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Glider Tuning

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I bought a new sail for my glider last December. It really improved the handling and it improved stability at higher speeds. I thought it flew like a new glider. Unfortunately, over the last couple months the handling and stability seemed to deteriorate. I knew I had a bit of a left turn. Rob and Dave and Ken told me to make sure the glider was symmetrical before doing any other adjustments. Everything looked right but I had a few battens that ran out of adjustment so the sail tension was probably not symmetrical.  Dave Aldridge helped me shorten all but about 4 of my battens and the next time I flew the roll pressure was less and the left turn was more pronounced, or at least more noticeable. So, following the advice of Dave and Ken I adjusted my tip wands to correct the turn. After that the glider flew really well, even better than when I got the new sail. I was very happy and thought I was set with a fine handling glider when Jonathan Dietch sent me an eMail asking what I was up to. In a follow up response he asked me if I knew about wax. Bingo. Before he answered I knew he was talking about waxing the tip wands. So, last Friday Jonathan and I flew Crestline and before we launched he helped me check the angle of my sprogs and put Zipper Ease wax on both ends of my tip wands. Turns out my inner sprogs were two turns (~3 degrees) too low. Frankly, I don’t think I noticed a difference in my glider performance from adjusting the sprogs. But the wax, the wax was the icing on the cake. It noticeably reduced the roll response time, especially roll reversal. From now on, I will keep Zipper Ease in my harness and will probably apply it every other weekend. Another tip that Jonathan gave me was to use the zipper ease on the keel to reduce the friction on the VG. While that certainly helped, it was overshadowed by the improved roll response. I guess I don’t really know what a brand new T2C feels like but right now mine feels great. So, here is what I learned and I hope it might help someone else:

  1. If you think your flying skills have taken a down turn, consider that it might be your glider tuning.
  2. Really, really, really pay attention to your batten tension. Follow the manual recommendations for setting the tension If your batten tips are already screwed in all the way, you can remove the tip, cut the batten and replace the tip. There are some important techniques to follow when cutting a batten so ask someone before you start.
  3. Check your glider to see if it has a turn. Because we always fly in mixing air one way to do this is to put it in a turn then let go of the control bar. I can only speak to my T2C but it will pretty much stay at that bank angle and maybe, just a little, gradually bank a little steeper. Most important, it does the exact same thing in both a left and right turn. You should consult with one of the WW guys (Rob or Ken or Dave or Alfredo) about how your glider should respond. Frankly, my glider response might not be exactly right but I’m so happy with the handling I probably won’t change anything.
  4. Lube your tip wands. They call these gliders flex wings for a reason. The sail needs to move freely and that includes tip rotation. I’m using Zipper Ease because that’s what Jonathan recommended and I think he worked this out with Dave Gibson, the comp and acro pilot from Utah who is also very meticulous about his gliders.

I hope you can forgive me for this long winded post but this tuning exercise over the past month has made a real difference in how my glider flies and even in how much fun I am having. Glider tuning matters and I hope this post might help someone else.

Gary stomped all over me, chewed me up then spit me out on Friday. I immediately regretted helping him correct his glider's maladies. Next time I'll know better. But seriously folks, there's a lot more to this story however the moral of the story is spot on:

Pilots lose interest in flying their topless gliders because they become burdensome, unpleasant and even unsafe to fly. Sail shrinkage, aluminum oxide buildup, tip wand fatigue, tip wand cup friction build-up, possible adjustment screw vibration drift, batten bending, sail fatigue, etc. All of these things can gradually turn your super-ship from a soaring eagle into an albatross around your neck. It can happen so gradually that the pilot thinks it's him or the weather and not the glider. Topless gliders need periodic tuning and maintenance and they don't typically get it. There's a fair amount of useful information on manufacturer websites and manuals but there's more tune-up technique that works very effectively.

Yes, it would probably work. 

No, I wouldn't use it because it will leave black crud everywhere.

I've been wanting a concrete means to determine the effect of my sprog and\or batten settings. I'm working on a system identification module which detects pilot position relative to the control frame along with glider pitch\roll response, in essence to find the transfer function of the glider. Its a tricky problem because there is often a lot of disturbance ("we always fly in mixing air"). Anyway, i feel certain that some useful data could be pulled out of the results in post-processing. I currently have the module sampling and logging to an SD card every so many milliseconds. Still some work to do in getting all the sensors to share the serial bus nicely and other minor details. Very doable though.

A precision gyroscope can measure\quantify any difference a pilot might feel.

 

 

I'll have to step back from taking the zipper ease with me in my harness or leaving it in the car. One afternoon in a hot car turned the pencil-shapped wax into a gooey mess. Fortunatly, the zipper eaze was in a zip-lock bag. It still works but I think I'll leave it in the garage and apply at home.

Does the wax applied to the tip wands pick up a bunch of dirt while setting up on launch?

Does the wax applied to the tip wands pick up a bunch of dirt while setting up on launch?

I have never had any issues with Zipper-Ease which also goes by the name Door-Ease. I use it on my harness zipper and all my glider zippers including the bag in addition to the keel and tip wands. All of these items roll in the dust and dirt and there isn't a trace of accumulation on anything. The melting point is pretty high and a vehicle can become extremely hot inside. Once it's applied I believe there are volatile compounds that evaporate out leaving a dry layer of wax compound that doesn't attract dirt. It needs to be re-applied every 20-30 hours or so for uninterrupted benefit and it's well worth the few minutes that it takes to keep things moving freely.