How tight should the standing rigging be....?

[max]

on an ageing westerly ketch? And what is the correct order of tightening? Sorry for such a basic question but I am sure I have not got the standing rigging set up right.

Many thanks in advance.

Max

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[yoda]

Max

Setting up a rig is not a straightforward thing and there will be differences depending on where the mast is stepped, what the rig is, angle of spreaders etc etc. While you may get somebody here to give you some idea I would look for a book on the subject and have a good read before you start. There have been some articles in PBO about it and worth a search through them on the web site. A better place to try may be the westerley owners web site where somebody with the same set up may be better placed to advise.

Yoda

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[AndrewB]

The question of rigging tightness has come up frequently in the past. <A target="_blank" HREF=http://www.ybw.com/cgi-bin/forums/showthreaded.pl?Cat=&Board=pbo&Number=225224>Here's a thread</A> with a number of useful tips and links to further website advice.

You may also find useful some advice I copied from an answer given by PVB in 1999, which can no longer be reached by searching:

<font color=blue>"Rigging is a bit of a black art, and I’ve never been terribly satisfied by the assurances that it’s impossible to overtension using hand tools. There are lots of books which will tell you how to tension rigging and, more importantly, set up the mast correctly. In the meantime, here’s a quick and easy answer.

"You ask whether there’s an optimum tension for stainless standing rigging, and whether there’s a method of testing which you can use to check that your rigging is about right. The answer to both is "Yes".

"Optimum tension is generally considered to be about 15% of the wire’s breaking strain for the cap shrouds; less for the lowers; and about 20% of breaking strain for the backstay on a masthead sloop. Fine, all you need now is a method of testing.

"You can buy rig tension gauges. They’re quite costly, and usually only fit a small range of wire sizes. And you may need to know the breaking strain of the wire first.

"There’s another method which costs nothing and is easy to do. It also works regardless of wire size, and you don’t need to know what the wire’s breaking strain is. It relies on the fact that a 2-metre length of wire stretches by 1mm when 5% of its breaking strain is applied (and 3mm for 15% and 4mm for 20%). It’s easier to explain with a diagram, but as we’re restricted to words, here goes...

"Assuming your mast is up and more or less in the right position, slacken off the shroud rigging screws (by equal amounts on port and starboard) and the backstay rigging screw. Take an ordinary DIY steel metric tape measure. Pull out just over 2 metres of tape. Fix the end of the tape measure to one of the cap shrouds, above head height, using sticky tape, so that the 2 metre mark on the tape measure is hanging a little way above the top of the rigging screw. Put a bit of string loosely around the tape measure and the shroud at the lower end, to hold the tape measure against the wire. Wrap a piece of masking tape around the shroud, in line with the 2 metre mark on the tape, and put a pen mark on the masking tape exactly at the 2 metre mark. Now, as you tension the rigging, you can see at a glance how much the 2 metre length of wire has stretched.

"Tighten the rigging screws (by equal amounts on port and starboard) until the pen mark on the masking tape shows a 3mm stretch (which equals 15% of the breaking strain of the wire). You only need to measure the stretch on one side of the boat, because the other side will be equally tensioned. Then tighten the lowers so they feel a bit looser than the cap shrouds, keeping an eye on the mast alignment. Then put the tape measure on the backstay and repeat the operation, using 4mm stretch to indicate 20% of the breaking strain.

"That’s your starting point. Watch the lee shrouds when you’re sailing. If they go slack, you need more tension. Purists may scoff (and probably will) but at least this method is something you can do yourself, easily and without incurring expense. My big worry is that it’s so simple it might be considered too close to the "Blue Peter" school of marine engineering!" </font color=blue>

Finally, the age of your yacht makes no difference. Some hard-used boats start to bend (hog) if the rigging is done up fully, but that shouldn't be a problem with a Westerly.

 

[max]

Many thanks.

I thought there would be more to it than just tightening up the bottle screws until the mast popped through the coachroof!

I will try the WOA site and see whether anyone with one of the 31ft ketches can give me a steer.

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[VicS]

As well as the owners assoc'n, the mast manufacturers should be able to provide guidance. I have an informative booklet published (a good few years ago now ) by what was then Kemps.



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[vyv_cox]

Here\'s one I made earlier....

Start by slackening all shrouds and stays until all feel very slack. Then, set up the forestay a few turns tighter than hand tight, with the backstay so that it is only hand tight. Any runners, checkstays or other running rigging should be slack. Haul a thin line attached to your main halyard shackle to the top of the mast and tie on a plumb bob at the level of the boom gooseneck. Thin line and a symmetrical weight will minimise the influence of any halyard stiffness or shape, especially with wire halyards. Adjust mast rake by adjusting the turnbuckles on the forestay and backstay and referring to the plumb-bob. Most cruising boats have a mast rake somewhere between upright and a few inches back. Once the desired amount of mast rake has been set, tighten the turnbuckles on both forestay and backstay one turn at a time to achieve the amount of tension you want. The tension required for these two wires is quite considerable and the wires will not move more than inch or so to a good push or pull by hand. The actual value will be determined later when sailing. Check again that the rake is as you want it.

Determine two reference points on the toe-rail, hull-mounted chain-plates or somewhere well outboard, approximately in line with the mast fore-and-aft, exactly the same distance from the mast step and of equal height. Make no assumptions about symmetry, boats can often be different on each side.
With a keel-stepped mast, centre it at the partners by measuring from the reference points and chock it fore/aft at the partners to the maximum "J" value.
Now begin to centre the masthead by measuring from the main halyard to the reference points. This can be done using the halyard itself, but stretch is difficult to estimate. One way is to use a spring balance attached to the end of the halyard to give a constant value each side, perhaps 10 kg. The best way to do it is to attach a steel tape measure to your main halyard’s headboard shackle. Hoist the halyard and extend the tape measure aloft. You can now measure the distance from the masthead to each reference point. Adjust the cap shroud turnbuckles so that you get the same measurement on both sides of the boat, ensuring that the mast is centred in the boat.
Now begin to tension both turnbuckles, keeping the mast straight up. Turn the turnbuckle barrels either one or half a turn at a time. The tension needed on the cap shrouds is almost as much as you have on the forestay/backstay. A useful guide is that they should produce a deep musical note when struck with the flat of the hand. Final adjustments will be made later.

Now sight up the mainsail luff track. Compression from the cap shrouds may well cause it to be slightly bent or bowed. Tension on the babystay will pull the mast forward, normally taking out either of these. If you have twin lowers, take up the one that will pull any sideways bow straight, then tension the other one to match. At this point, the mast should be raked the amount that you want and exactly straight up and down relative to port or starboard lean.
A decision now needs to be taken regarding pre-bend in the mast. Pre-bend has the effect of pulling some of the fullness out of the mainsail to flatten it. It is normal to have a small amount of permanent pre-bend on a masthead rig, whereas tension on the backstay of a fractional rig will apply bend when required.
Increase the tension equally on both forward lower shrouds, or the babystay, until two or three inches of bend is pulled into the middle of the mast. A normal amount is about half the mast diameter. Sight up the mast as you pre-bend it to make sure that you aren’t getting an "S" or a bow left or right.

The aft lowers balance the forward lowers or babystay, fine-tune the rig and give additional support to the mast. All you need to do with the aft lowers at this stage is tighten the turnbuckles about one turn past "finger-tight". Sight up the luff groove to make sure that the mast is still straight.
With these steps complete alongside, it’s time to set sail and make your final adjustments.

Sail the boat on a series of upwind tacks in 10-14 knots of breeze and examine the rig on each tack.. You are looking for three main points for the rig, and three more for the sails:
1. That slack in the leeward shrouds is not excessive. The wire should loosen but there should be no clearance in the swivel or other pin joints. This applies to cap and lower shrouds. If slack is excessive when hard on the wind, adjust by equal numbers of turns on each side.
2. Keep sighting up the luff groove to ensure that the mast remains in column. If the top of the mast is falling away tighten the cap shrouds, if the centre is bowing up wind loosen the lowers, if it is bowing down wind, increase tension. Increase backstay tension and check mast straightness with the added compression load. Check on both tacks.
3. Check headstay sag with maximum backstay tension. It should be no more than two to four inches for a 35 ft. boat in this wind range. If it is greater than this then tighten the headstay. If less than this, loosen it, otherwise your headstay will be too tight to provide proper power in the lighter air. Most jibs are cut with some headstay sag designed in. If you don't have an adjustable backstay, then do these tests with a moderately tight backstay
4. Pay attention to mainsail shape, especially down low, as the luff curve should be matched to the mast pre-bend. Pre bend is adjusted on a keel-stepped boat by moving the mast at the step and partners but on a deck-stepped boat be increasing babystay tension. . Make this adjustment if the mainsail is either too full or too flat in the lower third, with respect to the rest of the sail (i.e., the sail is out of balance).
5. Check helm balance with the main and jib sheeted for upwind sailing. If weather helm is excessive with the mainsail flat but not backwinded, jib sheeted in to maximum, and enough backstay on to yield about 3" of forestay sag, then you need to rake the rig forward a bit. Too little helm, or poor pointing ability, and you need to rake it aft. This adjustment is done by tightening or lengthening the forestay, perhaps three to ten turns, preferably when moored alongside. Don’t forget that changing forestay length will also change babystay tension. After doing this, again check headstay sag, mainsail shape, and rig athwartships position in 10-15 kts. If you have added rake, be sure to check that the genoa clew is not too close to the deck or the sheet lead is not too far forward to be sheeted properly.

When you get back to your berth, carry out final checks. First, verify that the relationship in tensions between the forestay/backstay and upper shrouds is still about the same. The forestay/backstay should still be slightly tighter than the cap shrouds. Next, measure the distance from masthead to toe-rails again. The measurement should be the same to both starboard and port toe-rails. Sight up the luff groove again and make sure that it forms a straight line. Make the appropriate adjustments to the turnbuckles.

With everything set correctly, secure the turnbuckles so that they won’t back themselves off and loosen the rigging. With closed barrel style turnbuckles, there is a locking nut on both bolts. Turn these nuts down to the barrel and use a small spanner to lock them tightly. With open style turnbuckles; use split-pins or seizing wire through the openings of the barrel and the small holes in the bolt ends.

Over time, there is every chance that your rig will loosen somewhat. This may be due to sailing in strong winds, changes in temperature, or combinations of other factors. Periodically check your standing rigging, at least annually, for tension and condition. Make your checks of the system both while at your berth and while sailing.
The combination of pre-band and mast rake can change the weather helm feel of the boat; the boat’s pointing ability, and the boat’s speed and efficiency through the water. So, don’t forget to check the standing rig from time to time. As your sails age and become fuller, increased mast pre-bend will help your upwind pointing ability and will decrease the amount of heel your boat develops in stronger breezes. The boat may also develop more weather helm. Reducing mast rake will improve this tendency.


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[saturn]

max, i got hold of a book, sail and rig tuning by ivar dedekam which i found really useful(fernhurst books).

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[max]

Re: May thanks to all

for the detailed and thoughtful advice. Now feel able to begin to tackle the'black art'

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[Jake]

Hi Max

Just to let you know that PBO will be having a 'standing rigging' skippers check-card in the next issue, written by a very experienced rigger, and well illustrated by the PBO art team. In the same issue is a Spring fit-out feature on rigging maintenance generally, written by another professional rigger. Hope this will add to the rich seam of material already posted by other forum users!

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[max]

Jake,

Thanks. I look forward to my copy dropping through the letterbox with greater than usual anticipation.

Incidentally, I like the evolving format - is this down to Sarah?

Max

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[tome]

Excellent book - well illustrated and simple to follow. I just set up my rigging following the step by step instructions and it's made a big difference, especially in windward performance in a stiff breeze.

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