Standing rigging tension is a peculiarly under-addressed subject. Easy to see how it would worry a new boat owner or someone going to sea.
Most experts step aboard, yank or twang the shrouds and stays and mutter, Pretty slack, Too Tight, or, Thats about right.
Youll find in the sailing literature very few discussions of the question: What does tight mean?
Even riggers rarely explain how much tension they like to see.
There are a few sailors who like the rigging so tight you could send an elephant up the backstay. It can result in excessive loads and wear on fittings, chain plates and the hull. The ultimate penalty for those who can’t stand any sag in the forestay is what ocean racing sailors call a gravity storm or, less dramatically, dropping the rig.
Others like to take up the slack just enough so that the rig is at rest when the boat is motionless. This approach sometimes leaves excessive slack to leeward that can result in shock loads, excessive wear and misalignment in fittings. It may take longer, but the ultimate penalty is the same.
In between (and probably in the most logical position) are those who like to take up the slack and stretch the wire just a bit. This is frequently accomplished, at least for the stays, with an adjustable backstay. When sailing, especially on the wind, tighten down to minimize slack in the forestay. When reaching, running or at anchor, ease off.
But the question is: How much stretch…especially in the shrouds?
If you stretch the wire 5% of its breaking strength, it will be considered moderate tension. Crank in 15% of the breaking strength and it is regarded as tight. These figures apply for any diameter of wire. You need only know the wires breaking strength.
Three years ago, in the June 15, 1995 issue, we published a discussion of the views of author Richard Henderson, Skenes Elements of Yacht Design and several riggers, along with an evaluation of an excellent booklet published by Sailsystems about a Selden Mast approach (described in detail in the October 15, 1991 issue) and an entirely new method developed by Michael Dimen, who called his gadget a Rigstick.
Mentioned was the familiar (see photo) Loos rigging tension gauge, which comes in two sizes. The Model 91 ($39) is for wire 3/32″ to 5/32″. The Model 90 ($45.50) is for 3/16″ to 9/32″. The gauge depends on the bending property of aluminum plate.
The strange-looking gauges don’t willingly produce great accuracy because you have to hold one reading steady while noting another, which also requires that you make a judgment about where the centerline of the wire falls on a scale. Not easy to do.
The big name in galvanized and stainless cable (as wire is called in the trade), cable hardware and tools, Loos & Co., Inc. went looking for a better mousetrap.
Who did Gus Loos go to? The guy who designed the original gauge, his old friend, Donald J. Jordan, an 82-year-old retired Pratt & Whitney engineer who has been sailing out of Marblehead, Massachusetts, in the likes of Lightnings, Friendship sloops, Sound Schooners (which was the prized New York Yacht Club class in 1918), Pearson Wanderers and currently in a 16′ Starling Burgess design, appropriately called a Marblehead.
The old tension gauge wasnt bad, said Jordan. But it tended to get bent. Then the patent ran out and I told Gus we could do a better one.
The new version (see photo) is a distinct improvement over the old aluminum version. A better design, its also much more substantially made of aluminum, stainless and nylon.
The design problems were interesting, Jordan said. A conventional cable tension gauge has two rollers at the ends with a spring-loaded plunger in the middle and a dial gauge to measure the plunger movement. The wheels have to rotate…because they must permit some small but vital movement. That makes the tool expensive. My approach was to have two stationary wheels and a carefully contrived square slider in a arc-slot on the other.
The new Loos gauges use a long-lasting stainless spring to produce the tension. Slip the lower grooved wheels on a shroud or stay, pull the lanyard to engage the upper hook, relax, read the tension at your leisure and consult the scale to learn the pounds of pressure on the wire and the percentage of breaking strength of the wire. There are three wire gauge notches in the edge. The gauge can be left on the wire while turnbuckle adjustments are made.
The accompanying booklet, very well-done, contains a good tight discussion of the subject; some recommendations; a table on how to equalize tension in different sizes of wire, and line-drawn diagrams clearly showing rig tensions (windward and leeward) created by light, medium and heavy winds.
The wire gauge comes in three sizes, for 3/32″-5/32″, 3/16″-1/4″ and 9/32″-3/8″. West Marine sells them, respectively, for $57.99, $69.99 and $$122.99. Defender Industries cuts them to $49.95, $51.95 and $105.95. Prices in the BOAT/U.S. catalog are in between.
What if, instead of 1×19 wire, you have rod rigging? There are four new models that are bigger, heavier and, of course, more costly. They work the same, but take some arm strength. One is for .172-.250 rod, another for .281-.375. Two others models are for metric rod. West Marine sells the rod gauges for $186.99. Neither Defender nor BOAT/U.S. shows them in their catalogs.
Contact- Loos & Co., Inc., 901 Industrial Blvd., Naples, FL 34104, 800/321-5667. Rigstick, 311 Jackson, Port Townsend, WA 98368; 800/488-0855. Sailsystems, PO Box 1218, Marblehead, MA 01945; 978/745-0440.