Shroud Plates and Metal Fatigue – Word of Warning

[Kittiwake]

Here’s some food for thought…

During last year’s Isle of Wight Circumnavigation, our port shroud plate parted at deck level, while reaching off Bembride in a F4/5 (fuller account under the IoW Circumnavigation thread). We were lucky not to be dismasted, and managed to make it back to Calshot in one piece.

Later inspection showed the cause to be metal fatigue. The shroud plate had parted flush with the deck, and inpsection of the fracture surfaces showed it had clearly been weakening over a period of time – approximately 25% of the fracture surface was dull, as if exposed to the elements for sometime.

My guess is that the plates were as old as the boat, the originals glassed in when she was built. Not sure when that was, but with sail number 6536 no spring chicken.

You cannot see metal fatigue by inspection, failure is sudden and catastrophic. The metal, after many 1000s (100,000s?) of small deflections suddenly hardens and becomes brittle, and snaps. Metal fatigue was first discovered when planes started falling out of the sky in the 30s and 40s. Not good. We were lucky, a dismasting and rescue would have been the more likely outcome.

The point is, if you are cruising in an older boat, and think these are the original fittings, you may consider having them replaced, before it happens to you. Replacing both shroud plates and the forestay fixing cost around £300, by Porters in Emsworth. Ian Porter doubled up the new fittings, so I now have two shroud plates back to back on each side.

Happy sailing

Geoff
W6536

[Author]

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