Standing rigging question - SailNet Community
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post #1 of 18 Old 09-17-2015 Thread Starter
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Standing rigging question

I am about to change out original 1978 rigging on my bombay pilot 31. I will be using a rigger to get the work done. But before we start I want to make sure we have a solid foundation in terms of chain plates and mast base. While both of those issues look good to my eye I still have a question. The current rigging shows all connections bottomed out at the turnbuckles. In other words there is no room left to tighten. So the new rigging will have to be made shorter in order to get rigging tight. But what would cause rigging to bottom out? Does this point to a potential mast or chainplate issue or is it common for stays to lengthen/stretch from use and age? if so over time can it sufficiently stretch as to bottom out any adjustment?

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post #2 of 18 Old 09-17-2015
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Re: Standing rigging question

Some reasons for turnbuckles to be bottomed out:

1. Mast butt / step (either deck stepped or keel stepped) has corroded away. (Mast no longer at original length dimension).
2. Mast was replaced, not rigging.
3. Rigging was often stressed past the 'yield' value of the material. Rigging is stretched.
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post #3 of 18 Old 09-17-2015
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Re: Standing rigging question

It could also be that the chainplates have been pulled out of the deck. Honestly on a 30+ year old rig I would probably pull everything and at a minimum do some non-destructive testing. It's likely not much more to just replace everything though.

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post #4 of 18 Old 09-17-2015
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Rich said it. You need to know why the rigging settled. Hopefully it's as simple as aged, stretched rigging that was just tuned over time.
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post #5 of 18 Old 09-17-2015
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Re: Standing rigging question

If it's a deck stepped mast, you may also have a deck sag (entire deck, not just cabin top), which lowers the mast height. I would look very closely at your mast support structure. You have to properly transfer the load from under the mast to keel.

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post #6 of 18 Old 09-17-2015
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Re: Standing rigging question

No expert by an means but what Krisscross says makes sense. Other wise that is a lot of "stretch" distance that would have been taken up, if it were chainplates I think you would notice they had pulled by that amount.
We have to be talking inches here, not just a few fractions.
And the fact that it is all the turnbuckles that are bottomed out?
Needs to be looked at, sounds kind of serious to me thinking about the whole picture.
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post #7 of 18 Old 09-17-2015
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Out of curiosity, why was the original rigging standing for so long? Has the mast been dropped for storage or maintenance? Has it been in storage? Has the rigging been inspected? I'm hoping it's something simple.
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post #8 of 18 Old 09-17-2015
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Re: Standing rigging question

For ALL the turnbuckles to be 'bottomed', Id look carefully for a single cause: mast butt corroded away, mast step plate corroded away, sagging mast base support (sagging coach roof, deformed compression post, or keel/shoe) to have changed dimensions. Forensically, It would be pretty rare for all the standing rigging to have 'yielded' (stretched) that 'uniformly'; hence, suggestive of a singular cause.
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post #9 of 18 Old 09-17-2015
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Re: Standing rigging question

Quote:
Originally Posted by RichH View Post
For ALL the turnbuckles to be 'bottomed', I'd look carefully for a single cause:
Or they were simply built the wrong length? Remember this the marine industry that is famously unable to do much of anything consistently right. Easily could have come from the factory with too long wire...

When you write "all" do you include the stays, or only the shrouds? A shrinking mast or failing mast step will affect the stays less than the shrouds (by about 30%). Failing chain plates will not affect the stays at all.

Pretty simple to see mast or chainplates issues of this magnitude.

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post #10 of 18 Old 09-17-2015
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Re: Standing rigging question

For all or almost all turnbuckles to be bottomed out, on a boat that size and assuming 3" (76mm) turnbuckles (or 1.5" / 38mm displacement from the 'middle') that 38mm deflection of 'permanent stretch' would translate to (from http://www.riggingandsails.com/pdf/selden-tuning.pdf P29) 5% strain per millimeter change (elongation) per each 2 meters of wire length ....... Approx./SWAG = 5 X 38 = 190% stress .... which is functionally impossible; therefore, there most likely has been a dimensional change in the 'base structure' that is supporting that wire rigging and/or mast.

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