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Old 26 September 2008, 21:39   #1
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Guess how it broke

I was horrified last week to find that my RIB had somehow managed to come untied at the bow. It was still tied at the A frame but the bow was free to hit the pontoon and the boat next to it - no damage thanks to large rubber tubes!!!

Because of the lack of suitable cleats on a RIB and the fact that my harbour is extremly rough I had 4 ropes attached to the bow eye. This is one of the strongest points on a boat - how the hell did it fail?

I would like to point out that it was NOT corrosion or similar. I have worked out the answer but I was stunned and nobody I know has ever seen anything like it.

The eye is a VERY heavy duty unit - anyone know where I can get one exactly the same?
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Old 26 September 2008, 23:34   #2
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If it wasnt a close encounter with Ury Geller How about friction/fatique .It would suprise me but it has snapped at its narrowest point on the thread
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Old 27 September 2008, 01:49   #3
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Quote:
Originally Posted by codprawn View Post
I was horrified last week to find that my RIB had somehow managed to come untied at the bow. It was still tied at the A frame but the bow was free to hit the pontoon and the boat next to it - no damage thanks to large rubber tubes!!!

Because of the lack of suitable cleats on a RIB and the fact that my harbour is extremly rough I had 4 ropes attached to the bow eye. This is one of the strongest points on a boat - how the hell did it fail?

I would like to point out that it was NOT corrosion or similar. I have worked out the answer but I was stunned and nobody I know has ever seen anything like it.

The eye is a VERY heavy duty unit - anyone know where I can get one exactly the same?
What is the thread size
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Old 27 September 2008, 02:21   #4
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Were any of your four ropes tied in apposing directions? If so then the stresses are trying to bend the fitting from side to side. Over time this will cause fatigue and fracture. I also want to bet the fitting has a rolled thread not a machined one. Easy to tell the difference. Rolled threads are bad as they impart compression and brittleness ( work hardening)
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Old 27 September 2008, 02:25   #5
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The eye is a VERY heavy duty unit - anyone know where I can get one exactly the same?
I am sure we either have one or can get one, what are the specs?
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Old 27 September 2008, 02:27   #6
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If there were 2 ropes on this, was one of them set up as some kind of spring? (although with no cleat around the centre of the boat I'm not sure how you'd do it) So when the water has pushed her about you've had opposite forces which has made it go clink ?

If not I haven't got a clue and I'm calling in Scooby doo!
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Old 27 September 2008, 04:01   #7
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Yep, stress fatigue. The only way this would happen would be a take off in opposite directions and the boat moving in a sideways manner or a take off all to one side with a 90 degree angle to the Bow, the boat would be tugging from one side.

You should find a good selection of U bolts from hardware internet sites like here or Here at the Bottom of the page

This should get you started. Just check the dimentions from the online drawings in the websites to identify which one is suitable.

If this might happen again, it might be an idea to look for a different soloution than using a U bolt?

Good Luck.
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Old 27 September 2008, 04:48   #8
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Polwart with an angle grinder
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Old 27 September 2008, 04:52   #9
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Polwart with an angle grinder
I would have subcontracted it to garfie!
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Old 27 September 2008, 04:59   #10
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I'll be interested in the answer to that one Codders. I know someone with a brig rib approx 3mtr long, as far as I'm aware it's (the u bolt) only ever had minimal use ,never any more than one rope yet we tried to pull it up on the pontoon with this and got the same result...straight pull......so .... lets hear it
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