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  #21  
Old 01-22-2012
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In some OD classes, you can't even change certain parameters of the rig between races.


Dynamic Tuning ? - so that is like when we are late to the start, rushing to get out there in sloppy chop, and I have my mainsheet trimmer drive while 3 of us try not to lose any tools overboard while fiddling around with with the leeward shrouds

is it getting looser or tighter ?
Where the ring ding go ?
NO you cant tack - wait !
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  #22  
Old 01-23-2012
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What about backstay adjusters? When you round the weather mark and ease a backstay adjuster, or, when you start to become overpowered on a windward leg and you increase the tension on the backstay adjuster, bending the mast on a fractional rig, or reducing headstay sag on a masthead rigged boat, doesn't that make a radical change in rig tuning on the fly? It seems to me that using a backstay adjuster is the essence of dynamic rig-tuning.
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  #23  
Old 01-23-2012
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Hello! Sorry that I took awhile to comment on this thread! I made that big claim and then left it to you guys to fill in the details; not on purpose, but that's how it happened.

Anyway, since the concurrent breaks of 2 starboard main chainplates, while crossing the Atlantic last summer, I've had numerous opportunities to discuss this with people.

What seems to make the most sense, besides the suspect underlying condition of the chainplates themselves, is that without having tuned the rig while under way after the stepping of that mast, the mast in question was most likely vibrating / wrenching forward and backward in relation to the boat.

This "fits" with what I saw of the broken chainplates; i.e., they broke at the point where the chainplates were sticking up from the ribs of the hull where they were thru bolted to.
These "tabs" were perpendicular to the boat. Lets say they were 4 inches wide; well the plane of those 4 inches was perpendicular to the plane of the hull. Such that the portion of the chainplates sticking up, above the ribs, sticking up and through the deck was like a tab of metal.

Those tabs broke, just below the deck. And it appeared as though they broke from being bent, forward and backward, repeatedly, until the bending caused the infamous metal fatigue which will break any metal.

Now, many people will claim that using titanium or perhaps bronze chainplates, and ideally bran new ones, wouldn't have sufferred this breakage. But, shy of actually testing new ones vs. old ones, with and without the tuning which should keep that mast vibration / wrenching from occurring, I can not agree that it is OK to not fully tune your rig if you have new / titanium / bronze chainplates.

Without properly tuning the rig, you are abusing the chainplates / metal, with an eventually disasterous result, regardless of the intitial strength of the metal.
What will be effected by the quality / age of the chainplates, is how long they will last given this abuse. But, it is abuse, nevertheless.

For me, I would choose to sail across the Atlantic with old chainplates, as long as the rig was properly tuned, as opposed to with new chainplates without properly tuning the rig.

Now, what is this "dynamic tuning"? Well, as was described to me, by more than one source, is basically what a few of you did describe here already.

After installing your mast, and adjusting all the turnbuckles to provide a similar / tight tension of the stays / cables at the dock, per your specific boats' rigs' pounds of tension requirements, you are then supposed to take her out under full sail, and adjust the downwind turnbuckles again.

Yes, this would include all the shrouds / stays, i.e., the backstays, etc., all of them.

Now, as for the exact amount of tension to set these to, I am pretty sure this varies by boat and rig.

Many of you apparently already know this, so this isn't anything new to you! For you, fair winds, and have a great day!

But, for the poor saps like me, especially those who are stepping their mast(s), I highly suggest asking your rigger about the final / dynamic / "tuning under sail", and, or, read that book suggested earlier! Because, as was quoted, 2 riggers who were hired by us for our main mast stepping process in Fort Lauderdale never mentioned a thing about this, and it didn't take all that long for the repurcussions of not doing this to become my worst night mare.

Without having read that book, I would greatly appreciate, as many others might, any specific inflormation about how to dynamically tune your rig, per these experts, or any other information about these specifics.

Because all I have heard is to "tune the downwind stays / shrouds" while underway".
And that still leaves much to the imagination about the details.... :-)
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  #24  
Old 01-23-2012
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Sailormon, yes it is. Some classes even let you adjust mask rake on the fly, but it all depends on the class rules. OD, handicaped, IRC, ORC, MORC, IOR, etc.

Usually the class will limit the puchase of the backstay, or state that it must be 'fixed' and not adjusted during the race.
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Old 01-23-2012
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If the standing rigging is toggled correctly it would really have to be out of wack to bend the chain plates OR the mast would have to be pumping something fierce
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  #26  
Old 01-23-2012
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Quote:
Originally Posted by tommays View Post
If the standing rigging is toggled correctly it would really have to be out of wack to bend the chain plates OR the mast would have to be pumping something fierce
What constitues this: "If the standing rigging is toggled correctly.." ?
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Old 01-23-2012
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I keep hearing things like: If you have titanium chainplates, or, things like the prior comment: If the standing rigging is toggled correctly.... then what? You don't need to tune your rig correctly?

I really think it's more like having oil in an engine.... without it, it is just a matter of time, no matter what kind of engine, or how things are adjusted; you don't want to abuse metal if you want to get the full "life" from those parts.

As far as how much a mast has to "pump" to cause metal fatigue to ruin / break a chainplate, well, from what I understand, you really don't want any pumping at all.

Sure, there will be some flexing from wind changes, but when it gets to the point of having a vibration / pumping action, something is really wrong.
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Old 01-23-2012
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I dynamically tune my boats ... but I have a healthy dose of material science, metallurgy, engineering, amateur sailmaking, etc. background; so my reasons may be quite different from anyone else.

I dynamically tune for the following reasons:
1. first and foremost - sail shape ... if the forestay tension (improper sag when windloaded) doesnt precisely match the leading edge shape of the sail as cut/designed, then I readjust (while underway) to get it 'close'.
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).

So, I do use a tension gage the rigging while getting the boat over 'towards' a 45° heel angle ... as after the 45° heel angle the loads diminish due to 'trigonometry'. If I cant get the boat to 45° I simply measure what I have at the max. angle and then calculate what the loads would be @ 45° over, etc. ... and then assuming that my rig has an appropriate inbuilt design safety factor (probably at least 3X+ for a "perry-boat") I arrive at the max. tension and then reduce the 'static' tensions as needed and still to get the needed mast 'pre-bends', forestay 'shape', etc.
When Im sailing 'hard', I simply dont want any part of the rig tension to (much) 'go over' 30% UTS ... and will apply 'helpers' (runners, etc.) to get what I want ... (hopefully) less than 30% UTS at 'max'. conditions.
When 'sailing' I monitor the backstay tension (gage attached) and if that backstay is going much over 30%, I then reduce/reef of change a sail, head off, etc. etc.
(FWIW I sail a Taiwanese made Ty37 and the Formosans are long noted for their lack of metallurgy expertise ... and I claim so too many 'riggers' also fit in this category but 'graciously understand' and 'accept' this .... as I dont want my cost of maintenance exceeding the cost of the national debt of the USA.).

I didnt do this when I was actively racing my 'sport boat' (dynamic on-the-fly mast raking and 'very' bendable mast, independent forestay tension, etc. and over-design Safety Factor of 1.5X) and did lose a few masts, rigs, etc. overboard - all due to 'catastrophic' fatigue failure.

Thats my 'impression' of dynamic tuning ... for sail 'shaping' and for keeping the rig up without undue fatigue failure 'surprises'.

Ultimately one has to consider that since there ARE noted rig failures, increasingly insurance underwriters demanding (panic, seemingly) a total rigging changeout every 10 years, etc. ... that the 'inherent design and selection' of the these materials ... is quite 'faulty' ... and 'someone' is erroneously designing rigging etc. in accordance to 'ductile' values and not 'fatigue endurance' values. Cant be otherwise.
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Last edited by RichH; 01-23-2012 at 01:20 PM.
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  #29  
Old 01-23-2012
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I am also concerned with my rig and truly only feel confident in it after I do the inspection and tune it myself. I purchased a Loos rig tension gage (model PT3-M) so I could determine the tenstion of all shrouds and stays. The tension gage can be used while under sail, so it will give me real time rig tensions.

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).

Last edited by casey1999; 01-23-2012 at 01:44 PM.
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Old 01-23-2012
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Quote:
Originally Posted by RichH View Post
2. 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).
.
So if I keep loads under 30K psi and inspect for corrosion and cracking (and find none)- can I keep using the standing rigging, or should it still be replaced say every 10 years?
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