Kitesurfing: Replacing a strut bladder with U-Stick orange bladders

Here is a story of a bladder (replacement) on an inflatable kite.

Twice-Broken valve

Recently, I had a failure in my Flexifoil 9m Atom3 after I left it simmering in the sun for several hours (at Rio Vista, CA.) After having an "interesting" session with half-deflated kite I was faced with a repair. The heat caused delamination of the strut valve from the bladder. I have had local repair shop repair it. They glued the valve back but the repair looked terribly (with some part of bladder glued together, ripped apart and left hangin and bladder folds). I have reinstalled it anyway and tested it overnight. It held the air. I did not go out for several days (no, the kite was no longer on the sun).

Next time I have inflated it on the beach the kite quickly lost lots of air. I discovered that although the glue held, the valve become cracked and it had a serious leak. Apparently the repair damaged the valve base. The damage looked like it was heat induced. I bet it was overheated during the repair (the valve is usually completely unglued by "coocking" it). So much for "professional" repair.

Orange and original bladders.

So, a full bladder replacement was in order: U-Stick orange bladder and valve. The Airtime Kite people were awesome. They quickly advice me what I should use. The strut valves, both on main and strut bladder are called "option" as you can choose different stems. Flexifoil has a 11mm valves with straight stems. There is also a "replacement" option valve which does not have "options" as it comes only with straight stem. Also, Airtime has nice on-line bladder selection tools. My kite needed 50cm bladder. The valves fit the opening in the kite and did not need rings. Ordering and shipment was a snap, thanks Airtime!

I followed instructions attached to the bladder and valve. However, there were few small surprises.

The 50cm bladder is visibly much bigger then the original Flexifoil one. Too big is OK as the kite will restrict the expansion, too small would be bad (too much stretch). The original bladder was also 50cm (just much smaller). 


The material is more brittle sounding (it sounds more like a "shopping bag" while Flexifoil's is more like "sex-rubber", if you know what I mean.) Just observing the visual difference which has nothing to do with other physical properties like strength. I just said "oh well it must work fine."

REALLY be careful when cutting the hole in the bladder for the valve. The bladder is completely air tight when shipped so pulling it apart is hard. Never thought that vacuum can be so hard :-)

Bladder prepared for surgery

When sticking the valve there were more surprises.

The bottom of the valve protrudes from the base so it is perhaps better to use soft surface to glue on, like a towel.

Bottom of stem protrudes beyond the base

It is hard to align it with the hole before the valve sides will start catching the bladder and when they do, it is over; perhaps a helper could stretch the bladder flat when you align the valve and stick it, mine cough bit early and got slightly misaligned with the cutout.

The valve glued to the bladder.

The diameter of the opening in the end of strut is so small that I had to bend the base of the valve to fit it in. Then I had to push it in through with some force. Needed to get a bit medieval with it, but it worked. The rest of the way was traveled with a "string attached."

Size matters?

The bladder is so much longer than the original even though I followed the instructions and folded top and bottom inside to match original length. I have folded it more so it flashed with the pocket.

Too long?

The valve is a bit shallower then the original so the pipe between main the strut seems too short and bends the new valve. I wonder how it's going to work long term?.

Too short stem?

So far so good, the kite flies and makes his owner smile. The replacement was $35, a mare $15 more then the "professional" repair that failed.


References:

• AirTime
• what to use to stick it back on (forum post) 
• KiteFix Peel2Fix system (double sided sticky tape)
• FixMyKite Valves and goodies.