C Johnson wrote:Cabrinha uses Poly Ether Bladders instead of Poly Urethane.
airtimekite wrote:C Johnson wrote:Cabrinha uses Poly Ether Bladders instead of Poly Urethane.
Polyurethane film can be either polyether or polyester. Yes, it is a polyether just like all other PU bladders should be. The polyester is much stronger but not suitable for marine applications (used in airships, conveyor belts, etc). Polyester PU was accidentally used by Cabrinha in 2001 (might be off by a year) and they had bladders disintegrating if packed up wet and left for any amount of time.
You do have to remember that a bladder can not swell or rupture if it's supported by the sewn sleeve of the kite. A bladder that is properly supported by the fabric can't rupture without the sleeve failing first.
I have seen incidents where bladders do get out of whack when folding or rolling a kite. That's why it's pretty important to have the bladders talced very well so that they don't catch on themselves and can slide back into place as you pump them up. We found that talc would slowly wear off after use so we went with a matte finish on the PU film that we make our assembled bladders out of. Took one more variable out of the equation.
It does appear that Cabrinha has chosen to use a slightly thinner film to save on weight. I think it's just under .003" when most are .0033"-.0039". We have built race bladders out of .001" material and they work. However, the thinner they get the more fragile they are. It's just the price you have to pay for performance. We could make bombproof bladders that weighed 10 lbs each but no one would enjoy using them.
I recommend always keeping an eye on the leading edge of your kite when inflating it just to make sure it's filling out correctly. If you're vigilant you will probably be able to avoid surprises when you least want them.
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