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post #81 of 107 Old 01-26-2012
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Dynamic Tuning is explained in Dennis Conner's book, Sail Like a Champion.
First you tune the rig to specs, generally 12-15lbs on upper shrouds, 15lbs on lower shrouds, and 10lbs on foestay. Backstay is used to bend mast to point better, or slack-off downwind.
Take the boat on a 10-15kt day, go from a close reach to a beat. Observe the leeward shrouds for slackness and tighten them just until the slack is gone. Remember how many turns you had to make on each shroud. Change tacks and do the same thing on the leeward side. He then recommends doing the same thing in 15-20kt winds.
When you get back to the dock measure the distance from the top of the mast to each shroud, using your main halyard. Make sure they are all equal. If they are not then you must make them equal by re-checking the tune and making adjustments accordingly.
Take her back out and repeat the process. It is a lot easier and faster if you make your distances equal with proper tune before you go out the first time.
Depending on your rig, you may have to sacrifice tune to get an equal distance, but not by much! Warning: don't overtighten rig to get equal distances. If it comes to that then the mast is not stepped on the c-line of the boat or your shrouds are of different lengths.

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post #82 of 107 Old 01-26-2012
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I forgot to mention that when you go on the opposite tack, if the shrouds are slack, try to tighten them the same amount of turns you did on the other side. Also the shroud measurement is taken to the turnbuckle.

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post #83 of 107 Old 01-26-2012
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Also, to measure if the mast is aligned athwartship, use the main halyrard and run it down to the chainplate bottom of the same shroud on both sides of the mast. The amount of haly'rd should be the same.

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post #84 of 107 Old 01-27-2012
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Quote:
Originally Posted by sea_hunter View Post
"That's not completely true, Mr. President." Bobstays, (on boats that have them) can also be used to adjust the forestay tension.
I would suggest that this is near total misinformation since bobstays should almost never be used to adjust forestay tension. I say 'almost never' because there is one design that does allow this. Traditional English cutters had a "reefing bowprit" which could be retacted back onto the deck, and was set up with tackles. Here the trust on the heel of the bowsprit could be used to tension the forestay, but I do not believe even here there was a tackle on the bobstay which would allow the bobstay to impact forestay tension.

The much more normal condition is that Bobstays are typically engineered with larger diameter wire rope (or solid rod these days) than the forestay, even though they are much shorter in length and are often on more efficient angles than forestays, with the fullest intent that there will be very minimal amounts of stretch in the bobstay when loaded and therefore almost no vertical movement at the tip of the bowsprit.

In most cases, over or under tensioning the bobstay would place unnecessary strains on its mounting points and would also have minimal impact on the forestay. On a reasonably sized boat, properly tensioning a forestay typically requires several inches of take up. Few, if any designs permit this kind of movement as way to get the required amount of tensioning through moving the tip of the bowsprit up and down.

As mentioned above, more typically on modern rigs with bowsprits and furlers, the backstay and lowers are eased allowing the mast to sag forward until the forestay can be attached. Then the backstay is retensioned to tension the forestay. Some furling systems do permit some small amounts of adjustment which intended to allow the length of the forestay to be adjusted for stretch, but which does not work very well for tensioning purposes.


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Last edited by Jeff_H; 01-27-2012 at 09:35 AM.
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post #85 of 107 Old 01-27-2012
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Quote:
Originally Posted by Piratesoul View Post
Dynamic Tuning is explained in Dennis Conner's book, Sail Like a Champion.
First you tune the rig to specs, generally 12-15lbs on upper shrouds, 15lbs on lower shrouds, and 10lbs on foestay.
Is that right 12-15lbs or do you mean 12-15% of UTS?
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post #86 of 107 Old 01-27-2012
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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?
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Don't you keep records of replacement and inspections for all wear parts? Yes we do.
How old are the oldest parts? Some cable is 40 years old (100 ton crane)- only replace if it fails inspection.
Also is shock loading much of an issue? Shock loading is not much of an issue if you have a proper crane operator.
What is the safety factor engineered in? The loads on lifting equipment are 1 to 5, that is we take load up to 20% of breaking strength of the item. This matches somewhat to most recommendations that rigging cable stay at 20% or below, although some may go up to 30%.

Last edited by Faster; 01-27-2012 at 02:09 PM. Reason: fixed quote
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post #87 of 107 Old 01-27-2012 Thread Starter
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How old are the oldest parts? Some cable is 40 years old (100 ton crane)- only replace if it fails inspection.
That is interesting. This is steel cable not stainless though.
Seems like steel can last indefinitly if kept greased.
Also steel appaently is easy to inspect and stainless is effectivly impractical to inspect.
At least that's what it is starting to sound like.
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post #88 of 107 Old 01-27-2012
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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. ....Omitted for space.... value, then it is important to know this value is higher on your forestay and therefore need to reduce backstay tension accordingly.
I understand the importance of not overloading the Forestay. However, that will be avoided by any competent rigging procedure, including the one I have cited. My only point was for any novice who is tunning their own rig to find such a procedure, follow the steps, and (hopefully) understand why they are doing what they are doing. As opposed to stabbing at it willy nilly as some have indicated they have done in this thread, with poor results. Obviously, sailing a poorly tuned rig is no fun and can be dangerous. Of course, there is always the option of paying a Rigger to do it. However if you wanted to use that option, you probably wouldn't be reading this thread!

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post #89 of 107 Old 01-27-2012
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Quote:
Originally Posted by davidpm View Post
That is interesting. This is steel cable not stainless though.
Seems like steel can last indefinitly if kept greased.
Also steel appaently is easy to inspect and stainless is effectivly impractical to inspect.
At least that's what it is starting to sound like.
My understanding is stainless can work harden- then fail abrutly without warning, and undetected even by close inspection. Maybe this is the down side to stainless.
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post #90 of 107 Old 01-27-2012
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Quote:
Originally Posted by L124C View Post
I understand the importance of not overloading the Forestay. However, that will be avoided by any competent rigging procedure, including the one I have cited. My only point was for any novice who is tunning their own rig to find such a procedure, follow the steps, and (hopefully) understand why they are doing what they are doing. As opposed to stabbing at it willy nilly as some have indicated they have done in this thread, with poor results. Obviously, sailing a poorly tuned rig is no fun and can be dangerous. Of course, there is always the option of paying a Rigger to do it. However if you wanted to use that option, you probably wouldn't be reading this thread!
I am not quite sure I follow your point. All I am saying is I like to know as much about my rig as possible including what loads it is seeing. If I loose my rig, thay will probalby just about do it for my sailing activity. I cannot afford to install a new mast so I will do everything I can to keep the one I have "up". And being in the middle of the Pacific is no place I want to deal with a demasting.

You reccomended the book by "Dedekam" on sailing tuning and rigging. I also have and like this book. But one interesting item in the book is the suggestion to load your back stay up to 40% of breaking strenght. That means on a mast head rig such as mine the forestay will be loaded to 50% breaking strength. That seems high to me and I would not want to load it this high. Now maybe most recreational sailors can get by without knowing all the details of their rig, and maybe a few rare demasting among these sailors is somthing than can deal and live with. But not me, and maybe I am in a different situation. Knowledge is power. And I would be careful about trusting the experts on everything. In reality, there are very few experts.
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