I have a knot in one of my center lines that I use for Ozone foils 6M to 12M. In the past I have used a needle to carefully work the knot loose but have noticed some damage to the fibers of the line. I know a knot lowers the ability of the line to handle a max load but so does damage to the line fibers. Better to leave the knot or damage fibers and remove the knot? Does a knot decrease the strength of the line to a point that failure is a factor?

If it's an overhand knot, I seem to recall something like a 50% reduction in strength ?? That would equate to a fair bit of line damage. I think I'd be removing the knot too. Having said that, there's a knot on one of the front lines of the Peak 2 that's there to stop the bar from going too far towards the kite and while I don't like the idea of any knots in the line, the line looks like it's been sized up to handle the reduction in breaking strength the knot would cause. I guess that one's a factory knot. :D

The knot should be removed. If you can't pick it apart, sometimes it helps to get it wet and then freeze it and then mush it out by pressing hard down on it. I usually pick them out.

The problem is in the construction of the line. While Dyneema and Spectra line is 10 times stronger than steel of the same diameter, it has a very low melting point. When you have a knot in the line, under tension it creates friction and heat, this heat will eventually 'melt' through the line causing line breakage/failure. I would pick the knot out of the line and be careful to not damage any of the fibers if possible. Even if you do have minor damage, having the knot ouf of the line will be stronger than leaving it in.

Obviously damage to the fibers will be a weak point but probably not as weak as leaving the knot.

Yep remove the knot. If the fibers are more damaged than you are comfortable with then it needs replacing. The knot is at least as bad as damage but the knot is like rust. It will make it fail sooner.

Take a hammer and tap on the knot and that will loosen it up. Maybe run it under warm/hot water too. The hammer method will work though.

Is this in a powered line or steering line?

The knot is on a power line. I would not be nearly as concerned if it were a steering line.

Thank you everyone. The forum always gives me information that helps me improve my kiting. Following everyones advice I removed the knot with no damage. Thank you for pointing out that leaving a knot in the line can lead to further trouble.

I would remove the knot to retain the same line length and not because of strength concerns. In widespread knotphobia people don't mind knots at the end of lines but anything in between generates horror and fear mongering. I particularly like the idea of a heat generating knot...

I suggest that if you end up with some fraying, put a little, very little of Aqua Seal on it. Leave it for about an hour until partially cured and then with WET fingers smooth it out to a thin layer. This will make your line almost as good as new. For those unfamiliar - Aqua Seal is an excellent sealer and glue, commonly used to repair wetsuits and the like. It cures very tough but flexible. Other than wetsuits I use it on all my lines to make my numerous knots happy.

While we are on the subject of knots, do you have any relationship to the Prussik knot, or are you just a fan?

In my younger days, when I was capable of something more worthwhile like soloing fairly difficult routes, prussik knot saved my life on two occasions - good enough reason to honour it.