Should I Worry About this Mast Tang?

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Trident

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Small cracks on the lower stay tangs just below the spreaders - I've ordered in material (4mm 316 stainless) to make new ones but a rigger said its not urgent ... should I believe him ?

It should be noted there are no corresponding cracks on the "back) of this tang in the same place so they are not all the way through but I have no idea how far they go .

IMG_9820.JPG
 
That would worry me.
Zooming in shows a bit of brown discolouration too, which adds to the worry.
This reminds me to examine mine before the mast goes back up!
PS, the Nylock nut on the through bolt is also Donald Ducked if you hadn't noticed.....
 
Prime example of low cycle fatigue, emanating from inherent stress points.
Would suggest that you don’t do the next Vendee Globe until you’ve carried out your proposed repair.

Mike
 
Rum Run said:
That would worry me.
Zooming in shows a bit of brown discolouration too, which adds to the worry.
This reminds me to examine mine before the mast goes back up!
PS, the Nylock nut on the through bolt is also Donald Ducked if you hadn't noticed.....
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Yes I had noticed thanks and as it’s imperial and I need new ones on both sides and of course new thread too - all in A 4 stainless- it’s about £120 just for the fixings! If I’m lucky, the mast compression tube will let me use modern 16mm instead at about 1/3 the cost!
 
mikegunn said:
Prime example of low cycle fatigue, emanating from inherent stress points.
Would suggest that you don’t do the next Vendee Globe until you’ve carried out your proposed repair.

Mike
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Yes, I’ll leave the blue water stuff for a while- hopefully I’ll have the bar stock in a few days and can get bending and drilling as soon as it arrives . These are 41 this year and survived two Cat 5 hurricanes so not doing too badly really .
 
I can't see from the photo but I'm wondering if the crack has been caused by the terminal eye being wider than the gap between the tangs, and forcing them apart when it was pushed in.
 
Poignard said:
I can't see from the photo but I'm wondering if the crack has been caused by the terminal eye being wider than the gap between the tangs, and forcing them apart when it was pushed in.
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You might be right - the rigger who replaced the wire told me no new mast fittings were needed (which I should have ignored given the age but trusted his opinion) - but the eye fittings he put in do look tight in there - I'll add an extra 1mm on the gap between the new plates to be safe.
 
One question for everyone here: do the two leaves of the fitting actually need to be welded together as in the picture? I don't think it adds strength and might localise stresses so making a crack more likely. Sealing between the two could be Duralac or Tefgel maybe.
 
Trident said:
Yes I had noticed thanks and as it’s imperial and I need new ones on both sides and of course new thread too - all in A 4 stainless- it’s about £120 just for the fixings! If I’m lucky, the mast compression tube will let me use modern 16mm instead at about 1/3 the cost!
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Wow, that's a lot for studding and two nuts. Presumably you are not in the UK?
 
Rum Run said:
One question for everyone here: do the two leaves of the fitting actually need to be welded together as in the picture? I don't think it adds strength and might localise stresses so making a crack more likely. Sealing between the two could be Duralac or Tefgel maybe.
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My plan is not to weld for that very reason - they’re bolted together at the top with a big old nut so there is no need
 
just one point. I think it desirable that the tangs be able to move fore and aft ie swing on the through bolt so they can align themselves perfectly with the load. Any clamp up might induce the cracking over time. So the nylock nut with safety wire might indicate it is not done up too tight. ol'will
 
I wouldn't be happy if it was a tang in my rigging.
It also looks to me that the clevis pin is wrongly sized - its diameter is smaller than the hole in the tang through which it passes
 
dansaskip said:
I wouldn't be happy if it was a tang in my rigging.
It also looks to me that the clevis pin is wrongly sized - its diameter is smaller than the hole in the tang through which it passes
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Also, the marks on the innermost tang suggest the diameter of the hole in the terminal eye may be much greater than the diameter of the clevis pin, enabling the terminal eye to move up and down.

Perhaps larger diameter rigging wire than originally specified has been fitted at some stage, with consequent increase in the dimensions of the rigging terminals, ie too thick and hole too large.
 
Poignard said:
Also, the marks on the innermost tang suggest the diameter of the hole in the terminal eye may be much greater than the diameter of the clevis pin, enabling the terminal eye to move up and down.

Perhaps larger diameter rigging wire than originally specified has been fitted at some stage, with consequent increase in the dimensions of the rigging terminals, ie too thick and hole too large.
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I’d decided a bigger fitting previously had caused them - certainly the current fitting cannot move on the pin
 
Trident said:
I’d decided a bigger fitting previously had caused them - certainly the current fitting cannot move on the pin
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Yes, I can see some wear inside the fitting that suggests something bigger than the terminal that is currently there. It may well be that the cracks were caused by forcing something larger in there. Poor welds may be contributors. They do not look like fatigue cracks to me; cracks on both arms would be most unlikely with this mechanism.
 
I think the original fitting had a bigger head but was narrower in section and the new fitting has been pushed in to a space slightly too tight … I suspect if when made they’d not ground all the weld back where the plates joined that the issue wouldn’t have occurred ?

Cracks are only one side of each tang as far as can be seen .
 
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