JW's Upgrades for 2016 - Anchoring

[Deleted User YDKXO]

The Chain Lock will be a totally different matter - I'm hoping that all we will need to do is flip the little flap and its - job done.
The chain lock that I've bought is one of these:-

I'm not sure a chain lock replaces the snubber though? At least on my boat, when it swings from side to side in the wind at anchor, that snatching load is resisted by the side plates of the bow roller structure and the roller bearings which I'm not sure is good for either component in the long run. A chain lock wouldn't relieve that loading which is why I'd still fit the snubber.

I also plan to fit a chain lock in the winter but I would just use it to take the load off the winch when I'm setting the anchor

 

[Hurricane]

I also plan to fit a chain lock in the winter but I would just use it to take the load off the winch when I'm setting the anchor

Yep - that was my thoughts

BTW - I haven't left the snubber club yet!!

 

[MedMilo]

I'm not sure a chain lock replaces the snubber though? At least on my boat, when it swings from side to side in the wind at anchor, that snatching load is resisted by the side plates of the bow roller structure and the roller bearings which I'm not sure is good for either component in the long run. A chain lock wouldn't relieve that loading which is why I'd still fit the snubber.

I also plan to fit a chain lock in the winter but I would just use it to take the load off the winch when I'm setting the anchor

I agree. My bow roller has a couple of metal plates which hold the final nylon roller in place about 10 inches proud of the bow. As the boat weaves around in the wind the lateral pull on the plates would easily be enough to bend them over time. And, as mentioned before, the noise in the forward cabin with all this going on would make sleeping impossible - even to a non boater reading this thread.:sleeping: The snubber obviously removes all the weight from this 'protrusion'. So IMHO the chain lock is a worthwhile belt and braces addition but no more than that.

To JFM's point I should say that I haven't opted for a loop at the bitter end of each bridle so can just undo at the cleat in order to release the whole thing even if the snubber is under pressure - the anchor hook drops off immediately it's not holding any weight. Haven't had to get going quicker than the 60 seconds it takes to 'get the hell out of there' - even when the Guardia di Finanza turned up at and anchorage in the Costa Smeralda in July!

 

[MedMilo]

I'm not sure a chain lock replaces the snubber though? At least on my boat, when it swings from side to side in the wind at anchor, that snatching load is resisted by the side plates of the bow roller structure and the roller bearings which I'm not sure is good for either component in the long run. A chain lock wouldn't relieve that loading which is why I'd still fit the snubber.

I also plan to fit a chain lock in the winter but I would just use it to take the load off the winch when I'm setting the anchor

I agree. My bow roller has a couple of metal plates which hold the final nylon roller in place about 10 inches proud of the bow. As the boat weaves around in the wind the lateral pull on the plates would easily be enough to bend them over time. And, as mentioned before, the noise in the forward cabin with all this going on would make sleeping impossible - even to a non boater reading this thread.:sleeping: The snubber obviously removes all the weight from this 'protrusion'. So IMHO the chain lock is a worthwhile belt and braces addition but no more than that.

To JFM's point I should say that I haven't opted for a loop at the bitter end of each bridle so can just undo at the cleat in order to release the whole thing even if the snubber is under pressure - the anchor hook drops off immediately it's not holding any weight. Haven't had to get going quicker than the 60 seconds it takes to 'get the hell out of there' - even when the Guardia di Finanza turned up at and anchorage in the Costa Smeralda in July!

 

[Neeves]

One reason for the chain lock, and they can simply be a(nother) hook attached to a cleat on a short strop is that snubbers should be considered as consumables. If your snubber/bridle does not fail after good usage every 1-2 years - then its too big (edit, not elestic enough close edit). When they fail they fail with a bang - and its then you need the chain hook, or chain lock (or risk pulling the windlass out). You also need to carry spare snubbers.

 

[jfm]

When they fail they fail with a bang.

. Crikey. A 10m bit of nylon rope elastic ally stretched 1m and failing with a bang. Doesn't bear thinking about for the person who gets that in their face

I did some maths. A boat has a drag coefficient say 0.5. Say 40 knots wind =20m/sec. Say 25msq frontal area =my boat. Density air 1.225kg / metre cubed. That amounts to 3000 newtons horizontal force. Say 300 kg

Now plug that into a catenary calculator eg http://www.spaceagecontrol.com/calccabm.htm?F=3000&a=50&q=3.8&g=9.81&Submit+Button=Calculate. Assume you have 50 m of chain out, none lying on seabed. 12mm chain is 3.8kg per metre. The catenary droop is 4 metres and the chain has 0.8m of stretch left in it. Well 0.8m is similar to 1m so you have approx the same amount of stretch as proposed above, and waaaay more stretch than any actual snubber I have ever seen, without messing around with an actual snubber

Members should be leaving the snubber club in droves:encouragement:

 

[MrB]

^^^^^^^^^^ he's fecking good lol ^^^^^^^^^^

 

[Neeves]

Nylon stretches 40% to failure and the stretch is roughly linear - so it 'works' all the way to its failure point (unlike catenary which works less and less - the more load the less catenary is left to offer relief from snatch loading - even 12mm chain has a limit). A 10m length of nylon that stretches 1m has simply stretched to 25% of its capacity. However nylon degrades with use, UV, salt and mud in the structure etc. They thus wear out. Ideally you retire your snubbers and do not wait till they snap.

If you size, diameter, your snubber correctly it will work upto whatever maximum windspeed you want - even 70 knots.

edit I can see a few people slowly seeing the light and joining the snubber club!

If you do not believe in snubbers - think of a bungy jumper. They feel little shock load when they reach the bottom of the fall - all that 'load' (its actually energy) is absorbed into the bungy cord. Now think of a bungy jumper using a chain instead of elastic - that's your yacht with no snubber. You need to use you imagination to relate the bungy jumper and your yacht - but its not difficult. Or think of your car with suspension (the snubber) and without (that's your chain). Rubber snubbers are equivalent to about 2m of nylon cord - you need 4 or 5 of them to be equal to 10m of nylon. close edit.

 

[Portofino]

When I look at big boats /ships at anchor there chain drops vertical well as good as .
Never seen any snubber arrangement
I,have snorkelled a high wind ,anchorage shallow enough to see what going on .
With enough chain out .say 75 M in 4-5 depth the anchor never gets a a tug .Sat on its side or what ever .
There is so much chian lifting and dropping ( catenary ) even with the bows pitching up and down .
Horizontal chain weight does the "snubbing " resting on the sea bed .
If its that windy it reaches the anchor -time to bug out -find a sheltered cove ,
Usually early hours dark ,dazed tired crew ,so anchor needs to be up smart ish .
In my boat pref with out anybody going fwd ,all staying in the cockpit .

 

[Neeves]

Next time you see a big ship at anchor in 40 knots take a picture, there's a Captain about to lose his ticket. With the threat of winds over 25 knots big ships lift their anchors and sit out the winds in open sea. Big ships have permanent crew on board and for many big ships (this may be company specific) the Captain is simply not allowed to leave his ship when at anchor - whether the weather is good, or bad.

But I get mixed messages, some use snubbers some claim them unnecessary - both cannot be correct. And if people are posting here about buying better anchors that are also bigger then they have a reason - as I'm not aware large, galvanised, steel anchors have ever been considered a fashion accessory.

 

[benjenbav]

Nylon stretches 40% to failure and the stretch is roughly linear - so it 'works' all the way to its failure point (unlike catenary which works less and less - the more load the less catenary is left to offer relief from snatch loading - even 12mm chain has a limit). A 10m length of nylon that stretches 1m has simply stretched to 25% of its capacity. However nylon degrades with use, UV, salt and mud in the structure etc. They thus wear out. Ideally you retire your snubbers and do not wait till they snap.

If you size, diameter, your snubber correctly it will work upto whatever maximum windspeed you want - even 70 knots.

edit I can see a few people slowly seeing the light and joining the snubber club!

If you do not believe in snubbers - think of a bungy jumper. They feel little shock load when they reach the bottom of the fall - all that 'load' (its actually energy) is absorbed into the bungy cord. Now think of a bungy jumper using a chain instead of elastic - that's your yacht with no snubber. You need to use you imagination to relate the bungy jumper and your yacht - but its not difficult. Or think of your car with suspension (the snubber) and without (that's your chain). Rubber snubbers are equivalent to about 2m of nylon cord - you need 4 or 5 of them to be equal to 10m of nylon. close edit.

I was trying to think of the bungee jumper using a chain but it made me feel offal...

 

[Neeves]

Very droll, but think how your yacht feels.

 

[Deleted User YDKXO]

I agree. My bow roller has a couple of metal plates which hold the final nylon roller in place about 10 inches proud of the bow. As the boat weaves around in the wind the lateral pull on the plates would easily be enough to bend them over time. And, as mentioned before, the noise in the forward cabin with all this going on would make sleeping impossible - even to a non boater reading this thread.:sleeping: The snubber obviously removes all the weight from this 'protrusion'. So IMHO the chain lock is a worthwhile belt and braces addition but no more than that.

Yes I forgot to mention that. On my boat the grinding noise as the chain slips from one side of the bow roller to the other as the boat swings can be heard throughout the whole boat and without a snubber nobody would get any sleep

To JFM's point I should say that I haven't opted for a loop at the bitter end of each bridle so can just undo at the cleat in order to release the whole thing even if the snubber is under pressure - the anchor hook drops off immediately it's not holding any weight. Haven't had to get going quicker than the 60 seconds it takes to 'get the hell out of there' - even when the Guardia di Finanza turned up at and anchorage in the Costa Smeralda in July!

My snubber has an Osculati hook http://osculati.com/en/cat/Scheda.aspx?id=249 which just drops off as soon as you take the weight off it with the winch so removing the snubber adds very little time to the anchor weighing process. The downside of that is that attaching the snubber is a 2 person job because you have to keep tension on the bridle ropes to stop the hook falling off until it comes under tension

 

[Deleted User YDKXO]

.
Members should be leaving the snubber club in droves

I'm not arguing with your calculation but for me at least, fitting a snubber has nothing to do with adding elasticity to the chain. Its only about transferring anchoring loads from components on the boat that are not built to take them to components that are so on this boat at least I'm a fully paid up member of the snubber club. If you've got a boat with the chain being fed through a substantial hawse pipe though I can see why you might not bother with a snubber and a strong chain lock would suffice

 

[noelex]

Next time you see a big ship at anchor in 40 knots take a picture, there's a Captain about to lose his ticket. With the threat of winds over 25 knots big ships lift their anchors and sit out the winds in open sea.

OK here you go

I am not sure what the regulations say, but in the winter storms in the Med it is not unusual for large ships to seek shelter in an anchorage. They often appear to drag slowly and simply keep re anchoring, but it is hard to make out any details as visibility is always bad in these conditions and they are in deeper water.

There were about 4-5 ships in this particular anchorage with us. It was blowing about 40 knots when I took the photos, but had been stronger in the night. The white layer is not fog but spray, as the tops of the waves are blown off:

This is what it looked like at the back of the boat. I would not like to be in these conditions without some elasticity:

 

[Hurricane]

The downside of that is that attaching the snubber is a 2 person job because you have to keep tension on the bridle ropes to stop the hook falling off until it comes under tension

Yep - we switched to that type of hook this year when we upgraded the chain.
The old hook was easier to attach - the new one often needs two people - we need to research/design a better technique - maybe a fitting on the end of a boat hook would make it easier.

 

[Hurricane]

I'm not arguing with your calculation but for me at least, fitting a snubber has nothing to do with adding elasticity to the chain. Its only about transferring anchoring loads from components on the boat that are not built to take them to components that are so on this boat at least I'm a fully paid up member of the snubber club. If you've got a boat with the chain being fed through a substantial hawse pipe though I can see why you might not bother with a snubber and a strong chain lock would suffice

This has been my reason for attaching (shall we say) a bridle - to transfer the load from the chain to the substantial deck cleats.
Actually, the snubbers were an after thought!!

 

[Hurricane]

OK here you go

I am not sure what the regulations say, but in the winter storms in the Med it is not unusual for large ships to seek shelter in an anchorage. They often appear to drag slowly and simply keep re anchoring, but it is hard to make out any details as visibility is always bad in these conditions and they are in deeper water.

There were about 4-5 ships in this particular anchorage with us. It was blowing about 40 knots when I took the photos, but had been stronger in the night. The white layer is not fog but spray, as the tops of the waves are blown off:

This is what it looked like at the back of the boat. I would not like to be in these conditions without some elasticity:

OK - I see your point but in conditions like that, my boat would be in a marina and I would be in a bar or better still a nice comfortable restaurant.

Now - lets get real
We anchor our boats for pleasure.
Thus we go into tight anchorages to enjoy ourselves.
An elastic rode would give me an unpredictable swing.
I don't think that my bridle constitutes the kind of elasticity that you are suggesting.
Usually, we are in anchorages with other types of boats (sailing yachts mainly) which swing completely differently.
An elastic portion of our rode would just make everything more complex.
Actually, my upgrade for next year is to allow me to shorten the rode and get in closer to the yachties and avoid getting wacked by other boats as we all swing differently.
To this end and in this circumstance, I may choose to use just the chain lock and not my snubber fitted bridle.

And, as I say above, if the weather gets really bad we just go into a marina.

 

[jfm]

Nylon stretches 40% to failure and the stretch is roughly linear - so it 'works' all the way to its failure point (unlike catenary which works less and less - the more load the less catenary is left to offer relief from snatch loading - even 12mm chain has a limit). A 10m length of nylon that stretches 1m has simply stretched to 25% of its capacity. However nylon degrades with use, UV, salt and mud in the structure etc. They thus wear out. Ideally you retire your snubbers and do not wait till they snap.

If you size, diameter, your snubber correctly it will work upto whatever maximum windspeed you want - even 70 knots.

edit I can see a few people slowly seeing the light and joining the snubber club!

If you do not believe in snubbers - think of a bungy jumper. They feel little shock load when they reach the bottom of the fall - all that 'load' (its actually energy) is absorbed into the bungy cord. Now think of a bungy jumper using a chain instead of elastic - that's your yacht with no snubber. You need to use you imagination to relate the bungy jumper and your yacht - but its not difficult. Or think of your car with suspension (the snubber) and without (that's your chain). Rubber snubbers are equivalent to about 2m of nylon cord - you need 4 or 5 of them to be equal to 10m of nylon. close edit.

Hi Neeves.
First, you describe the fact that the catenary gets stiffer as a disadvantage but it's exactly what you want. (Like car suspension springs that have progressively tighter pitch at the ends so they go coil bound progressively thereby stiffening as the load increases). This is a good thing it is better than straight line elasticity to the point of breaking.

But getting back to the elasticity claims generally, I don't think anyone on here is using snubbers as you describe them with stretch even approaching 40%, and indeed I'm curious about whether you do. I bet you are way down in the single figure percentage zone. Look at Hurricane's picture of Jenny Wren above: two snubbers, let's assume they are 3 strand nylon, 20mm diameter. There are many data tables you can use, but yield (breakage) = 70KNewtons. For stretch at yield I'll take your 40% although the data tables I found all say less (so my maths is giving you the benefit of the doubt).

Hurricane's boat has a wind drag load in the order of 3000N in 40kts of wind (which isn't any weather you want to be anchored in of course- see pictures above). Let’s switch everything to Kg rather than newtons, as we're on planet earth, and let’s round g to 10. So 3000N is 300kg, or 150kg per snubber rope on Hurricane's boat. Now if the rope stretches elastically to 40% then breaks @7000kg, then at 150kg it has stretched <1%. Let's say Hurricane's snubbers are each 5m long: the stretch is <5cm. Great!

I appreciate that the snatch loads can be higher and these 5m ropes might, on a very hard snatch stretch more than 5cm. But let’s do some maths on that. Let’s consider a boat with 150kg steady drag and then a snatch that imposes 1000kg horizontal boat load. Using the catenary calculator linked above, 50m of 12mm chain will reduce its catenary droop from about 12m to 1m, and let the boat will move backwards about 7m. The progressive spring concept will apply too, which is nice. Now let’s add a really stretchy nylon snubber to this boat – 16mm dia (too small obviously, but let’s use it to get some stretch) and a full 10m length (also daft, because you are throwing away 10m of catenary benefit, but let’s get this baby stretching). The nylon rope yields at 5600kg and you say 40% stretch, so 1000kg is 7% stretch ie 70cm on 10m. Yep, you risk whiplashing guests with a too thin snubber line and you let it out 10metres so wasting catenary, and what do you get? 70 poxy centimetres stretch with a tonne of horizontal load on the boat! Give me the catenary every time

You can’t get away from the physics here. The elasticity of a catenary is greater than a bit of nylon rope in this application, unless you use nylon rope that is so thin it risks whiplashing your guests or is so long that you might as well throw the chain away. And it has the nice feature that as it stretches more it gets stiffer like the progressive car spring. Look around the world: there are zillions of professionally managed and crewed boats that anchor all the time without snubbers. Commercial ships, superyachts, etc etc etc. In >>20 knots of wind btw, when needed. Then there are a few leisure sailors who use snubbers. Go figure

For those who use snubbers to eliminate noise of chain on roller in bow cabin, or who don’t have a chain stopper/haven’t got round to fitting one and need to unload their winch gears, that’s all ok. I’m only disagreeing on the elasticity aspect.

 

[Hardmy]

I think you will notice an enormous difference.

I did also swap my anchor (a Danforth style, 48 kg) which was totally unfit for Greece against a Mantus (85 lbs) which looks very similar to JW's Rocna. The difference is like day and night albeit the Mantus beeing much lighter! We weathered without any problems the recent Ionian storms which washed some yachts ashore. The wind direction shift was brutal, nevertheless it resetted without any problem.