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Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation
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Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


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  #61  
Old 01-25-2012
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Hugh?

Quote:
Originally Posted by hellosailor View Post
First, you replace ..... INSERT CONDESCENDING SARCASM......market because, well, even at today's cheap hardware prices most recreational sailors can't afford it.

Back on the other planet...
Yeah, even 30 years ago you'd find J/24 sailors retuning their rigs before every race to match the expected wind conditions. Mast rake, tension, they'd have a little card and change everything just a little bit to match the expected wind range. But on cruising boats with "ain't-gonna-bendy-me" masts? Nuh-uh. Kinda sounds like the riggers have found a way to finesse the ultimate in rig tuning--and book a *hitload more billable hours in the process. The kind of stuff that a local rock start from the local sailing loft used to do for free when you bought new sails.
I assume you are referring to the book I recommended. I purchased it because my boat had excessive Weather Helm on Port Tack. It not only allowed me to cure that problem, it taught me MANY other things in the process.
As I recall, it set me back all of $15 Dollars. Yeah....I'm sure the author is sitting in a big house on a hill, counting his wealth!
I honestly suspect he has forgotten more about sailing than I will ever know, and I thank him for sharing some of that knowledge!
BTW I can certainly effect the efficiency of my Main using the back stay. Do I use it for Bay Sailing? No. Would I use it if I was racing seriously with a crew or cruising on the same tack for extended periods when it would be beneficial and worth the effort? Yes.

Last edited by L124C; 01-26-2012 at 11:00 AM.
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  #62  
Old 01-25-2012
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Quote:
Originally Posted by ron_hudson View Post
I am not capable of tuning under sail simply because I need to keep my hands on the wheel and would probably lose the tensioner over the side, but I do try and balance the rib dockside. My problem is trying to tension the forestay as it has the self furling covering the stay and therefore I cannot connect the tensioner directly. Is there a solution to this?
I did some calcs on my mast head rig with self furling also covering the stay. I figure the fore stay will see about 125% of the tension on the back stay due to the smaller angle between the forestay and mast as compared to back stay and mast. So if you angles are similar, then take back stay tension and multiply by 1.25 to get approximate forestay tenstion. If you send me you mast height from deck, and distance from mast to bow and also mast to the stern, and your backstay tension, I will calculate exact number, otherwise 1.25 x should be close.
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  #63  
Old 01-25-2012
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Quote:
Originally Posted by davidpm View Post
Doug
I just got off the phone with my son.
As far as replacing standing rigging how far should one go? Should I replace all bolts that hold tangs and the spreaders? Should the spreader fittings be removed to inspect for mast corrosion (my fittings wraps 3/4 of the mast circumference)? Should all fittings that are rivited be removed and new rivets installed?
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  #64  
Old 01-25-2012
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Quote:
Originally Posted by hellosailor View Post
So if conventional tuning (and cable sizing) depends on the leeward side going slack, and that constnatly cycles the load causing cyclic stressing which in turn weakens the cables...

Does that mean it would be better for the working life of the shrouds, to spec shroud cables that could be tensioned down enough so that the leeward side never went slack? Keeping a uniform tension, or a more uniform tension, on the shrouds all the time?
Does someone have an answer? Good comment. Kind of like pre-tensioned concrete slabs.
http://en.wikipedia.org/wiki/Pre-tensioned_concrete

Last edited by casey1999; 01-25-2012 at 12:44 PM.
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  #65  
Old 01-25-2012
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Quote:
Originally Posted by RichH View Post
2. Most rigging is stainless steel and that presents a special problem all by the very nature of 300 series stainless --- vulnerability to fatigue failure. Fatigue is vastly accelerated any time 300 series stainless is cyclically loaded beyond ~30,000 psi (even that the material has a ~90000 psi 'ultimate tensile strength' ... but that applies only to 'ductile failure' & non repetitive load conditions). The all important material characteristic for 'boat rigging' and plates, etc, I adhere to, is that I expect that the material/rigging WILL catastrophically fail when there are more than (estimated) 1 million 'cycles' (about 1 circumnavigation) where the component goes beyond 30K psi. Keep that loading UNDER 30K psi (30% of rig tension, etc.) and the part 'can' last virtually 'forever' (theoretically from a materials science or metallurgical point of view).

Would say galvanized cable have the same fatigue problem as stainless?

Last edited by Faster; 01-25-2012 at 01:26 PM. Reason: fixed quote
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Old 01-25-2012
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Quote:
Originally Posted by casey1999 View Post
As far as replacing standing rigging how far should one go? Should I replace all bolts that hold tangs and the spreaders? Should the spreader fittings be removed to inspect for mast corrosion (my fittings wraps 3/4 of the mast circumference)? Should all fittings that are rivited be removed and new rivets installed?
This is a good question.
Next time I talk to Steve I'll ask. He is working long hours and studying for an ABYC exam so I think I'll give him a few days. Last thing he wants to do is talk shop with his dad after a 12 hour day.

In the mean time I'll bet I can guess based on prior conversations.
If it's coastal, take a really good look, I'm guessing with a magnifying glass, and if you see anything amiss replace the part.
If it is off-shore and the parts are over 10 years old replace it all if you can afford it otherwise pick and choose and take your chances.

Look we all know we take chances every day we drive a car or eat a big Mac.
None of this is news. It would be really easy to spend 200% of our income on insurance. Some of us worry about risk more than others and we all draw the line in a different place. That is not what the intention of this thread is.

The lesson I have learned From Steve and Doug and others is a very limited metallurgical one.

1. Stainless steel as used in sailboat chain plates and other rigging components is a phenomenal material but it can and does deteriorate to the point where it is no longer safe.
2. Often indications of this deterioration can be seen in the form of micro-cracks and pits.
3. Sometimes this deterioration can not be seen because it occurs in hidden places.
4. Sometimes this deterioration can not be seen because of damage by lighting or work hardening.
5. Sometime this deterioration process is accelerated by a design that allows flexing.
6. Sometimes this deterioration is accelerated by improper loading caused by a failure of other parts or improper use or improper tuning.
7. The older a part is the higher the chance it has suffered one of above processes and no longer has its like new strength.

Did I miss anything?


The only thing we have learned, I hope, from this is that we can no longer look at the stainless on the decks of our boats and cavalierly think, "IT'S STAINLESS I DON'T HAVE TO WORRY ABOUT IT".

How often you check it and how often you replace it depends on your tolerance for risk combined with how you sail just like everything else.
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  #67  
Old 01-25-2012
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This is a great older thread on this same subject:
chainplate followup
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Old 01-25-2012
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Quote:
Originally Posted by casey1999 View Post
I did some calcs on my mast head rig with self furling also covering the stay. I figure the fore stay will see about 125% of the tension on the back stay due to the smaller angle between the forestay and mast as compared to back stay and mast. So if you angles are similar, then take back stay tension and multiply by 1.25 to get approximate forestay tenstion. If you send me you mast height from deck, and distance from mast to bow and also mast to the stern, and your backstay tension, I will calculate exact number, otherwise 1.25 x should be close.
Thanks I dont have to get an exact number but the approach you gave will help a lot. I have sailed many years and up to now I have not tried to be scientific about this; more pulling on the stays and feeling that 's about right ????. Then spening the rest of the season with the stays sagging badly and poor performance to boot.I spend about an hour last year doing this and it made all the difference. Another question If you leave the mast up during the offseason should you back off on the tension a bit?
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Quote:
Originally Posted by ron_hudson View Post
Thanks I dont have to get an exact number but the approach you gave will help a lot. I have sailed many years and up to now I have not tried to be scientific about this; more pulling on the stays and feeling that 's about right ????. Then spening the rest of the season with the stays sagging badly and poor performance to boot.I spend about an hour last year doing this and it made all the difference. Another question If you leave the mast up during the offseason should you back off on the tension a bit?
I have no off season here in Hawaii so my rig has been tensioned for nearly 40 years with no problems. You may cause more problems by backing tension than just leaving as is, since a lower tension on the rig may allow more movement which may accelerate fatigue on the rig and lead to earlier failure.
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Old 01-25-2012
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The thing I find interesting about failure of sail boat rigs is that there seems to be this big unkown about if the rig is good or not. Because of this unkown, we are told best to replace say every 10 years.

Now where I work I have just be assigned to be weight handling (lifting) inspector. I have started some training on inspecting weight lifting equipment- cranes, hoist, shackels, lifting cables, slings. This is for lifting things that failure is not an option. It just seems like a simple inspection is good enough for these items, and if they pass they rarely fail. But with sailboats, seems even with good inspection, they still, and regulary do fail.
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