How long a mooring line on the anchor snubber

[HoratioHB]

As far as I know one of the primary reasons for chain is because it is capable of being stored in a very compact manner with very little effort. Rope and wire if simply fed down a spurling pipe will not form anything like the neat heap that chain will.

Er - and you need a shed load more out for the same depth for rope which means in a crowded anchorage you have a much larger swinging circle and that's fairly anti social. In two years I must have anchored over two hundred times and had I not used a snubber apart from anything else I would have put strain on my anchor windlass that its not actually designed to take. We even put the snubber on to take the load before reversing under engine to set the anchor. In the same way that you see people using them to drag the boat through the water when raising the anchor rather than motoring slowly forward and using the windlass purely to take up slack chain. Fine if its not your boat or you anchor only occasionally but when you do it on a daily basis on your pride and joy it all takes on a different slant.

 

[Neeves]

The friction of the chain in the water helps keep the boat from swinging wildly.

If the chain is pulled all but straight there is no give so the boat will not snatch at the anchor as long as it is holding it will just pull a little harder for each gust... She will not gain a little momentum with the stretch of the nylon, then potentially over compensate when the nylon returns and start snatching?

..

I assume your first comment actually means the friction of the chain on the seabed (as I'm guessing the friction of the chain in water is not relevant). I've only done this with 8mm chain but at 5:1 scope, 30m of chain all the chain will be off the seabed prior to 20knots (so there will be no friction on the seabed). Knowledgable comment, which I have not tested, suggests that above F6 (for the amount and size of chain realistically carried for that size of yacht) all the chain will be off the seabed (so, again, no friction). There will be catenary - but no friction.

Winds are not stable, look at any plot of wind over time and wind direction over time and you will find that though the windspeed average might, say, be 30 knot the lulls and gusts will be 18-42 knots and wind direction will vary (even over flat countryside) by 60 degrees. (You can see the same effect at airports in a wind, the aircraft wander all over the place as the gusts and lulls occur). Wind direction variation will differ based on a whole host of factors but will not be stable.

The idea of having constant wind is illusory, gusts and variation in direction are transitory and a yacht on single anchor will react to those changes. If the wind is sufficiently strong (storm force) the chain might be taut but that will not stop snatch loading as the yacht will be swinging from side to side and during its return from one side, may move 'sideways' allowing the chain to slacken - prior to the next snatch load. Depends on the anchorage - but you can also expect seas to develop under such strong winds that the chain is bar tight - these will also generate dynamic loads (call them snatch loads) - without any elasticity those dynamic loads are imposed on your anchor (and windlass if you think it strong enough).

Obviously if you do not stray far from home and have totally reliable weather forecasts then the chance of being caught out in storm force winds is minimal (or non-existant) and the necessity for a decent, ie elastic, snubber is academic. But visit the nether regions of the UK, or in our case Oz, and you would be stupid not to be able to take advantage of any device that secures your vessel, whether it be a 'real' snubber, deploying a second anchor, dropping an anchor as a 'friction' brake - or whatever

I do not have the answers, but I'm willing to try (almost anything) and share. We have used nylon snubbers in storm force winds in Perkins Bay, Tasmania for 3 days. We did not drag nor had snatch loads imposed as sharp dynamic 'hits', 38' x 6t cat, 50m of 8mm chain maximum water depth 6m, 2 x 13m nylon snubbers, 16kg Excel anchor (Fortress FX-23 on 30m of chain with 40m of warp ready to deploy - but unused). Seabed (obviously) good holding sand. There might be better systems, but we have not found it yet.

In Refuge Cove, Wilson's Prom we also sat out Storm Force winds (never sail with us - every year we sit out one storm force wind event!), its a really sheltered anchorage. But bullets came down from the hillsides at 180 degree variation. We anchored and tied to a tree - but you do need long warp in anticipation.

Lots of oil rigs are anchored using Dyneema now - it is sufficiently strong, their anchors are factorially better than ours (if the rig needs to move the anchors can be so well set they are simply abandoned), they use a web of anchors (so the whole complex is stationary). There are lessons from oil rig anchors - but the situations are slightly different.

 

[onesea]

Neeves,

I did actually mean through the water, boats on chain do tend to sail around less at anchor,
Early on I stated that the theory is over F6 chain is said to be totally of the sea bed,
I have not mentioned a constant wind,

Cats do react differently and require a different set up,
Your right Dyneema is getting used more and more offshore, as I understand more in deep water installations where the rules are very different. Cattenery systems have there own issues. Again that is like chalk and cheese, I was thinking the comparable shallow water (say less than 200m?) operations.

As for comments about where, and how much I am afloat, I always dip out when people start getting personnel. Have Anchored in assorted manners and locations using various different techniques. Although it is over 10 years since I visited your shores...

 

[Neeves]

Sorry, Onesea.

When I said 'Obviously if you do not stray far from home...' that was an inexcusable slip. I should perhaps have written 'obviously if one does not stray etc' it was not meant to be personal and there was never a suggestion as to where or how often you (personally) are afloat.

You did suggest that

'If the chain is pulled all but straight there is no give so the boat will not snatch at the anchor as long as it is holding it will just pull a little harder for each gust... '

Which seemed to ignore the idea that wind direction might also vary - in my experience causing snatching (and seas might build (if the wind is strong enough to pull a chain straight), also causing snatching

I love your comment 'shallow water (say less than 200m?)' - it really puts it all into perspective.

But there was no intent at personal questioning of your integrity nor experience, just clumsy or careless wording. I am suitably chastised.

Jonathan

 

[dolphin]

good day to all !

windlass - it is not designed to take the load of the chain once the vessel/boat is anchored !

in one of the post have read
qte
...an anchor snubbers only real purpose is to take the load of the anchor chain off the brake on the windlass. The windlass its self should be more than capable of taking any shock loads without parting company with the deck and personally I would be more inclined to attach the snubber to it rather than trust deck cleats.
unqte

it is wrong ! never leave the load on the windlass !
on board of the vessel, from smaller one up to the VLCC, once on anchor, the load is transferred to the chain stopper !
this way prevent the damage of the windlass ! just imagine, the damage windlass and the problem/s to recover the anchor !
if the weather deteriorated to stormy conditions, for the vessel is more safe to leave the anchorage and drift at open sea than to remain on anchor !
in my personal opinion the snubbers improve the holding capacity of the anchor because transfer the load of the boat, generated by weather conditions, to the chain/anchor system more gradually and without snatch loads !
on board of the vessel, the snubbers are practically not applicable due to the size !

usually, when i anchor, i leave out the chain of about 25-30 m as a minimum, irrespectively of the depth! in calm weather - no snubber, if the weather is windy - double snubber of about 5 m 12 mm rope each on both cleats! if needed can increase the length up to about 9 m each! in case more windy, over 6, raise the riding sail! the boat is 12 mt, chain is 10 mm and the anchor is CQR about 30 kgs
i have tried also with angel of about 12-13 kgs but when the wind pick up do not see any improving and consider the snubber much better and more easy to deploy !

regards

 

[KellysEye]

One thought on snatch loads: we always used a riding sail when at anchor. Attach it to the backstay and tie the two clew lines to port and starboard stanchions. You will be amazed how much it's cuts down the swinging and thus snatch loads. I amazed that very few boats use one.

 

[prv]

we always used a riding sail when at anchor. [...] I amazed that very few boats use one.

I used to put the mizzen up occasionally on KS. With the peak halyard and the sheet both nice and tight it went quite flat and made a good "tail fin". But with her deep forefoot and long keel, KS was usually well-behaved at anchor anyway.

Pete

 

[GrahamM376]

Neither do I. A mate had me refix his windlass to his Bavaria. Surprise though, it wasn't the Bavaria platform which had failed, the studs had stripped out of the rear of the windlass body and bent the front ones through 45 degrees. Fortunately, there was enough meat to drill and tap oversize. He'd never heard about snubbers and spent a rough night in Camaes Bay with the chain snatching until it tore the windlass loose.

 

[GrahamM376]

One thought on snatch loads: we always used a riding sail when at anchor. Attach it to the backstay and tie the two clew lines to port and starboard stanchions. You will be amazed how much it's cuts down the swinging and thus snatch loads. I amazed that very few boats use one.

I've only seen a couple of boats with riding sails and wondered about the benefits and when to or, not to hoist. Do they help in gusty wind over tide situations also, how would one size the sail to boat length - would the storm jib suffice?

 

[NormanS]

All anchoring situations are different. We sail mainly on the outer fringes of the West Coast of Scotland, and frequently experience strong winds. However the West Coast is blessed with many many excellent sheltered anchorages, some bullet proof in any wind direction. That means that, with care, one is never anchored in a place exposed to sea, and seldom in strong current, but there is no realistic escape from the wind.

IMHO with the tendency to lighter boats, the weight of gear has been cut to the minimum, and so it is with anchors and chain. There is now a tendency to select chain in terms of tensile strength, instead of weight suitable to give a useful catenary in all conditions. We see many boats now equipped with what we term "lavvy chain". (People of a certain age will remember the flushing of toilets being achieved by pulling a chain). Light chain may well be strong enough, no argument, but it is useless for providing a catenary. So the moral is, if your chain all comes off the bottom, it's probably not heavy enough, therefore you need a nylon snubber of an adequte length to give some elasticity. In very shallow water, the advantage of using chain is reduced, because a useful catenary cannot be achieved, and there, a short section of chain with the rest in stretchy nylon is probably the best combination.

I quite agree that the load should be taken off the windlass, either with a chain hook or hitch etc. In my own case I use a fabricated s/s device with a slot, attached to a special strong point, with a strop, so that without lifting the chain off the gypsy, the load is taken off the windlass. Please dont wrap anchor chain round a cleat!

Curiously, the worst winds that we have experienced, while at anchor, have both been in June, of 74 and 68 knots, neither of which were pleasant.

 

[Woodlouse]

good day to all !

windlass - it is not designed to take the load of the chain once the vessel/boat is anchored !

in one of the post have read
qte
...an anchor snubbers only real purpose is to take the load of the anchor chain off the brake on the windlass. The windlass its self should be more than capable of taking any shock loads without parting company with the deck and personally I would be more inclined to attach the snubber to it rather than trust deck cleats.
unqte

it is wrong ! never leave the load on the windlass !
on board of the vessel, from smaller one up to the VLCC, once on anchor, the load is transferred to the chain stopper !
this way prevent the damage of the windlass ! just imagine, the damage windlass and the problem/s to recover the anchor !


regards

It depends what you have to attach your chain stopper/snubber too. Personally I would expect a windlass to be better fixed down than the average bow cleat, especially on modern tupperware yachts. If you have a decent set of bitts, or a samson post then by all means fix it there, but a lot of windlasses feature a hitching post which would be my choice over a cleat.

 

[BelleSerene]

Witchard have a lovely and expensive chain hook with a pin on a spring. The pins are prone to bending but the biggest issue is that you need 2 hands to undo them.

I found the same with that Wichard chain hook with sprung pin. So I broke the pin off. It's completely unnecessary: once you take any tension on the warp so the chain is slack above the hook, there's no way the hook will come off the chain. Then the thing's trivial to attach, and easy to detach once you take up tension on the chain with the windlass.

FWIW I use a couple of those rubber bungees to give a 3-4m line some elasticity to absorb snubbing.

 

[Neeves]

It depends what you have to attach your chain stopper/snubber too. Personally I would expect a windlass to be better fixed down than the average bow cleat, especially on modern tupperware yachts. If you have a decent set of bitts, or a samson post then by all means fix it there, but a lot of windlasses feature a hitching post which would be my choice over a cleat.

That's a worry. I had romantically thought all cleats were backed up with reinforcing (ours are). If a yacht need to be taken under tow in rough seas - to what is the tow rope attached?

Jonathan

 

[Woodlouse]

That's a worry. I had romantically thought all cleats were backed up with reinforcing (ours are). If a yacht need to be taken under tow in rough seas - to what is the tow rope attached?

Jonathan

Naturally cleats are backed up and reinforced. But I would expect the windlass to be even more so. As for taking a yacht under tow, I think standard procedure is either take the line around the mast at deck level if keel stepped or run a bridal from the primary winches. The Bristol Channel Pilot Cutters used to have a massive king post that went through the deck and was bolted to the keel for towing. In rough conditions no cleat is designed to take that sort of strain.

 

[onesea]

That's a worry. I had romantically thought all cleats were backed up with reinforcing (ours are). If a yacht need to be taken under tow in rough seas - to what is the tow rope attached?

Jonathan

From what I understand, normally a turn around the mast. and lead back to the jib sheet winches in a spider web arrangement.

I know on my present boat, I would not rely on the deck cleats under tow or at anchor in serious conditions. Then I have no plan to be in those situations, if it happens its a spiders web for me...

If people already haven't its worth having a look at the securing arrangements for your mooring gear, its always wort knowing were your weak link is...

 

[charles_reed]

2-10 m of 14mm polyester Octoplait on <65m of 8mm chain.

I always have a bight of chain from bow-roller to chain link which has totally transformed the behaviour of my boat at anchor and virtually eliminated any dragging.

I anchor about 120 nights pa and since starting this arrangement 4 years ago have had 4 anchoring "situations" 1 x bower on a towel, 1 kedge on an abandoned bight of rope, 2 kedge when incompetents have fouled my line around their props.

PS having had a backed cleat pulled out and broken, I never use my windlass and usually have the chain round one cleat and the textile rode round another

 

[GrahamM376]

From what I understand, normally a turn around the mast. and lead back to the jib sheet winches in a spider web arrangement.

I know on my present boat, I would not rely on the deck cleats under tow or at anchor in serious conditions. Then I have no plan to be in those situations, if it happens its a spiders web for me...

If people already haven't its worth having a look at the securing arrangements for your mooring gear, its always wort knowing were your weak link is...

Whilst agreeing that chain without a snubber may cause damege to whatever it's fastened, I think you worry too much about the strength of deck cleats for anchoring. Mooring dwellers have to use their cleats regardless of conditions and it's a very rare occurence for a cleat to fail.

 

[tudorsailor]

I found the same with that Wichard chain hook with sprung pin. So I broke the pin off. It's completely unnecessary: once you take any tension on the warp so the chain is slack above the hook, there's no way the hook will come off the chain. Then the thing's trivial to attach, and easy to detach once you take up tension on the chain with the windlass.
QUOTE]

The Wichard Chain hook comes with a 23mm line fattached to the hook for a 12mm chain. Not much stretch in the line I would imagine!

TudorSailor

 

[dolphin]

It depends what you have to attach your chain stopper/snubber too. Personally I would expect a windlass to be better fixed down than the average bow cleat, especially on modern tupperware yachts. If you have a decent set of bitts, or a samson post then by all means fix it there, but a lot of windlasses feature a hitching post which would be my choice over a cleat.

everyone know his boat but just have in mind that the hitching post of the windlass, usually on top, will be on some distance from the deck or much higher than the deck cleat ! this way the force on the fixing points of the windlass will be much bigger than on the cleats! on my boat the hitching post is about 40 cm from deck and the cleats are only about 5 cm or the force on the windlass will be 8 times greater than on the cleat! it is much better to fix the snubbers/stoppers on both cleats than on the windlass or at least this is valid for my boat!
regards

 

[BelleSerene]

The Wichard Chain hook comes with a 23mm line fattached to the hook for a 12mm chain. Not much stretch in the line I would imagine!

TudorSailor

View attachment 28317

It comes alone and you can splice (or bend) a line to it. But you're right, there'd be no stretch in that line, so I use a couple of these rubber 'mooring compensators' which seem to take all the snubbing out of it.

View attachment 28318

I just removed the pin when it started bending, and found it's superfluous.