Setting up a cutter rig

[andybussell]

I recently bought a cutter-rigged Barbican 33 and would like advice on the rig set up procedure please, my last boat only had 7 bits of wire to fiddle with, this one has 11:

7 mm: forestay, backstay (at the stern) and cap shrouds,

6 mm: lower shrouds (2 on each side), a backstay on each side about 9" aft of the aftmost lower shroud, and an inner forestay.

Both forestays have roller furling.

I've got a tension meter. Advice from those with experience would be appreciated, in particular should there be any fore-and-aft bend?

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[bruce]

thought appears to be tension lowers (inner) first, upper shrouds second, about 10% of advertized working strength of cable, would not bend mast till sails are up and show need. could ask builder, if still around. fair winds...

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[Rick]

Hi Andy, and congrats on new purchase.

Bruce is on the money - static load of between 10 and 15% is the starting point. I'd suggest however you get hold of a good work on the subject - my favourite is "The Riggers Apprentice" by Brion Toss.

I'm a little unclear about your description however regarding the 'backstays 9 inches behind the aft lowers' - these wires run from chain plate to masthead without passing over any spreaders? If yes, do you know if the boat was rigged professionally? If not, are they running only to the height of the inner forestay, which presumably is above spreader / lowers attachment? I ask as those wires don't seem to make sense if they're attached to the masthead.

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[William_H]

Bruce and Rick this concept of setting up static rigging tension to 10 to 15% of rated max working load of the wire really worries me. If someone has deliberately over designed the rig with larger than necessary rigging wire you would end up with excessive static load on the rig. I could accept a figure of 10% of max working load of the wire (Not the manufacturers max working load rating) but the actual load under sail. It would however be difficult to measure that load. You would have to measure the forestay and sidestays when the boat is at max heal sails hard on beating to windward while you would have to measure the backstay load under full pressure of a large spinnacher while running in a strong breeze. Excessive load may distort the hull mast and fittings. At 15%v of max safe working load of 7mm cable you could end up with something like 500kg static load surely that is too much.
Can anyone please explain where I am wrong?

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[Rick]

Will,

I suspect we'll have to agree to differ, but I'm of the school that firmly believes the figures the engineers give us - the correct static load for a stainless steel wire holding a mast up is unlikely to ever be less than 10% of the ultimate strength of the wire. This is largely a function of the amount of work the wire would be doing (and resultant fatigue) if it had less load than that.

I hear what you say about oversized wire, but according to my designer friends, that's not over design, it's bad design. If the rigging wire is heavier than it needs to be, it still needs 10+% static, but the mast needs to be thicker to withstand the compressive load, and the hull needs to be stronger to withstand the force, which makes everything heavier, that'll need an even bigger rig to drive it ........

Wire size calcs are published in various books (like Skene's 'Elements of Yacht Design'). There are literally hundreds of thousands of boats sailing around with wire sizes that would fit into the calculated results of such authors, apparently without any trouble. Rigs certainly fail, but almost always a maintenance program would have picked it up before it occured.

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[andybussell]

Hello Rick,

Thanks for the help. The lateral backstays connect with the mast close to the inner forestay. I spoke to a rigger who recommended adjusting the lowers and cap shrouds first for lateral set up, then the backstay + forestay, finally the inner forestay + lateral backstays

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[bruce]

i must say one thing, having moved up one size in shrouds/stays, i still tighten to the old value because of the loading on the mast.

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[Rick]

Hi again Andy,
That makes a lot more sense - those wires are then opposing the forward pull of the staysail when it's flown.
What values are you going to use for your static tuning?


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[andybussell]

Hello Rick,

I'll go for the 10% for starters which is what I always used with the simpler masthead sloop rig on my earlier boat. I agree with earlier worries about over-specified wire and agree that overspecified means badly designed.

After static set up I will see if the lee wires go slack at less than 20 degrees heel before tightening up further, and will look at the mailsail shape before building in any pre-bend.

Many thanks to you and all others who have commented.

Regards .............. Andy

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[johnsomerhausen]

To answer William´s cioncern about distorting the hull, heree´s the method I used to make sure that I wasn´t deforming my hull when tensioning the fore and backtsays: I tied a nylon fishing to the pulpit at its center and ran it down over the pushìt" at the stern and then attached a weigth to the line. At the point where it touched the mast, I stuck a piece of adhesive tape. After I had taken up the slack on the backstay rigging screw, I would check whether the tape was moving in relationship to the fishing line. As long as it didn´t, I knew tdhe hull was not being deformed.
These "backstays" thgat are 9" behind the mast are the "runneres" (runbning backstays" (runners for short) which certainly have another belaying point further aft and a tackle to put tension in the one that´s used (the weather one). If you scrounge around the boat, yopu shopuld be able to find two 4 to 1 tackles which are meant for that purpose; if not, you´ll have to buy them....
john

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[andybussell]

Hello John,

I don't think they are runners, no sign of any such tackle, and I did look on taking over the boat. They go to fixed chainplates via bottlescrews. I should say the staysail is a rather small blade sail. My view is it is probably best used to windward and rolled when reaching in any breeze.

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