How To Measure Standing Rigging Tension

Whether or not you’ve replaced your standing rigging, you may be wondering how to adjust it. How tight should the rig be? How can you measure it? After all, what good is great rigging if it isn’t tensioned properly to perform its best?

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A properly tuned rig isn’t only important for racing, it’s also a good idea for cruisers. It minimizes uneven stress and wear on hardware, it’s safer, and it protects the shape of your sails.

Close only counts in horseshoes and hand grenades

Unfortunately, without a tension gauge, tuning your rig is mostly subjective guesswork.

The 1987 (last) edition of the Catalina 22 Owner’s Manual and General Handbook puts it this way:

Adjust forestay and backstay so that the mast is straight up and down.

The upper shrouds should be firm but not far apart. A 50 pound push should deflect the upper shroud about 1″ at shoulder height.

The lower shrouds (4 of them) should be adjusted so that they are looser than the upper shrouds. While at dock, they should have no slack, but no tension either. No lower shrouds, when pushed, should deflect the mast more than any other shroud when pushed equally hard. If this can’t be achieved, the upper shrouds are too tight. Back off one-half turn at a time on the upper shroud turnbuckles until the tension of the lower shrouds is brought into balance. [Emphasis added]

Not very precise, huh? It doesn’t take very much tension at all on the forestay and backstay just to make the mast plumb and that’s too loose for anything but light air sailing. How much is “far apart?” How exactly do you measure a 50 pound push horizontally against a wire at shoulder height? Standing where, on the cabin or on the deck? How much is “looser” but “without tension?” How do you measure balance between four shrouds without a tool?

That’s like your mechanic telling you that the best way to tune your car’s engine is by ear alone so that it idles well but not too fast and not too slow. It should accelerate smoothly with good power but no cylinder should exceed 10% less compression than any other.

You can’t lose with a Loos

You can skip all the guesswork with a tension gauge. Loos & Co. has manufactured cable in the US for over 50 years. They make the most popular and economical tension gauge for sailors. It’s available in several models depending on the range of cable sizes that you want to measure.

The current model numbers are:

  • PT-1 (3/32″ to 5/32″)
  • PT-2 (3/16″ to 1/4″)
  • PT-3 (1/4″ to 3/8″)

Older models of the gauge can still be found for sale new and used:

  • Model A (3/32″ to 5/32″)
  • Model B (3/16″ to 9/32″)

The major differences between the newer models and the older models are:

  • The older models use a flat spring built into the gauge to measure the tension. The newer models use a coil spring.
  • The older models have a slot for the cable. Measuring very tight cables can produce a very slight kink in the cable. The newer models have two round, plastic guides that don’t harm the cable.
  • You read the tension on the bottom of the older models. This means you either have to stoop down to read the gauge or use the gauge over your head. You can read the tension on the front of the newer models from a more natural stance.
  • The older models have fewer parts and are all metal construction except for the lanyard. The newer models have more parts, some of which are plastic.
  • Unlike the older models, the newer models can be hooked onto the cable while you are measuring it so that you can read the tension and your hands are free to adjust the turnbuckle. This is a nice feature that reduces trial and error.

Each gauge has handy notches in the side for measuring cable diameter.

The gauges work on the principle that if you bend a cable by applying a specific amount force, it will bend more or less depending on the size of the cable and how much tension is on the cable. The larger or the more tension on the cable, the less bend. The smaller or the less tension on the cable, the more bend. The gauges use a spring (flat or coil) to measure the amount of bend that results when you bend a cable slightly and they convert that amount into a tension number.

Dialing it in

I use my gauge whenever I modify my standing rigging in any way and periodically to recheck it, especially because I step the mast for every launch.

To measure tension with an older model Loos gauge (the process is slightly different for the newer models):

1. Hook the gauge on the cable. If you have cable covers on the cable, the gauge won’t fit over them, hook the gauge on a bare part of the cable. You read the gauge from the bottom so hook it over your head.

Hook the gauge onto the cable
Hook the gauge on the cable

2. Pull the lanyard until the indicator aligns with the mark on the gauge.

Pull the cord until the indicator aligns with the mark on the gauge
Pull the lanyard until the indicator aligns with the mark on the gauge

3. Read the (bend) number from the scale.

Read the scale
This forestay has a tension of 13 or 110 pounds for a 1/8″ cable

4. Measure the cable size and look up the tension in pounds that corresponds to the cable size in the chart on the gauge. This step is optional unless you’re trying to set the tension to match a recommendation stated in pounds of tension (300, for example). Some recommendations are stated as the equivalent and easier to remember scale number (24, for example). In that case, you don’t need to look up the tension in pounds.

When you know the cable’s tension, you can adjust its turnbuckle to either increase or decrease the tension by measurable amounts. With a little trial and error, you can “dial in” a very accurate amount of tension. Dial in all of your stays and shrouds, and you will have a well-tuned rig. For instructions on using the new model gauges and a video, go to How to use PT Series Tension Gauges.

Once you get your basic rig tension set, you only need to remember the scale numbers and you can confidently adjust it to best suit your style of sailing or changing conditions. There are good guides available online that recommend settings for different conditions. One of the better ones for the Catalina 22 is the Catalina 22 Tuning Guide from North Sails. They have guides for other sailboats as well.

If you don’t know anybody that you can borrow a gauge from, consider getting one of your own from Amazon. Then you’ll have one to loan to others in need.

Stop hoping that your rig tension is close enough. Tool up and dial it in!

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14 Comments Add yours

  1. Mikey says:

    Hey Ken……One of your better articles. Thanks. This has always been a point of interest for us!

  2. Dave M says:

    Thank you, $tingy! What a great resource!

  3. Diego says:

    Ken, for those who don’t want to fork out roughly a $100 bucks for the gauge, they can use my poor man’s version too, which I adopted from a great resource on rig tuning (“Sail & Rig Tuning” by Ivar Dedekam). To determine wire “tension,” I measure wire “stretch.” I do this by first marking a 1-meter length on the respective wire PRIOR TO TIGHTENING TURNBUCKLES. Every 1.0 mm of stretch equals 10% of the wire’s breaking strength, so if I wanted to set my wire’s tension at 15% of breaking strength, I would start applying tension (by tightening my turnbuckles) until the 1-meter length has been stretched to 1-meter plus 1.5 mm. The wire would then be tensioned at 15% of the wire’s breaking strength. If you wanted to use 20% as your base tension, then you would tighten your turnbuckles until the wire stretched an additional 2.0 mm. (Note: This only applies to wire, not rod rigging.) Thanks for another great article!

    1. Good point, Diego. That’s a good way to get in the ballpark.

  4. bigsnit says:

    Thanks Ken. I have an old model Loos that I’ve been using for almost 10 years. I like that it’s got very few moving parts 😉 and i’m pretty sure it’ll hold up another 10 years with no problem. For reference I use the North Sails tuning guide figures you mentioned.

    For anyone just starting, keep in mind that you’ll get a lot faster doing it once you’ve done it a few times.

    1. The old ones are built tough. The ability of the new ones to clip it onto a shroud and dial in the right tension on the first try would be convenient, though.

  5. Stephen G Hardy says:

    The owner’s manual for the Cat 25 says the standing rigging sizes are 1/8, 5/32, and 3/16. Does that mean I will need both a PT-1 and a PT-2 Loos gauge? The real question: Since I am not going to buy two, which rigging is the most important to tune? The back and fore stays or the the shrouds? Seems to me I ought to be able to “eyeball” the fore and aft rake and use the gauge on the the shrouds. Your opinion?

    1. Hi, Stephen

      You must be looking at the halyard wire sizes being 1/8″. All the standing rigging on a C-25 is 5/32″ or 3/16″. At any rate, I wouldn’t want to buy two gauges either.

      The shrouds are the most important because they hold your mast in column and centered on the sailboat. The forestay and backstay tension can be adjusted with the backstay adjuster (assuming you have one) depending on sailing conditions so the gauge isn’t as useful for those.

      If it were me, I’d get a PT-2 so I knew my upper shrouds were correctly tensioned. Then I’d either extrapolate the 3/16″ settings down to 5/32″ mathematically or borrow a smaller gauge, set the tension on the lower shrouds and then see what the corresponding setting is on the PT-2 and label it right on the gauge. Do that for several settings and you should have a one-size-fits all gauge.

      1. Stephen Hardy says:

        Thanks. Good advice as usual.

        On Sun, Jun 26, 2016 at 9:19 PM, The $tingy Sailor wrote:

        > $tingy Sailor commented: “Hi, Stephen You must be looking at the halyard > wire sizes being 1/8″. All the standing rigging on a C-25 is 5/32″ or > 3/16″. At any rate, I wouldn’t want to buy two gauges either. The shrouds > are the most important because they hold your mast in column a” >

  6. Tom Beetham says:

    Hi Ken,

    I’m a new C-22 owner (1985 model year). Should I go with the PT-1 version? I believe I have the original rigging. Thanks for a most helpful post for this novice sailor!

    1. Welcome to the tribe, Tom

      Yep, a new model PT-1 or old model A is what you want.


      1. Tom Beetham says:

        Perfect. Thanks!

  7. Tim Myers says:

    Hi Ken. I’m a new owner of a 1973 C22. I bought the PT1. I’m having a hard time finding what my tension should be. Can you share what tension you use? Thanks for all the great info. I’m a fan!

    1. I use the North Sails guidelines as a starting point, which are 28 on the upper shrouds and 24 on the lowers.

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