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Old 18-10-2009, 13:08   #1
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Catamaran Rig Tension

We have a Voyage 440 cat, 5 years old. Have just found a broken strand on the baby stay. I'm in the process of replacing it and wondering about rig tension. When we are at anchor and the wind is blowing 25+, the mast sometimes starts to pump. When we are sailing the leeward shrouds seem quite loose. Does anyone have suggestions for appropriate rig tensions (I've checked the owner's manual - nothing).
While on the subject of cat rigging, does anyone have thoughts about the advisability of flying the genoa or spinnaker without the main? We've been flying the chute without the main up for the past year in winds to 18 apparent and so far no problems (nice not to have to worry about jibing the main). But maybe its stretched our shrouds and that's why we they are now loose...? Any advice welcome.
Derek Gale
s/v idyll Island

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Old 18-10-2009, 15:52   #2
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The further south you go the faster your rigging ages.

Mast pumping is bad. Fix it.

Leeward shrouds should not flop around. If mine bow more than a couple inches in a 12 knot breeze when I lean on them, they need to be taken up.

Forestay tension is particularly difficult when you don't have a backstay to tighten, but a sagging genoa won't point as high as one on a tight forestay.

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Old 19-10-2009, 09:01   #3
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Stay tension at rest is what you are asking about. I tighten mine as hard as I can using an 10" spanner (wrench) on my 35 footer.

Uner load I have plenty of slack on the unloaded side, this depends on the stregth of the wire, rig loads and hull stiffness, so while Sandys boat is not that big and probably stiffer than most, his way might not work for you.

I retighten my stays whenever they get a bit slack at rest.

I have now converted to Dynex Dux all over, rather than stainless steel. Check out Colligo Marine. This will save you weight aloft which is always good. Just use your winch to tighten when required. Fewer bits to fail and therefore safer....

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Old 22-10-2009, 08:06   #4

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Different boat, but it may help. This is the procedure I use on my Catalac.

Catalac 8M Rigging Tune
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Old 22-10-2009, 14:01   #5
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The leward stay on our Belize 43 is always nearly tight and never flaps around even in winds of more than 40 knots. We have owned the boat for two and a half years and have never done any changes to the set up since.

When running the spinnaker only I taighten the mainsheet tight using the boom topping lift as a backstay, works a treat.

When I was crewing on a 36' cat in Perth Australia and I could not tighten the stays because the entire boat would flex! So we always had flapping leward stays. This was a mast with three stays and no diamonds.

I strongly advise to get spcialist advice before tensioning up the rig hard to avoid hull/bridgedeck connections damage.

Happy lead free sailin'
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Old 23-10-2009, 13:36   #6
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I am not sure about your rigging but I assume (from memory) that you have a fractional rig, with aft-swept spreaders, no backstay but two fixed "runners" or normal runners.

First thing to check is if your mast is centered. Take the main halyard to the toerail and adjust it so that it just touches a reference point (stanchion). Now take it to the other side and compare. There's a little difference when your halyard is on a masthead sheave that isn't centered at the masthead.

Next thing is the tension on the capshrouds, which also act as backstay. For your rig, they must be tensioned to 20% of their breaking strength. You do that by measuring their stretch on a 2-meter section. I explained that in detail in another thread on this forum, use the search function to find it.

(a fractional rig needs 15% of breaking strength tension but if you have aft-swept spreaders, regardless of fractional or not, you need 20%).

Your baby stay attaches to where the lower spreader is? I find that strange because you wouldn't need it in that case (the aft swept spreader pushes the mast forward instead) so I guess maybe you don't have spreaders where the baby stay attaches. But the fact that a strand broke there, plus the lack of tension on the leeward shrouds under sail point to too little capshroud tension.

You need the runners when you fly a spinnaker/genoa only. If you have the fixed runners you are fine. Tension the runners for mast bend and fore-stay sway.

If you have intermediates: you pretension those to tight while looking up the mast-track so that the mast is straight. Final tensioning is done under sail by tensioning the leeward one to tight while counting the number of turns. Tack the boat and do the same number of turns on the other side.

The lowers can be trouble. These are probably the same size wire as the capshrouds and should also be tensioned to 20% of their breaking strength. If you tension them, you change the tension on the capshrouds too, plus you might not be able to tension them enough. The trick is to loosen the capshrouds again and tension the lowers more and re-tension the capshrouds again and check everything and repeat if needed. You can use a runner to help you tensioning the capshrouds.

The forestay isn't tuned for tension but for mast-rake only. You tension it with the capshrouds and runners.

there's a good little book from one Mr. Dedekam (?). I mention it in the other thread also, incl. ISBN number.


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