crossbar hold-down strap is another big culprit in VG friction. Spraying the keel works, but some pilots put a strip of Teflon or Tyvex right at the bearing point. It tends to stay in place without even fastening it to the strap. Good luck.
UNCLIPPING CLIPS Recently I was appointed safety honcho for the CIVL (the international organization for para- and hang gliding). In this capacity I get a lot of information concerning accidents and potential problems relating to gliders. I receive the German DHV magazine with all its insightful articles on weather, flying skills and accidents. Unfortunately it is in German, but I have an Amish lady friend who helps me translate. In the latest issue there is a report about an intermediate glider entering a steep spiral dive that it could not recover from. It turns out the glider was tightened to the extreme at the curved tip wands, resulting in a high load on the tip-batten end flip clips. The DHV test pilot set up an identical glider in this manner and tried the spiral (getting past 60 degrees bank angle). He could not stop the spiral and had to throw his parachute. Apparently what happens in this case is the tightened trailing edge plus the additional load imposed by the high Gs in the spiral popped open the end clips on the outboard battens of the lowered inside wing. Once the batten clips are open, the sail rides forward, creating more drag on the lowered wing (acting like a small drogue ’chute attached to the tip), which exacerbates the spiral. Yikes! A little discussion: It seems some pilots have the mistaken idea that: “If tightening a glider’s sail a little bit can gain some performance (usually at the expense of handling), then tightening it as much as possible reaps even more gains.” In the next section we deal with
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HANG GLIDING & PARAGLIDING MAGAZINE
a similar problem. Here we’ll simply say that there is a law of diminishing returns in effect, and in this case (and others) there is also a rule of diminishing safety. Do NOT over-tighten any adjustable part of your glider (tips, battens, VG line). Also, it should be noted that intermediate gliders (such as the U2, Discus, MastR-M, Litespeed, etc.) may be more vulnerable to the above described problem because they typically have battens distributed a bit farther apart at the tip, and sometimes have a greater curve in the sail trailing edge, which also increases the load on a given tip batten. (Single-surface or easier gliders tend to have even fewer battens, but the looser sails reduce batten tip tension.) The fix as suggested by the DHV article is to not over-tighten a glider, but also keep the tip clips in good
working order by detaching them carefully (depress the tab well before flipping it up) and replacing them every few years. Note, the tip battens are the ones under the most tension and the only ones of concern. Another fix or safety addition they suggested is to add a small safety cord or plastic tie wrap to the batten flip clip as shown in figure 1. This safety device is moved forward as shown once the clip is fastened and it prevents the clip from releasing, even under great force, according to the tests they performed. On my previous glider I had a batten clip on one batten (third from the tip) that would often come unclipped in flight. I changed the clip more then once, but the angle of the sail pull still opened it. I solved the problem with a safety as illustrated. Finally, here’s a little flip-clip tip tip. If you are setting up, and you find