Standing Rigging dimensions and engineering

[The great unwashed]

I own a Colgate 26 which is in the water here in Hawaii 24/7/365. Obviously tropical salt water year round is the worst possible environment for metal rigging.  I lost the mast about 10 years ago—the swaged fitting on the bottom of the windward lower pulled out and the mast snapped at the spreaders.  Inspection showed that the wire inside the swage had rotted away about 1 inch into the socket. No way to tell without x-ray inspection. A little extra tension and boom, no more mast.

It’s about time to replace the new standing rigging (the old rig had 10 year old wire on it when it failed), and I wonder about a couple of things:

1) It blows a lot harder on average here in Hawaii than it does on the East Coast, the area for which the boat was designed.  Can I upsize the standing rigging wire, or is there some complex equation taking stretch etc into account that would be violated if I went up a couple of sizes on the shrouds? I know that the weight of the rig would increase, with more heel etc., but I’m not racing.

2) Would Norseman style fittings at the bottoms of the shrouds be less likely to encourage corrosion in the wire?  Is there a minimum wire diameter for such fittings?

Thanks!

 

[mgs]

A mechanical fitting at the bottom would help some. Biggest hurdle with going a size larger with wire is the pin diameters, bigger wire might not have the correct size pin available. 
 

Id point out that the wire didn’t fail because of strength issues though. You’re being prudent replacing the rigging that’s the right approach 

 

[Max Rockatansky]

Ten years is expected replacement schedule for rigging

 

[littlewing]

This could be from left field, but have you thought of synthetic rigging? 

You would need to rethink you terminations, but dyneema  dux, is just single braid: very secure and easy to splice.

If you get it covered it would last for years - quite indestructible.

 

[MiddayGun]

The fittings failed due to corrosion, not lack of strength. Unless you like weight aloft I would stick with what it has. 
A failure due to corrosion after 10 years suggests that the quality of the original stainless wasn't quite what it should be 10 years is the normal life & many people go way past that (not that its recommended), as long as you're replacing with a good quality 1x19 wire then 10 years should be easily achievable. 
 

Someone above suggested Dyneema, which is possible, but evey time I see someone that's done it, they seem to forever be tinkering with it. 1x19 Stainless can be setup at the start of the season & by and large left alone. 

 

[The great unwashed]

As you say, the synthetic stuff seems to be constantly creeping and needing to be rejiggered.  The sizing up issue is sort of a tangent, but when I’m punching into square chop off of Diamond Head in 18 knots, I do wonder about the specs for the (thin) wire.

a more general question: other than weight and possible compatibility issues for fittings, is there an actual engineering / spar bend issue with less elastic standing rigging? I mean, I could go nuts and replace the wire with carbon, right?  

 

[longy]

Having served an apprenticeship under Larry Stenek and being constantly asked to upsize rigging: the original spar/hull design has all the components holding up your rig designed to the same load numbers. Arbitrarily increasing one piece of the system does very little, it just shifts the failure to another point. Rig systems are designed for the maximum loads that the design stability can impart to the rig. Unless you've added sail area or lead to the keel these numbers are the same, so loads on the rig are the same. These calc's do assume the wire is close to it's rated strengths. Trained visual inspections and age dated replacement are the only way to ensure this.

Larry keeps a file for every spar he's rigged. We had owners show up insisting that we upsize the rigging. When shown proof that this had been done by the previous owner, some would still demand bigger wire, guided by some 'pro' on their dock

 

[Irrational 14]

You might want to consider Dyform or Rod rigging. Same size. A bit more strength and less stretch.

 

[longy]

I think Dyform has a bit less strength due to using 316 ss instead of 306/304

 

[Irrational 14]

https://rigworks.com/yacht-rigging-services-in-san-diego/standing-rigging/wire-rigging/dyform-compacted-wire-rigging/

Common stuff on High Performance SS Cable rigs including most Skiffs and Sport Boats.

 

[MiddayGun]

a more general question: other than weight and possible compatibility issues for fittings, is there an actual engineering / spar bend issue with less elastic standing rigging? I mean, I could go nuts and replace the wire with carbon, right?  

I'd say in general no.   
Certainly in the case of your rig (which google suggests is a pretty standard 3/4 fractional) I can't see it causing any issues. 

As has been said though, unless everything's designed around it, you just move the weak point somewhere else. 

 

[Zonker]

When you lost the mast was the rigging 10 years old? If older than that, and it failed, then replacing every 10 years is prudent. Upsizing isn't required. 

 

[ctutmark]

For the old piece that failed, do you have any pics of the parts?

From the description I wonder if the failure was lack of insertion in the swage that finally gave up versus the wire degrading. Saw a Hobie 33 drop a rig where the swages were improperly done, had nothing to do with the strength of the parts

 

[jamhass]

Brion Toss (rigger's apprentice) notes that the loads on the rig are limited by the boat's righting moment.  Going up in size only adds unneeded weight high up.

 

[The great unwashed]

I’ll see if I have a picture.  Hard to tell if the wire that pulled out of the swage had rusted and broken off, or had only been inserted part way.  I admit I hadn’t even thought of the second option.  I’m guessing that another advantage of mechanical terminals is that you know that the wire is fully inserted and seated.

 

[neuronz]

You do not need to upsize your rigging as it is specified according to the righting moment of the boat which is independent of the area you are sailing in. Even if you are sailing with relatively more heel due to stronger winds you will still be far away from the maximum load all the time since maximum righting moment will occur somewhere around 90 degrees of heel and you will be sailing at maximum of approximately 30 degrees.

 

[Captain Jack Sparrow]

You'd be better off shortening the maximum replacement cycle for standing rigging from 10 years to a shorter interval. As you said, year round sailing in a tropical salt water environment is not an ideal environment, and your season is probably twice that of the Northeast- where properly maintained boats replace wire at ~10 years max. It's cheap insurance compared a rig.

The end fittings are typically what fail on a wire rig, so even upsizing the wire wouldn't eliminate or even really lessen the risk of the swage going bad around the 10 year mark. The advantage of the Norseman/ Sta-lok would be that you could open it up and look to see if there's any corrosion or failure of strands, but you'd still need to replace the wire. Insurance companies often (not always) require standing rigging replacement every 10 years, with inspections every few years (you should do that yearly in any case). Your specific policy may or may not have details regarding that. 

 

[The great unwashed]

Thanks to everyone for the advice.  I’ve decided to replace the aluminum mast with a treated fir telephone pole and use served and parceled galvanized wire and deadeyes.  Fuck it.

actually, I’ll see if a local rigger can get me a quote using mechanical fittings on the lower ends of the stays….

 

[Frogman56]

10 years is optimistic, particularly in the tropics.

Here (east coast oz, sub tropical) the insurers are headed for 5 year replacement for race boats.