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post #21 of 45 Old 12-11-2015
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Re: Service life of a Sta-Lok fitting?

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Originally Posted by casey1999 View Post
http://209.20.76.247/ss/assets/howto...Prevention.pdf
Not quite sure of your point. From what I read, the purpose of the Inspection Note from the CG is to provide guidance on what to look for and how to note the inspection if one is a rigging inspector. Although it states 95% of the passenger carrying sailboats in Hawaii are catamarans, the inspection is still good for the 5% mono-hulls. And just because many boats in the Caribbean cannot pass an inspection, that means the inspection is at fault?
My point is that these guide lines have little or no relevance to any of us not operating COI day boats, that's all.
During the season, I would operate three to five 2 hour trips a day, seven days a week, (6 to 7 months). Only down days were weather related, if we had no break downs.
None of us operate our personal boats that relentlessly, do we?

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post #22 of 45 Old 12-11-2015
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Re: Service life of a Sta-Lok fitting?

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Originally Posted by dorymate1 View Post
We use swage terminals for the tops since they face downward we don't see the cracking seen on the lower terminals filling up with water.
Have always used the navtec recommendations however fresh water and short season usage can add to service life.

I have never seen a Sta-Lok fitting fail Hi Mods are however more user friendly.
With all mechanical fittings when tuning rigs do not hold the nut surface of the fitting. You may wynd it out.
I have a coworker who had a swage terminal at the top fail causing the rig to come down. He had just had it inspected as well because he had had some repairs done via an insurance company and they insisted on a full rig inspection. Had been done no less than 2 months prior to the failure. Fresh water in protected river (Hudson) for the last 10 years. Not sure how old the rig was though.

I thought the whole reason for using the mechanical fittings was because they can be reused. But the CG recommendations don't sound encouraging.

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post #23 of 45 Old 12-11-2015
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Re: Service life of a Sta-Lok fitting?

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Originally Posted by capta View Post
My point is that these guide lines have little or no relevance to any of us not operating COI day boats, that's all.
During the season, I would operate three to five 2 hour trips a day, seven days a week, (6 to 7 months). Only down days were weather related, if we had no break downs.
None of us operate our personal boats that relentlessly, do we?
And if the primary failure method of rigging was fatigue then you would be right, these recomendations would have zero validity. On the other hand the primary reason rigs fail is due to corrosion. So the relavent question is how long is too long to expect stainless fittings to last.

So long as the temprature is above the critical threshold (which is true for most boats) and salt is present, the conditions are there to cause inter granular corrosion, leading to stress crack corrosion. Sure heavy use may accelerate this, which is why Navtec recommends full rig inspections at a certain number of moves sailed. But they also recommend it based on age.

The Navtec recommendations are a little less conservative than the USCG recommendations, but not massively so.

Greg
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post #24 of 45 Old 12-11-2015
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Re: Service life of a Sta-Lok fitting?

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Originally Posted by roverhi View Post
Rigged our Westsail with mostly Norsemans and some StaLoks in 1975. The terminals are still on the boat though the wire has been changed multiple times. Boat has spent its entire life in SoPac, based in Hawaii with 3 cruises South and the last 15 years doing dinner cruises. The mechanical terminals are easy to disassemble and inspect for cracks or corrosion and have held up just fine. The terminals could last another 40 years.

Swages are prone to cracking from crevice corrosion. The bad thing about them is you can't tell when they are getting close to failing bt their appearance. A boat publication did some destructive testing on swages taken off boats. Some swages with bad cracks exceeded the wire breaking strength while other swages that appeared to be sound failed at low loads.
So you reuse the ends after inspection and replace the wire at a service life interval. Correct? Seems fair the wire doesn't have the same inspection criteria aside from something totally obvious like fish-hooks. Can the assembly be inspected at say the first 5 years and with good wire and fitting just reassemble or is there a recommendation to replace the wire rather than just reassembling. I think I'm seeing here a general open and inspect being in order frequently.
Interesting comments on the Swage tests BTW seems more luck is involved here since the inspection suggestions are not all that reliable.
Some destructive testing on the reusables would be nice but probably harder to obtain samples as these fittings are not tossed regularly like the Swages.
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Re: Service life of a Sta-Lok fitting?

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Originally Posted by albrazzi View Post
So you reuse the ends after inspection and replace the wire at a service life interval. Correct? Seems fair the wire doesn't have the same inspection criteria aside from something totally obvious like fish-hooks. Can the assembly be inspected at say the first 5 years and with good wire and fitting just reassemble or is there a recommendation to replace the wire rather than just reassembling. I think I'm seeing here a general open and inspect being in order frequently.
Interesting comments on the Swage tests BTW seems more luck is involved here since the inspection suggestions are not all that reliable.
Some destructive testing on the reusables would be nice but probably harder to obtain samples as these fittings are not tossed regularly like the Swages.
You can test the wire, but it isn't practical. The only good way to test it would be to X-Ray the entire piece, then have a qualified expert look at the film. By the time you pay to have that done it is gene really cheaper to just replace it.

Unlike fittings that can be tested with dye, wire typically fails from the outside in, so dye doesn't help much.

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post #26 of 45 Old 12-12-2015
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Re: Service life of a Sta-Lok fitting?

Thanks for all the knowledge detailed here. Has anyone used the Suncor fittings? I'm curious the opinions of this manufacturer. They appear to grab the whole cable from the outside instead of separating the core. It would appear separating the load would be much better.
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post #27 of 45 Old 12-13-2015
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Re: Service life of a Sta-Lok fitting?

Swaging and compression fittings (stalock,etc.) are two completely different animals. The swage is deformed metal, which will have areas of compression and work hardening and areas of shear stresses where the metal is stretched. There are substantial differences in the structure of the metal within the fitting. More deformed metal= more potential for cycle failure, corrosion, fatigue. This sets the stage for failure of the swage or wire/swage junction. This fixture is also highly dependent upon the application of the force to the swage. If the wire is swaged quickly, the wire/fitting can be worked hardened and become more brittle. If you apply too much pressure to the swage, it can become worked hardened. Does the person fitting the swage have a torque/pressure limited tool? Do they have training in compressing these fittings? Yeah, I thought so.

If the fitting can be inspected, passed, and subsequentially prematurely fail, then the fitting design has to be changed so that its inspection and passing can lead to a predictable safe service life.

In high reliability electrical/mechanical connections (aerospace), swaged type connections are increasingly out of fashion, there are too many variables to obtain a 100% reliable connection. The aerospace field is moving towards compression type fittings. The compression fitting is not deformed, the wire is not gouged, stressed,etc. Compression is better. The service life of a compression fitting is very very long; It depends on the application.

Coming from aviation, I am stunned at the lack of safety engineering/failure mode analysis in nautical engineering. Standing rigging and keel attachments would be to me, primary structure- absolutely critical for nautical safety. If primary structure fails (eg: wing in airplanes or keel / less so the mast in boat) then the trip is over. There are no TBO (time before overhaul) rules? No inspection procedures after grounding? The letters NDT are unknown in sailing? Nobody (USCG, operator, manufacturer?) can agree upon standing rigging inspection or replacement? If your standing rigging and mast fail because of a poorly applied 5 dollar part, is this acceptable to you? Remember the chances of the system failing are directly proportional to its need to be functional at that moment.

What we know is that wire will fail. More corrosive environment, will lead to earlier failure. More stress/strain cycles, with greater loads- earlier failure. Stainless wire is corrosion resistant (good) less ductile and more brittle (bad). Compression fittings, if properly designed, applied, and maintained have a very very long service life. If properly designed, the chance of wire failure at the fitting is very very low as well. So on the next ocean boat I own, it will have compression type fittings and the wire will be fresh. Current boat is a Macgregor on an interior lake, with a huge overdesign factor. Swaged, but because of the application, I feel comfortable.

Disclaimer: I do not work in any way,shape or form for any nautical-related business.

At the end of this rant, please forgive me. I find it completely unforgivable that a captain and their crew is screwed because of the mast/standing rigging failing them. Or the keel falling off. If the boat is rated Cat A, it's rated A. and that should include a wide latitude for substandard maintenance and driving skills. I also firmly believe in the superiority of a compression type fitting on rigging.

Rant off, cheers, Leo.
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post #28 of 45 Old 12-13-2015
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Re: Service life of a Sta-Lok fitting?

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Originally Posted by northernsquirrel View Post
Swaging and compression fittings (stalock,etc.) are two completely different animals. The swage is deformed metal, which will have areas of compression and work hardening and areas of shear stresses where the metal is stretched. There are substantial differences in the structure of the metal within the fitting. More deformed metal= more potential for cycle failure, corrosion, fatigue. This sets the stage for failure of the swage or wire/swage junction. This fixture is also highly dependent upon the application of the force to the swage. If the wire is swaged quickly, the wire/fitting can be worked hardened and become more brittle. If you apply too much pressure to the swage, it can become worked hardened. Does the person fitting the swage have a torque/pressure limited tool? Do they have training in compressing these fittings? Yeah, I thought so.

If the fitting can be inspected, passed, and subsequentially prematurely fail, then the fitting design has to be changed so that its inspection and passing can lead to a predictable safe service life.

In high reliability electrical/mechanical connections (aerospace), swaged type connections are increasingly out of fashion, there are too many variables to obtain a 100% reliable connection. The aerospace field is moving towards compression type fittings. The compression fitting is not deformed, the wire is not gouged, stressed,etc. Compression is better. The service life of a compression fitting is very very long; It depends on the application.

Coming from aviation, I am stunned at the lack of safety engineering/failure mode analysis in nautical engineering. Standing rigging and keel attachments would be to me, primary structure- absolutely critical for nautical safety. If primary structure fails (eg: wing in airplanes or keel / less so the mast in boat) then the trip is over. There are no TBO (time before overhaul) rules? No inspection procedures after grounding? The letters NDT are unknown in sailing? Nobody (USCG, operator, manufacturer?) can agree upon standing rigging inspection or replacement? If your standing rigging and mast fail because of a poorly applied 5 dollar part, is this acceptable to you? Remember the chances of the system failing are directly proportional to its need to be functional at that moment.

What we know is that wire will fail. More corrosive environment, will lead to earlier failure. More stress/strain cycles, with greater loads- earlier failure. Stainless wire is corrosion resistant (good) less ductile and more brittle (bad). Compression fittings, if properly designed, applied, and maintained have a very very long service life. If properly designed, the chance of wire failure at the fitting is very very low as well. So on the next ocean boat I own, it will have compression type fittings and the wire will be fresh. Current boat is a Macgregor on an interior lake, with a huge overdesign factor. Swaged, but because of the application, I feel comfortable.

Disclaimer: I do not work in any way,shape or form for any nautical-related business.

At the end of this rant, please forgive me. I find it completely unforgivable that a captain and their crew is screwed because of the mast/standing rigging failing them. Or the keel falling off. If the boat is rated Cat A, it's rated A. and that should include a wide latitude for substandard maintenance and driving skills. I also firmly believe in the superiority of a compression type fitting on rigging.

Rant off, cheers, Leo.
For the purposes of this debate I appreciate the comments on the Aviation industry going away from Swage fittings. For the Marine industry to do the same thing would be a long shot not that you're suggesting that but your point is taken.
As far as industry standards Maritime and Aviation will always have some gap. To subject all sailing vessels to the standards applied to every Comanche or Piper out there would surely result in less sailing vessels on the water at least our only choice is not to fall from the sky when something goes wrong.
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post #29 of 45 Old 12-14-2015
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Re: Service life of a Sta-Lok fitting?

Quote:
Originally Posted by northernsquirrel View Post
Swaging and compression fittings (stalock,etc.) are two completely different animals. The swage is deformed metal, which will have areas of compression and work hardening and areas of shear stresses where the metal is stretched. There are substantial differences in the structure of the metal within the fitting. More deformed metal= more potential for cycle failure, corrosion, fatigue. This sets the stage for failure of the swage or wire/swage junction. This fixture is also highly dependent upon the application of the force to the swage. If the wire is swaged quickly, the wire/fitting can be worked hardened and become more brittle. If you apply too much pressure to the swage, it can become worked hardened. Does the person fitting the swage have a torque/pressure limited tool? Do they have training in compressing these fittings? Yeah, I thought so.

If the fitting can be inspected, passed, and subsequentially prematurely fail, then the fitting design has to be changed so that its inspection and passing can lead to a predictable safe service life.

In high reliability electrical/mechanical connections (aerospace), swaged type connections are increasingly out of fashion, there are too many variables to obtain a 100% reliable connection. The aerospace field is moving towards compression type fittings. The compression fitting is not deformed, the wire is not gouged, stressed,etc. Compression is better. The service life of a compression fitting is very very long; It depends on the application.

Coming from aviation, I am stunned at the lack of safety engineering/failure mode analysis in nautical engineering. Standing rigging and keel attachments would be to me, primary structure- absolutely critical for nautical safety. If primary structure fails (eg: wing in airplanes or keel / less so the mast in boat) then the trip is over. There are no TBO (time before overhaul) rules? No inspection procedures after grounding? The letters NDT are unknown in sailing? Nobody (USCG, operator, manufacturer?) can agree upon standing rigging inspection or replacement? If your standing rigging and mast fail because of a poorly applied 5 dollar part, is this acceptable to you? Remember the chances of the system failing are directly proportional to its need to be functional at that moment.

What we know is that wire will fail. More corrosive environment, will lead to earlier failure. More stress/strain cycles, with greater loads- earlier failure. Stainless wire is corrosion resistant (good) less ductile and more brittle (bad). Compression fittings, if properly designed, applied, and maintained have a very very long service life. If properly designed, the chance of wire failure at the fitting is very very low as well. So on the next ocean boat I own, it will have compression type fittings and the wire will be fresh. Current boat is a Macgregor on an interior lake, with a huge overdesign factor. Swaged, but because of the application, I feel comfortable.

Disclaimer: I do not work in any way,shape or form for any nautical-related business.

At the end of this rant, please forgive me. I find it completely unforgivable that a captain and their crew is screwed because of the mast/standing rigging failing them. Or the keel falling off. If the boat is rated Cat A, it's rated A. and that should include a wide latitude for substandard maintenance and driving skills. I also firmly believe in the superiority of a compression type fitting on rigging.

Rant off, cheers, Leo.
Great stuff squirrel. Thank you.

I love when experts from different industries and backgrounds cross-pollinate.

My dad was an NDT guy for Boeing with s masters in metallurgy, so much of what you say rings true.

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post #30 of 45 Old 12-14-2015
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Re: Service life of a Sta-Lok fitting?

Quote:
Originally Posted by northernsquirrel View Post
Swaging and compression fittings (stalock,etc.) are two completely different animals. The swage is deformed metal, which will have areas of compression and work hardening and areas of shear stresses where the metal is stretched. There are substantial differences in the structure of the metal within the fitting. More deformed metal= more potential for cycle failure, corrosion, fatigue. This sets the stage for failure of the swage or wire/swage junction. This fixture is also highly dependent upon the application of the force to the swage. If the wire is swaged quickly, the wire/fitting can be worked hardened and become more brittle. If you apply too much pressure to the swage, it can become worked hardened. Does the person fitting the swage have a torque/pressure limited tool? Do they have training in compressing these fittings? Yeah, I thought so.

If the fitting can be inspected, passed, and subsequentially prematurely fail, then the fitting design has to be changed so that its inspection and passing can lead to a predictable safe service life.

In high reliability electrical/mechanical connections (aerospace), swaged type connections are increasingly out of fashion, there are too many variables to obtain a 100% reliable connection. The aerospace field is moving towards compression type fittings. The compression fitting is not deformed, the wire is not gouged, stressed,etc. Compression is better. The service life of a compression fitting is very very long; It depends on the application.

Coming from aviation, I am stunned at the lack of safety engineering/failure mode analysis in nautical engineering. Standing rigging and keel attachments would be to me, primary structure- absolutely critical for nautical safety. If primary structure fails (eg: wing in airplanes or keel / less so the mast in boat) then the trip is over. There are no TBO (time before overhaul) rules? No inspection procedures after grounding? The letters NDT are unknown in sailing? Nobody (USCG, operator, manufacturer?) can agree upon standing rigging inspection or replacement? If your standing rigging and mast fail because of a poorly applied 5 dollar part, is this acceptable to you? Remember the chances of the system failing are directly proportional to its need to be functional at that moment.

What we know is that wire will fail. More corrosive environment, will lead to earlier failure. More stress/strain cycles, with greater loads- earlier failure. Stainless wire is corrosion resistant (good) less ductile and more brittle (bad). Compression fittings, if properly designed, applied, and maintained have a very very long service life. If properly designed, the chance of wire failure at the fitting is very very low as well. So on the next ocean boat I own, it will have compression type fittings and the wire will be fresh. Current boat is a Macgregor on an interior lake, with a huge overdesign factor. Swaged, but because of the application, I feel comfortable.

Disclaimer: I do not work in any way,shape or form for any nautical-related business.

At the end of this rant, please forgive me. I find it completely unforgivable that a captain and their crew is screwed because of the mast/standing rigging failing them. Or the keel falling off. If the boat is rated Cat A, it's rated A. and that should include a wide latitude for substandard maintenance and driving skills. I also firmly believe in the superiority of a compression type fitting on rigging.

Rant off, cheers, Leo.
Leo,
Fully agree with you. I am a licensed mechanical engineer am amazed at some of the "nautical engineering" that is done by so called professionals within the boating industry. Even some of the well regarded "professionals" in the marine industry publish a lot of information that is just wrong. Seems to me one of the problems is the marine industry has no real standards. For example, what degree or work experience or test do you need to pass to call yourself a professional sailboat rigging inspector? Or what qualifications do you need to design and boat hull or rig? Do you see and engineers seal on any boat or rig drawings? Are the boats and rigs tested for life cycle? Also, a lot of boating and rigging parts have no standards they need to be manufactured to- who knows what your are buying. Take a look at a sailboat mast. In many cases one failure of any part on a single wire stay or shroud will bring the mast down. If that is the case, we need to have better standards than what we have now. And that mast coming down could (and has) killed a passenger.

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