Wednesday, April 26, 2017

More Detail on Bobstay Failure




This is the welded nut on the lower end. Failure occurred about ½ way inside the nut. Inspection would not have revealed an incipient problem. I suppose turning the nut would have broken the rod. The threads backed right out, no sign of stress near the threads.



Broken ends of the ¾” dia. stainless rod. Color is distorted by flash  by crystalline structure is apparent.



No flash color here. Not much held the rod together! This failure was a long time in coming. The threads into the fitting are ugly but seemingly not affected by the fatigue.





The solid end fitting for the rod ends had no toggle, no way to dissipate sideways motion imparted by an anchor line rubbing on the stay, so there is no doubt fatigue caused the failure and water/salt corroded in the fatigue cracks. The top end fitting had no sign of stress.

The replacement was simple and inexpensive:



I hope this experience can keep somebody from the problem happening when it would lead to serious damage.

Carl Miller

3 comments:

  1. Thanks for sharing, Carl...I am going to have the bobstay on Veneeni (41LN#49) carefully inspected and adjusted...adjustment may be a way to reveal potential failure...keep posting this stuff...Greg

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  2. Thanks Carl, I will put that on my list. I had our bowsprit rebuilt as it had rotted away significantly under the stainless fittings and the ends and the middle. The loose nature of the inner forestay gave it away and the more we looked the more rot was found. Good to have that solid again. Regards, Geoff

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  3. Mine broke last month in almost identical fashion. We split a SS rigging screw and inserted the solid rod into the middle. Had to do a bit of grinding to get every thing to clear, but it seems as good as new.

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