Neeves
Well-known member
Refueler,
Please read post 14, including the links - and then comment.
Jonathan
Please read post 14, including the links - and then comment.
Jonathan
How much anchor chain?
- Thread starter Sprout
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lw395
Well-known member
You might 'know' that, but I think it's total cods.
Strong is good, but the thickness of the rode provides damping as it moves through the water.
Neeves
Well-known member
Sorry LW,
Have you any quantitative evidence to support that? I'd love to see the maths.
Jonathan
Neeves
Well-known member
More focussed at Refueler than LW - and showing less bias with my sources
https://www.petersmith.net.nz/boat-anchors/catenary.php
Jonathan
and to both LW nd Refueller - I'm not believer in gut feel - this commonly means - the poster does not know. So quantitative evidence does it for me.
https://www.petersmith.net.nz/boat-anchors/catenary.php
Jonathan
and to both LW nd Refueller - I'm not believer in gut feel - this commonly means - the poster does not know. So quantitative evidence does it for me.
Last edited:
Stemar
Well-known member
Not to me, at least, not in the rode. I'd far rather have an oversized anchor and lighter rode than the converse.
I haven't got time to do the maths, but I'm struggling to see how the difference in thickness will make a significant difference to resistance to moving through the water at the speed a boat moves at anchor, even with quite violent swinging, nor would the difference in weight between, say, 6mm and 8mm chain make much difference to the inertia of the chain.
KellysEye
Active member
>We hold our aquabell 30 with 18feet of 10mm chain, to rope, the hook is a 17kg Delta, Operating on the East coast Thames Estuary, mainly mud, at depths of 30 to 65 feet
48 feet of chain and rope but depth of 65 feet?
48 feet of chain and rope but depth of 65 feet?
doug748
Well-known member
Very true, it is filthy stuff to bring in, difficult to keep clean, makes use of a winch a problematic, rots chain under the splice, is hard to stow, is subject to chafe and tends to drift under keels, props and rudders. Apart from that it is grand.
No doubt if the OP wants to race his cruiser/racer, he will want to use rope, if he wants the cruise (and it sounds to me like he does) he will want chain. The original First 30 is quite traditional, has plenty of reserve buoyancy in the bow and, in ordinary use, he is unlikely to notice the extra 50 lbs.
Refueler
Well-known member
Post 14 was read ... and makes far more sense than the BS you posted later .... in fact I could not believe same person wrote each post !!
If anyone wants to create a long argumentative thread .... make sure title has ANCHOR in it !!
As to 6mm vs 8mm ... it comes down to how much rode you want to put out and what anchoring you will be doing ...
If you are the type that anchors in sheltered areas with little risk of weather etc ... anchoring in rivers, closed harbours etc. - then lighter tackle is fine. Move to anchoring in more open areas - then the weight and type of tackle takes on greater importance.
The problem with this subject is that people tend to apply their own limited experience / view to a very wide subject. They forget that not everyone is happy to use an alloy anchor ... rope rode ... light chain ... etc. Some people like myself evaluate the areas and possible conditions I will be anchoring in.
We can all be Hooray Henrys at the bar with pint in hand ... but out there is a different ball game.
Refueler
Well-known member
mmmmm I don't think so, to have effect it would have to be moving at great speed ... weight is far more important.
Refueler
Well-known member
Just for the record ... Fraysse has been called into question many times by other 'experts' ...
Similar to the guy who wrote a long novel about testing anchors on a beach using a tractor !!
The simple facts are ... 1. the more horizontal the pull on an anchor - the better .... (that is also supported by your linked site), 2. the rode used must be capable of resisting the action of lifting off the seabed and imparting an upward component to the pull ... (again supported by your linked site).
It does not take Einstein to work out this ... and Jonathan ... "poster does not know" ...... nice one. That just about does it for me ... I have better things to do.
Neeves
Well-known member
Just a point of accuracy
The tension on the anchor is not dictated by the scope but by the angle of orientation of the shackle. The shackle angle is dictated by the burial depth of the anchor and the shear strength of the seabed. The shackle angle has little to do with scope.
Now that should raise a few comments
Jonathan
The tension on the anchor is not dictated by the scope but by the angle of orientation of the shackle. The shackle angle is dictated by the burial depth of the anchor and the shear strength of the seabed. The shackle angle has little to do with scope.
Now that should raise a few comments
Jonathan
Baggywrinkle
Well-known member
I don't know which version of the First 30 the OP has, but all of them are cruiser/racers .... weighing somewhere between 3,200Kg and 3,750Kg depending on what version it is. They have fully equipped galleys, sea toilets, saloon tables, and all the mod-cons needed for cruising as well as being racers.
I guess someone using one only for racing would strip everything unnnecessary out of the boat to reduce weight, and that would include anchor chain swapped out for a mix of chain and rope. On a completely empty boat I guess 50m of 8mm chain plus a hefty anchor on the bow would make the nose a bit heavy - but what about cruising?
I've been coastal cruising since I was about 5 years old in a number of boats ranging from 22 to 45 feet and the one common thing with all of them was the vast amount of gear we brought on board for any extended time away. I would imagine that with full tanks and a full compliment of cruising gear and crew you could easily add 1250-1500 Kg to the weight of the boat.
I've never felt the need, in the 45 years I've been coastal cruising, to move the anchor and chain off the bow - if only because the proximity to the coastline makes it essential to be able to deploy the thing as quickly as possible. I've certainly never thought of doing it to improve the boats performance - but I've never raced.
If I were crossing oceans, I'd probably stow the anchor below, maybe the chain too once I was offshore as it is accepted wisdom to put the weight low and near the centre.
Can someone please explain the difference they notice (boat 30ft or larger) when, for example, 50kg is in the anchor locker on the bow instead of 100kg .... I guess it's supposed to reduce pitch but I've never felt the need to reduce pitch to the point where I would remove the anchor or chain from the bow. I have noticed my boat is more tender and slams slightly more when it's empty though.
I guess someone using one only for racing would strip everything unnnecessary out of the boat to reduce weight, and that would include anchor chain swapped out for a mix of chain and rope. On a completely empty boat I guess 50m of 8mm chain plus a hefty anchor on the bow would make the nose a bit heavy - but what about cruising?
I've been coastal cruising since I was about 5 years old in a number of boats ranging from 22 to 45 feet and the one common thing with all of them was the vast amount of gear we brought on board for any extended time away. I would imagine that with full tanks and a full compliment of cruising gear and crew you could easily add 1250-1500 Kg to the weight of the boat.
I've never felt the need, in the 45 years I've been coastal cruising, to move the anchor and chain off the bow - if only because the proximity to the coastline makes it essential to be able to deploy the thing as quickly as possible. I've certainly never thought of doing it to improve the boats performance - but I've never raced.
If I were crossing oceans, I'd probably stow the anchor below, maybe the chain too once I was offshore as it is accepted wisdom to put the weight low and near the centre.
Can someone please explain the difference they notice (boat 30ft or larger) when, for example, 50kg is in the anchor locker on the bow instead of 100kg .... I guess it's supposed to reduce pitch but I've never felt the need to reduce pitch to the point where I would remove the anchor or chain from the bow. I have noticed my boat is more tender and slams slightly more when it's empty though.
RupertW
Well-known member
Now that is special - evidence for that very odd assumption? The forces of the boats movement compared to the fluid resistance of even an enormous diameter rode are many orders higher.
Refueler
Well-known member
Fine - no argument there. Please see my other post where I mention location and general conditions each anchor in.
The typical anchor on a yacht is larger in comparison to boat than commercial shipping, but that is a fact due to weight and holding property. It is often wrongly used to say a yacht can have a smaller anchor.
Take my Progress4 motor boat ... soviet alloy job. 4m long and 6 people can lift it.
If the % comparison was true ... I could hold that boat with a bent fork !! I actually use a 5kg miniature Admiralty Patent Anchor. Because I need the weight to dig in.
My 5m day sailer has a similar anchor - but because of the windage - I would not rely on it to be left unattended.
If I was going to anchor that and leave her unattended - I would like 8kg or more ... with chain.
The fact I'm trying to convey - anchor needs to have 'force' and 'area' dug in to provide hold for chain / rode end. The lightweight anchors rely on that rode pulling them horizontally and their digging in. Instead of a cobination of anchor weight and pull doing the job.
Ships have anchors weighing tons ... largest anchor I've used is near 40 tons ... which holds the anchor chain for a 440,000 ton ship. Its weight is more than enough to dig in and that chain even in a 'blow' is still in a good curve catenary.
Like my Motor Sailer ... I have yet to see even in rough weather my anchor rode pulled out straight ...
lw395
Well-known member
Take two Sigma33s.
Sail upwind in choppy water.
Put 50kg on the bow of one of them.
See the difference.
Sail upwind in choppy water.
Put 50kg on the bow of one of them.
See the difference.
doug748
Well-known member
Refueler
Well-known member
No-ones arguing that ....
The topic is : "How much anchor chain?"
Second - the OP has not indicated whether he wants to race, cruise fast, cruise slow etc.
As I have indicated before - choice of tackle depends on what person wants and expects to do.
RupertW
Well-known member
Fine - no argument there. Please see my other post where I mention location and general conditions each anchor in.
The typical anchor on a yacht is larger in comparison to boat than commercial shipping, but that is a fact due to weight and holding property. It is often wrongly used to say a yacht can have a smaller anchor.
Take my Progress4 motor boat ... soviet alloy job. 4m long and 6 people can lift it.
If the % comparison was true ... I could hold that boat with a bent fork !! I actually use a 5kg miniature Admiralty Patent Anchor. Because I need the weight to dig in.
My 5m day sailer has a similar anchor - but because of the windage - I would not rely on it to be left unattended.
If I was going to anchor that and leave her unattended - I would like 8kg or more ... with chain.
The fact I'm trying to convey - anchor needs to have 'force' and 'area' dug in to provide hold for chain / rode end. The lightweight anchors rely on that rode pulling them horizontally and their digging in. Instead of a cobination of anchor weight and pull doing the job.
Ships have anchors weighing tons ... largest anchor I've used is near 40 tons ... which holds the anchor chain for a 440,000 ton ship. Its weight is more than enough to dig in and that chain even in a 'blow' is still in a good curve catenary.
Like my Motor Sailer ... I have yet to see even in rough weather my anchor rode pulled out straight ...
You clearly haven’t looked properly - all your thoughts make no sense below ship sized chain. It’s easy to see the catenary almost disappear in a 10 or 12mm in surprisingly low winds - 20 knots plus. Catenary has long been proved both practically and mathematically to be irrelevant even for larger yachts as soon as the holding of the anchor is actually needed, providing neither damping nor a smaller angle to the seabed. Scope and anchor design provide the angle to ensue the anchor is digging downwards and an elastic snubber can provide the damping.
You can’t extrapolate downwards from ships and expect the same physical behaviour.
webcraft
Well-known member
Just a point of accuracy
The tension on the anchor is not dictated by the scope but by the angle of orientation of the shackle. The shackle angle is dictated by the burial depth of the anchor and the shear strength of the seabed. The shackle angle has little to do with scope.
Now that should raise a few comments
Jonathan
Very strange statement. As the shackle is free to swivel so the pull is in line with the chain, and as the anchor - with a considerably bigger cross-section than the shackle - has already penetrated the seabed, I fail to see any realistic circumstances where the shackle cold lie anything but in line with the rest of the chain once any moderate pull comes on it.
If you have evidence to the contrary I would be very curious to see it.
- W
AntarcticPilot
Well-known member
I have about 55m of chain, and that has been plenty wherever I've anchored on the West Coast of Scotland. It's complete overkill on the East Coast!. I also have a long rope I could use to extend it, but have never used it.
Worth remembering that chain is heavy. I once deployed all of it (I was anchoring in 20m of water after the engine failed), and it was a very heavy job to recover it; two of us were blowing hard after getting it in, and the other guy is a big chap.