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Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


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  #71  
Old 01-25-2012
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Quote:
Originally Posted by casey1999 View Post
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.
Are you sure about that. I was under the impression that if you had a crane cable that was in service for 30 years someone would think about replacing it.

Don't you keep records of replacement and inspections for all were parts? How old are the oldest parts?
Also is shock loading much of an issue?
What is the safety factor engineered in?
Are your parts stainless? The old time riggers say that super heavy iron rigging brushed with tar and oil every day lasts for almost ever and is easy to see if it is rusted and needs to be replaced.
Stainless is much cleaner for sails and decks and can be ignored for months but hides its impending failure better than plain steel that is continually greased.


Your the expert but I suspect that in an industrial setting a 5 year part and certainly a 10 year part just wouldn't even be around. On a sailboat we figure hey it's stainless, looks good and is only 30 years old, lets go sailing.

Last edited by davidpm; 01-25-2012 at 09:24 PM.
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  #72  
Old 01-26-2012
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All my lifting chains and cables have tags and certifications as to there use
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  #73  
Old 01-26-2012
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Quote:
Originally Posted by davidpm View Post
Are you sure about that. I was under the impression that if you had a crane cable that was in service for 30 years someone would think about replacing it.

Don't you keep records of replacement and inspections for all were parts? How old are the oldest parts?
Also is shock loading much of an issue?
What is the safety factor engineered in?
Are your parts stainless? The old time riggers say that super heavy iron rigging brushed with tar and oil every day lasts for almost ever and is easy to see if it is rusted and needs to be replaced.
Stainless is much cleaner for sails and decks and can be ignored for months but hides its impending failure better than plain steel that is continually greased.


Your the expert but I suspect that in an industrial setting a 5 year part and certainly a 10 year part just wouldn't even be around. On a sailboat we figure hey it's stainless, looks good and is only 30 years old, lets go sailing.
As far as I know, there is no age limit on certified industrial weight handling equipment. Some of this equipment is used on docks and is made of stainless due to the corrosion environment. One other thing, all industrial lifting equipment does need to be manufactured and tested to certain ASTM standards. I never see these ASTM standards listed for boat hardware- maybe this is the problem- manufacture and quality control has no standards in boat rigging. Some of our cranes date to the 1950 (over 100 ton capacity) and are still working- as long as the cable and rigging pass inspection it is good to go. And yes all the lifting gear is id tagged with test dates and certified wt capacity.
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  #74  
Old 01-26-2012
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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 tension. 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.
Dedekam says: "Forestay length determines the mast rake. Backstay tension has only a small effect on mast rake. On a masthead rig, backstay tension mainly controls forestay sag. On a fractional rig the running backstays (runners) do the same. On a fractional rig without runners the tension of the cap shrouds mainly determines the sag."
Notice he said Forestay length (pre determined in the case of my furler), not tension. BTW, he also mentions several other factors that relate to Mast rake, but the issue here was Forestay adjustment.
As I said, it's not rocket science (I wish I could even attempt the calculations you did!). However, I strongly recomend we find a credible source of information and understand how the system works BEFORE adjusting our rigs.

Last edited by L124C; 01-26-2012 at 03:16 PM.
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  #75  
Old 01-26-2012
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Quote:
Originally Posted by L124C View Post
Dedekam: "Forestay length determines the mast rake. Backstay tension has only a small effect on mast rake. On a masthead rig, backstay tension mainly controls forestay sag. On a fractional rig the running backstays (runners) do the same. On a fractional rig without runners the tension of the cap shrouds mainly determines the sag."
Notice he said Forestay length (pre determined in the case of my furler), not tension. BTW, he also mentions several other factors that relate to Mast rake, but the issue here was Forestay adjustment.
As I said, it's not rocket science. However, I strongly recomend we find a credible source of information BEFORE adjusting our rigs.
I am not sure why you included my quote in your reply. Sure, if you want to change your mast rake you must change your forestay length. But the forestay tension in a mast head rig will be determined by your back stay tension. And if you back stay is longer than your forestay (generally the case), then your forestay will always be at a higher tension than the backstay- in my case 1.25 x the backstay tension.
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  #76  
Old 01-26-2012
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"Sail & Rig Tuning" by Ivan Dedekam"
I have this book and was re-reading last night- very good book. One thing Dedekam says is to tension the rig as tight as possible, with forestay (as I remember- going above 30% uts). According to other posters, this could lead to fatigue failure over time.- Thoughts?
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  #77  
Old 01-26-2012
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Quote:
Originally Posted by casey1999 View Post
As far as I know, there is no age limit on certified industrial weight handling equipment. Some of this equipment is used on docks and is made of stainless due to the corrosion environment. One other thing, all industrial lifting equipment does need to be manufactured and tested to certain ASTM standards. I never see these ASTM standards listed for boat hardware- maybe this is the problem- manufacture and quality control has no standards in boat rigging. Some of our cranes date to the 1950 (over 100 ton capacity) and are still working- as long as the cable and rigging pass inspection it is good to go. And yes all the lifting gear is id tagged with test dates and certified wt capacity.
.... and most such equipment, etc. used in 'critical' / hazardous / lethal service is routinely retested and validated ... verified/'proofed'.

Its not all that hard for a technically able sailboater to periodically 'proof load' the rigging - I do this routinely to ensure the 'efficacy of remaining strength and safety condition of the wire', etc. I wont divulge how I do this as there are dangers in doing so .... and I live in the USA where there is a voracious 'lawyer problem' ... .
Faster likes this.

Last edited by RichH; 01-26-2012 at 03:34 PM.
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  #78  
Old 01-26-2012
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Quote:
Originally Posted by casey1999 View Post
I am not sure why you included my quote in your reply. Sure, if you want to change your mast rake you must change your forestay length. But the forestay tension in a mast head rig will be determined by your back stay tension. And if you back stay is longer than your forestay (generally the case), then your forestay will always be at a higher tension than the backstay- in my case 1.25 x the backstay tension.
I quoted your post because you were responding to ron hudson who was questioning how he could measure the tension on his furlered Forestay. IMO the simple answer is: You can't. Also confirmed here:
How to use 90 & 91 Series Tension Gauges
I don't think the Forestay tension should matter as long as :
You have proper mast rake, correct forestay sag, and don't exceed the maximum tension limit of your backstay. I don't understand what the 1.25 number does for you.
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  #79  
Old 01-26-2012
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Quote:
Originally Posted by L124C View Post
I quoted your post because you were responding to ron hudson who was questioning how he could measure the tension on his furlered Forestay. IMO the simple answer is: You can't. Also confirmed here:
How to use 90 & 91 Series Tension Gauges
I don't think the Forestay tension should matter as long as :
You have proper mast rake, correct forestay sag, and don't exceed the maximum tension limit of your backstay. I don't understand what the 1.25 number does for you.
The quote from the gage instruction is "Backstay tension would, of course, have to be adjusted to maintain a straight mast with the desired forestay tension. Since the backstay makes a greater angle to the mast, the backstay tension will be lower than the forestay tension.

NOTE ! ROLLER FURLING CAN ONLY BE SET BY BACK STAY TENSION."

That is what I said, you cannot measure directly forestay tension, but you can calculate it based on the angle of the backstay and forestay, and since you know backstay tension it is a simple calculation to calculate forestay tension. And forestay does matter if you want to keep your stay tensions below say 20% UTS. Because of the 1.25 factor, you will want to keep backstay tension at 16% to have a forestay at 20%. Note this is for my rig, others depending on stay angles may be different. In order to change mast rake, you can change the length of your forestay (and keep tension the same), my rig has an adjustable plate at the bow connection where I can move the connection to vary forestay length.

If you take your back stay to your maximum desired tension, your forestay will exceed that amount by 25% (again, based on my rig dimensions). If you are trying to keep the tensions below a certain value, then it is important to know this value is higher on your forestay and therefore need to reduce backstay tension accordingly.

Last edited by casey1999; 01-26-2012 at 08:39 PM.
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  #80  
Old 01-26-2012
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Quote:
Originally Posted by casey1999 View Post
The quote from the gage instruction is "Backstay tension would, of course, have to be adjusted to maintain a straight mast with the desired forestay tension. Since the backstay makes a greater angle to the mast, the backstay tension will be lower than the forestay tension.

NOTE ! ROLLER FURLING CAN ONLY BE SET BY BACK STAY TENSION.

If you take your back stay to your maximum desired tension, your forestay will exceed that amount by 25% (again, based on my rig dimensions). If you are trying to keep the tensions below a certain value, then it is important to know this value is higher on your forestay and therefore need to reduce backstay tension accordingly.
"That's not completely true, Mr. President." Bobstays, (on boats that have them) can also be used to adjust the forestay tension.
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