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Old 27-11-2013, 17:09   #1
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Rigging rod or wire in Super Duplex Stainless

Time is up for a rod rigging replacement. All rigging is currently Navtec rod and is now 6 years old, so according to Navtec's guidelines I should re-rig. Such a crazy waste of time and money. I have solid rod with a breaking strength of 48,000 lbs, yet after 6 years it needs replacing. I presume the reason for the early replacement is the vulnerability of 316 stainless to stress corrosion cracking and I am asked to replace nearly new with new, just to be sure it really is new and uncorroded.

Any cursory stainless spec sheet analysis will point to more modern steels such as 2507 or S32760 for high stress marine use that should be close to immune from SCC and corrosion in general and should last massively longer than 316. Price is not very different. Appearance is similar. Strength is similar.

I have never heard of it being done. Has anyone actually done it? Why not?
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Old 27-11-2013, 18:07   #2
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Re: Rigging rod or wire in Super Duplex Stainless

6 years is not old for rod rigging -- unless it has had a very hard life, very heavily campaigned racer, or RTW world cruiser. Navtec has a number of statements and white papers on the aging of and inspection of Navtec rod. They have 3 classes of inspection A,B,C, that they suggest are applied at different ages. The rod can be re=headed, if the inspection indicates issues with a head. Navtec rod is pretty corrosion resistant, more so than wire.
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Old 27-11-2013, 18:26   #3
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Re: Rigging rod or wire in Super Duplex Stainless

6 years is nothing for a well maintained rod riggin set, you can rehead the ends , cracks are located mostly in the head and in some cases in the small bushing in the cone fittings , Navtec is not 316 ss , the rod itself is called Nitronic 50 , most rod failures is not corrosion related but most probably stress fatigue .. the turnbuckles is something to wacht for, navtec turnbuckles are water traps... Good luck.
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Old 27-11-2013, 18:46   #4
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Re: Rigging rod or wire in Super Duplex Stainless

The rod rigging on my Valiant is 27 years old. I'll probably replace it before I next go offshore, but the heads are fine.

As mentioned, Navtec is very cagey about when their rigging needs to be replaced. Certainly they would never say it needs replacement after 6 years due to corrosion...that would be from extremely heavy use offshore and serious stressing.

But as to your original question and the suitability of 2507 or S32760, I have absolutely no clue.
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Old 27-11-2013, 18:48   #5
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Re: Rigging rod or wire in Super Duplex Stainless

Seems like thats a real short time for ANY good rigging to last !! Most of the posts on here seem to agree that 12 yrs is the time to think about re-doing wire rigging!! Ive always kept a good watch on my rigging for signs of possible trouble! and I sorta think that 15 yrs is a better time frame for replaceing wire rigging! Never had rod rigging, but always thought that it would last longer then wire! Am I wrong?? would not be the first time LOL
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Old 27-11-2013, 19:01   #6
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Re: Rigging rod or wire in Super Duplex Stainless

Our 1981 rod is all original, except for the forestay. When we removed the Tuff Luff to get roller-furling gear installed a few years ago, we found that the original forestay was kinked near the hounds. Don't know how long it was like that - it was totally hidden. We look over the remaining rigging carefully every season. It seems to hold up well. We've been out beating 30 miles up Long Island Sound into 35 knot winds and 6' waves, roaring down combers in Massachusetts Bay at 11 knots, coming down from Maine, and taken her out in conditions that had Laguardia Airport closed, just to see how she handled. Though I don't know how your rigging was sized for loads and cycles, 6 years seems a bit premature.
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Old 27-11-2013, 19:18   #7
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Re: Rigging rod or wire in Super Duplex Stainless

Not sure where the 6 years came from, this is what I found that Navtec had to say:

Quote:
With all the factors listed above, it is clear that there are many variables that must be considered to determine the life of the rod. As a general rule, Navtec uses a figure of 40,000 sailing miles as a time when a thorough inspection should be done. This would include inspection of all the rod heads and end fittings. If any of the heads are cracked or worn, the rod should at least be reheaded. That doesn't mean that the rod itself would need to be replaced; that would depend on whether the turnbuckles had enough stroke to compensate for a shorter piece of rod. In a good installation, the rod will typically last significantly longer than the heads on the end of the rod.

After a thorough inspection with no problems found, depending on the installation, it may be reasonable to expect the rod to last another 40,000 miles. However, prudence would dictate what should be done. If the boat is going to be used for just local day sailing, you could make frequent inspections and perform repairs as soon as they were needed. But if the boat is going to do a long ocean passage or an extended cruise, it would be smarter to rehead or replace the rod prior to departure.

One item that Navtec does recommend replacing after 10 years of use or 40,000 miles (whichever comes first) is the turnbuckle screws. With the stress concentrations due to the threads, cracks could be forming that may not be noticed until they fail. The screws may last for many additional years, but it is much cheaper to replace a few rigging screws than to replace a mast and all of the rigging.
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Old 27-11-2013, 21:24   #8
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Re: Rigging rod or wire in Super Duplex Stainless

The super duplex 32750 or 32760 are stronger than the nitronic 50. They also have a better resistance to the marine environment. At the wholesale level they are higher priced than 316 stainless.

Pm me with thee sizes I think I have super duplex down 1/2 or 5/8 in stock. For the Nitronic think we only have 60 in the small diameters but I'll check when I am back in the office Monday.

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Old 28-11-2013, 04:28   #9
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Re: Rigging rod or wire in Super Duplex Stainless

Quote:
Originally Posted by neilpride View Post
6 years is nothing for a well maintained rod riggin set, you can rehead the ends , cracks are located mostly in the head and in some cases in the small bushing in the cone fittings , Navtec is not 316 ss , the rod itself is called Nitronic 50 , most rod failures is not corrosion related but most probably stress fatigue .. the turnbuckles is something to wacht for, navtec turnbuckles are water traps... Good luck.
This is correct, but Nitronic 50 is a slightly higher nitrogen content 316 stainless steel and its performance whilst better is not massively better as is the case the the Super Duplex types.

The stress fatigue you mention is the probable failure mode, but it is promoted by corrosion, it is otherwise known as stress corrosion cracking and 316 types are particularly vulnerable to it.

Navtec's advice is to replace all the stainless at this age including turnbuckles.
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Old 28-11-2013, 04:51   #10
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Re: Rigging rod or wire in Super Duplex Stainless

Quote:
Originally Posted by Dsanduril View Post
Not sure where the 6 years came from, this is what I found that Navtec had to say:
Navtec's maintenance requirements are here and similar to your quote:
http://www.navtec.net/%5Cassets%5Cim...ng-Service.pdf

Look at page 3, paragraph 6:

6. Routine inspections with no rod problems
After a thorough inspection (Level C: 40,000 to 60,000m or 6 yrs) with no evidence of
damage, it may be reasonable to expect the rod to last an additional 20,000 to 30,000
miles. However, Navtec Recommends rod re-heading, and this is when a maintenance
and inspection schedule becomes of paramount importance.


The 6 year life is a consequence of this. What this means for me and most people after 6 years is up is that all stays, which are discontinuous with no adjustment and therefore can't be cold headed, must be replaced. All the other stays have been cold headed once and there is no length left to do it again, so they must be replaced. They do offer the option of inspecting and dye testing, but once you commit to the time and expense of doing that you may as well jump to replace anyway. A major cost/hassle every 6 years. Actually the subsequent inspection is given as 20-40,000 miles, half the first interval and no time period given, so I take that really to mean 3 years, so I am pushing it at 6.

Also Navtec advise to replace turnbuckle screws at 10 years as you point out in your quote. The source of that is here for the benefit of others:
http://www.navtec.net/%5Cassets%5Cim...ng-Service.pdf

Wire rigging components also has frequent and rigorous inspection/replacement requirements.
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Old 28-11-2013, 06:13   #11
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Re: Rigging rod or wire in Super Duplex Stainless

Are you saying that you have re-headed the rod in under 6 years?
You can add a toggle or longer turnbuckle screws to add some additional length on the re-headed rod. I still don't see how you come up with a Navtec recommeded 6-year life based on their suggestion to do a Level C inspection (drop the rig and inspect all heads).
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Old 28-11-2013, 06:56   #12
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Re: Rigging rod or wire in Super Duplex Stainless

Quote:
Originally Posted by Paul L View Post
Are you saying that you have re-headed the rod in under 6 years?
You can add a toggle or longer turnbuckle screws to add some additional length on the re-headed rod. I still don't see how you come up with a Navtec recommeded 6-year life based on their suggestion to do a Level C inspection (drop the rig and inspect all heads).
Not under, actually just over 6 yrs. Then it was decided not viable to test and to rehead where possible. Half were reheated, half were replaced as some stays are non adjustable and reheading couldn't be done. Now there is no adjustment left in the other half and again I plan to replace the fixed rods rather than test and risk early failure. I don't want any more turnbuckles and toggles as they are in fact the weakest link and I don't want any more failure points than I have.

As to the 6 year life on the rods, it is not indeed the rule but the result of what I believe is a sensible response to the rules. Anyone who goes to the trouble of removing the mast and rigging and die testing might as well save the die test cost and extend the next service interval and buy new. The whole life cost may be no more expensive and it is a safer option.
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Old 28-11-2013, 07:12   #13
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Re: Rigging rod or wire in Super Duplex Stainless

It depends a lot on what the total cost of the Level C inspect will be. Since many boats have their rig taken down for off season, the incremental cost may not be that much in some places. I think doing what you imply at 10 years, instead of 6, is more reasonable for most boats, unless they have lived an extremely tough life.
The actual rate of dismasting with rod rig in the 10-15 year age is not high (not that I have actual stats).
Another issue is rig insurance. Some popular cruising insurance policies don't cover standing rigging over 10 years old. I was offered one of these policies on a boat with older rod and they finally agreed to cover the standing rig if I did a Level C inspection every 2 years -- not practical while cruising.
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Old 28-11-2013, 08:34   #14
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Quote:
Originally Posted by poiu View Post
As to the 6 year life on the rods, it is not indeed the rule but the result of what I believe is a sensible response to the rules.
Everyone has their own tolerance for risk and only you know the type of sailing done on the rig. But I don't agree that rod rigging on typical cruising boats needs replacement in 6 years based on a reasonable risk assessment.
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Old 28-11-2013, 09:50   #15
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Re: Rigging rod or wire in Super Duplex Stainless

Last time I checked, Navtec made it pretty clear that the "life" of rod rigging was actually dependent on load cycles. You put tension on a rod, then you release it. And the rod stretches and then contracts back. That's one load cycle. Every time you tack the boat and the rig shifts from one tack to the other, that's one load cycle.

Navtec suggests that since no one is actually counting load cycles, they can be estimated based on the type of use and amount of sailing time for any particular boat, i.e. one owner using his boat for four days per month in a six month season is putting twentyfour "days" on a boat. One boat in heavy charter use, might be putting ten times that wear on the rigging, in the same single year.

Just going by the calendar without accounting for the amount of use, or the type of use (relaxed cruising versus intense racing and heavy weather) is going to be very expensive.

If you were at sea for all six years, sure. If you were at sea three or four days every week for six years, sure. If you weren't...Well, you could always install strain gauges and actually count load cycles on the rigging if you wanted to.

Or re-rig some other way, if you felt rod was an expensive and useless thing for your boat.
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