Forums, Mast, Rigging and Sails, Kicking Strap Failure

Alan Dixon at 21/09/2014 16:06:40
Twice this season (once today) the kicking strap anchor point on the boom has failed.
I have a Selden mast and boom, the kicker is attached to the boom by a fitting in a slide, the fitting is anchored in the slide by a 5mm or 6mm bolt tapped through the fitting and locating in a hole in the boom.
Both failures have been caused by the bolt shearing during a gybe
Any thoughts or suggestions welcome
Alan

Brigitte at 21/09/2014 16:44:10
Can you supply a picture of the fixture/bolt in question? How violent was the gybe?

I’m no expert but I know there are various reasons bolts fail. A good look at the sheared bolt itself could be quite informative, assuming it didn’t immediately launch itself overboard. If nobody comes up with a specific response, there are plenty of websites giving pictures of various types of failure if you Google.

For example, you’d be able to tell if it was down to simple overload (beef up the fixture), over torquing (don’t do it up so tight next time), undertorquing/loosening (do it up tighter; use a lock nut), corrosion (check/replace regularly), etc. any of which might tell you the best fix.

Or it might be it was the wrong type of bolt. Cracks can start in the weaker, threaded portion so it is best to ensure that the load is being taken by an unthreaded shank.

Or, dare I say very quietly, it might be a badly designed fixture. As far as I understand, bolts should be used to apply a clamping force, not withstand gallumphing great sideways forces, which job should be done by the parts being clamped

Alastair D Pugh at 22/09/2014 10:25:13
My Seldèn boom/kicker attachment also suffered. My solution was to move the slide, drill 6mm holes into new metal and use monel rivets. This has now lasted for 8 years without a problem and not all gybes have been gentle!

Alastair