Mooring failures

[Lady Campanula]

I’d like to share my awareness of an intriguing booklet, recently published by retired aviation engineer Jim Izzard, called “Towards Zero Failures In Swinging Moorings”. It is clearly authoritative on a subject in which many of us have a considerable interest, and points towards a consensus on best practice which is, I know, wanted by all and provided by few.

This booklet pools the experience and practices of the main West Country mooring contractors and over a score of other specialists. As one might imagine, most of the standards, specifications and practices developed by them over the years achieve a broad consensus. Where there are differences in approach, the reasons are explored.

The following short extracts are included to provoke interest, but should be read in proper context before agreeing or disagreeing vehemently..…

A heavy ground chain being moved around a block can scour out a deep saucer-shaped trough…. This can lead to the block being pulled into the trough….onto its side or upside down.

Cheap mild steel forged or welded swivels are prone to failure, particularly those held together with a nut locked only with spot-welds which corrode quickly….

Conventional 3-strand rope is not used for swinging boat-ropes/bridles because it can unlay and splices then fail….

There has been no case of failure in 24mm multiplait nylon boat-rope or bridle….

The wrong concrete mix ( in mooring blocks ) leads to a high erosion rate and crumbling...

Inflated ‘Buff’ type buoys sink when punctured. … long-life ‘Hippo’ buoys are preferred.

Pin threads are…. The part of the shackle most likely to corrode and fail….

A 12mm riser chain is likely to last 2 or 3 years but, if dropped for winter, life expectancy extends to 4 or 5 years. A swivel is likely to last for 3 or 4 years….

A single s/s cable tie took 8 times more torque to break compared with…. Monel wire mousing.

A failed s/s 12mm bow shackle where a missing sector reduced the cross-sectional area to just 25% after just six months.

This is a private book production and there are a few copies left at around £10. Should readers consider, as I did, that they want a copy on their boating bookshelf, then they are encouraged to ask Jim directly at ‘zerofailmooring@yahoo.co.uk’. Conversely, it is rumoured that PBO magazine may run a short article on this topic ‘sometime in the new year’, and that the mag’s editor – the Svelte Sarah – welcomes emails inquiring about it.

 

[savageseadog]

There's been quite a few failures on the Menai Strait last year.

 

[Gaffcut]

mooring failure

So there I was, on beach in Lanzarote at Xmas, twelve months ago, when a text came in from S.Ireland. "Your Mirage has dragged it's mooring(two large concrete filled tyres) in severe wind, but rescued and now safe".
Peeling another grape I reflected on this disturbing news and remembered a guy in W.Scotland telling of the cubic metres of concrete used for summer moorings were generally up on the beach by the end of winter. His answer was to use the local sub-aqua club to screw one of those ground augers into the sea bed,- generally used for farm straining-post hole boring. He said it was magically safe if used with appropriate swivels etc. I may take a walk around the idle Plant Hire places!

 

[jimmcgee]

So there I was, on beach in Lanzarote at Xmas, twelve months ago, when a text came in from S.Ireland. "Your Mirage has dragged it's mooring(two large concrete filled tyres) in severe wind, but rescued and now safe".
Peeling another grape I reflected on this disturbing news and remembered a guy in W.Scotland telling of the cubic metres of concrete used for summer moorings were generally up on the beach by the end of winter. His answer was to use the local sub-aqua club to screw one of those ground augers into the sea bed,- generally used for farm straining-post hole boring. He said it was magically safe if used with appropriate swivels etc. I may take a walk around the idle Plant Hire places!

? Do you mean like this
http://www.westmarine.com/1/1/14907--sand-anchor.html

was thinking the same thing.

 

[SHUG]

I have had a deep water mooring for 15 years and had it checked annually.
A fundamental problem is that of getting reliable top quality components. I have seen shackles where the pin was fine but the bow was corroded and vice versa. Some swivels have just lasted one season before corroding away.
There is a testing and certification scheme for lifting tackle. Could there be something similar for mooring gear???

 

[craigsmith]

A fundamental problem is that of getting reliable top quality components. I have seen shackles where the pin was fine but the bow was corroded and vice versa. Some swivels have just lasted one season before corroding away.
There is a testing and certification scheme for lifting tackle. Could there be something similar for mooring gear???

Any marine classification society, like Lloyd's or RINA, provides the appropriate rules applicable to all components. It just has to be demanded.

 

[William_H]

Moorings

The book sounds very interesting. The thing about a swing mooring is that any mistake that precipitates a failure of a single component can set the boat free.
Re testing of components. IMHO it is bulk of material that is needed so that with rust /wear there is still adequate material until next inspection. IMHO it is different metals in contact that can precipitate rapid wear or loss of metal.
My mooring is currently all stainless steel mm 10mm diameter, with some mild steel additions connected by nylon rope. No sign of wear after a few years leaves me wondering is it really as good as I think. I can and do dive on it often.
olewill

 

[SHUG]

Any marine classification society, like Lloyd's or RINA, provides the appropriate rules applicable to all components. It just has to be demanded.

That just doesn't work if you drop by the local chandelry here.
On the internet , the only classified shackles and swivels I can find are for lifting gear.
Do you mean "demanded" by the boating community??

 

[Lakesailor]

Conventional 3-strand rope is not used for swinging boat-ropes/bridles because it can unlay and splices then fail….

Tosh.

 

[alan_d]

Tosh.

I think you should reconsider that comment.
I know you don't have tides on the lake, but in places where they do it is not unusual for moored boats to swing predominantly in either a clockwise or anticlockwise direction, so potentially imparting a twisting force to stranded rope. A combination of adverse events could therefore lead the rope to unlay and weaken the splice. In the pursuit of "zero failures" it would seem reasonable to prefer plaited over laid cordage.

 

[Lakesailor]

Read it again.................

Conventional 3-strand rope is not used for swinging boat-ropes/bridles because it can unlay and splices then fail….

Oh yes it is.

Boats will swing with the wind as well as the the tides. It may be that they wind-up as well as unwind. On the lake the constant wind shifts will see boats turning around their moorings several times a day. We normally have swivels at the bottom of the riser and also under the mooring buoy to avoid the strops winding up.

 

[TradewindSailor]

Tosh.

You are mistaken.

I have seen several three-strand mooring penants in the process of unlaying or of cobbling up. Either way it weakens the rope ..... and can severely weaken any splicing. I would be very wary of any three strand located in the mooring system where it could not be easily inspected.

 

[Lakesailor]

Erm.......The only part of a mooring I would expect anyone to use 3 strand is the strop from the riser to the boat.
Surely you can inspect that?

 

[JayBee]

Short and out of context

As the OP says:

"The following short extracts are included to provoke interest, but should be read in proper context before agreeing or disagreeing vehemently..…"

.....including this short extract, perhaps:

"Conventional 3-strand rope is not used for swinging boat-ropes/bridles because it can unlay and splices then fail…."

.....which probably refers to accepted practice and experience in Jim Izzard's neck of the woods, but I wouldn't know as I haven't read the book, yet.

 

[Lady Campanula]

'Jaybee' takes the appropriate meaning from the quotes, which reflect the practices of one or more of the professional mooring companies quoted in the booklet, and thus their preferences.

It is obvious to anyone with eyes that other practices are utilised in all sorts of places and circumstances.

The quotes are - as mentioned - to provoke interest, but not controversy without reading them in their full and proper context, and there is plenty within Jim Izzard's booklet for amateur and pro to chew on....

Does it help if one adds "....not used by us...."




Edit: If this post provokes just one reader to look longer and harder, and change something in his mooring setup 'past it's sell-by date', then it'll have earned its keep....

 

[William_H]

3 strand rope in mooring strop

yes I have seen a three strand rope untwist at the splice. It didn't let go but it looked iffy and 'orrible.
A mooring must have a functioning swivel. I have seen chain wind up tight where the swivel has fouled up. (same boat which is not often used or checked)
I think 3 strand is OK for mooring strop however it should be backed up by another mooring strop which means the 2 will twist around one another. You would do well to use an extra long splice. Of course all moorings need to checked monitored for things like stuck swivel. olewill

 

[Maine Sail]

I have been studying and watching mooring failures for about the last 25+ years. I sat on our towns mooring committee and was tasked with the research into why they fail. This put me in touch with over 85 harbor masters throughout the US and even a few in Canada. The bottom line is that good records are NOT kept on mooring failures but I was stil able to gather lots of good info. I also have two good friends who are mooring installers and who make a living doing this. One of them services over 900 moorings and has not lost a boat in over 15 years. There are best practices that work.

One of my pet peeves that I have been ranting bout for years is that pendant failures are often incorrectly assigned to chock chafe when in fact many of them part due to anchor chafe from anchors left on bow rollers. Seeing as I live right near the local harbor which has over 1200 moored boats I have plenty of access to mooring failures.

Some of you who frequent the US sailing forums will remember my many rantings about folks leaving anchors on their bows, in exposed mooring fields, during rough weather. If your mooring field has the fetch to build waves that can pitch the bow of your boat then it is rather rude & inconsiderate to the boaters around you, who may get hit by your drifting boat to not remove your anchor when a blow is expected. Many times chafe comes from the chocks but after motoring around the anchorage the morning after this short storm I saw that most of the chafe was anchor related. This is not the first nor the last storm I have or will monitor for mooring failures.


For the rest of the article and a LOT more photos you can read it here:

Mooring Preparations & Precautions (LINK)


For some time now I had been trying to capture the "moment" on film to really drive the point home about REMOVING your anchor if a storm is coming. Some folks actually get it, but still many don't. I think this Island Packet is a PRIME example of "my anchors are protected by a bow sprit, I don't need to remove them" line of reasoning.

Here it goes:

Here it goes:

Both pendants still intact but hooked on a Delta. It was still holding but chafing badly:

And DOWN!!!

And UP! And SNAP!!!!!

The Parted Port Pendant IS Blowing Back Against The Hull:

Notice The CQR Holding The REMAINING Pendant And The Bend In It:

This boat owner was VERY, VERY lucky that the storm was winding down as these pics were taken. The remaining pendant actually held an good reason for using dual pendants.

PLEASE, if not for your boat, think of the others around you and what your boat would do in 30+ knots drifting through an anchorage after the anchor has sliced through the pendants. I watched it happen in real time, it leaves a pit in your stomach. Thank god MOST moorings in Falmouth are dual pendant rigged. This boat owner came very close to owning a pile of off white fiberglass splinters..


Mooring Preparations & Precautions (LINK)

 

[LeonF]

Maine Sail an interesting post. I have an achor on my bow roller, but it's set to starboard and I lash it up out of the way of the pennants. I use two three-ply lines, with a large swivel betweeen them and the mooring buoy. To avoid chafe on the bob stay I lash a large shackle as far forward as possible on the bowsprit and lead the pennants through the shackle. The Thames can blow up something with strong tides, and a couple of times last year I returned to find everything intact but the shackle on the front of the bowsprit had somehow clipped itself to the bob stay. No harm was done. I shall change it for a locking shackle this season. Re the comment in the featured book commending the use of hippos over inflatable buoys, I used an inflatable for some 8 years with no problems whatsoever. It had a 24mm rope core which hadn't been replaced, but I had examined it from time to time. The club I belong to has had a double trot laid professionally, and I requested inflatables. We had a batch of them deflating, but this turned out to be a manufacturing fault. I find that the inflatables are much kinder to the hull, and soften the snatching action.

 

[craigsmith]

That just doesn't work if you drop by the local chandelry here.

Do you mean "demanded" by the boating community??

Yes, but not necessarily directly; the only way to enforce this sort of thing (along with the extra costs implied) is by regulation. With larger vessels or anything commercial, you will find that the case in the marine industry anyway. If the relevant local requirements don't go into great detail themselves, they will refer to IACS classification standards. It's just that no such requirements exist with small private boats, so you end up with real cheap junk in a lot of retailers driven by lowest-price market forces, stuff that the likes of myself would rate as unfit-for-purpose, being sold perfectly legally. You can't blame the chandlery because either they can't be expected to know better, not everyone is a materials engineer, or they will go out of business if they don't compete with the other guy down the road.

On the internet , the only classified shackles and swivels I can find are for lifting gear.

Shackles are shackles, no shackle manufacturer produces them exclusively for use in anchor rigs. The lifting industry is just obviously subject to tougher safety standards so you find more adherence to classification when looking. Many marine suppliers do provide shackles and chain etc that are tested, classified, and can be certified if required. My point is the framework exists even with the present reality, and the cautious boater (and mooring installer... we can only hope...) can make use of it.

 

[Mooring Book Man]

I am grateful to ‘Lady Campanula’ for his, I promise, unsolicited review of my book. I had 100 copies printed in August last year and have about 10 copies left. The decision about another print-run will depend on the response to a possible PBO review, perhaps quite soon now. The whole initiative is at my own expense, and any profit that comes to hand will go to the RNLI. Other places to get a copy from are the National Maritime Museum Cornwall, Bosun’s Locker and Mylor Chandlery, all in and around Falmouth. Comments on the book would be most welcome to inform a second edition. In response to feedback, I’m already looking, for instance, at corrosion in weldments, say where shackle pins are welded instead of being moused.