Inspecting stay fittings

pcatterall

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Our insurers have 'invited us' to produce our own insurance survey on our 70s Neptunian. It has been interesting and, I hope instructive! I propose to bend your ears and, hopefully get the usual good advice on this and other related issues.

The standing rigging was replaced 6 years ago and looks good at deck level. The deck fittings are 12mm SS and look good externally ( there was a recent article about these fittings on older boats) ours have the' correct angle of pull' related to the stays and are 'triangular' rather than 'U' shaped.
I have inspected them all below decks and taken photos. The SS backing plates look good, they seem a little small but I believe that the deck area above is solid and they have held the rigging up for 40 odd years!! There is some surface rust on all the fittings, slightly worse where there is internal condensation ( above the galley sink and heads).
basically what I can see looks good but should we 'draw' at least one of them to see what may have been going on inside ?? I have seen pictures of SS fittings where the hidden bits tell a different story to what you can see externally often due to the dreaded crevice corrosion.
So what's the opinion guys? Is it safe to leave these fittings after 40 years in place?
Coming up soon questions on CO2 for engine room fires and ( of course) the usual gas locker issue!
 

rszemeti

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It sounds like you have done all you reasonably could, short of dye penetrant or similar NDT techniques. I might be tempted to draw the main shroud plates and examine them more carefully, but apart from that ...

If you do remove them to inspect, dye penetrant is very easy to do.
 

William_H

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Some measurement of dimensions of the chain plates and other fittings will allow you to work out a cross sectional area of the material perpendicular to the load or most likely failure path. Check in worst case where holes are drilled. My theory is that most chain plates etc will be many times the area dimensions of the wire and of the threaded part of bottle screws. This factor should provide enough confidence to you and the insurance company of the likely integrity of the fittings. Yes Dye Penetrant NDT could be used if you have doubts but the mark one eyeball is still considered the first practical NDT method. ol'will
 

rotrax

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Jerry the Rigger from Gosport gave our winter talks club a good and practical couple of hours a few years ago. During it he told us about some of the horrors he had found over the years. One recurring fault was the shroud top fittings that often hook into holes formed in the mast. Crevice corrosion/fatigue cracks on the underneath part- the ones out of sight. Also severe wear and cracks in boom mainsheet fixings. As well as wire stranding, terminals cracking-the list is so extensive I wonder why we take the risk of going to sea...............................
 

mattonthesea

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I pulled the bolts on the backstay chainplate on my Rival 32 - presumably the originals. Out of six bolts, four of them had crevice cracks up to a third of the diameter. Still, the remaining steel in those bolts combined made up more ss than the rigging parts!
 

vyv_cox

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On the past year I have added a couple of case histories about SCC in chain plates to the website. Look under Metallurgy<SCC. Small seawater leaks can have a very damaging effect on stressed components.
 

pcatterall

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On the past year I have added a couple of case histories about SCC in chain plates to the website. Look under Metallurgy<SCC. Small seawater leaks can have a very damaging effect on stressed components.

Great stuff again, thanks for the work you put into your site. ( I always get side tracked by your other interesting topics though!!)

What I think emerges is that we should ( after 40 years) pull at least some of the chain plates, and if they look at all compromised, use some sort of NDT.
Thanks all.
 

vyv_cox

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Great stuff again, thanks for the work you put into your site. ( I always get side tracked by your other interesting topics though!!)

What I think emerges is that we should ( after 40 years) pull at least some of the chain plates, and if they look at all compromised, use some sort of NDT.
Thanks all.

Thanks for the kind words. As you will have seen, a couple of those problems were on my boat. Not disastrous but worrying. I was not aware of any leaks prior to these inspections.
 

rszemeti

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Still, the remaining steel in those bolts combined made up more ss than the rigging parts!

That isn't quite how it works ... the crack acts as a "stress concentrator" ... a perfectly smooth smaller bolt will be a lot stronger than a larger bolt with a crack in it, even of the area of remaining material is the same as the smaller bolt.
 

pcatterall

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That isn't quite how it works ... the crack acts as a "stress concentrator" ... a perfectly smooth smaller bolt will be a lot stronger than a larger bolt with a crack in it, even of the area of remaining material is the same as the smaller bolt.
And isn't the crack an opportunity for water to enter, 'loose' its O2 and start crevice corrosion?
 
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