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chain plate design change

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blue-max:
I have seen the posts regarding the weakness of the cup and ball detail of the below deck  shroud support. Rather than replace like for like I wonder if anyone has made a modification to strengthen  the support. The rod linking the deck plate to  the bracket on the hull looks very slim - I guess about 12 mm. Perhaps 16 mm would be better? Is there a way to do  away with the "link"  in the original design and have a rod from the deck plate run through the hole in hull bracket and held with a nut/nuts on the underside?     

Yngmar:
The rod has a ball head, allowing it to rotate to ensure correct alignment. Without any articulation, you're creating sheer loads that can lead to rapid failure. So if you want to replace it all, you need to have articulated fittings on the inside, same as outside. You could use a toggle and swaged eye just like outside, on either rod or wire rope to achieve this. Rod is generally neater and will last indefinitely inside (unless you leave it leaking for a long time). However, rod riggers with the right tools are hard to find and more so now that synthetic is replacing rod.

If you go with wire rope, you also need a turnbuckle to tension it correctly. The rod has simply a thread cut into one end and is tensioned with nuts against the bulkhead fitting, at least on our boat it was.

You do not need to oversize things, rod rigging is used in yachts above deck and has well documented working load limits, typically about 30% higher than 1x19 A4 wire rope of the same diameter. Bavaria has already sized them accordingly (although I think it's Selden that did the rig calculations for them).

blue-max:
Thanks for your comment which  I take to  heart. I have been keeping an eye on these below deck  fittings . There is some evidence of deck  leakage in the past (previous owner) but I have had nothing there (plenty  elsewhere!) I can't see anything on the metal that would make me anxious  but I wonder if I should replace anyway. No way to  strip  and reassemble as the threads distort. Its not just the expense but also  finding the expertise and having confidence in the outcome.

Yngmar:
I've had the shroud chainplates out twice, first time to rebed them as they were leaking and second time to replace the bolts, as one had a small crack in the head.

You will not see crevice corrosion from the outside, only if you remove the deck fittings. It's no big deal and you don't have to unstep the mast, you can support it with halyards and do one side at a time, won't even lose your rig tuning if you count the turnbuckle turns.

Once the outer part is off the inner part can be slid down for inspection/cleaning. The rods itself I didn't remove as they were dry and unaffected.

The failures I've heard of didn't occur at the rod ballhead, but at the deck fitting or bolts. One 38 Ocean owner lost his mast this way in Turkey and had quite a story to tell.

blue-max:
On FB there are more accounts of rig failure from this component. Keeps me thinking a better design is needed.

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