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Old 18-10-2015, 21:57   #1
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Rig tension

Hi there, I'm hoping to get advice on tension for rig on my 22 ft trailer sailer. It's got upper stays, lower stays, aft swept spreaders and no backstay.
I've read around on the internet and the information seems inconsistent with original rig tune notes that come with boat. All the advice on the net seems to suggest firm tension ie. 20% break strain on on uppers and a little give on the lowers, stays should still be firm on leeward when sailing. The original notes suggest a more loose arrangement ie. forestay sag normal, sag on leeward stays when sailing, 3 inch play on lower stays when at rest.
I find it a bit confusing to say the least, as I can see how a loose rig could over stress stuff in a stiff breeze and bumpy sea.
Any tips or advice is most appreciated as I'm fairly new to sailing and I really would like to avoid any catastrophes with rigging.

Thanks

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Old 18-10-2015, 23:34   #2
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Re: Rig tension

Use the tuning guide specific to your boat until you are ready to custom tune the rig.
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Old 19-10-2015, 02:15   #3
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Re: Rig tension

I can't see sailing with such a loose rig either, despite what the manual says.
You might invest in a Loos Gauge, which lets you accurately measure stay tension, & aim for the numbers which you mentioned, or a bit under. However, you'll need to keep an eye out for the signs of an overtensioned rig. In the hull, deck, & bulkheads I mean. Ditto on the compression post & related structures, assuming it's a deck stepped rig.

The one other thought (which was the first one which came to mind for me) is to ask a sailmaker or three. As, for a lot of boats, they'll have tuning guides or notes. Albeit typically for larger, & or racing boats.
You can also look around online to see if your boat has an online owner's group. And consult with them.
Ditto on talking to the boat's manufacturer, & expressing your observations & concerns.

Also, before you go cranking things up, take a few measurements so that you can checl how much your rig's state of tune affects/causes deflection in the boat/hull.
For instance, tie a taught string from the bow pulpit to the stern one, & see how much it's length, & or vertical travel changes with your tuning. When a constant, measurable force is applied to the string, for the vertical travel thing, that is.

A similar test can be done with a centerline halyard, & it MUST be centerline. But tie it off with the shrouds loose, & measure the height from the masthead to either side of the hull @ the chainplates (when applying a constant, measurable load to the halyard).
Then, repeat this with the shrouds tensioned.

They're not perfect tests, but... sometimes they're all we've got. Though I'm sure that with some digging, you could find some more. For instance, over on Sailing Anarchy Forums, talking to riggers, etc.
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Old 19-10-2015, 12:49   #4
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Re: Rig tension

Keep in mind than a rig should be as loose as possible in the given conditions. Designers have to balance a lot of contrary issues to design a good rig but principle among them are the mast weight. The stronger the extrusion the less support you need from the rigging, and thus the lower the shroud tension can be. The lighter the rig the more complicated the rigging, and the higher the tension will likely need to be. So a thick heavy wall section generally needs far less tension than a thin walled light weight extrusion.

All of rig tune comes down to basically three things.

1) get the mast located properly for and aft, rake, and side to side. This is done by adjusting where the mast base hits, and the wedges in the hounds (for a keel step boat).

2) does the rig have the proper pre-bend. How much is determined by the cut of the sail, and the leingth of the forestay. Adjusted mostly with the side shrouds

3) is the mast in column under the wind conditions. The higher the wind the more tension you need to keep the mast from falling out of column. Any more tension than this just introduces excess loads on the boat, principly in compressing the mast, and is not needed. Again adjusted with the side shrouds.


Obviously there are other complications, but this is the basics. Adding more tension doesn't help anything. And the old cruiser short hand to tension the shrouds down to 15-20% of the wire breaking strength is nonsense. It is true this is where a lot of boats wind up for breezy conditions, but it is thinking of the problem backwards.
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Old 19-10-2015, 15:28   #5
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Re: Rig tension

I've always tuned my boats loose but I'm not a racer. The leeward shrouds were loose in decent wind on a close reach. Has worked fine for me in over 10,000 miles of ocean voyaging.

Recently had a rigger do a survey for insurance purposes and he tuned the rig in the process. To say the least, the wires were way tighter than I had it tuned. Got my handy Loos gauge out and loosened the wires back to the 15% of breaking strength that I've heard is recommended. That was still tighter than what I've normally tuned my rigs by feel. As Stumble says, any more tension than is required to keep the mast in column is just force trying to drive the mast through the bottom of the boat, pull the boat ends together, and hog the sides.
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Old 19-10-2015, 19:55   #6
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Re: Rig tension

thanks for the good advice, I've got a better idea of how it all works now. Sounds like a tension gauge could be useful. For now, I'll check the tension on the leeward stays when in a stiff close hauled breeze and make sure there is a bit of give in them. And still have the 2 - 3 inches of sideways movement in the lower stays when at rest.
Cheers
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Old 19-10-2015, 20:02   #7
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Re: Rig tension

Great guide from Selden. See page 32 for home made tensioner.

http://www.seldenmast.com/files/1416.../595-540-E.pdf
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Old 19-10-2015, 20:18   #8
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Re: Rig tension

Be careful of following advice you read online, including mine!
A lot of it is in good faith, but wrong.
Check out this site for the sail and rig tuning book Sail trim: "Illustrated Sail & Rig Tuning" it is a really great place to start if you have no tuning guide, and a very worthwhile small investment.
You don't need a tension gauge - you can measure the stretch over a 2m section with a tape measure. There is a reason for preload - read the book - it reduces the loads on the rig and boat.
If you have no info, start with a mast with a 3 deg aft rake, caps to 15-20% load, and lowers keeping the mast in column. If you have no tuning guide that is. The preload will be "used up" when fully powered and time to reef. You should not sail with loose shrouds - the risk of shock loading is too high, for example if caught aback. IMO, after 45 years sailing and more miles than most...
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Old 19-10-2015, 22:01   #9
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Re: Rig tension

Again, the idea a boat needs to be tensioned to 15-20% of the wires MBL is absurd. Just as an example...

A J-22 uses 5/32 1x19 wire with a MBL of 3,000. So by these numbers the uppers should have a static tension of 450-600lbs of tension. However the actual numbers used in the fleet vary between 145lbs (<3kn breeze) to a max of 550 lbs in +20kn.

Fr a J-30 with 1/4" wire (MBL of 8,200lbs). Again the bandied about numbers indicate tuning to 1,200 to 1,600 lbs on both the uppers and lowers. Where in reality the fleet is sailing with 1,500 on the uppers, and 1,000 on the lowers in 10kn of breeze. With about 2000lbs on them both in <20kn.


Again, as the wind changes the rig tune needs to be adjusted just like halyard tension or main sheet tension. Setting the rig tune arbitrarily as some multiple of the MBL of the wire just doesn't work. It very well might be ok, since it's close to what most boats need, but it also may be off substantially. In this case the OP has a tuning guide for his boat, unless there is some justification to deviate I would follow it.
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Old 19-10-2015, 22:19   #10
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Re: Rig tension

Quote:
Originally Posted by Stumble View Post
Again, the idea a boat needs to be tensioned to 15-20% of the wires MBL is absurd. Just as an example...

A J-22 uses 5/32 1x19 wire with a MBL of 3,000. So by these numbers the uppers should have a static tension of 450-600lbs of tension. However the actual numbers used in the fleet vary between 145lbs (<3kn breeze) to a max of 550 lbs in +20kn.

Fr a J-30 with 1/4" wire (MBL of 8,200lbs). Again the bandied about numbers indicate tuning to 1,200 to 1,600 lbs on both the uppers and lowers. Where in reality the fleet is sailing with 1,500 on the uppers, and 1,000 on the lowers in 10kn of breeze. With about 2000lbs on them both in <20kn.


Again, as the wind changes the rig tune needs to be adjusted just like halyard tension or main sheet tension. Setting the rig tune arbitrarily as some multiple of the MBL of the wire just doesn't work. It very well might be ok, since it's close to what most boats need, but it also may be off substantially. In this case the OP has a tuning guide for his boat, unless there is some justification to deviate I would follow it.
I dunno man, for folks who aren't re-adjusting their tension every hour or two when the wind changes, I'd say 15-20% sounds like a pretty reasonable number to stick with for the example boats you gave.
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Old 19-10-2015, 23:12   #11
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Re: Rig tension

Another point: The op states that this is a trailersailor. I'm not familiar with the specific boat, but most t/s are pretty lightly built, and have light rigs to facilitate mast erection on the trailer. I suspect that this being the case, the designers have gone for lower rig tensions than might be seen on a similar sized keel boat. IN the OP's place, I'd not deviate from designer's tuning.

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Old 20-10-2015, 00:49   #12
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Re: Rig tension

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Originally Posted by chris95040 View Post
I dunno man, for folks who aren't re-adjusting their tension every hour or two when the wind changes, I'd say 15-20% sounds like a pretty reasonable number to stick with for the example boats you gave.
Then set the rig for your average day of sailing and be happy with the results. But setting to the very high end of the spectrum is going to damage the boat over time. Racers at the end of the day reset the tune to 'base' settings. Which are typically set between 5-7kn.

Secondly the op HAS a tuning guide for the boat. Setting the tension to those numbers is always to be preferred to just making something up.
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Old 20-10-2015, 07:38   #13
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Re: Rig tension

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Originally Posted by Stumble View Post
Then set the rig for your average day of sailing and be happy with the results. But setting to the very high end of the spectrum is going to damage the boat over time. Racers at the end of the day reset the tune to 'base' settings. Which are typically set between 5-7kn.

Secondly the op HAS a tuning guide for the boat. Setting the tension to those numbers is always to be preferred to just making something up.
I've always set to 10%, to be honest. I agree the 15-20% seems to favor the heavier wind scenario. But 15% certainly doesn't sound "absurd" (your words) to me. And if I was worrying about damaging the boat with 15% tension in the rig, I think I'd worry about sailing the boat, too. (I'm from a slow, overbuilt boat background though.)

Regarding the OP, yeah, if you've got the benefit of a tuning guide from the builder, why not use it?
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Old 20-10-2015, 09:11   #14
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Re: Rig tension

Many trailerable boats are designed with 'slackish' (by offshore keelboat standards) standing rigging. You simply keep the stick straight and make the screws tight by hand and that's that (e.g. McGregors). Imagine tuning with loos every time you set up the mast (that is every time you go sailing). At times such boats have no screws but only plates - nothing to tension there.

Talk to other sailors on identical and similar boats and see how they tune the stick. There is no magic and no science to it (unless you have some very specific boat as say a sportsboat with very fine racing extrusion, etc.)

If you have screws at all, you cannot over-tighten the rig if tightening the screw by hand (no tools applied - just your hand on the turnbuckle).

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Old 20-10-2015, 09:52   #15
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Re: Rig tension

Quote:
Originally Posted by Stumble View Post
Again, the idea a boat needs to be tensioned to 15-20% of the wires MBL is absurd. Just as an example...

A J-22 uses 5/32 1x19 wire with a MBL of 3,000. So by these numbers the uppers should have a static tension of 450-600lbs of tension. However the actual numbers used in the fleet vary between 145lbs (<3kn breeze) to a max of 550 lbs in +20kn.

Fr a J-30 with 1/4" wire (MBL of 8,200lbs). Again the bandied about numbers indicate tuning to 1,200 to 1,600 lbs on both the uppers and lowers. Where in reality the fleet is sailing with 1,500 on the uppers, and 1,000 on the lowers in 10kn of breeze. With about 2000lbs on them both in <20kn.


Again, as the wind changes the rig tune needs to be adjusted just like halyard tension or main sheet tension. Setting the rig tune arbitrarily as some multiple of the MBL of the wire just doesn't work. It very well might be ok, since it's close to what most boats need, but it also may be off substantially. In this case the OP has a tuning guide for his boat, unless there is some justification to deviate I would follow it.
Yeah, that's a bit too much detail for cruising......

Mine are at 440 all around except the foward lowers are at 550. I put in a little prebend. This was around the 10-15% breaking strength I believe

If I had it to do over, I'd probably go a little lighter on the tension maybe 350 - 450. My boat is old and I may have tweeked it a bit cranking on the rig like that.

When racing beach cats, we set our diamond wire tension anywhere from 300 - 1000 on smaller diameter wire for prebend and some guys have their shrouds and forestay piano wire tight

This was 3 years ago and I haven't touch it since.
Racing beach cats I've seen guys cranking in rig tension between 45 minute buoy races.
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