaking strength (typ. 1000-1200 lbs) is quite popular, and poly rope used with a nylon weak link at the glider end and a poly weak link (made by simply tying a knot in a short length of poly rope) at the tow-plane end is also reasonably popular.

      (Polypropylene ropes are generally preferred because they are not elastic -- a lot of spring and stretch in a tow rope can be dangerous. Nylon ropes are undesirable specifically for that reason.)

      There are also specific weak-link devices made with color coded metal links for clubs that have a variety of gliders with different weights.

      Even 80% is pretty strong; I've known people to try to deliberately break ropes, and it is fairly difficult to do. I've also known people to break them accidentally in rotor (swirling air currents found under the peaks in wave conditions). Typical tow stresses are 20% or less for aero-tow, although that does not include 'snatch' events. Winch launches require considerably more strength; breaks are also much more common.

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