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Old 28 September 2008, 09:38   #21
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Need to see a photo of the fracture surfaces.

My bet would be on stress corrosion cracking allied with fatigue.
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Old 28 September 2008, 10:47   #22
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All the Stainless I have seen with Crevasse corrosion looks like Aero bubbles at the corrosion point. Plus the main cause in all the steels I have seen has been lack of Oxygen which I wouldn't expect near the sea surface. There are other causes but oxygen starvation is the main culprit in my own limited experience.
From the pic it just looks like no stretching has occurred and since the break is at the thread end which is the weakest point and near the interface between the hull outer surface I would say sideways movement over time has work hardened and snapped it at this point.
Small movements often enough would be enough.
Or, alternatively, somebody doesn't like you, is there any body on the forum or elsewhere that may come into that category
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Old 28 September 2008, 12:33   #23
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I haven't been anywhere near it and I didn't have my bolt croppers with me either
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Old 28 September 2008, 12:40   #24
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I'm curious, what were the ropes made from as i wouldnt have thought nylon and synthetic materials would have swollen sufficienty with water? maybe if the water had frozen i would've understand it better.
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Old 28 September 2008, 13:54   #25
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Quote:
Originally Posted by codprawn View Post
The eye is a VERY heavy duty unit...
Apparently, not heavy duty enough...!

I imagine that this failure was caused by repeated side to side stresses caused by the opposing mooring lines.

Perhaps if you were to use one of this spiffy "shock absorbers" in the mooring set up, it would absorb some of the stresses.

I was surprised at how easily stainless bolts can be sheared off just by wiggling them back and forth a few times using use vice-grips or something. It's a great way to shorten a bolt that's too long once it's in place and the nut tightened...

I am doubtful of the swollen rope theory as well. Assuming you aren't using cotton or hemp lines, I just don't think that they're would be enough water absorption in synthetic lines to cause this, even if it were possible.
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Old 28 September 2008, 15:18   #26
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Originally Posted by iandl View Post
...if you can find 12mm stainless U bolts that arent crimped let me know ...
Here ya go.
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Old 28 September 2008, 16:31   #27
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It was the tightness of the ropes on the eye that made me realise just how much they had swelled - there were several nots there as well. As I said I had to cut every rope just to get the bow eye out.

I can't see it was a sideways force as the holes in the boat havent been enlarged.
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Old 28 September 2008, 16:31   #28
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I also doubt that the failier was caused by the "over expansion" of rope knots causing a tensile break. I suspect what many have said already and that is the movement of the bow against either two oppositely tied Painters or a 90 degree painter. I suspect the rope tightness on the U bolt was caused by this.

Would be useful to see the ends of the break though.
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Old 28 September 2008, 16:33   #29
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from the pictures it looked around the 12mm x 150mm .....It seemed to fail at its weakest point ...just where the crimping hammer forces the lugs into it .....

if you can find 12mm stainless U bolts that arent crimped let me know cause i'm looking for another .......they seem to call them 'sealed' and offer them in 8 and 10mm sizes .....they do make them cause i already have 1 which i got from our local chandler ...but he only had one and it was old stock he got rid of and didnt know the maker


I

it wasn't crimped!!!
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Old 28 September 2008, 16:33   #30
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These look better!!!
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