Loos Tension Gauges and 316 Stainless Steel Rigging Wire

[jviss]

I noticed that Rigging Only uses 316 wire exclusively for boat rigging.

At Rigging Only our yacht and sail boat rigging wire is the highest quality wire available. The standing rigging 1x19 wire rope is type 316 stainless steel, strand polished, and every spool has an actual pull test certification as well as chemical analysis. We stock 1x19 wire from 3/32 wire to 5/8 diameter wire and metric wire diameters from 4mm through 16mm rigging wire.

Reading Loos' web page, about their tension gauges, I read this:

NOTE ! THE INTENDED USE OF THIS GAUGE IS TO BE USED ON 302 / 304 1x19 S.S. CABLE IN APPROPRIATE SIZES. IF USED ON OTHER CABLE TYPES, SIZES, AND CONSTRUCTION YOUR READINGS WOULD BE CONSISTENT (REPEATABLE) BUT POUND TENSION VALUES WOULD DIFFER FROM THOSE LISTED ON THE LABEL. GAUGE MAY NOT READ "O" WHEN AT REST, AS THEY ARE CALIBRATED AT MIDRANGE OF TENSION.

(emphasis theirs)

So, where does this leave the yachtsman who has 316 standing rigging and wishes to tension the rig properly?

I just made a technical support request of Loos, asking if there's a conversion table available for 316 1/19 SS wire.

 

[justsomeguy]

You could ask Rigging Only for their guidance.

 

[jviss]

You could ask Rigging Only for their guidance.

That was my next move!

I also started wondering about the whole topic of rigging tension. I kind of doubt that the yacht designers have given this a lot of deep thought. What do you think?

 

[justsomeguy]

I kind of doubt that the yacht designers have given this a lot of deep thought. What do you think?

I don't know. It would likely depend on the designer's control of production. The designer may leave such minutia to another engineer for specifications.
Or not.
As to your original question, https://www.s3i.co.uk/1x19.php
The difference in the modulus of elasticity of the different wires causes the Loos gauge issue. Not insurmountable.
Sorry about the need to "do the math".

 

[Ross S]

316 will have about ±90% of the breaking strength of 304 for 1 x 19 wire construction.

My Loos has two readings: One in "percent of breaking strength" and the other is "pounds of tension". The "percent of breaking strength" would be wrong for 316. But the actual amount of tension in pounds would be correct because 304 and 316 will have nearly identical stretch characteristics. (Modulus of elasticity). Just use the Loos gauge as you always would to achieve the desired tension in pounds. Understand that in terms of percent of breaking strength, it'd be slightly higher than what the gauge is telling you.

Example:
Ø5/32 1 x 19 304 wire: 3300# breaking strength
Ø5/32 1 x 19 316 wire: 2800# breaking strength

I want my tension to be 495 lbs. So I use the Loos gauge to tension to 495 lbs. It tells me that this is 15% of breaking strength which is correct for 304 wire. For 316 however, it'd actually be closer to 18%. But your mast doesn't care what the shroud material is, it just needs the correct amount of tension. So that "percent of breaking strength" reading is a little useless in my opinion.

 

[Justin_NSA]

I use my gauge mostly to make sure I have even side to side tension once I get it close.

 

[The Shadow Knows]

JV,

I agree with Ross,
I started out 20 years ago with 304 SS rigging & bought my loos gages.

Yes, they have a start-reference point for tension & regardless if 304 or 316, the tension numbers
are tension numbers. Boat designs may differ but tension is tension.
My C30's mast leaned abit forward so, I went all 316 then, I tensioned the lower forward shrouds abit
then took up tension on my backstay to add a slight rake in my mast. That was 15 years ago & all is well.

I also tune my friends' boats with Loos & they too, sing like a piano.

A friend whose rigging I tuned right before the Cozumel race one year finished in the top 10.
He could've finished higher but, he took that stupid bounce off West Cuba.

 

[dlochner]

I use a Loos gauge and have 316 rigging. The gauge is accurate enough to get close to the correct tension. The 10-155 of breaking strength is really about building in a safety margin. The tension needs to be tight enough to reduce shock loading and loose enough to allow proper mast bend.

The real test is to go sailing close hauled in 12-15 knots of breeze. A properly tuned rig will have slack shrouds on the leeward side. Slack, not sloppy and floppy.

Racers will often retune their rigs for different conditions, very loose for light air to very tight for heavier air.

 

[jviss]

A properly tuned rig will have slack shrouds on the leeward side.

Thanks, Dave, but unfortunately, that's a piece of folklore that is not correct, and can be damaging and dangerous as well. This from the Loos website (and confirmed by other authoritative sources):

Masthead Rig There is a simple criterion for shroud tension. The initial rigging tension should be high enough that the leeward shrouds do not go slack when sailing close-hauled in a reasonably brisk breeze. The proper value for your boat can be found by a few trial runs under sail. Once the correct tension is known, the gauge can be used to maintain the value.

See:
http://loosnaples.com/how-tos/tension-gauges
and
http://loosnaples.com/how-to-use-pt-series-tension-gauges

The shock loading from a loose shroud going tight quickly can break it. There are other reasons you don't want this, too.

 

[jviss]

This just in, from Loos, on gauge readings:

The reading of tension will be the same only the percentage of breaking strength is more as type 316 is less break strength than 304 SS. Use the gauge the same way.

So, Ross, et.al., you are correct. Now, what's the correct tension for my boat??? I will check the docs, I think they give starting points.

 

[Bob S]

Isn't your boat still in the water? Have you checked the tension on it now? Just curious and congrats on the new boat, she is beautiful!

 

[Ross S]

This just in, from Loos, on gauge readings:

So, Ross, et.al., you are correct. Now, what's the correct tension for my boat??? I will check the docs, I think they give starting points.

If there is specific information for your boat, either in the form of a manual or from a users forum then I'd go with that.

In lieu of that, a good starting point is the tuning guide from Selden:

http://www.seldenmast.com/files/1456145028/595-540-E.pdf

In the end, all you really need to do is get close and then go sailing to fine tune it from there.

 

[dlochner]

Thanks, Dave, but unfortunately, that's a piece of folklore that is not correct, and can be damaging and dangerous as well. This from the Loos website (and confirmed by other authoritative sources):

Well, it seems either I wasn't clear in my explanation of "slack,not sloppy and floppy" or there is disagreement in the field. According to Brion Toss, a master rigger from Port Townsend:

"Wait until there's enough breeze to heel your boat at 15 to 20 degrees, so the rig will really get loaded up. If it's new wire, go out and juts thrash around for a while, to get the initial slack out. Then get on a tack to weather, and take a look your leeward shrouds. They will always be slacker than the weather ones, because the weather ones always stretch some. That's as it should be, but they should never be flopping loose. If they are, take up on them until you feel a slight increase in resistance in the (well-lubricated) turnbuckle." Page 287 The Complete Riggers Apprentice (emphasis added)

The best use of the Loos is to get repeatable settings. The gauge is not accurate enough to fine tune the rig. Get it close, check the tune by sailing, and record the numbers. My gauge is on the boat, so I can't reference easily, however, IRRC, the difference between the numbers is not linear and the difference in rig tension between say, 26 and 27 is not the same as 27 and 28. Also the difference in per cent of breaking strength is not that precise. A 26 might be 10%, a 27 might be 14% and a 28 might be 20% of breaking strength.

The most important part of rig tune is keeping the mast in column, when a mast goes out of column it comes down. A second concern, especially for deck stepped masts is not over tensioning the rig and causing damage to the deck, bulkheads and compression post. A keel stepped has similar concerns at a somewhat lesser level as the rig tension is transmitted more directly to the keel.

When tensioning the rig remember the tension is not just about keeping the mast straight, the tension is trying to drive the mast down through the hull and keel. The rig tension wants to fold the sides and bow and stern up to the mast. The goal is just enough to keep things standing while maintaining hull integrity.

The Complete Riggers Apprentice is an excellent source for information on rigging and rope work. Well worth the money spent on it. Covers both practical and theoretical issues.

Edit: fixed a couple of auto correct misspellings.

 

[jviss]

Isn't your boat still in the water? Have you checked the tension on it now? Just curious and congrats on the new boat, she is beautiful!

Thanks, Bob! It's in the water, haven't measured it, but I know it's too loose.

Sailing it home (30 miles), leeward shrouds were slack - a lot slack! Baby stay is doing nothing.