Line Weight For Kites
1. What's the best type of string to use for flying?
2. Is there a rule of thumb for what line weight to use depending on wind strength?
I'll make a big assumption here and assume you are flying single line kites...
1. The general favorite for flying single-liners is Dacron, which is a polyester. This material combines reasonable cost with superior strength compared to cotton and nylon. It does have some stretch, but this is of little concern for a stable single-liner. People who fly single-line fighter kites probably prefer less stretch in order to feel the kite better. Any keen fighter kite pilots want to comment?
More exotic line materials do exist, for even greater strength and less stretch, but you pay for it. For example Dyneema and Spectra. People who are trying to break altitude records with single line kites use this kind of stuff! Performance at any cost. Due to the low stretch, these kinds of lines are particularly suited to traction kites. That is, multi-liners used for land boarding and kite surfing.
2. I've found that lighter winds tend to vary much more in strength than heavier winds. Hence I wouldn't fly any of my kites on much less than half the weight of line I usually use.
After a little research I found a KAP (kite aerial photography) enthusiast who had an interesting approach to line weight. He routinely measures the pull of his kites, and chooses line accordingly.
You could use an ordinary set of fish-scales for this. Anything with a pull-spring arrangement, so you can just put a few wraps of line around the hook, point it at the kite and read the tension off the scale. I would do this for a minute or 2, in order to make a reasonable estimate of what pull the maximum gust strength might generate over the next hour or 3.
Whatever figure you arrive at, multiply it by 6 to give the minimum strength line you should use. For KAP, this guy upped the factor to 10 for extra security! No point in losing expensive cameras.
This might seem a little more bother than a true 'rule of thumb' for line weight, but I think this is an excellent method for getting the most out of your kite in the conditions, while retaining a good safety factor!