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Author Topic: Order Of Breakage  (Read 975 times)
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chilese
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« on: June 18, 2012, 01:06 AM »

Today at the park, the STX 2.3 was out for a while.

Winds were very bumpy and sometimes hit maybe 12 mph.

I was taking a chance and flying my trusty old, old 100'x90# lines.

On one pass, low and at full power, the kite sort of instantly flapped

its 2 sides like a bird once and then spun to the ground.

Upon examination I found 3 failures:

1 Lower leading edge APA connector failed around leading edge.
2 Center-T outer ferrule was gone and the female lower spreader
     was sticking through the remaining center-T piece.
3 One of my lines had broken near the strap at the sleeving end.

The engineer in me wants to know the order of the failures, but I
don't know. It happened so quickly.

I'm guessing the line broke first. But I'm open to any expert opinions....

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zippy8
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« Reply #1 on: June 18, 2012, 01:27 AM »

1 Lower leading edge APA connector failed around leading edge.
2 Center-T outer ferrule was gone and the female lower spreader
     was sticking through the remaining center-T piece.
3 One of my lines had broken near the strap at the sleeving end.
Interesting mix  Smiley

Quote
I'm guessing the line broke first. But I'm open to any expert opinions....
Hmmmm..... so the inference being that this was the part closest to breaking point (not necessarily under the greatest load though). You don't mention if this is all on one side of the kite. If it is then if the line broke first then all (~most) of the load on that half of the sail would have disappeared so I don't see the frame damage coming afterwards unless it was impact damage and that's not what you describe.

So...

Seeing as how it's an oldish kite and following on from other threads about fittings' lifespan I propose that the LE connector failed first as a result of old age, the whiplash of the spar unloading fractured the centre-T assembly (which would have been heavily loaded in a ground pass anyway) and the lines simply threw up their hands in disgust. I would guess that the line that failed was attached the the intact side of the kite.

Kudos for the multifail though  Cheesy

Mike,
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Ca Ike
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« Reply #2 on: June 18, 2012, 01:34 AM »

HMM.   Have to agree with Mike here.  Damn no chance to yank his chain Tongue  Fitting first then center t then lines.  I'm going to guess the line on the side of the failures broke though.  THe extra billow created by the fitting failure would have scooped up a lot more wind quickly surpassing the lines breaking point IMO.
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chilese
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« Reply #3 on: June 18, 2012, 12:08 PM »

Line has been thrown away.

From memory,

the left side APA failed
the right line failed
the lower spreader (female) from the right side
   went through the center-T
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John Chilese: Las Vegas, NV
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Ca Ike
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« Reply #4 on: June 18, 2012, 12:14 PM »

Line has been thrown away.

From memory,

the left side APA failed
the right line failed
the lower spreader (female) from the right side
   went through the center-T

Your luck amazes me.  If it was my kite that spreader would have went through the sail.
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Ca Ike
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« Reply #5 on: June 18, 2012, 01:22 PM »

Here's a new theory.  Line breaks on the right side.  Extra stress on the left bridle breaks and already age worn fitting (out haul on STX is under the fitting and not the stop IIRC). KIte hits the ground on the LLE at just the right angle to drive the spreader through the T.
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Rx8doc
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« Reply #6 on: June 18, 2012, 01:35 PM »

My theory ahem, God of flight Hermes angry that John flies kites to well has Zeus knock the kite from the air causing the entire range of breakage.
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Ca Ike
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« Reply #7 on: June 18, 2012, 01:46 PM »

My theory ahem, God of flight Hermes angry that John flies kites to well has Zeus knock the kite from the air causing the entire range of breakage.
With no melted cloth from the lightning strike?  Either Zeus was lazy or took pity on John  Grin Cheesy
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chilese
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« Reply #8 on: June 18, 2012, 03:28 PM »

Okay, here is my new theory (we can rule out John flies too well):

1 Setscrew on center-T loosens (assumption)
2 Higher pressure sail pulls female lower spreader through center-T
     as outer ferrule slides out also
3 Lower spreader APA connector on male side gives up from the twisting motion
     caused by the male LS pushing
4 Shock from APA failure travels down the line and takes out the old 90# line.

Do I win a prize?  Tongue

« Last Edit: June 18, 2012, 03:33 PM by chilese » Logged

John Chilese: Las Vegas, NV
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eolemag
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« Reply #9 on: June 19, 2012, 11:29 PM »

Line has been thrown away.

From memory,

the left side APA failed
the right line failed
the lower spreader (female) from the right side
   went through the center-T

Correct

JPC
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ndcmpc
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« Reply #10 on: June 20, 2012, 01:08 PM »

I had a similar experience, but different sequence than you have here.  I broke a line in high wind under high power in the center of the window.  The sudden slack on the bridle allowed the wings to fold back, pulling the lower spreaders from the center T and the upper spreader from one APA.  Being low in the window, it hit almost immediately.  I fully expected the kite to be destroyed, but it was fine after I put it back together.  I surmised it didn't get any sail holes because the wings pulling back angled the various rods away from the sail.

Your experience may vary.
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Doug
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