Anchor size. I know. Sorry.

[melvynpatrick]

I have a 42 foot wooden ketch. She came with a 45 lb cqr. I replaced it with a 20 kilo rocna. I’m now thinking I should have bought a 25 kilo rocna instead. I haven’t anchored much with it yet. But I think I may have gone too small. Chain is 8mm and the windlass is a 24v ,lewmar h3. Any thoughts. If I’ve gone too small I will have an almost unused 20 kilo rocks for sale

 

[RupertW]

A 15kg Delta has held my 42 footer in all wave and wind combinations for 17 years without dragging ever once set. And some conditions have been vile, anchoring 50-100 nights a year.

Almost all dragging issues are down to technique not the anchor itself, not its weight or its design. My old CQRs in earlier boats rarely dragged.

So if your technique is decent then your 20kg Rocna will be identically perfect to my 15kg Delta except in conditions worse than the 65 knot gusts and 1m steep waves where the Delta was fine. Then the 20kg Rocna will beat the hell out of my anchor. But part of technique is finding the right bays and right conditions.

 

[Neeves]

Stop worrying and go sailing. You will be fine.

You are one of the few who appears to have the correct size of chain, most have chain unnecessarily too big.

Personally I would have bought something a bit more modern than a Rocna but you will be fine. Rocna are now an old design and there are better, Viking being a prime example.

But relax

I might add a snubber, enter 'snubber' in the YBW search facility.

Just to underline your choice include a picture of your ketch and its weight. What shackle are you using. If you include a picture of your ketch add a picture of your chain to anchor connection. I'd say you biggest problem is getting a shackle to fit the anchor and a chain (and DON'T use a swivel)

Jonathan

 

[melvynpatrick]

Aah. I do have a swivel. It’s a mantus. I also do use a snubber

 

[zoidberg]

You'll be aware of the ROCNA recommendations charts HERE.

The manufacturer indicates that their his suggestions are pitched on the conservative side. My reaction is that a 20kg ROCNA anchor, well and properly-set, should meet the need in most conditions. Do read the text below the chartlets ^.

I'd recommend you persevere with the ROCNA you have, for you'd take a large cost-hit in changing it for a larger one.
You could, to advantage, fork out for a Fortress Fx-23 as an additional arrow in your quiver. They're often available in the For Sale forum here, in different sizes, sometimes at silly money.

All the pundits on 'ere would likely agree you ought to have TWO really good anchors. What they cannot agree on is what type/size/colour....

 

[noelex]

For a cruising boat anchoring frequently, a good starting point is the largest anchor you can comfortably manage. A 25kg Rocna has around 25% more ultimate holding ability in most substrates than a 20kg model. This extra holding ability would be helpful, especially if you encounter poor holding ground or want to use shortish scopes. A bargain for only an extra 5kg if you are confident that this will fit.

A 20kg Rocna is a popular style and size, so hopefully you can find someone who will take it without too much of a financial penalty.

 

[wonkywinch]

Aah. I do have a swivel. It’s a mantus. I also do use a snubber

Nothing at all wrong with a swivel as long as it's good quality and installed properly. Here's Vyv's opinion ..

Swivel problems and solutions

 

[Neeves]

Aah. I do have a swivel. It’s a mantus. I also do use a snubber

The Mantus swivel is far too big, other swivels are also big

When your anchor sets the toe and shackle point dive simulataneously. Th rode inhibits diving, as when the anchor gets deeper and deeper it has to pull the rode down with it - the Mantus swivel is not your friend (and is not really the friend of your anchor.) Your anchor struggles to set as deeply as it was designed.

Take the swivel, any swivel, off and your anchor will set more deeply. Why do you use a swivel? A Boomerang, the name given it by its developer before it was copied, has no moving parts, is thinner than the rode - and will right your anchor

search with Google "Boomerang your anchor right back

How long is your snubber, if it is short it has little snubbing characteristics.

Jonathan

 

[Dockhead]

For a cruising boat anchoring frequently, a good starting point is the largest anchor you can comfortably manage. A 25kg Rocna has around 25% more ultimate holding ability in most substrates than a 20kg model. This extra holding ability would be helpful, especially if you encounter poor holding ground or want to use shortish scopes. A bargain for only an extra 5kg if you are confident that this will fit.

A 20kg Rocna is a popular style and size, so hopefully you can find someone who will take it without too much of a financial penalty.

This is the correct answer.

Someone said the Rocna recommendations are "conservative" -- not in my book. Maybe for light weather weekend cruising, but not for "a cruising boat anchoring frequently", as Noelex wrote, which means, not just in fine weather.

I would go up in size at least one, or better two, depending on what will fit in your bow roller.

Another tip -- Rocna is a decent anchor, but because of the roll bar, harder to fit in your bow roller, and not well balanced, for the same reason. You might try a non-roll bar anchor like the Rocna Vulcan, or a Spade. The Spade in particular is ballasted and so very well balanced -- you won't need a swivel, which as Jonathan correctly says, will inhibit the anchor from setting as well as it will without.

 

[Dockhead]

Nothing at all wrong with a swivel as long as it's good quality and installed properly. Here's Vyv's opinion ..

Swivel problems and solutions

Vyv doesn't say anything in that article on the question of swivel or no. Just good vs. bad swivels.

I agree with Jonathan here. A fat swivel seriously interferes with anchor setting.

And is not needed with a reasonably well balanced anchor.

 

[zoidberg]

You ask a question about anchors in here.... four stalwarts reply - and give you five different answers.

 

[thinwater]

You ask a question about anchors in here.... four stalwarts reply - and give you five different answers.

His search box doesn't work.

 

[Tranona]

Vyv doesn't say anything in that article on the question of swivel or no. Just good vs. bad swivels.

I agree with Jonathan here. A fat swivel seriously interferes with anchor setting.

And is not needed with a reasonably well balanced anchor.

Not all swivels are fat and a Kong when used with the 3 links of chain between it and the anchor minimises the negative impact on setting. I have used that arrangement for many years with a Delta and now an Epsilon.

BTW if you use a recommended size anchor and deploy it properly there is no need to go up a size unless your boat is "exceptional" in some way such as a high windage for lrngth multihull or a heavy old boat with extra "stuff" on top such as an arch and solar panels, davits and a RIB. Loads on boats are a function of wind pressure far more than weight or length of boat. Plenty of real life research to demonstrate this all of which is freely available and has been shared many times here over the years. Anchor designers understand this which is why efficient anchors are often made of lighter materials than less efficient ones.

And still "bigger is better" sticks despite no consistent evidence that it is true.

 

[Dockhead]

Not all swivels are fat and a Kong when used with the 3 links of chain between it and the anchor minimises the negative impact on setting. I have used that arrangement for many years with a Delta and now an Epsilon.

BTW if you use a recommended size anchor and deploy it properly there is no need to go up a size unless your boat is "exceptional" in some way such as a high windage for lrngth multihull or a heavy old boat with extra "stuff" on top such as an arch and solar panels, davits and a RIB. Loads on boats are a function of wind pressure far more than weight or length of boat. Plenty of real life research to demonstrate this all of which is freely available and has been shared many times here over the years. Anchor designers understand this which is why efficient anchors are often made of lighter materials than less efficient ones.

And still "bigger is better" sticks despite no consistent evidence that it is true.

I agree that a Kong separated by some links of chain from the anchor is far better.

I disagree about the rest, however. A standard-size anchor of good design will hold you in a good bottom and average scope and reasonable weather. A larger anchor of the same design gives you more options -- will hold you in a wider range of conditions. You will have more flexibility with regard to all three factors. This is objectively and obviously true and there are tonnes of evidence.

Which is why it's often said that standard-size anchors are fine for sailors who always choose when and in what conditions they anchor -- so weekends in good weather, say. In such cases, if you have a poor bottom or need to use less scope or there's bad weather in the offing, or God forbid some combination of those factors, you just stay in port and don't go out. That's fine for many.

But if you are cruising long distances and in all weather and long term, you might not always have such a choice, and a larger anchor gives you a wider range of feasible conditions. The larger the anchor, the wider the range of feasible anchoring conditions, which is why it's pretty standard advice, for long-term cruisers, to use the largest anchor you can fit in your bow roller, and handle reasonably, as Noelex suggested above.

 

[geem]

I agree that a Kong separated by some links of chain from the anchor is far better.

I disagree about the rest, however. A standard-size anchor of good design will hold you in a good bottom and average scope and reasonable weather. A larger anchor of the same design gives you more options -- will hold you in a wider range of conditions. You will have more flexibility with regard to all three factors. This is objectively and obviously true and there are tonnes of evidence.

Which is why it's often said that standard-size anchors are fine for sailors who always choose when and in what conditions they anchor -- so weekends in good weather, say. In such cases, if you have a poor bottom or need to use less scope or there's bad weather in the offing, or God forbid some combination of those factors, you just stay in port and don't go out. That's fine for many.

But if you are cruising long distances and in all weather and long term, you might not always have such a choice, and a larger anchor gives you a wider range of feasible conditions. The larger the anchor, the wider the range of feasible anchoring conditions, which is why it's pretty standard advice, for long-term cruisers, to use the largest anchor you can fit in your bow roller, and handle reasonably, as Noelex suggested above.

I have said this numerous times on here. We have the correctly sized anchor for the weight of our boat, as sized off the Spade selection chart. Weight and windage are the issues. A 42ft boat could be very light or very heavy. If its very heavy and has high windage then you need to be selecting appropriately. It won't be the lightest possible anchor you can select. It will likely be the one that takes weight and windage into consideration.
Thousands of nights at anchor on my correctly, not oversized anchor, and I have no need to go bigger. I also never use an anchor alarm. My confidence in my anchor is high

 

[noelex]

My confidence in my anchor is high

You have a 33kg Spade on a 44-foot ketch. The OP is debating between a 20kg and 25kg Rocna on an only slightly smaller 42-foot ketch.

 

[Dockhead]

I have said this numerous times on here. We have the correctly sized anchor for the weight of our boat, as sized off the Spade selection chart. Weight and windage are the issues. A 42ft boat could be very light or very heavy. If its very heavy and has high windage then you need to be selecting appropriately. It won't be the lightest possible anchor you can select. It will likely be the one that takes weight and windage into consideration.
Thousands of nights at anchor on my correctly, not oversized anchor, and I have no need to go bigger. I also never use an anchor alarm. My confidence in my anchor is high

Very glad to hear you've had such good success.

But the issue with specifying anchors is not indeed only weight and windage. What about bottom type? Scope? Weather? All of these parameters are relevant to anchor specification, and some of them HIGHLY relevant. Holding power per a given type of anchor falls off very steeply with decreasing bottom quality; likewise with scope below a certain level. Wind force goes up with the square of the wind speed. There are a lot of potential situations where you might need more holding power, than you get from the standard sized anchor.

Have you ever been through a storm on 2:1 scope? In an area with ice in the water and no rescue services and no harbours? I have. If I'd had a normal size anchor, I'd be dead. It's not everyone's use case, of course. But recommended sizes apply to particular use cases; and the variables in possible use cases cover a lot of factors besides weight and windage.

 

[wonkywinch]

I love the fact this is probably one of the few safe places on the internet that blokes can openly compare the size of their tackle without embarrassment.

 

[noelex]

I love the fact this is probably one of the few safe places on the internet that blokes can safely and openly compare the size of their tackle without embarrassment.

 

[geem]

Very glad to hear you've had such good success.

But the issue with specifying anchors is not indeed only weight and windage. What about bottom type? Scope? Weather? All of these parameters are relevant to anchor specification, and some of them HIGHLY relevant. Holding power per a given type of anchor falls off very steeply with decreasing bottom quality; likewise with scope below a certain level. Wind force goes up with the square of the wind speed. There are a lot of potential situations where you might need more holding power, than you get from the standard sized anchor.

Have you ever been through a storm on 2:1 scope? In an area with ice in the water and no rescue services and no harbours? I have. If I'd had a normal size anchor, I'd be dead. It's not everyone's use case, of course. But recommended sizes apply to particular use cases; and the variables in possible use cases cover a lot of factors besides weight and windage.

Are you assuming in the thousands of nights at anchor that I have only ever anchored in a perfect conditions? Do you know how silly that sounds?
I have anchored by mistake in 35kts on 2:1 scope when we end to ended our chain and we mixed up the chain markings. We spent a couple of weeks in strong gusty conditions in a crowded anchor at 2:1 scope. I thought we had put out 3:1.
Bottom type and condition are of course an issue. I have dragged when we anchored on a stone shelf with 4 inches of sand covering it. No anchor, regardless of size could have set. Impossible. You would also have dragged.
I will let you know when my correctly sized anchor doesnt work anymore. I suspect it will be a long wait