Spreaders and shrouds

[joe17]

I just had my spreaders replaced because the old ones were a mess.

Now I come to think about putting the rig back up I have a question. Should the shrouds be free to move in the spreader tips or should they be fixed in place?

The shrouds of the old spreaders were effectively fixed by a ball of ancient insulation tape.



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[qsiv]

I'd say fixed... if they can move you run the risk of them being flexed up or down and effectively slackening the shroud. With a small boat, and light rigging load it probably isnt critical - but you'd never want a bigger boat allowing such movement.

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[yoda]

The shrouds need to be free to move across the spreader tip but prevented from jumping out while setting up the rig. Mine are wired on with siezing wire so they can do this and once the rig is set up you can put some form of protection on the end to prevent chaffing.

Yoda

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[joe17]

Re: How to know where to fix them?

If they are fixed then how will I know at which point to fix them?

Should I set up the rig and get the correct tension on the shrouds and then fix the shrouds at the spreader tips?

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[nodder]

Surely if you fix the shrouds to the spreaders, then when you tension the shrouds the loading will tend to be put on the spreader rather than to the mast , then you will be pulling down on the spreaders causing them to bend. So i would say they need to be able to slide in the spreader ends and then as previous writer says wired and capped.

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[qsiv]

Re: How to know where to fix them?

Conventional wisdom is to bisect the angle. You will almost certainly need to fix them after setting up the rig (unless you have a very good idea where they should fixed first).

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[jimi]

Have a look at <A target="_blank" HREF=http://www.glen-l.com/weblettr/webletters-2/webltr16b.html>Spreaders</A> this suggests they should be free to move but with a fitting to ensure they do'nt fall off

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[qsiv]

But only if they were initially fixed at the wrong angle.

I'd argue the best example is that most larger boats (even mine) have discontinuous rigging (for weight reasons). In that case the shrouds are absolutely fixed at the spreader tips and can never, ever move, unless there is a breakage.

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[nodder]

As the boat in question is not a big boat but a 17' trailer sailer, unless you can tension the shrouds to the exact same degree every time you set up the rig, then .the shrouds surely need to be able to slide

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[PeterGibbs]

There should be a fixture at the end of each spreader to firmly secure the shroud. No movement whatever is the rule. If no fixture go see a rigger and get the necessary clamps.

Spreaders must be clamped at an angle to bisect the line formed by the shroud - normally about 5-6 degrees sloping up from the level. This spreads the load and makes the rig more secure under load.

PWG

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[oldharry]

The function of the spreaders is to support the centre of the mast to stop it curving under load. To acheive this the spreader must be able to transfer the compression load along its axis, and the compression load at the outer end must be at right angles to the spreader. This means the angles between the upper and lower portions of the shroud wires and the spreader must be the same for the spreaders to function correctly.

To understand this take a drinking straw, stand it vertically on a flat surface and try to compress it vertically down. Now do the same, holding the bottom in place but applying pressure to the top at an angle - it fails much more quickly.

On a trailer sailer where the mast is being taken down regularly, it is important to ensure the angle is correct each time, and the only way to acheive this is to secure the wire at the correct point. In my experience most trailer sailer spreaders are fairly loose in their brackets for easy dismantling, so it is important to have them pre-set so they are right each time.

Modern rigging wires have very little stretch in them unless they are grossly overloaded, so there is no need to allow movement - in fact allowing the spreader to move is more likely to cause failure as there is risk of work hardening the wire as it flexes across the angle at the end of the spreader.

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[Porthandbuoy]

Ensure the spreaders bisect the angle and are fixed at the shroud ends. On a trailer-sailer, where the mast will be raised and lowered more than the norm, allow some articulation at the spreader socket. This will ensure the spreaders return to the same angle every time you set up the rigging.
On no account use a "big ball of tape" to secure the spreaders. Take away access to oxygen and st/st will corrode, and down will come mast and spreaders and all!

Fair winds

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[joe17]

An answer from a rigger

Thanks for the answers.

A local rigger just told me that the shrouds should be fixed at the spreader tips.

He said the way they do it is to pull the shroud tight down the side of the mast and mark the shroud where it is level with the mast/spreader bracket. Then the shroud should be fixed to the spreader tip at the point marked.

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