what is a bladder is it the innertube?

is it the innertube?

close enough. It's the long skinny airbag(s) which gives an inflatable kite its structure, usually one really long one around the leading edge of the kite (leading edge inflatable = LEI) and a few more, up to seven, usually three or five, running from the leading edge straight back to the trailing edge.

unlike a innertube though there is no stretch to a bladder, with 6-8 lbs of pressure ( I think) they are tight and strong.

sometimes they are connected to each other (one-shot, one-pump), you'll see that more in more recent kites.

advantage: floats in water, usually water relaunchable, unlike open foils. And I guess they would hold their shape much better in wiggly and/or weak winds.

disadvantages: often useless once you pop a bladder, def so it is a one-pump, and inherently less aerodynamic than a foil, so about 25-40% less power than a foil of the same size, and tend to shred / abrade badly at the leading edge so their durability can be limited, that combined with the bladder-pop problem (rolling it in surf is BAD!) makes them more fragile in general than foils, with less of a lifetime.

That said, depower LEI's, especially bows, are getting dramatically (just in the last couple years, really) nice. I've never flown one, but it will be likely less than a year before I find a way to finance one (and a board...) and finally get me out on the water...

that should get you going...

furbo