Portofino
Well-Known Member
See post # 140 --that's exactly the point I made
"who in there right mind" ----- would put 48M down in 8 M in a F8 gale in the Antartic ?
Still waiting for an answer -----
Stainless steel anchor chain
- Thread starter Magnum
- Start date
See post # 140 --that's exactly the point I made
"who in there right mind" ----- would put 48M down in 8 M in a F8 gale in the Antartic ?
Still waiting for an answer -----
Neeves
Well-Known Member
I think you will find that sailing catamarans have no, or small keels, and relatively huge windage. On a single chain they yaw. They solve the issue with a bridle. Now tell me you do not have 2 bow fairleads.
But you will not use a snubber, so you certainly will not consider 2 of them so you will continue to yaw.
But you will not use a snubber, so you certainly will not consider 2 of them so you will continue to yaw.
Neeves
Well-Known Member
Obviously not the man who designed the Rocna
BartW
Well-Known Member
Indeed, in many occasions, when you have enough scope, the chain is not pulled straight, and part of it rests on the seabed untouched, (I tend to straight it while dropping)
Also the surface / windforce on your boat is much smaller compared to our big flybridge,
So on average you need a lot less holding force from the anker&chain, compared to our boat.
But I don’t agree with your frist expression that the anker could be a bottle top, at least not in cases where I am more on the edge of holding,
Meaning, a much bigger and heavier boat, and less scope
This minimum or optimum chain length is something one has to learn from experience,
I can “feel” if there is catenary effect/reasonable length of chain on the seabed
or
if the chain is pulling straight on the anker ; not enough scope, but anker is holding between rock’s
I usually drop more chain than that I think that is necessary, and yes very often (but not alway's) I find the anker "untouched" on the seabed when snorkling or diving, (in quite weather)
Magnum
RIP
I cannot argue with the fact that a snubber will reduce yaw. Perhaps that alone makes it worth having one.
Neeves
Well-Known Member
I'm not alone in thinking that any constant yawing and snatch loading on an anchor is not beneficial. I accept that if you have 80m of chain deployed and you are keeping it all on the seabed then any yawing is not a major influence to the anchor but if the chain is off the seabed, for whatever reason, deep water or not enough room to deploy the ideal then minimising yawing and any snatch loading is supporting the anchor. This all becomes more important if the holding is hard seabed and when you dive you find the anchor is not well bedded in. It is at a time like that a snubber can be advantageous - they are totally unnecessary if its only blowing 15 knots and you are in 5m of water with 50m deployed. Being able to deploy the snubber as a bridle will reduce the yaw, any snatch loading and stop the chain grinding and rattling on the bow roller.
here is a science behind it - its not all some idea to make a MoBo looking like a tarted up fishing boat nor to be contrary - its all about making the vessel as secure as possible and making life more comfortable for you, your family and the guests.
its also about offering you another way of looking at a problem.
here is a science behind it - its not all some idea to make a MoBo looking like a tarted up fishing boat nor to be contrary - its all about making the vessel as secure as possible and making life more comfortable for you, your family and the guests.
its also about offering you another way of looking at a problem.
Portofino
Well-Known Member
Agree with all that .
But with a pocket anchor fitted under the bow and a concealed locker the snubber route is a bit tricky if not impossible to rig up -for a MoBo with that set up .
So ,s that why I,am an advocate of loads of chain and excess scope .Where it's not possible ,to anchor and it blows up -we run cos we can .
This season we were 70 miles away from home port ,and aMistral forecast ( they blow from the W) -no Problem found a nice E facing cove along with others to shelter.
Had 60 m out in 8 m of 10mm -so scope 7.5 .Could not get in closer -due to smaller boats .
It was sheltered I was happy ,buy wife uneasy -incase wind changed .
So 6pm up anchor down wind we in abig sea we hoofed it back covering 70 miles in 2 hours .
8m dusk in Marina ,
9 pm sat at a nice table in a restaurant
Depends how you use your boat ,I can,t "snubber " and we are not on an expedition , it's a Holliday
If some how I ( not weedy armed wife ) managed to via boat hook haul up 8-10 M -of chain - attach hook -rig up snubber +briddle etc
Then the risk is what happens in a emergency bug out ? Going Fwds in the dark , wind howling -can,t hear each other ? engines on etc .
How ever we all have different boats and use them slightly differently in various cruising grounds .
Just saaaaaying -won,t work for some ---so we lean towards heavey and long chain out .
Without a briddle we can do a rapid bug out
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vyv_cox
Well-Known Member
The CQR was designed and patented by Geoffrey Ingram Taylor, renowned physicist and mathematician, in 1933!
sarabande
Well-Known Member
a Snubber carries out two functions:-
it absorbs shock loads from wind and wave forces on a taut/nearly taut chain
it can be used as a spring to adjust the angle at which the boat lies to the wind and waves, and make life much more comfortable.
As for mobos yawing at anchor; a number of raggies have a small triangular sail that can be hoisted on the back stay to keep the bow to wind. Would it be possible to arrange for an awning or similar to be rigged on the stern platform of a mobo ? . In strong winds you aren't going to be using the swim platform anyway, and if it makes life more comfortable, that's bonus points from the family.
I remain unconvinced that an anchor with no chain on the sea bed (i.e. with an upward component in the forces) is as firmly attached as one with chain keeping the shank horizontal. Otherwise Deleted User's point about attaching the boat to the anchor by a steel rod is valid. I want my chain to be able to respond in six axial directions, not four.
it absorbs shock loads from wind and wave forces on a taut/nearly taut chain
it can be used as a spring to adjust the angle at which the boat lies to the wind and waves, and make life much more comfortable.
As for mobos yawing at anchor; a number of raggies have a small triangular sail that can be hoisted on the back stay to keep the bow to wind. Would it be possible to arrange for an awning or similar to be rigged on the stern platform of a mobo ? . In strong winds you aren't going to be using the swim platform anyway, and if it makes life more comfortable, that's bonus points from the family.
I remain unconvinced that an anchor with no chain on the sea bed (i.e. with an upward component in the forces) is as firmly attached as one with chain keeping the shank horizontal. Otherwise Deleted User's point about attaching the boat to the anchor by a steel rod is valid. I want my chain to be able to respond in six axial directions, not four.
Hurricane
Well-Known Member
Until this season, this was the way we deployed the anchor.
This year, I fitted the chain stopper and haven't used the bridle since.
There is no noticable difference between using it or just flipping the chain stopper's flap.
The boat always yaws.
Having said that, I expext to use the bridle on windier times when visitors are sleeping in the bow cabin.
Other than that, I can see no advantage using my bridle/snubber.
Our boat weighs about 45 tonnes on the travel hoist and has much more windage than a monohull sailing boat or catamaran.
Neeves
Well-Known Member
Hurricane,
I sympathise with the issues. Our cat has a larger beam, well large to us, 6.67m, which means our bridle is much wider than anything you can achieve (and I'm not going to suggest you add further fairleads!). I think with our sails, mast, boom cover, rigging and our hull height above the water is 3m we do have serious windage (but I've never sat against a MoBo to compare). There are other options but none of them are really appealing. The only further thought is more elasticity - those rubber dog bone things are equivalent to about 2m of nylon, adding more should help but you bridle is very narrow (but better than a single snubber).
I note your comments on the chain lock - but if you are ever exposed to over 25 knots, I'd attach the bridle as well particularly if you cannot deploy 'more' chain. But you'll feel it first - it will be obvious when you are snatching, the champagne glasses fall over, been there, done that (some cats serve gin as well!).
I sympathise with the issues. Our cat has a larger beam, well large to us, 6.67m, which means our bridle is much wider than anything you can achieve (and I'm not going to suggest you add further fairleads!). I think with our sails, mast, boom cover, rigging and our hull height above the water is 3m we do have serious windage (but I've never sat against a MoBo to compare). There are other options but none of them are really appealing. The only further thought is more elasticity - those rubber dog bone things are equivalent to about 2m of nylon, adding more should help but you bridle is very narrow (but better than a single snubber).
I note your comments on the chain lock - but if you are ever exposed to over 25 knots, I'd attach the bridle as well particularly if you cannot deploy 'more' chain. But you'll feel it first - it will be obvious when you are snatching, the champagne glasses fall over, been there, done that (some cats serve gin as well!).
Zing
Well-Known Member
The yawning at anchor is essentially caused by the centre of effort of the wind on the boat being forward of the centre of lateral resistance of the water on the hull. The bridle isn't going to do much, especially in a monohull boat. Put a dagger board down off the bow, ok not practical. Hang extra windage off the stern. Not too easy on your shape of boat, so I'm afraid you will probably find it best to put up with it. You could in theory pull the anchor chain around the boat to hang it off the stern. That would work I expect, but again, not a great solution.
Magnum
RIP
Hurricane, any pics of your chain stopper in situ please?
BartW
Well-Known Member
+1
our bridle doesn't have snubbers, and I use it hardly ever, but only if I'm very sure that weather is not going to be worse, as I don't want anybody to go faffing on the bow,
in bad weather, nor at night ...
Magnum
RIP
I have quotes for 2 makes of 12mm galvanized G40 chain - Lewmar and Maggi. There's not much in it price wise, but there is a difference in proof load and breaking load, according to the sample test certificates.
Lewmar / Maggi
Proof load kN 35.7 / 45
Breaking load kN 71.4 / 90
I am told the reason for this (from Lewmar) is that Lewmar quote minimum loads whereas Maggi quote maximum loads. I'm not sure about that as the load required to break is what it is!
However - and this is important - Lewmar or Princess will not accept liability for damage caused to the windlass or it's components caused by use of third party chain.
Confused!
Lewmar / Maggi
Proof load kN 35.7 / 45
Breaking load kN 71.4 / 90
I am told the reason for this (from Lewmar) is that Lewmar quote minimum loads whereas Maggi quote maximum loads. I'm not sure about that as the load required to break is what it is!
However - and this is important - Lewmar or Princess will not accept liability for damage caused to the windlass or it's components caused by use of third party chain.
Confused!
Neeves
Well-Known Member
As far as i can ascertain Lewmar have quoted you for G30 and Maggi G40.
Min Break Load is a mathematical contrivance.
Chain strength os determined by the minimum strength of the steel wire, 300 MPa, or 400 MPa (galvanised G70 is different - no need to go there). So chain makers must use, say, a 400 MPa wire but can use stronger. It is possible then to calculate, knowing the diameter of the wire, to calculate the min break strength. The weld should always be stronger then the wire. Wire is made to a 4:1 safety factor (different in America with imperial wire) this then provides the WLL which is 25% of min break. Proof test is 2 times WLL, except for some imperial chain. There appears to be a surfeit of 'stronger' wire maybe becuause it is used in the construction industry and G30 and G40 are both overstrength.
The UTS, actual break strength should always be higher than the minimum, obviously - and for G30 (in smaller sizes) is typically near G40 strength and G40 can be 10% stronger. I've never tested a 12mm chain so cannot comment - but I see no reason why it will not be similar to 6mm, 8mm and 10mm.
Metric chain is meant to have the same link dimensions but I find they do vary, not much but enough that shackles will fit, say, some 8mm but not others.
Lewmar do not make chain, they buy in. I don't know from where but I guess China (but one should never guess). Maggi make their own chain and have it galvanised by a subcontractor - but the owner of Maggi has an interest in the galvaniser. There is nothing wrong with Chinese chain, some can be a bit iffy but most is excellent - Lewmar should be keeping a tight watch. Maggi's galvanising is not reputed to be that good. Chinese galvanising is usually adequate.
There are hundreds of Chinese chain makers though only a few will export (like maybe 10 or 20!). It is impossible to test them all and in many cases impossible to be able to define sources. Maggis chain comes with a unique mark, A4 - so you know its Maggis. I don't know about Lewmar.
Because link size can vary, slightly (even the wire varies, slightly) I can see that Lewmar might ensure their chain matches their gypsy.
If I were buying chain I would check that my gypsy physically matched the gypsy (I would take gypsy to chandler and actually check). The alternative is to ask for 0.5m of chain and try it. You look, very, very stupid with 100m of any chain in your locker if it does not fit!
Good suppliers (and there are not many) will take your gypsy and run through the complete length you want to buy.
When you check the chain to the gypsy then is the time to get shackles that match the chain and anchor. I strongly recommend you buy genuine Van Beest Green Pin shackles, Grade B. Do not use stainless shackles. Grade B shackles are twice as strong as grade A shackles and as fas as I know are avaiable in the sizes you will need.
But as far as I can make out Lewmar have you in something of a corner if they demand you use their chain.
I would be demanding a test certificate from whoever you buy from for the batch you are going to buy. If you cannot get one - start to ask questions. Batches should be individually tested (its not an onerous test as a batch can be 1,000m and they only need to test 9 links minimum. Proof test is usually done during production. You should get affirmation that the chain passes Proof, Break strength and eleongation to break. The latter should be a min 0f 15% but typically would be 20%, or more. There is no max.
Min Break Load is a mathematical contrivance.
Chain strength os determined by the minimum strength of the steel wire, 300 MPa, or 400 MPa (galvanised G70 is different - no need to go there). So chain makers must use, say, a 400 MPa wire but can use stronger. It is possible then to calculate, knowing the diameter of the wire, to calculate the min break strength. The weld should always be stronger then the wire. Wire is made to a 4:1 safety factor (different in America with imperial wire) this then provides the WLL which is 25% of min break. Proof test is 2 times WLL, except for some imperial chain. There appears to be a surfeit of 'stronger' wire maybe becuause it is used in the construction industry and G30 and G40 are both overstrength.
The UTS, actual break strength should always be higher than the minimum, obviously - and for G30 (in smaller sizes) is typically near G40 strength and G40 can be 10% stronger. I've never tested a 12mm chain so cannot comment - but I see no reason why it will not be similar to 6mm, 8mm and 10mm.
Metric chain is meant to have the same link dimensions but I find they do vary, not much but enough that shackles will fit, say, some 8mm but not others.
Lewmar do not make chain, they buy in. I don't know from where but I guess China (but one should never guess). Maggi make their own chain and have it galvanised by a subcontractor - but the owner of Maggi has an interest in the galvaniser. There is nothing wrong with Chinese chain, some can be a bit iffy but most is excellent - Lewmar should be keeping a tight watch. Maggi's galvanising is not reputed to be that good. Chinese galvanising is usually adequate.
There are hundreds of Chinese chain makers though only a few will export (like maybe 10 or 20!). It is impossible to test them all and in many cases impossible to be able to define sources. Maggis chain comes with a unique mark, A4 - so you know its Maggis. I don't know about Lewmar.
Because link size can vary, slightly (even the wire varies, slightly) I can see that Lewmar might ensure their chain matches their gypsy.
If I were buying chain I would check that my gypsy physically matched the gypsy (I would take gypsy to chandler and actually check). The alternative is to ask for 0.5m of chain and try it. You look, very, very stupid with 100m of any chain in your locker if it does not fit!
Good suppliers (and there are not many) will take your gypsy and run through the complete length you want to buy.
When you check the chain to the gypsy then is the time to get shackles that match the chain and anchor. I strongly recommend you buy genuine Van Beest Green Pin shackles, Grade B. Do not use stainless shackles. Grade B shackles are twice as strong as grade A shackles and as fas as I know are avaiable in the sizes you will need.
But as far as I can make out Lewmar have you in something of a corner if they demand you use their chain.
I would be demanding a test certificate from whoever you buy from for the batch you are going to buy. If you cannot get one - start to ask questions. Batches should be individually tested (its not an onerous test as a batch can be 1,000m and they only need to test 9 links minimum. Proof test is usually done during production. You should get affirmation that the chain passes Proof, Break strength and eleongation to break. The latter should be a min 0f 15% but typically would be 20%, or more. There is no max.
Magnum
RIP
The Lewmar Certificate of Conformity quotes the chain as G40.
Neeves
Well-Known Member
Hurricane
Well-Known Member
I'm away in Waikiki Beach - Honolulo at the moment (Magnum's home - I believe).
So it is difficult to upload pics at the moment.
I have som bad shots that I can post early next week.
However, I back out on the boat in Spain next Wednesday.
I'll take some new pics and post the final fit.
BTW
Just got back from a tour round the USS Missouri.
You should see the size of chain that she carries - and the size of the windlasses.
I'll ppst dome pics later but I bet she doesn't fit a snubber and I bet that there is chain on the sea bed when she anchors.
Neeves
Well-Known Member
The Ark Royal used to anchor, obviously. One officer had responsibility for status. It was his duty, I think it was the only duty he had at the time, to monitor the drag of the vessel and when she had dragged a specific distance they would lift the anchor motor back to the original position and start the procedure again. I think her anchor is on display in Plymouth now.
I assume (without any foundation) that anchors and chains on commercial (and naval) vessels follow a standard spreadsheet - so I'm not sure I would rely on any of these vessels to give any indication that their ground tackle gave security - come what may. We had the Pasha Bulker (not sure of spelling) up on a beach at Newcastle (Oz), her anchor did not save her. Commercial vessel are sent offshore in winds over 25 knots - which to most leisure sailors is not a particularly strong wind. Chain might be on the seabed - but its not a panacea.
Interestingly some commercial and naval vessels deploy 2 anchors, in a 'V' to stop veering. An alternative approach was to deploy a second anchor so that it just scraped the seabed, a sort of friction brake. Large vessels may not use snubbers - but they always have a crew on watch and they use techniques that some leisure vessel owners might find novel or too much trouble.
Also interesting - the US Coastguard in their fleet of 150' craft use a FX 125 as the primary anchors (as do their assault hovercraft - though I'm not sure of the size) weight is not everything.
I assume (without any foundation) that anchors and chains on commercial (and naval) vessels follow a standard spreadsheet - so I'm not sure I would rely on any of these vessels to give any indication that their ground tackle gave security - come what may. We had the Pasha Bulker (not sure of spelling) up on a beach at Newcastle (Oz), her anchor did not save her. Commercial vessel are sent offshore in winds over 25 knots - which to most leisure sailors is not a particularly strong wind. Chain might be on the seabed - but its not a panacea.
Interestingly some commercial and naval vessels deploy 2 anchors, in a 'V' to stop veering. An alternative approach was to deploy a second anchor so that it just scraped the seabed, a sort of friction brake. Large vessels may not use snubbers - but they always have a crew on watch and they use techniques that some leisure vessel owners might find novel or too much trouble.
Also interesting - the US Coastguard in their fleet of 150' craft use a FX 125 as the primary anchors (as do their assault hovercraft - though I'm not sure of the size) weight is not everything.