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  #11  
Old 09-23-2012
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Re: What else could I have done?

David,

Sorry this happened and I'm glad that there appears to be minimal damage. That phone call must have produced that cold gripping feeling in ones chest.

Disclaimer on the flowing advice: I have never kept my boat on a mooring and really know nothing about moorings.

It seems to me that chafe is THE issue with moorings. Ropes can be large enough that strength is not an issue but still chafe through easily.

What about adding a reinforced bow eye below all possible points of chafe? The photo below is a nice example of what a local stainelss steel shop could weld you up for $150 or so. It has ears on it to help prevent lateral loads from shearing a regular U-bolt.



If the interior was beefed up to chainplate standards with glass and backing plates then strength would not be an issue. Chafe would be nearly eliminated as well. Also, instead of just glass and backing plates you could do something more exotic like this:



As a final thought I would sleep better at night if I knew that my last resort attachment was all chain. With enough shock absorbers in the system I think an all chain pendant would be possible.


All the best to getting back to 100% quickly!
MedSailor
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  #12  
Old 09-23-2012
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Re: What else could I have done?

Here is my take. Chafe is determined by several things, the primary ones being movement, loads, heat, angle, chafe gear and rode type.

Things chafe because they are moving relative to something else. In a simple system of a piece of nylon passing through a chock to a cleat, there is often a lot of movement through the chock. This is because the nylon is stretchy and it is fixed at the cleat so when your bow goes back or up, it stretches the pendant which means that a bit of nylon will be pulled out through the chock. There are 2 ways to minimize movement, either go to a non stretchy rode or minimize the distance because the movement through the chock is a function of the amount of line on the boat side of it (engineers will recognize this as strain). Ideally, we would all have pendants that had no give until we got through the chocks and then were very stretchy between there and the mooring ball. The closest we can get to this is a 2 part rode where the boat end is poly or dyneema and the ball end is nylon. Testing has actually shown that these rodes work extremely well. Coupled with this, moving the cleats as close to the chocks as possible will help a lot. For that matter, some people/builders eliminate the chocks and put the cleats right on the rail which in many cases is best.

The amount of chafe is a function of the load on the pendant because this determines the friction between the chock and pendant. Therefore minimizing loads is important. The 2 best ways that you can minimize loads on the mooring end are to put shock absorption in the system and to ensure adequate scope. Shock absorption can take many forms, the best being something like a hazelette mooring system but really heavy chain (along the lines of what Mainesail shows) and good pendants is acceptable as well. Scope matters because as your scope becomes shorter, you start to add a vector to your mooring load which is trying to pull the boat's bow down/pull up on the mooring.

For nylon, heat management is critical. Water is the best cooling medium present in a mooring system so letting everything breath and get soaked is best. It is worth noting that there is heat from the friction in the chocks but also from the internal friction of the line on itself.

Angle is important because it determines the side load on a line which determines the chafe. An extremely sharp angle concentrates that load at a specific point. Therefore, having good radius to your chocks is really critical, sharp edges make this load go through the roof. Also, adequate scope will help a lot on this.

Chafe gear works in a few different ways. Its primary purpose is to be sacrificial so that it will chafe but not the line. The chafe gear should be attached the line so that it does not slide relative to it but even with this, it will move some so having a low friction coefficient is important. Because of this, many people like tubular webbing. Also, because of heat management, having something that is not watertight is crucial.

Finally, you can control what your pendant is made out of. Poly rode will do excellently through the chocks but it is a terrible shock absorber so your loads will be really high. Nylon is a good shock absorber but it chafes a lot. Chain is best of all for chafe but it will have virtually no shock absorption in extreme conditions unless it is unreasonably heavy. In my opinion, a combination pendant is best. This can be accomplished by making a short poly/dyneema pendant that goes through the chocks and cow hitching it to a long nylon pendant or you can buy one made by Yale which packages the two materials differently but accomplishes the same thing.

My storm pendant consists of a piece of chain to go over the bow which is shackled to a piece of nylon spliced onto a thimble to minimize chafe. If I was going to set things up again, I would seriously consider an elastic pendant such as the ones sold by boatmoorings.com hitched to a dyneema pendant.
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Old 09-23-2012
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Quote:
Originally Posted by Maine Sail View Post
2- All pendants should be of unequal length. This buys MORE TIME throughout the storm as the remaining pendants are brand new, unloaded and not chafed.
I'm going to disagree with this, with a disclaimer that my argument is from a rock climbing perspective.

When we build climbing anchors, we are very careful to be sure all the lines going to the anchors are equalized. The theory is they share the load equally, splitting how much load each takes, and nothing gets shock loaded if one lets go.

If you have two pedants, and your boat is exerting a 1000lb force on the whole system, each pendant will take half the load, 500lbs (not exactly of course, depending on the angle they make in respect to the mooring, but close enough). If you add two more and they are equalized, each now only takes 250lbs. If one breaks, there is no shock load on the others.

But, if these other two are slack the whole time, the original 2 are taking 500lbs each, till they break. Depending on slack, your other two are now not only going to take the full force, but will be subjected to a significant shock load.

In climbing situations, this has killed people.

Chafe of course is still a huge issue. Chafing is directly related to the amount of strain each cord is under, among other things of course, and I would argue that cutting the load in half for each pendant will significantly reduce the chafing.
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  #14  
Old 09-23-2012
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Re: What else could I have done?

Quote:
Originally Posted by MysticGringo View Post
I'm going to disagree with this, with a disclaimer that my argument is from a rock climbing perspective.
I'm going to try to channel MaineSail now, I've I'm wrong he will correct me.

The engineering behind the mooring system is mostly concerned with chafe.
In climbing you have to balance weight and strength.

In the mooring system where weight is of minor concern each pennant can be sized to be more that enough for strength.

Chafe however is a worry no matter how heavy the line is. With un-equal pennants if the chafing gear fails on one pennant after a couple of hours the second will take up the fight etc.

In climbing you are managing strength, shock loads vs weight. In mooring it is shock loads and chafe.

If my mooring lines would have hung in for just another hour I would have been OK. With the MS system I would have had two or three more pennants to wear through giving the storm plenty of time to blow through.
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Old 09-23-2012
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Re: What else could I have done?

Quote:
Originally Posted by MysticGringo View Post
I'm going to disagree with this, with a disclaimer that my argument is from a rock climbing perspective.

When we build climbing anchors, we are very careful to be sure all the lines going to the anchors are equalized. The theory is they share the load equally, splitting how much load each takes, and nothing gets shock loaded if one lets go.

If you have two pedants, and your boat is exerting a 1000lb force on the whole system, each pendant will take half the load, 500lbs (not exactly of course, depending on the angle they make in respect to the mooring, but close enough). If you add two more and they are equalized, each now only takes 250lbs. If one breaks, there is no shock load on the others.

But, if these other two are slack the whole time, the original 2 are taking 500lbs each, till they break. Depending on slack, your other two are now not only going to take the full force, but will be subjected to a significant shock load.

In climbing situations, this has killed people.

Chafe of course is still a huge issue. Chafing is directly related to the amount of strain each cord is under, among other things of course, and I would argue that cutting the load in half for each pendant will significantly reduce the chafing.
That whole premise is mostly based on breaking strength. Properly sized pendants do not break and are far from breaking strength even in storms. Our primary pendants are each rated at 31,000 pounds. What does happen is they chafe. With equal length pendants they chafe nearly equally until the both fail. I have watched this and observed it many times.

My neighbor Tom had this exact thing happen to him in that storm pictured above. His pendants were equal length and both parted at near the same time. His boat drifted many miles before coming grounded near Portland..

Quite by accident I caught pictures of his boat drifting away. I could not see it from land and only saw it when I cropped in on the photo and cleaned up the rain clutter.

This is how close his boat is to ours:


The boat in the distance with her stern to us is his boat drifting away after parting both of the equal length pendants:


These are the bow chock end of his dual equal length pendants and they were less than a month old:


Our boat survived that storm beautifully only 80' away on triple unequal length pendants.....

Another boat neighbor, in the same storm, lost one pendant, his primary. His secondary, longer one, was still in near perfect condition when the storm ended.

Boats also yaw back and forth in storms and rarely equally load both pendants at the same time. If on every yaw port wears then stbd wears then port wears then stbd wears etc. they do fail within a short time of each other even though it may have taken 6 hours for that to happen. With unequal length pendants you buy yourself almost double the time because you now have a bran new pendant.. Seen equal length pendants fail too many times to do it any other way on my own boat. I will NEVER go back to dual equal length pendants.


This is an email I got from a guy who read my article:

"Dear RC,

I wanted to write you to say thanks. We lost our boat 6 years ago in a dreadful Noreaster. I had gone beyond the towns requirements for years by using two bow pennants. After every storm, we are highly exposed, I always found them equally worn away but kept using that method as I felt it to be better. When we lost our boat both pendants had worn through at the bow chock location.

After reading your article I chose to try the two different lengths for my pennants. We just had a storm that was worse than the one we lost our last boat in, you did too, and all I can say is thank you. The shorter pennant broke in the storm and the second one saved our boat. Seven boats around us broke away and went up on the shore. That second pennant hardly showed chafe and got us through the tail part of the storm with reserve left. I think I will order a set of those yellow pennants you showed for next year. If I ever run into you in Maine I will buy you a beer.

Thanks,

TM"


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Last edited by Maine Sail; 09-23-2012 at 10:05 PM.
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  #16  
Old 09-23-2012
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I'm glad to know this, and that I've been using the wrong premise setting up pendants. In climbing, we certainly do deal with chafe too... I guess my main concern was with shock loading the second system.
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Old 09-23-2012
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Re: What else could I have done?

Quote:
Originally Posted by MysticGringo View Post
I'm glad to know this, and that I've been using the wrong premise setting up pendants. In climbing, we certainly do deal with chafe too... I guess my main concern was with shock loading the second system.
With a properly designed system shock loading should not be an issue. Many harbors however allow chain that is far to light and scopes far to short to deal well with storm surges. Couple that with a tendency for people to use pendants that are too short and you can shock load the deck hardware. Longer stretchy pendants help...
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  #18  
Old 09-24-2012
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Re: What else could I have done?

I like the idea of clipping to a hard point, like a towing eye. My previous boat had the short line to a beefy clip on the towing eye, and a longer one to a bow cleat. Another trick (may not be appropriate for some mooring balls) is to attach the primary to the chain under the ball, and the secondary on top of the ball. You can see from shore, if the ball tips, the primary failed.
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  #19  
Old 09-24-2012
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Re: What else could I have done?

Glad your boat escaped relatively unscathed...
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Old 09-24-2012
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Re: What else could I have done?

Quote:
Originally Posted by davidpm View Post
Already re-floated. Towed to marina, mast stepped and boat hauled. Season over.
I could find no evidence of rudder damage despite the apparent bending in the video.
Well David, this recovery kind'a puts paid to the idea of the "poor quality" of Beneteau construction, eh? Good for you.


After looking at the damage to your bow roller--



--and your chafed snubber/pendent, I suspect that the failure was caused by the plunging of the bow in the seas. With the bow down and driven the starboard, and yet a taught starboard pendent, I could see the snubber/pendent easily being "hooked" by the starboard side plate of the bow roller as the bow rose. With that, the pendent would have loaded up the side plate with each subsequent plunge and roll of the yacht, overloading the plate across the plane of the plate and eventually breaking it off while certainly deeply chafing the pendent at a point where it was unprotected. When that finally snapped leaving only a single snubber/pendent on the port side, the boat's fate was likely sealed. I don't know if a pin, alone, in the forward most pin-holes on the roller fitting would have prevented the foregoing but it might have helped. A bowed "keeper" strap between the outboard side plates, held by the roller pins, would prevent the possibility entirely.

FWIW...
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