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God, not this again.

Rigs aren't tuned by hitting some number on a loose gague. They just aren't. The ideal mast tune is set by having the mast perfectly in colume at the current wind speed and sail selection, with the proper forestay tension, and mast bend.

That's the goal. Period.


But just a FYI if you are carrying 30% of the shrouds MBL then you are way past the max design load of most standing rigging. The normal safety margin is 5:1, so the max load most shrouds are designed to is 20%. Past this you start doing fun stuff like bending the hull, causig the deck to pop off, ripping chainplates thru the deck, ect.

 

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Rich,

My J-22 had tune setting that ranged between 135 and 467lbs depending on the wind. On 5/32 304 1x19 wire (3300lbs MBL). So our tuned settings ranged from 5% to 14% on the nominal MBL of the wire. Sure 12% falls inside that range, but so do a lot of other numbers. And getting enough tension on the wire is only the last step in a process of getting the mast tuned properly.

 

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You don't tune the leeward side at all. Period. Don't. Even if they are slapping around like wet noodles you don't tighten the leeward shrouds. If it gets really bad a piece of bungee cord to keep them from hitting things is fine. But if the shrouds are this lightly loaded cycle loading is not an issue.

The correlary however is that if your leeward shrouds are this loose it likely means that the windward side shrouds are too loose and need to be snugged up.

 

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Cope,

I have never sailed a Catalina 22, so I have no direct information to impart. But to answer a few questions...

1) this is the North sails tuning guide for your boat. http://www.onedesign.com/Portals/106/docs/Tuning Guides/north-catalina22-tuningguide.pdf it is a really good place to start.

2)The reasons it doesn't matter if the leeward shrouds are loose is that they really aren't. Starting with the mast in column at the dock, and the shrouds snug. When you put up the sails the shrouds don't change leingth, but the leeward shrouds start to loosen. This is because the mast has fallen off to leeward and is no longer where it should be. The problem isn't that the leeward shrouds are to long, but that the windward shrouds are. So you need to tighten the windward shrouds until the mast is back in column.

The easiest way to do this is to tack the boat and tighten up the now leeward shrouds a bit then tack back over and see what happened. This gets a little confusing, and is why many people seem to think you tighten the leeward shrouds. Technically you do (since they are the leeward shrouds during the brief moments you are adjusting them), but you decide how much to tighten them while they are the windward ones.

3) the reason it doesn't matter how loose the leeward shrouds are is that... Well they really don't do anything. It is quite possible to take the leeward shrouds off the boat (not a good idea however). And for some extreme boats it has actually been contemplated while doing things like the transpac where you are on starboard tack for weeks at a time to reduce windage.

It is never a good idea to have things just bouncing around, but in reality if the shrouds are properly tightened for the conditions the leeward shrouds shouldn't be much looser than they were at the dock since the mast is in the same place. Excluding times in very light air where you don't need any pressure on some shrouds (J-22 in <3kn of breeze for instance).

4) the rig won't slam over, what happens is as the mast moves back to centerline the shrouds equalize pressure and transfer the load. If the mast doesn't move relative to the boat then there is no slamming. If it does then the windward shrouds were too loose, not the leeward ones.

 

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For the sake of simplicity let's talk about port and starboard instead of using windward and leeward for a moment. And keep in mind that it is always better to have looser shrouds than tighter (or generally so) for a lot of reasons including sail shape, equipment durability, pressure on the boat, ect.

The order of tuning a mast is to
1) get the mast step in the right place. Fore and aft then side to side (actually the order doesn't matter I just like doing it this way.
2) get the mast centered side to side in the partners. And properly set for and aft
3) set the forestay length
4) get the mast in column with correct prebend.
5) go sailing in 8-10kn of breeze.
6) this is the tricky bit...

6a) While on starboard (wind coming from the starboard side) tack take a look up the mast and see how much the mast is falling off to port and guess how much the starboard shrouds need adjusting.
6b) Tack
6c) Adjust the starboard side shrouds
6d) tack
6e) repeat 6a-6d

Congratulations you now have gotten the gross tune for the starboard side set correctly.

7) Back at the dock (or just take down the sails in calm water) use a loose gague to measure what the starboard side shrouds are set at. Then duplicate the settings on the port side. Now reset the starboard side to the old settings (when you reset the port shrouds the starboard will tighten up a bit). And keep working the shrouds back and forth until you get both sides set at the original starboard side numbers.

8) These are gross numbers, and have you in the right ball park, but you have to redo steps 6a-6d again. The pressure of the port shrouds change this a little (how much depends on the boat).

9) repeat step 7

You can continue doing this cycle as many times as you want, but eventually the changes become pretty small and it isn't worth messing about anymore. I typically find two cycles thru the process enough for cruising, but for race boats you can get as finicky as you want.

Keep in mind that these are only the proper settings for this wind speed, higher breeze adds more side load to the mast so more tension is required, while lighter wind allows looser settings.

For a cruiser it is perfectly fine to get set up for your normal wind conditions and leave it at that, racers get pretty precise about it, with different tuning numbers for every wind speed and wave conditions. This can make a substantial difference in upwind performance even on a small boat, but it isn't structurally necessary so long as you don't use light wind tuning numbers when it is howling.


Oh it's always worth tacking over to port at the end just to double check everything, but if you have done everything properly it actually isn't necessary.

 

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Any typical mast, not originally intended for radical 'mast bending', should have only a ~3/4" pre-bend for a single spreader rig. If a multi-spreader rig, should only have 1/2" pre-bend for each spreader set.

Are you talking pre-bend here to increase mast stiffness? .... or are you mast bending to radically reduce mainsail draft/flatten?

This is nonsense. Every boat has its own prefered amount of prebend, and it has nothing to do with the number of shrouds. You might be able to argue that it has something to do with mast leingth, but even that isn't really the case.

I couldn't find a different link for the North Tuning Guide for the Catalina 22, but this is from that...

The mast rake is probably the single most important element of tuning your boat. Note the mast rake should vary from fixed to swing keels with swing keels having slightly less rake.

Start with boat sitting on its lines in the water. Hang a weight from the end of the main halyard and cleat off halyard with weight and shackle 12" below the boom. Measure distance from the aft face of the mast to where the halyard crosses the boom. This measurement should be 8" for fixed keels, 6-7" for swing keels. Adjust the headstay turnbuckle to achieve desired measurement.

Tighten backstay until snug, no slack. Remove weight from halyard, attach a tape measure to halyard and haul to top of mast. Measure from side to side tightening or loosening upper shrouds until mast is centered.

Now start tightening upper shrouds until they have show 28 on the gauge. Tighten forward lowers until they show 24 on the gauge. Tighten aft lowers until they are 24 on the gauge too. To measure shroud tension use a Loos Model A Tension Gauge. The end result here is to have the mast straight fore and aft with a small amount of rake to give the boat some "bite" upwind.

 

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Christian, that was a direct quote from the North Sails Catalina 22 tuning guide. Which means it was probably written by Chris Snow who if I remember correctly is a multi time Catalina 22 world champion. While you may dispute my process, I doubt there are many people in the world better qualified to discuss the proper way to tune a Catalina 22 than the North Sails OD experts.


Christian,

I think you and I are pretty much in agreement. I am not sure exactly where the conflict is to be honest. If you think I am lumping you in with those who tune rigs incorrectly then I appologize. I don't think that is the case.

 

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John,

How precise do you want to be?

I generally just do it by eye, but there are better ways, it just takes a bit of equipment.

For the big boat I used to work on we used a jib with a laser line. We set the jig on the boat in the centerline of the boat, and could shoot a sight line up the mast right down the center of the rig. This allowed micro adjustments even on a 115' tall mast to get it as precise as possible.

More simply you can just use a spare halyard to measure the distance from the top of the mast to known points on the boat. If you are doing this you need to create an offset if the halyard doesn't exit the mast from the dead center of the boat. Most spinnaker halyards for instance are slightly favored to either port or starboard and this needs to be taken into account.

 

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. It seems to me that if the mast is "in column" at the slip, then it would have to be the same when sailing (even though that column is at an angle) and that the looseness of the shrouds comes only from hull flex, which would not necessitate adjustment to the shroud tension as that would take the mast "out of column" when the stresses are removed.
John

Not at all. Systems are only static while they are in fact static. We tend to think of masts and rigging as being static because in normal conditions it is a little odd to think of steel and aluminum stretching. But under the loads expected and the length involved there is a substantial amount of stretch that is expected.

Just a quick run thru the numbers using a Pearson 28 as an example. The upper shrouds are 1/4" 1x19 wire 38' 6.5" long. The tuning guide indicates 700lbs on the upper shrouds.

The in/in/1000lbs stretch for 3/16" 1x19 wire is 0.0013059.

So the length in inches is 38*12=456+6.5= 462.5"

Just from the static load expected then the wire has already stretched...

462.5 * (700/1000) * 0.0013059 = .422 inches.

 

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Instead of a laser pointer I use a laser level from lowes. It projects a line from the base of the mast to the top. It's bright enough to see in the middle of the day, but gets squirmy with some polarized sunglasses.