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-   -   Swage Corrosion (http://www.sailnet.com/forums/gear-maintenance/33664-swage-corrosion.html)

tdw 06-15-2007 01:33 AM

Swage Corrosion
 
I've just had a quite disturbing phone call from my rigger. I'd asked him to have a look at forestay tension (it needs to be shortened) and remaking the backstay(s) to allow for proper adjustment. All very well and good and he had a look, said Ok but then went on to tell me that the swaged terminals on my shrouds are rotting out from the inside. Now he didn't do this rig and I trust this man implicitly so I don't believe he is telling me porkies just to gouge some extra buckazoids out of me but has anyone else had this problem and does anyone know what causes it ?


I do inspect my rig before going out and I'd not noticed any problem, yet rigger seems to think that we were damn close to losing the rig. :eek:

Should have said that yes the rig is stainless not galvanised. The shrouds themselves are only a couple of years old.

sailingdog 06-15-2007 06:56 AM

Unfortunately Mr. Wombat... that is a pretty good description of how swaged fittings fail. And generally, they fail at the lower ones, rather than the upper ones, since the lower ones are exposed to far more salt water and tend to trap the water, as they face up—like a tiny little cup.

This is enough of a problem that one of my friends, who is a rigger, often suggests to his customers that they should get the top of the stays and shrouds swaged, but that the lower ends should be mechanically fastened, using something like a Sta-Lok or HiMod fitting.

Another option is to coat or soak the lower swages in oil, wax, etc, to prevent the water from seeping into the wire and swage fitting itself. This can prolong the life of lower swages dramatically, at least according to my friend. I've not tried it—but he's been making rigs almost as long as I've been around...so I tend to believe him.

Idiens 06-15-2007 07:28 AM

SD - I have heard that advice too. Do the mechanical fixtures offer a way for the water to exit and oxygen to enter? The mechanical one on my forestay looks capable of trapping water. I suppose it might have the advantage that it could be reopened and inspected (?)
I can see that the lower swaged connections are a water trap, but under the sun's heat, I guess there may be a bit of evaporation and air entry. A rigger I asked, said basically, until strands start breaking (in life or on a test rig), its very difficult to judge the residual strength.
Some insurance companies are demanding (variously) replacement after 5 or 10 years. I suppose that is to reduce their risk to breakages.

TXS-ALAMO 06-15-2007 02:50 PM

Sailingdog. One of my dockmates recently replaced all his standing ss rigging. Per his rigger, the wire was swaged at the top and Staylock used at the deck fittings. Anhydrous lanoline was also used at the Staylock fittings. Incidently, the rigger refused to replace his steel spliced to line halyards; saying he would use high-modulus line only. :confused:

sailingdog 06-15-2007 05:19 PM

TXS-Alamo-

Nowadays, with high-tech lines, there is no real need for wire-to-rope spliced halyards. The dyneema or spectra cored lines are about the same stretch as the wire...and the halyard overall is going to stretch less than a spliced one.

sailaway21 06-16-2007 01:50 PM

Fluffy,
I am curious to know how he determined they were close to failure. Did he physically take them apart from the stay/shroud?

The Sta-lock suggestion makes sense only to the extent that one would disassemble, inspect, and reassemble. What type of maintenance is advised during the inspection process of the Sta-lock?

Standing rigging, whether on ship or boat, seems to just get replaced periodically because we just figure "it's due" versus running rigging, which is much more likely to actually exhibit signs of wear. IIRC, every five years on a cargo ship for standing rigging with running rigging inspected monthly and torn down (blocks, goosenecks, etc...) annually.

Good topic.

morganmike 06-16-2007 06:42 PM

Just had all my standing rigging replaced, and the rigger recommended swaged lowers, but he uses 5200 inside the terminal ends. The connections look really good now, with the collars completely compressed and a thin line of 5200 squeeze-out just visible. Seems to me it's a good choice for preventing water intrusion into the swaged connection.

My rigger also refused to replace my spleced wire to rope halyards, and made the same points about stretch as described above. He wanted what seemed to me to be a lot of money to replace them with rope, so I just went and bought some Spectra cored line and made them myself.

tdw 06-17-2007 07:59 PM

Quote:

Originally Posted by sailaway21
Fluffy,
I am curious to know how he determined they were close to failure. Did he physically take them apart from the stay/shroud?

The Sta-lock suggestion makes sense only to the extent that one would disassemble, inspect, and reassemble. What type of maintenance is advised during the inspection process of the Sta-lock?

Standing rigging, whether on ship or boat, seems to just get replaced periodically because we just figure "it's due" versus running rigging, which is much more likely to actually exhibit signs of wear. IIRC, every five years on a cargo ship for standing rigging with running rigging inspected monthly and torn down (blocks, goosenecks, etc...) annually.

Good topic.

S'way,

Having had a look at what he talking about I now see what he means. While there is very little obvious corrosion when you have a bit of a dig around the top of the swage it's all just corroded metal.

I dare say he wasn't trying to suggest he had proof of impending failure, more that it worried him and he suspected possible failure.

Judging by the crap I saw yesterday I think he is correct.

tdw 06-17-2007 08:02 PM

Ref SD's comment and on the subject of mechanical terminals my guy is strongly opposed to using them at all. Why I don't know but I'll ask him when we meet later this week.

tdw 06-17-2007 08:14 PM

Quote:

Originally Posted by morganmike
Just had all my standing rigging replaced, and the rigger recommended swaged lowers, but he uses 5200 inside the terminal ends. The connections look really good now, with the collars completely compressed and a thin line of 5200 squeeze-out just visible. Seems to me it's a good choice for preventing water intrusion into the swaged connection.

My rigger also refused to replace my spleced wire to rope halyards, and made the same points about stretch as described above. He wanted what seemed to me to be a lot of money to replace them with rope, so I just went and bought some Spectra cored line and made them myself.

5200 ? I've found something by 3M and presume that is what you mean. I'll check it out. Sounds like good advice to me.


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