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


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  #91  
Old 01-27-2012
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Quote:
Originally Posted by casey1999 View Post
"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?
Do you mean using your formula? I'm looking at the book, and don't see "tight as possible" though I certainly could be missing something. For masthead rigs, he says adjust forestay/backstay to a achive rake, then adjust forestay sag (forestay tension, correct?) by adjusting Backstay. He states that boat designers often choose 30% to 40% of the stays breaking load as Max allowable Backstay tension. He says adjust to 30% and mark as Max., then back off the adjustment to 2/3 of Max. I guess using your formula that does bring the forestay over 30% on your boat. Wonder what "boat designers" would say?
Regarding cap shroud tension he suggests pre tensioning cap shrouds to 150kg, (In one example). "Pre tension acts as a shock absorber in variable wind strengths and the masthead is kept under better control."
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  #92  
Old 01-27-2012
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Quote:
Originally Posted by L124C View Post
Do you mean using your formula? I'm looking at the book, and don't see "tight as possible" though I certainly could be missing something. For masthead rigs, he says adjust forestay/backstay to a achive rake, then adjust forestay sag (forestay tension, correct?) by adjusting Backstay. He states that boat designers often choose 30% to 40% of the stays breaking load as Max allowable Backstay tension. He says adjust to 30% and mark as Max., then back off the adjustment to 2/3 of Max. I guess using your formula that does bring the forestay over 30% on your boat. Wonder what "boat designers" would say?
Regarding cap shroud tension he suggests pre tensioning cap shrouds to 150kg, (In one example). "Pre tension acts as a shock absorber in variable wind strengths and the masthead is kept under better control."
Yea that is what I was looking at, don't have the book but as you state he mentions boat designers often go to 40% breaking strength for a backstay. Seems high to me as all the other publications (including ones from mast suppliers) I have read never state to go above 30% breaking. Maybe on a race boat where you don't care if you loose the rig after crossing the finish line (in first of course) 40% would be good. The book does state Americas Cup boats typically load the standing rigging to the maximum possible.
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Old 01-27-2012
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Dynamic Rigging

My bad! Yes it's % of breaking strength, not pounds
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  #94  
Old 02-13-2012
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Quote:
Originally Posted by casey1999 View Post
The instructions that came with the gage say you should tension the rig at the dock (several tension values are given depending on your rig). Then you take the boat for a sail in a stiff wind and basically tune the rig so that the lee shrouds do not go slack (dynamic tune?). As long as there is no slop in your rig including mast pumping, and the tensions are close to what is considered typical, rig should be considered well tuned (assuming rake and mast bend are acceptable).
Here is a interesting article in Practical Sailor regarding tunning.
Practical Sailor - Boat Clinic: Tuning the Masthead Rig - Tips Article
It says: "If you have absolutely no slack in the leeward Cap Shrouds going upwind in 12 knots of wind, the shrouds are probably too tight for most boats."
I just tunned using the article and seemed to reach the prescribed tension (according to Loos), and I've got a lot of slop in the Leeward shrouds in those conditions. The PS article also differs for the technique used by Dedekam in several respects. I'll bet if you asked three different Riggers, you would often get three different opinions. So, paying someone to do it isn't necessarily the answer either!

Last edited by L124C; 04-04-2012 at 10:37 PM.
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Old 02-13-2012
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Quote:
Originally Posted by L124C View Post
Here is a interesting article in Practical Sailor regarding tunning.
Practical Sailor - Boat Clinic: Tuning the Masthead Rig - Tips Article
It says: "If you have absolutely no slack in the leeward Cap Shrouds going upwind in 12 knots of wind, the shrouds are probably too tight for most boats."
I just tunned using the article and seemed to reach the prescribed tension (according to Loos), and I've got a lot of slop in the Leeward shrouds in those conditions. The PS article also differs for the technique used by Dedekam in several respects. I'll bet if you asked three different Riggers, you would often get three different opinions. So, paying someone to do it isn't necessarily the answer either!
The attached article seems to say 1.2 knots not 12 knots--typo?
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Old 04-04-2012
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Quote:
Originally Posted by casey1999 View Post
The attached article seems to say 1.2 knots not 12 knots--typo?
I assumed it was, as at 1.2 Knots, all I care about is that there is enough oil in my crankcase, and diesel in the tank! Even the AC cats would be hurtin in 1.2!

Last edited by L124C; 04-04-2012 at 10:34 PM.
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The more I learn, the less I know!

Quote:
Originally Posted by L124C View Post
Here is a interesting article in Practical Sailor regarding tunning.
Practical Sailor - Boat Clinic: Tuning the Masthead Rig - Tips Article
It says: "If you have absolutely no slack in the leeward Cap Shrouds going upwind in 12 knots of wind, the shrouds are probably too tight for most boats."
I just tunned using the article and seemed to reach the prescribed tension (according to Loos), and I've got a lot of slop in the Leeward shrouds in those conditions. The PS article also differs for the technique used by Dedekam in several respects. I'll bet if you asked three different Riggers, you would often get three different opinions. So, paying someone to do it isn't necessarily the answer either!
I've never quoted myself before, but do it now to make a correction. Having done furtherer research on the matter, I think, 3 Riggers might give you 5 opinions!
I'm now a little suspect of Dekekam's stretch method, as older rigging (like mine!)does stretch over time, and therefore, I think the method might not be accurate on older rigs. Dedekam does say that you can't over tighten Keel Boat rigs using small hand tools. On the other hand, another "Author" (admittedly, in a forum) suggested tightening the rig as tight as possible using a 10" wrench AT THE DOCK! Most suggest hand tightening of the Cap Shrouds to the max prior to tunning under sail.
The method that now feels best to me intuitively (and is in contradiction to the PS article I cited above), is maximum hand tightening of the Cap shrouds at the dock, then sailing in 15 Knots and alternatively tightening Leeward shrouds equal amounts until the slack is eliminated. Of course, the the mast should be straight at the dock and while under sail, and the lowers should be adjusted to maintain the Mast alignment under sail. It seems to me that this method would allow some Leeward slack in heavy weather, yet prevent over tightening and shock loads in gusts and while tacking. Thoughts?

Last edited by L124C; 04-04-2012 at 11:38 PM.
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Old 04-05-2012
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Re: Dynamic tuning of rig

This is excellent / valuable information! I can't wait to close on our CT 56 in July and utilize all the great information here!

I sure do want to learn how to properly tune my rig. My previous / haphazard methods, were proven to have a down side....

I used to just pull on the shrouds / stays, at the dock, and adjust them to "feel" equally tight. That was all, and surprise, surprise, considering the ramifications, that was not enough.

Thank you very much gentlemen!
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Old 04-05-2012
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Re: The more I learn, the less I know!

Quote:
Originally Posted by L124C View Post
I've never quoted myself before, but do it now to make a correction. Having done furtherer research on the matter, I think, 3 Riggers might give you 5 opinions!
I'm now a little suspect of Dekekam's stretch method, as older rigging (like mine!)does stretch over time, and therefore, I think the method might not be accurate on older rigs. Dedekam does say that you can't over tighten Keel Boat rigs using small hand tools. On the other hand, another "Author" (admittedly, in a forum) suggested tightening the rig as tight as possible using a 10" wrench AT THE DOCK! Most suggest hand tightening of the Cap Shrouds to the max prior to tunning under sail.
The method that now feels best to me intuitively (and is in contradiction to the PS article I cited above), is maximum hand tightening of the Cap shrouds at the dock, then sailing in 15 Knots and alternatively tightening Leeward shrouds equal amounts until the slack is eliminated. Of course, the the mast should be straight at the dock and while under sail, and the lowers should be adjusted to maintain the Mast alignment under sail. It seems to me that this method would allow some Leeward slack in heavy weather, yet prevent over tightening and shock loads in gusts and while tacking. Thoughts?

Agree this is all good information.

One thing I think most of us could easily over tighten any rig even with just hand tools, so I would not use that as an indicator.

The other thing I don't understand is why you would want slack on the lee ward shrouds. Would it not be best if all shrouds never went to 0 tension that way the shroud would not see cyclic loads that would potentially lead to fatigue failure? I have heard of long distance sailors tieing bunges cord around the leeward shrouds to prevent fatigue failure (from the shroud swinging around for extended periods). Anyone know how say a volvo 60 is tuned in the arond the world volvo race?

Finally, to become a professional rigger /tuner what do you need to do? Go to college? Pass a test? Get a license? Rig and tune 1000 boats and not lose a rig at sea?
WTH is a professional rigger? Could any of us hang a shingle and call ourseves a professional rigger?

Regards
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Old 04-05-2012
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Re: The more I learn, the less I know!

Quote:
Originally Posted by casey1999 View Post
WTH is a professional rigger? Could any of us hang a shingle and call ourseves a professional rigger?
I think most riggers go through a (rather informal) apprenticeship and learn on the job from a (hopefully) skilled experienced person. I don't know of any official accreditation body (like SAMS for surveyors, for instance) but maybe Knothead will weigh in with better information.

I suppose any of us could hang a shingle as you say.. but be sure to have good 'mal-rigging insurance'!
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