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Pinhole woes

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fishyface
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Re: Pinhole woes

Postby fishyface » Sun Nov 13, 2016 8:26 pm

Hi Matt,

This is a situation I've found myself in many times :-?
My record is 26 (yes, you read that right, twenty-six!) pinhole patches in a LE bladder - a friend of mine crashed their kite into a gorse bush, which has thousands of nasty little needle-like thorns. Anyway I have found the best way to do this is to remove the bladder, close off the one-pump valves etc., and pump it up as hard as you dare. Then get a bowl of soapy water (you won't need much), and wet your hand with it. Slowly run your hand over the entire surface of the bladder, dipping your hand back into the soapy water frequently. What you're looking for is the tell-tale 'feeling' of the air bubbling out of a pinhole under your hand. You will be amazed how sensitive your hands are at detecting the tiniest of leaks. When you find a leak, dry the area and mark it with a sharpie. Then carry on and inspect the entire thing in case you find more.

This process can take a long time, but some benefits of my technique:

1. You can do it while on the sofa with Netflix or something to keep you entertained :thumb:
2. You don't need to break into the kiddies playground and wrestle with your bladder in the paddling pool
3. No tools except a bowl of soapy water and sharpie marker

Good luck! (Actually I've just noticed the date of the post, you've probably already fixed it, or given up and bought a new bladder already!)

langfordja
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Re: Pinhole woes

Postby langfordja » Mon Apr 02, 2018 2:42 am

There seems to be a little debate. Some say you can't find a slow leak with the bladder out of the kite, and some say you can. I am going to try the in-the-kite method, since I have never tried it before.

I am replacing my one-pump bladder (whose valves are coming off) with an old non-one-pump bladder with only one valve. The non-one-pump bladder has the slow leak. Once I get it holding air, I may go back and add one-pump strut valves. I I think I can get to the strut valve locations without removing the bladder from the kite. In the meantime, when kiting, I will just inflate all bladders separately.

Since my leaking bladder only has one valve, I am using an old C-kite to help find the leak. It is a lot easier to install the bladder in it since the main sleeve does not wrap around the wingtips. And I don't care if I mark it up with a sharpie. Finally -- a use for old C-kites.

langfordja
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Re: Pinhole woes

Postby langfordja » Wed Apr 04, 2018 8:00 pm

After some pinhole searching, I agree with those who say : really small holes can only be found under higher pressure, like when the bladder is still in the kite.

I marked a bubbling leak thru the kite bladder sleeve, then removed the bladder and found two small indentations near my mark. But I could not get them to leak with the bladder out of the kite. I think pressure to make them leak would have split the bladder seam, with it out of the kite.

After not finding the leak with the bladder out, I put it back in and checked for the leak again. But first I marked the two indentations. The second leak test bubbled right on the new mark, so I put a tear-aid patch over the indentations. I will test again back in the kite but I am confident that the slow leak is repaired (at least one leak).

I will now always find future leaks with the bladder in the kite.

And using my old c-kites for this testing makes things easier, at least for main bladders without one-pump strut valves. My newer kite, that the leak-free bladder will eventually go back in, remains dry until the bladder holds air inside the c-kite.

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GregK
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Re: Pinhole woes

Postby GregK » Thu Apr 05, 2018 1:01 am

In my experience, the screening leak test ( bladder in the kite, pumped up hard, coated with soapy water ) is only about 95% effective in indicating the general area of a leak. If the LE fabric is in near-new condition, leaking air will not get through the coating on the fabric, and instead will come out at the nearest stitching holes, unless the LE fabric has been punctured.

I attribute the 5% no-shows where a leak didn't make any bubbles to the over-sized geometry of bladders ( LE fabric pocket is slightly smaller in length and width than the bladder). If a fold-over of extra bladder material covers a pinhole, that may block a tiny pinhole to the extent that it doesn't present in the screening leak test. Deflate the kite, shake the LE to mover the bladder around some, re-inflate and repeat the screening L/T and bingo that previous no-show now makes bubbles at the nearest stitching in the LE.

As for the final exact pinhole leak location, IME dunking a lightly-inflated bladder into water creates a slight back-pressure on the outside of the bladder ( from the surface tension of the water ) that is enough to block a tiny pinhole. The bladder needs to be inflated drum-tight ( ping it and it's surface is very taught ), stretched 10 - 20 % so those tiny pinholes open up.

But how to do that on a tapered LE bladder, where only the large-diameter centre section is tight and the much smaller tips barely inflated ? I get around this by inflating a LE bladder in sections between one-pump valves. This has the added benefit of greatly reducing the length to a more-manageable amount. The section of the bladder not under soapy-water test/inspection in rolled up and WELL-secured in a small fabric bag or pair of bags when doing the middle sections between 1-pump valves.

Bagging sections not under test is a lot of extra work, but so is having to re-test the whole bladder because a tiny pinhole or two were missed. With only a shorter section of the bladder inflated, it's possible to get the entire test section drum-tight and slightly stretched. Added benefit is shorter sections are less-prone to permanent stretch or bulging-out that will occur at the largest diameter location if you pump it up past the bladder film's elastic limit.

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Re: Pinhole woes

Postby Qiter » Mon Apr 23, 2018 9:08 am

Did anybody try this method to find the really small holes?

https://www.youtube.com/watch?v=mhw0Q1T-Ge4

nothing2seehere
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Re: Pinhole woes

Postby nothing2seehere » Mon Apr 23, 2018 10:13 am

langfordja wrote:
Wed Apr 04, 2018 8:00 pm
After some pinhole searching, I agree with those who say : really small holes can only be found under higher pressure, like when the bladder is still in the kite.

I marked a bubbling leak thru the kite bladder sleeve, then removed the bladder and found two small indentations near my mark. But I could not get them to leak with the bladder out of the kite. I think pressure to make them leak would have split the bladder seam, with it out of the kite.

After not finding the leak with the bladder out, I put it back in and checked for the leak again. But first I marked the two indentations. The second leak test bubbled right on the new mark, so I put a tear-aid patch over the indentations. I will test again back in the kite but I am confident that the slow leak is repaired (at least one leak).

I will now always find future leaks with the bladder in the kite.

And using my old c-kites for this testing makes things easier, at least for main bladders without one-pump strut valves. My newer kite, that the leak-free bladder will eventually go back in, remains dry until the bladder holds air inside the c-kite.
Interesting finding. I would have expected it to be the other way around. The LE fabric should keep the bladder from stretching beyond a certain size. By removing from the fabric you should be able to pump up so the tube expands to be larger (diameter) so you would expect the stretch of the holes to become larger as well and therefore more noticeable.

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Mitaka
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Re: Pinhole woes

Postby Mitaka » Mon Apr 23, 2018 11:25 am

nothing2seehere wrote:
Mon Apr 23, 2018 10:13 am
Interesting finding. I would have expected it to be the other way around. The LE fabric should keep the bladder from stretching beyond a certain size. By removing from the fabric you should be able to pump up so the tube expands to be larger (diameter) so you would expect the stretch of the holes to become larger as well and therefore more noticeable.
From my own experience I can confirm that super small pinholes are leaking only when the bladder is pumped at high pressure inside the LE. You can not achieve such high pressure when the bladder is outside because you will damage it it or it will explode.
Once I had to remove and recheck the bladder three times using my bathtub and finally I found the following technique to work with such small pinholes:
I pump the bladder as hard as possible without damaging it and then I start to carefully submerge overlapping sections in the bathtub while holding the bladder with two hands and stretching the bladder (tested section) between them. In such a way I was able to find pinholes which were definitely not leaking if the bladder is submerged but not stretched.

nothing2seehere
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Re: Pinhole woes

Postby nothing2seehere » Mon Apr 23, 2018 12:33 pm

My bad. Didn't mean to sound sceptical. Just meant to say that it was slightly counter intuitive. I'm guessing its the greater elasticity in bicycle tyres that gives me a false point of view to work from.

Good tip about the stretching of the bladder!

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downunder
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Re: Pinhole woes

Postby downunder » Mon Apr 23, 2018 2:25 pm

If I may,

No one mentioned (or I did not see),

the higher inflation MIGHT destruct complete kite with LE explosion.

If pictures are needed, they are posted already on different thread.

So from one single pinhole you might end up with junk.

Be very careful with a pinhole and pressure.


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