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  #51  
Old 01-23-2012
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Then I wonder why in the V70 race a month or so ago, when one of the boats lost a mast, they took off, had to return, along with a quote, that it usually take 2-3 days of sailing as a full crew to tension things correctly! here we as cruisers, some of us as evening/weekend warrior racers trying to set the rigs up in an afternoon? sailing by ourselves? think we will succeed! doubt it. This is a constant you must always do! adjust some, keep a log, adjust some more, see if it works better,by gaining speed, degrees upwind etc.

Along with taking multiple measurements with a "STEEL" tape as usually recomended, as it will not stretch like the typical cloth/plastic tapes will that are long enough for most of our mast hts, ie a 50-100' tape is usually needed.

Then "ONCE" you figure out the where you need to be, you keep it there. Along with figuring out how tight to tighten the backstay, if you have an adjustable mini forestay, I have the mini, not adjustable, you can tweek the tune with either or both. Locally, folks do these adjusts thru out the race, tension back stay upwind, loosen down winds. Same with clew on main, halyard adjusting, boom vang etc.

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  #52  
Old 01-23-2012
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Quote:
Originally Posted by DougSabbag View Post

May I ask some questions?

1. When healed over at 45 degrees, are you checking and adjusting the windward or down wind shrouds / stays?
When I'm checking the rig tuning while underway, I'm mostly watching the leeward shroud. What I want to see is that the tension on the leeward shroud just barely relaxes when the boat is on a beat in about 12-15 kts of wind and the sails are loaded. If it doesn't relax, that says the shrouds are too taut. If it just barely relaxes without becoming slack, that says the shroud tension is just right. If the shroud relaxes to the point where it begins to become slack, then that says it is too loose. If the shrouds need to be adjusted, I make the adjustments by taking an equal number of turns on each side, and adjust the lowers accordingly, as needed.

Quote:
2. Using a Gulfstar 50 as an example, I usually had about 65 lbs of tension on my shrouds / stays. If that is the setting / reading, at the dock, what am I shooting for, i.e., how many lbs. of tension, while under way, while "dynamically tuning"?
The amount of tension that you might measure while underway depends on the windspeed, the size of your sails and the wind direction, because that is what determines the amount of load on the rig. I don't know any way the average sailor could make those calculations, so I don't attempt to take measurements with instruments while under sail. I'm only concerned with how the rig behaves under load. I want to see indications that the rig isn't too taut, but that it is sufficiently taut so that it is restrained from moving significantly. I don't want to see the mast move so much that it snaps to a stop and imposes an excessive shock load when it comes up short on the shroud. The mast should be restrained from moving to any significant extent.

Quote:
3. How would I determine what the "30% UTS" / ultimate tensile strength of the cables to be, related to lbs of tension as read from a guage?
The cable manufacturer should be able to tell you the tensile strength of his product. For my purposes, like most recreational sailors, I trust that the designer of my boat specified cable that is adequate for the sail area of my boat, and that, if I tune the rig with a sufficient amount of tension to prevent the rig from moving excessively, without over-tensioning it, the stresses on the cables will be within those parameters. I suppose I could try to make the precise measurements under a variety of conditions, but have never felt a need for such accuracy. If I felt I couldn't trust the designer's specifications, I suppose I could either find the appropriate engineering tables, or consult a professional rigger or marine architect. You either need to trust the professionals, or educate yourself to their level of understanding, and then trust yourself.
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  #53  
Old 01-23-2012
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Originally Posted by RichH View Post
Not necessarily, ..... even with apparent 'beefed up' thickness, etc. Many chainplates have kinks and bends that cause undue 'flex', etc. that are considered 'stress risers' by structural folks.
That sure sounds right, But.

1. Does an example come to mind? I would love to see a picture or drawing to really visualize this?

2. Would you buy such a boat or consider it a design flaw?

3. Possibly the boat would be safe enough if the chain-plates were replaced on a regular schedule just like you would replace racing sails.
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  #54  
Old 01-24-2012
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I am not sure how the OP meant the term 'dynamic tuning' or if he meant it as a specific form of tuning. My guess is that the intent of the phrase is simply to suggest that you cannot tell whether a rig is properly tuned until you see it loaded under sail.

When I worked with the rigging crew at Derecktors years ago, we would typically measure the rake of the mast before removing the spar. We would also count the threads on the stays. If we we were replacing a stay, we would take measurements of the old stay with the turnbuckle adjusted to the exposed threads count, and with the stay stretched to a specific tension.

All new rigging stretches after being initially put into service. We had a chart which was used to calculate the expected initial stretch, and the new stay was constructed shorter by the amount of anticipated initial stretch. My assumption regarding the VOR70's needing 3 days for tuning is that these are complex rigs, but I also assume that this is so the shrouds can be stretched and re-tuned.

When we restepped the mast, we would set the shrouds loosely with the mast centered, and then set the fore and backstay to the previously measured tensions and the previously measured rake.

From there we re-centered the masthead, and the centered the shrouds so that the mast track sighted straight athwartships and the tensions matched from side to side. As a broad generality, the cap shrouds had the highest tensions, with shroud tensions reducing as you moved down the mast.

Once set up, if any of the shrouds or stays were replaced, the boat was allowed to sit for a day or more to allow some prestretching and the tensions and alignments were rechecked and adjusted accordingly. Then the boat was sailed. Some owners took a rigger along, but most sailed their boat and made their own observations. The critical observation was that when sails were full, and the spar and rigging fully loaded, that the mast was essentially straight and/or that there was there a smooth, fair curvature.

It was assumed that the mast would not stay perfectly straight when loaded, and so shroud tensions were set to achieve a desired curve. There was a fad of cocking the masthead to windward when the lower shrouds were stretched under load, which was supposed to help going upwind. Today, we tend to adjust rigs for some sag at the masthead to leeward in a breeze in order to depower the rig.

In those days, no shroud was ever supposed to go slack, but today the tendancy is to set up rigs with flexible spars so the lee shrouds feel slightly soft when hard on the wind in stronger winds. On most but not all classes they should not be flopping around.

If any rigging was replaced, Owners were advised to check their rigs several times during the first season as the shrouds and stays would continue to stretch most dramatically when first being used and less so over time. At some point they settle in and should not need frequent adjustment.

Now all of that said, on race boats, we typically have different shroud tensions for different wind strengths and will adjust the shrouds for almost every race. And of course, we change backstay tension with almost every long gust.

Respectfully,
Jeff
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Last edited by Jeff_H; 01-24-2012 at 09:44 AM.
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  #55  
Old 01-24-2012
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Jeff,

Yes it could be possible that it takes 2-4 days of 6-8 hr days to stretch the rigging if you will on a V70, hence the quote I am remembering. But being as there was not explanation.....one does have to swag on the reasons why. Stretching of the rig is probably #1, along with getting things adjusted length wise to the 1/16" vs as one fellow I know that races on these, ie a sailmaker, for a cruiser, 1/8-1/4" difference per shroud etc per side is ample.

My boat when I bought her from the initial owner, the mast was almost an inch or two out of center, wires were in the 3-5% of breaking strength. Probably works well for the light wind days overall here in puget sound, but still, i find about 15% is a better overall tightness for my boat, then adjust the back stay while sailing. Even then not sure I have things absolute perfect all the time. I'm trying to get things with in 1/8" per side. Took some rake out, got better helm feeling etc.

Not sure frankly, that setting a rig up, then leaving alone per say is the way to do things. Constant checking is the way to go. This will also allow one to hopefully look at and find issues that may cause total failure. Then again....one never knows.

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  #56  
Old 01-24-2012
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Quote:
Originally Posted by DougSabbag View Post
3. How would I determine what the "30% UTS" / ultimate tensile strength of the cables to be, related to lbs of tension as read from a guage?
The Loos gages will read % UTS and actual pounds load based on 304 SS cable. Loos tells me for 316 SS read only the pounds load and calculate %uts (lbs load/ UTS).

Here is breaking strength for loos 316 and 304 cable- other manufactures should be similar in strength for the same type cable:
Marine Wire Rope & Cable, Yacht Rigging, Life Line - Loos & Co., Inc.
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  #57  
Old 01-24-2012
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Doug
I just got off the phone with my son. Stephen is a rigger at one of the busiest shops in Annapolis and has been doing this for quite a few years.
i asked about your situation and got some more information for you.
1. He mentioned the same thing one of our SailNet posters did about the designs. Some chainplate designs have curves and bends so during heavy use they flex and after thousands of cycles can become damaged and fail faster than more robust designs. If you have a boat like that you have to consider your chainplates to be even more disposable than usual.
2. The older a boat is the more likely it has been hit by lighting. This can damage the metal of chain plates.
3. Many boats include the chainplates in the grounding system. This can be a good thing but if something goes wrong you can loose some metal.
4. A temporary failure of a shroud can cause extream loading on the remaining shroud and chainplate causing it to fail prematurely. Sort of like the 30% rule on the wire.
5. Shock loading by poor tuning of the rig can cause extreme load of one chainplate causing pre-mature failure.

So at the end of the day the whole boat is a system. Neglect or failure of any component can cause wear and failure on any related component.

Another item I just remembered that we discussed last summer. I don't know if this could possibly apply to your Gulfstar but some lighter boats are currently a lot more flexible than they were designed to be. A boat that that has been ridden hard may have some damage to the hull laminates that will cause the boat "banana" more than specified when the full back-stay tension is put on it. In heavy weather conditions the weak boat would transmit some of the extra loading forces to the chainplates.
So this just goes to show it is a system where the design, quality, maintenance and loading of every component can easily combine to cause the failure of one part.

In your case it appears as if all of your experts are partially right.
The lessen is however that chainplates should be considered a consumable item just like:
running rigging, zincs, standing rigging, sails, impeller etc.
They may not be consumed as fast as the zinc but they may not last the life of the boat either.

This is especially true in off-shore sailing where the rig can be subject to repetitive shock loads for days at a time. In fact a rig inspection is probably prudent after every storm.
You can and should do it yourself.


That being the case the design and accessibility of the chainplates is probably as important as the location of the oil dip stick and stuffing box. This may affect the choice of boat.

Last edited by davidpm; 01-24-2012 at 09:40 PM.
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  #58  
Old 01-24-2012
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Quote:
Originally Posted by davidpm View Post
Doug I feel your frustration. I hate it when experts disagree.


I have a mental picture of what happened, let me know how accurate it is.
The shrouds were a little loose. The wind picks up and the top of the mast is whipping around more than it should. Maybe the top of the mast moving a foot out of column from where it should be. The mast is lets say about 60 feet tall. The top is a foot or two out of column. How much does that affect the angle of the shroud between the deck and the shroud. Maybe one degree.

So the theory that the chain plates were damaged by loading in one storm does not make any sense to me at all.

The place that they broke is exactly where they would be expected to break if they had oxygen depletion corrosion.

Now the mast whipping around certainly didn't help but there was another thread where someone gave his old chain plates to a friend with a machine shop to use for scrap metal because they looked perfect. A few months later the machine shop guy tried to cut one in a shear. It shattered and crumbled.

My son is a rigger in Annapolis and I asked him about this a long time ago. His response was that if you are going to go to the trouble and labor to remove and re-bed then he would never even consider not replacing them.
Of course at rigging shop rates it is a no-brainer but even for do-it yourselfers chain plates are not forever.

I would submit that if there is anyway you can damage a chain-plate by pulling in any direction that is generally up with the wire shroud meant to be attached to it, the chain plate is not properly designed or is damaged.
The chain plate should be able to handle much more than the wire.
Well, we stepped the main a little less than a year before the failure. Right after reinstalling the main, we tightened / adjusted the stays / shrouds at the dock, then we sailed from Fort Lauderdale to Boston. Then I checked the tension, and I did have to tighten the backstays.

A few day sails.... winter ..... spring, then we headed to Europe.

I was not aware of any main mast movement, at any time. From what I was told, there is this harmonic vibration condition which can occur wherein the mast might "pump" (fore and aftward) but almost imperceptibly. And, this occurs when the rig is not properly adjusted, specifically if you don't do the follow up / at sea / under load adjustments.

Considering the perpendicular juxtaposition of the chainplate tabs to the hull, i.e., the tabs' flat width was in the port / starboard plane, if the stays were pulling fore and aftward, then those tabs would have been stressed in their weakest direction..... theoretically.... :-)

However, I could never argue that these chainplates weren't quite probably well past their prime.

Is it just sort of coincidental(?) that fairly soon after the stepping project, the chainplates failed, especially after not doing the full re-installation process?

Imagine getting years out of a motor, incident free, and then after changing the timing chain, surprisingly enough, the motor throws a rod....
I guess this old codger is stuck in that sort of mind set.

Everything was fine until......................

Nevertheless, I suppose, (and following your later comment) BOTH issues were in play. The chainplates were old, AND I had not properly adjusted the rig after the stepping of the main.

I WILL be buying a guage and will be using this thread to try to address this issue as soon as we get a sailboat. And boy I sure do hope that is soon. :-)
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  #59  
Old 01-24-2012
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Quote:
Originally Posted by Sailormon6 View Post
When I'm checking the rig tuning while underway, I'm mostly watching the leeward shroud. What I want to see is that the tension on the leeward shroud just barely relaxes when the boat is on a beat in about 12-15 kts of wind and the sails are loaded. If it doesn't relax, that says the shrouds are too taut. If it just barely relaxes without becoming slack, that says the shroud tension is just right. If the shroud relaxes to the point where it begins to become slack, then that says it is too loose. If the shrouds need to be adjusted, I make the adjustments by taking an equal number of turns on each side, and adjust the lowers accordingly, as needed.

The amount of tension that you might measure while underway depends on the windspeed, the size of your sails and the wind direction, because that is what determines the amount of load on the rig. I don't know any way the average sailor could make those calculations, so I don't attempt to take measurements with instruments while under sail. I'm only concerned with how the rig behaves under load. I want to see indications that the rig isn't too taut, but that it is sufficiently taut so that it is restrained from moving significantly. I don't want to see the mast move so much that it snaps to a stop and imposes an excessive shock load when it comes up short on the shroud. The mast should be restrained from moving to any significant extent.

The cable manufacturer should be able to tell you the tensile strength of his product. For my purposes, like most recreational sailors, I trust that the designer of my boat specified cable that is adequate for the sail area of my boat, and that, if I tune the rig with a sufficient amount of tension to prevent the rig from moving excessively, without over-tensioning it, the stresses on the cables will be within those parameters. I suppose I could try to make the precise measurements under a variety of conditions, but have never felt a need for such accuracy. If I felt I couldn't trust the designer's specifications, I suppose I could either find the appropriate engineering tables, or consult a professional rigger or marine architect. You either need to trust the professionals, or educate yourself to their level of understanding, and then trust yourself.
THANK YOU VERY MUCH! I greatly appreciate your response.
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Old 01-25-2012
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Quote:
Originally Posted by DougSabbag View Post
I WILL be buying a guage and will be using this thread to try to address this issue as soon as we get a sailboat. And boy I sure do hope that is soon. :-)
I'll second both of those comments.
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