Boat Gone Adrift.

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pandos

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Twice my boat has gone adrift, the first time the riser broke in the middle of a storm and the boat went down the river and parked herself in the RCYC marina with no damage done.

the second time she dragged her mooring 500 m down stream and would have dried out but for a phone call..

I am wondering what are the most frequent (unwanted) causes of boats leaving their position??

Dragging,?
Broken Riser?
Swivel,?
Mooring Eye?
Strops,?
other?


A poll would be nice but I do not know how to do this....

Tony
 
From experience on Windermere, most boats seem to end up with the buoy on the foredeck when they turn up at the Wardens so riser or swivel would be favourite. It was swivel when mine went 2 winters ago. I have known of strops failing though, but only usually one of two or more.

On my tidal mooring I use a chain strop and it's serviced every year so it doesn't fail, ever.
 
I'd say 75% or so of the mooring failures I've seen - deep water and half tide moorings - the swivel has been the culprit.

Rope strops chafing through was a significant factor in the others.
 
I couldn't portion blame to any particular metal component. They are all susceptible to the rust/wear/rust cycle of rapid deterioration in the faying surfaces. Some swivel designs are difficult because the contact surface of the swivel is in a socket which a ball end sits in. It is not so easy to see and assess the wear on the ball and socket.
Chain and shackles must be unloaded and separated as far as possible to examine the wear surfaces.
Shackle pins that move in their thread can wear the thread quickly even if moused.
In my experience chain wears nearer the top. The bottom sitting on the sand does not move quite so much hence less wear. I don't believe silica has any real part in the wear process.
Rope strops should always be backed up with additional strops. One concern in a storm is if another boat comes adrift and hits /leans on your bow chafing the strop.
I don't think a storm should be quite as much concern re moorings as the inevitable deterioration of iron over time. Frequent inspection is the only answer. olewill
 
I have seen quite a few swivel failures over the years; I think those on deep water moorings were 99% simple age and should have been replaced.

On our half tide mud moorings however I noticed that my swivels were becoming dubious - as in not swivelling freely, not wear - after only 2 seasons.

I reckon this was due to the swivel laying in the mud & grit half the time, eroding / jamming the thing.

Also oxygen can get to and rust anything on the surface or just underwater much quicker than deeper down.

So I replace swivel annually and topchain every 2-3 years.

BUT a new moorings chap at our club - who also happens to be an engineer for Rolls Royce - introduced a new system...

Now we have large permanently floating buoys, the swivel on top - in fresh air - then topchain & pickup buoy to the boat.

The swivels last noticeably longer now, but at £7.00 a pop I still replace them.

The rope strops chafing through is just what one would expect, every time; a sharp bit on the stem fitting or mooring buoy - then a series of gales so the owner cannot get out to check it - and disaster.

I don't believe a short length of thick nylon like a strop has any significant elasticity, it's a red herring; so chain every time for me, one can always fit a rubber snubber which won't matter if it fails but I don't find the need.

The snag with backup chains / strops is that they can twist together and form a spanish windlass, putting a significant load on boat and mooring - so I just believe in one regularly checked, oversize, chain set up.
 
Niander said:
You need to start looking after your boat m8
double ropes up...have backup! etc
Click to expand...

Perhaps the original post is too unclear for some,

I am looking to establish the most frequent actual causes of boats going astray, not an explanation of why mine went astray, or a list of possible causes (other than any that I have listed) and I am especially not seeking advice on how to stop mine moving again.

Tony.
 
Shackles losing their pin is my top bet.
My top gear gets through cable ties as if they were not there. The mooring contractor put a flat metal tie on it in the summer it lasted 6 weeks. Monel wire can endure if it is tight and snug into the corner of the pin but I don't rely on it.
I now drill and use split pins + monel wire
 
JumbleDuck said:
Why not? QUOTE]

Because the cause of the original failure was self evident, and was dealt with by shortening the riser which years later was in perfect condition when changed again. Ten years later when the boat pulled the mooring block in a force 11 storm, again the cause of the failure was self evident and this was dealt with by adding a bigger weight, and an additional anchor,
Click to expand...
 
pandos said:
JumbleDuck said:
Why not? QUOTE]

Because the cause of the original failure was self evident, and was dealt with by shortening the riser which years later was in perfect condition when changed again. Ten years later when the boat pulled the mooring block in a force 11 storm, again the cause of the failure was self evident and this was dealt with by adding a bigger weight, and an additional anchor,
Click to expand...
Think this answers your own question. Failure of gear, whether it be through corrosion or defective fitting would be the major cause and in extreme conditions moorings can pull out.

The first can happen at any time, but the actual numbers of boats involved is likely to be extremely small, so you are unlikely to get any reliable statistical evidence, and the latter is rare - although those of us who remember events like the 1987 storm have seen what extreme winds can do, particularly when moorings are close to a lee shore and there is a long fetch to windward, as in Poole. Needed a shore based crane to lift my boat back into the water from the recreation ground it ended up on.
Click to expand...
 
doug748 said:
Shackles losing their pin is my top bet.
....
Click to expand...

I'd agree with that.
Next would be chafe on rope strops.
Then pure lack of maintenance allowing things to rust through.
fourth perhaps totally under-spec'd gear, like sinkers that get dragged around, or moorings that rely on the weight of a ground chain and it's not heavy enough, or somebody puts a big boat on a light mooring.
 
mattnj said:
Thinking about this (ive never looked!)....
Should I be checking my mooring (provided by Gosport Boatyard) or should I expect them to be maintaining them correctly?
Click to expand...
You should check your boat isn't chafing their strop IMHO.
GBY are pretty good at maintenance IMHO.
 
doug748 said:
Shackles losing their pin is my top bet.
My top gear gets through cable ties as if they were not there. The mooring contractor put a flat metal tie on it in the summer it lasted 6 weeks. Monel wire can endure if it is tight and snug into the corner of the pin but I don't rely on it.
I now drill and use split pins + monel wire[/QUOTE

From my experience when I had drying moorings the pins came out on two occasions even though they were moused once with monel wire and once with a cable tie. I think with cheap although big shackles the thread can rust and then any looseness can quickly wear the remaining threads and the mooring forces rotating the pin and tearing the siezing apart and the pin then drop out. I eventually sealed the threads with Sikka and also peined over the bolt heads both to stop them turning and impossible to come out. This worked for me. I never found great wear no swivels but I suppose in a strong tidal river wear may be much greater. The benefit of rope strops over chain is that of no rust stains and the rope strop is kinder to the hull in the event of the boat lying over the chain due to strong wind over tide.
Click to expand...
 
If you must mouse with wire, the fattest plastic coated garden wire is quite good.
Or an old wire coathanger.
Loctite
Lock washer
Lock nut
Drill and pin
Pick any 3 of those!
 
For what it's worth regarding shackles, in the early days of maintaining my mooring(s) I always used galvanised. I was forever finding the pins loose at end of season. The galvanising in the thread seemed to disappear allowing the pin to work. For the last 20 years or more I've been using black iron shackles. I have only very rarely found a loose shackle pin, more often than not it is near impossible to undo them. So I would say biggest black iron shackle, no grease, definitely no galvanising for any underwater connections. Mousing is normally Monel wire plus a couple of cable ties for luck.
 
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