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 Post subject: Re: Slow leak that I just can't find on my Cabrinha
PostPosted: Sun Feb 17, 2013 9:53 am 
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I tried to make sure it was definately the LE bladder that was slowly leaking by pumping it up a few times and also put soapy water on the valve. I had checked the valve was clean and tight. All the rubber tubes were clamped as tight as possible.

Took the LE bladder out and sumberged it bit by bit from one end to the other twice. No bubbles from the bladder, the valve or the rubber tubes. I left the LE bladder inflated for over an hour and it didn't seem to be leaking (although it was at low pressure so a fine leak may take a lot longer than that to show).

I'm now left wondering if its one of the rubber tubes that only leaks at high pressure?

Any other possibilities?


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 Post subject: Re: Slow leak that I just can't find on my Cabrinha
PostPosted: Sun Feb 17, 2013 11:21 am 
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ronnie wrote:
I tried to make sure it was definately the LE bladder that was slowly leaking by pumping it up a few times and also put soapy water on the valve. I had checked the valve was clean and tight. All the rubber tubes were clamped as tight as possible.

Took the LE bladder out and sumberged it bit by bit from one end to the other twice. No bubbles from the bladder, the valve or the rubber tubes. I left the LE bladder inflated for over an hour and it didn't seem to be leaking (although it was at low pressure so a fine leak may take a lot longer than that to show).

I'm now left wondering if its one of the rubber tubes that only leaks at high pressure?

Any other possibilities?

Had the same problem with my Cab 2009 crossbow. First I tried just submerging but that did not show any leaks. Second time I had it out I tried grabbing a small volume at a time there by increasing the pressure locally while pulling that bladder material apart. That reviled very small perforations which were fixable with some of the Cab patches.

I think the rubber tubes are very durable try pulling them while there is pressure in them with some soap water on them.


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 Post subject: Re: Slow leak that I just can't find on my Cabrinha
PostPosted: Sun Feb 17, 2013 12:07 pm 
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FrederikS wrote:
ronnie wrote:
I tried to make sure it was definately the LE bladder that was slowly leaking by pumping it up a few times and also put soapy water on the valve. I had checked the valve was clean and tight. All the rubber tubes were clamped as tight as possible.

Took the LE bladder out and sumberged it bit by bit from one end to the other twice. No bubbles from the bladder, the valve or the rubber tubes. I left the LE bladder inflated for over an hour and it didn't seem to be leaking (although it was at low pressure so a fine leak may take a lot longer than that to show).

I'm now left wondering if its one of the rubber tubes that only leaks at high pressure?

Any other possibilities?

Had the same problem with my Cab 2009 crossbow. First I tried just submerging but that did not show any leaks. Second time I had it out I tried grabbing a small volume at a time there by increasing the pressure locally while pulling that bladder material apart. That reviled very small perforations which were fixable with some of the Cab patches.

I think the rubber tubes are very durable try pulling them while there is pressure in them with some soap water on them.


Thanks Frederick - my kite is also an 09 Xbow.

I still have the bladder out, so I will try creating more pressure in the bladder underwater.
The LE bladder is tricky to handle because it is so big. I tie the ends together and connect them to a retractable clothesline hung up high to try to keep it under a bit of control. I dont want to cause more leaks.


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 Post subject: Re: Slow leak that I just can't find on my Cabrinha
PostPosted: Sun Feb 17, 2013 4:01 pm 
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Frederick has the right technique. The hard part is plugging the strut valves on the leading edge. This is why I typically do different areas at a time. starting with the area from the tip of the bladder to the first valve. Just getting enough air in that section and then squeezing from each end trying to force a bit of air through pin holes.

It's unlikely to be the rubber hoses connecting the LE to the struts. It could be, but if they aren't visibly cracked or old looking, it probably isn't. I would pull at them and stretch them a bit to see if this reveals any cracking.

*Also as someone mentioned, their O-ring on the inflate valve blew off several times upon deflation. I don't know if you had checked to see if your O-ring was still there. If you leave the valve open after deflating to fold and bag your kite, it is likely that this simply fell out with the rustling of the deflated kite in the wind, or by folding, or simply it fell out in storage and when you unfolded for the next session, it fell onto the ground. I found at least 10 O-rings in the yard of the school I was managing last season.

Are you positive the leak(s) are not in the struts? I usually pump the kite up and clamp all the struts to see what stays inflated. Have you put some plumbers tape on the valve screw and checked the glued area around the valve?

If you are good at getting the bladder back in, I might suggest starting over. Go to place where you can dunk the kite in the water. On dry land, pump up the kite, clamp the struts, see if there is a change in pressure in the struts or LE. Pump up again so you have good pressure, then dunk the whole kite in the water and focus on the whichever area seems to be losing air. Keep in mind there is air trapped between the bladder and kite material itself so in some areas there might appear to be a leak at first and disappear. It helps to have little wind when doing this as you need both your eyes to look for a continuous fizzy stream of bubbles as well as your ears listening for the sound this fizz would make. I also start with the leading edge down in the water, put my weight on the kite using a knee to submerge it and have my hands go along the seams to make sure I get excess air out of the canopy. Then I do the same with the kite flipped over, sometimes the oles come from areas where the canopy meets the LE and is hidden from view and disguising a leak.

It's tough to keep at it man. Have you pumped just the bladder up and ran your ear along every inch of the it? Sometimes your ears can pick up more sensory info than your eyes.


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 Post subject: Re: Slow leak that I just can't find on my Cabrinha
PostPosted: Sun Feb 17, 2013 5:54 pm 
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The valve was new recently and I have taken the rubber washer out and checked both sides are clean. The valve didn't show any signs of a leak when I inflated the kite and sprayed soapy water on it. I checked the LE and struts by inflating the kite 3 or 4 times and it was always the LE that went down. You cant put much pressure in the bladder, so if I cant see bubbles when its under more pressure underwater, I doubt if I would hear anything.

I will try again and put more pressure on underwater.


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 Post subject: Re: Slow leak that I just can't find on my Cabrinha
PostPosted: Sun Feb 17, 2013 9:34 pm 
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It sounds like you done just about everything.

As Frederick said, "Second time I had it out I tried grabbing a small volume at a time there by increasing the pressure locally while pulling that bladder material apart."

Doing this has worked for me but sometimes the holes are just so small. At this point you have probably put in enough man hours to warrant the cost of a new bladder. The last thing to do if you want to spend a few more hours is visually inspect the bladder as I described. I found lots of cracks in the Crazy Fly I was fixing that were suspect but not holes all the way through the bladder. I patched them anyways since I was there because they were going to be the next holes eventually. One Cabrinha patch sheet should get you at least 10 patches if you cut them out, especially if it is just pinholes. I think the kites usually come with two sheets of these translucent patch sheets. Might as well just go to town and patch everything you see, definitely check the seam on both sides and extra close inspection of the tips of the bladder. If this all doesn't work, just put in a new bladder and get that kite up in the air and reward your effort.

I have some old rotted bladders in storage. I could probably find some spider cracks and take some macro pics if you don't fully understand what to look for. I just don't know how else to describe it in text.


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 Post subject: Re: Slow leak that I just can't find on my Cabrinha
PostPosted: Sun Feb 17, 2013 9:58 pm 
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REALLY small leaks in the front tube (or bladders) are hard to find....

Taking the bladder out wont work very often - no matter how hard you push the sections, as you will most probably make it burst or bubble instead, if you got no idea whatsoever where the leak is !

Extremely small holes will close, when the bladder is not under high pressure.

So pumping the full kite up, REALLY hard, not just like when you fly, and then taking it in a pool or the sea when no wind - then you can find the leak approximately or precisely.
You might have to pump the kite when you have finished dipping and checking either the right or left side, before you take the other side - as the whole idea is you have the highest amount of pressure, thus for sure a bubbling hole somewhere :naughty:

The advantage of this technique is that you find leaks in one-pump systems and valves too, if that is the problem.

Another advantage is, that you only have to take the frontbladder (it is most often the front bladder that got a tiny hole from a sharp bush) out on one side of the kite, so only half the work to get it repaired and back in :rollgrin:

Using soap water might in rare cases work, but it can also be a lot of work without finding anything - as it is not easy to get EVERYTHING soaked and soaped so there is air trapped.
A bit of a trial and error method, that might work fine, but often dont work at all too...


When I talk about a really small leak, I mean a leak where the kite will get a bit more soft after using it 4-6 hours, but still okay to fly.

This is still no good if you ride a full day, or you go on a cruise along the coast or out on the sea :(
You can just pump the kite now and then if riding at the same spot, yes - but somewhere in the back of your mind you are piss.. about KNOWING there is even the smallest leak :roll: (I am...)

:D Peter


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 Post subject: Re: Slow leak that I just can't find on my Cabrinha
PostPosted: Tue Feb 19, 2013 5:11 am 
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Peter_Frank wrote:
REALLY small leaks in the front tube (or bladders) are hard to find....

Taking the bladder out wont work very often - no matter how hard you push the sections, as you will most probably make it burst or bubble instead, if you got no idea whatsoever where the leak is !

Extremely small holes will close, when the bladder is not under high pressure.

So pumping the full kite up, REALLY hard, not just like when you fly, and then taking it in a pool or the sea when no wind - then you can find the leak approximately or precisely.
You might have to pump the kite when you have finished dipping and checking either the right or left side, before you take the other side - as the whole idea is you have the highest amount of pressure, thus for sure a bubbling hole somewhere :naughty:

The advantage of this technique is that you find leaks in one-pump systems and valves too, if that is the problem.

Another advantage is, that you only have to take the frontbladder (it is most often the front bladder that got a tiny hole from a sharp bush) out on one side of the kite, so only half the work to get it repaired and back in :rollgrin:

Using soap water might in rare cases work, but it can also be a lot of work without finding anything - as it is not easy to get EVERYTHING soaked and soaped so there is air trapped.
A bit of a trial and error method, that might work fine, but often dont work at all too...


When I talk about a really small leak, I mean a leak where the kite will get a bit more soft after using it 4-6 hours, but still okay to fly.

This is still no good if you ride a full day, or you go on a cruise along the coast or out on the sea :(
You can just pump the kite now and then if riding at the same spot, yes - but somewhere in the back of your mind you are piss.. about KNOWING there is even the smallest leak :roll: (I am...)

:D Peter


forget the soap. the only full proof way to test the bladder is underwater. if air is escaping from the bladder, it will cause bubbles, no matter how small the leak.

I still think you have a valve leak. They typically only leak under full pressure. I had the same thing on my cab.. Now i blow off the valve and threads with my pump before inflating, and coat the whole mess with some vaseline. works great.

good luck.


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 Post subject: Re: Slow leak that I just can't find on my Cabrinha
PostPosted: Tue Feb 19, 2013 9:24 am 
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[quote="TPink]

forget the soap. the only full proof way to test the bladder is underwater. if air is escaping from the bladder, it will cause bubbles, no matter how small the leak.

I still think you have a valve leak. They typically only leak under full pressure. I had the same thing on my cab.. Now i blow off the valve and threads with my pump before inflating, and coat the whole mess with some vaseline. works great.

good luck.[/quote]

The last time I pumped it up as a kite, the LE seemed to deflate faster than on previous occasions and at a rate I would have thought would produce bubbles, so you may be right about the valve, although I did check the valve was clean and tightened.

Its still about 4C around here, so a bit cold for checking it outdoors.
There's only one suitable spot locally. I wonder if a Park Warden would think a man trying to drown a kite in the local duckpond is a bit strange?


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