Monday, April 10, 2017

Check Your Bobstay...

Just in from Carl Miller, Saphira 35LN23

In a fair breeze and a 110%genoa, the bottom end of our LN35 (1987) bobstay fractured. Since my local rigger said he had seen the EXACT failure in Hawaii on a 41 Lord Nelson, it makes me think there could be a design issue.

At one rod end, they drilled out a 3/4" nut, and WELDED it to the rod, so there is a hex to rotate the rod for tension adjustment. But the weld heat changes the metallurgy of the SST and with trapped salt under the nut, and some side flexing from the occasional anchor line rubbing, the fracture occurred inside the welded nut. The failure was clearly metal fatigue, and it was a long time coming. The fracture surfaces are crystalline looking, all dark and rusty across the fracture. Because the failure was occurring concealed behind that welded nut, there was nothing to inspect or a crack to see from the exterior. If you have a LN any size and the bobstay rod is OEM, please think about replacing it before something bad happens at a bad time.

2 comments:

  1. Can you share any pictures of this? I am having a bit of trouble visualizing the failure.

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  2. For some great pictures of the failure take a look at Carl Miller's last blog post: http://lnoablog.blogspot.com/2017/04/more-detail-on-bobstay-failure.html

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