Kiteboard Theory - Thread 13: Tuning Line Lengths

Postby James on Mon Mar 31, 2008 1:26 am

Kite lines stretch over time. The front lines usually stretch more because they're normally subject to more tension. If you anchor the ends of a well-used set of lines to a common attachment point on land, and lay the lines out, you may find that the front lines have stretched several inches more than the rear. That's a good time to adjust your lines.

Stretched front lines have the same effect as shortening the rear lines, which is likely to cause oversheeting. It's quite possible that your kite, even with your lines attached to the least-powered knots, could have a more powered setting than it did with new lines on the most-powered knots. This will dramatically reduce the amount of available trim to depower the kite.

It will also devastate your kite's efficiency. An oversheeted kite, which is easily caused by stretched front lines, tends to suffer aerodynamic stall, which is a problem I've referenced in several other theory threads. It is a common misconception that pulling in your bar necessarily results in more power, but this isn't always true. Pulling in the bar creates more power only up to the point of impending stall, after which power falls dramatically as the bar is pulled in farther. Stretched front lines make this circumstance hard to avoid.

That's why you should often lay out your lines and adjust them to the same relative lengths that they were when new. Many, if not most lines are meant to be the same length when the bar is sheeted in all the way to the stop and the "depower" adjustment is all the way out, in the "fully powered" setting.

Regardless of whether or not your line lengths are correctly adjusted, there are simple ways to make sure that your kite trim is optimal when on the water. Tell tales are a great way, but if you can't see them clearly, or more likely don't have them on your kite at all, here's another way: Ride on a steady course, and when the wind is relatively steady, gradually pull in on your bar. If, at some point, your kite moves back in the window perceptibly, even just a degree or two, it's probably beginning to stall. Repeat this process a few times to be sure that the kite's position isn't just responding to a wind shift. Then you should adjust your depower strap so that you can almost, but not quite, pull your bar in far enough to cause the kite to begin to stall. (Of course, if you're overpowered, you'll want to adjust the strap even tighter.)

A common problem with having improperly trimmed lines and depower strap arises during jumps. Even if you don't regularly pull in your bar as far as it will go while riding, you may purposely or intuitively pull it all the way to the stop during jumps. And if the trim is wrong, your kite will probably stall. If you've ever experienced jumps that seemed really weak, that's likely why.

Best regards,
James

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