Ketch rigging tune up

ghostlymoron

ghostlymoron

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I've used the search facility and also googled but can find no really helpful info on tuning the rigging on a ketch. Do you tune each mast seperately? How much tension on the triatic stay? Presumably the triatic doesn't take much load if the others are properly tensioned. I believe the caps should be tensioned to 15% breaking strain or 2mm per 2 m of length. I hope we're not going to pull the chain plates off!
 
ghostlymoron said:
I've used the search facility and also googled but can find no really helpful info on tuning the rigging on a ketch. Do you tune each mast seperately? How much tension on the triatic stay? Presumably the triatic doesn't take much load if the others are properly tensioned. I believe the caps should be tensioned to 15% breaking strain or 2mm per 2 m of length. I hope we're not going to pull the chain plates off!
Click to expand...

15% is 3mm/2m think you will find .
 
I had this question three years ago?

Do you 'really' need a a triatic. does your mizzen have substantial back stays to assist in any forward pull of the main?

It was suggested my two different riggers that they are a throwback to an earlier time when the triatic formed part of the fore and aft stiffening of the masts. I was also told that with a triatic fitted, if the main came down in a blow, it will surely clear the mizzen away as well. As was proved three years ago outside Cowes (during Cowes Week). It was a famous named large yacht but I cannot remember the name.

A triatic location twixt main and mizzen can also be a very fine place for a horizontal MF/HF antenna. ;)

I do not now have a triatic on my 50 foot ketch. ;)


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Triatic stay - depends on a rig configuration; there are many ways to rig a mizzen but this usually doesn't need to be set taut.

Tune the masts as if they are separate, then adjust the triatic. You do not want mainmast to pull the mizzen usually. Just imagine the loads in rig (I don't want to say wrongly not knowing your setup) and how those will be counteracted by wires.

All those "tension measurements" and "required pre-loads" are rubbish.
Depends on mast section, wire characteristics, boat displacement, stability, hull stiffness - on some new boats you could pull the hull a foot by chainplates while applying "recommended tension"... :o
Best way is to sail and observe what the rig is doing really.
Yes, I got a 500 pages book on rigs and tuning methods, still think it rubbish. Most theories on rig loads are based on wrong presumptions, and best calculation method I know comes from aircraft designer - finally results in "see for yourself to be sure" advice...

So see for yourself. :p
Put some tension initially in the rig, sail the boat - you want lee rigging to stay taut until the boat is overcanvassed and heeled too much - mast staying straight even then, when lee wires get slack. They should get slack all at the same time.
Fore and aft - mast not bending much, forestay taut enough when full drive is provided from foresail - and how much is enough, how a forestay should deflect to leeward depends on foresail cut. So you will see on foresail luff if this is too much or not.
When this is set on backstay - mizzen should not be pulled forward by triatic. Triatic stay is there to prevent breaking the mizzenmast, that is all.
 
We had a ketch and used to tighten the rigging so that there was no slack on the leeward side when beating, it's impossible to break the rigging with a spanner. The triatic stay should be tight and not bending the mizzen mast forward.
 
I would love to be able to do away with my triatic stay, but without it there wouldn't be enough support from forrard to counteract the mizzen sheet tension when going to windward. Any forestay(s) from the head of the mizzen would foul the main boom.
I set up the rigging on each mast independently, and just have the triatic not slack.
 
On most ketches i would say that the triatic is neccesary but not vital. What i do is put a 'fuse' in it (small tested shackle or line) so that if put under huge load by mainmast falling it will snap.

I completely agree that rig guages are cock of the poppiest variety. No substitute for experience. Upwind leeward rigging tension is definitely a good indication.
 
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