36ft sailboat, anchoring not going well

[Tranona]

The boat in question is 10 metres in round figures. It displaces over 5 tons. The suggested anchor size from Rocna is 15 - 20kg for a boat between 5 and 9 tons. Your choice depends both on the boat and your proposed use, as Green says:

"Consider the worst-case scenario for your anticipated Anchoring - this will dictate whether you go for the minimum required or the ocean cruising approach"

Of course if you don't believe that performance increases with size, you are free to choose the smallest you think you can get away with.

.

Not sure where you get that from. Nowhere in the Rocna guide jimmygreen.com/content/205-rocna-and-vulcan-anchor-size-guide does it say that you need a 20kg - nor even a 15kg if you plan to sail within the parameters they use for their sizing (which you said in post 125 you did). On that basis 15kg is "oversize" and 20kg grossly oversize. The boat you are quoting has the same dimensions as mine so I am faced with the same choice.

There is no dispute that a larger anchor of the same design will have higher ultimate holding power. That is only part of the story as the key variable is whether the boat in question can supply sufficient load to access that higher holding power. Plenty of evidence, both theoretical and empirical that shows loads applied by a boat do not reach, let alone exceed that required to reach the ultimate holding power of the recommended anchor sizes.

This is reflected in the advice given by manufacturers that a larger size anchor may be considered if you plan to use it in conditions outside those used in the sizing recommendation, or your boat is marginal in size/weight or type (multihull vs mono or sailboat vs motorboat).

Nothing to do with "smallest you think you can get away with" - it is understanding what is involved and following the recommendations to choose the anchor that suits your boat and type of sailing. For the vast majority that is following the makers guidelines.

So, with the exception of any reference to a 20kg anchor we are in agreement.

 

[Tranona]

If the largest anchor size you can comfortably manage is 10kg then we are both in agreement that this is the best choice for your boat.

If you can comfortably manage a 15kg model (this is not clear from your post) and you anchor frequently rather than using moorings or marinas, then in my view this would be a better choice. Rocna’s sizings are more conservative than most anchor manufacturers, but they are still based on a maximium wind strength of 50 knots, a moderate holding bottom and an "adequate" scope.

We anchor around 300 days a year and have done so for the last 17 years so we have experienced more harsh conditions than most. On occasions conditions have exceeded the criteria Rocna use for their sizing table. If you anchor frequently there is a risk that sooner or later you will do the same.

More importantly, in everyday anchoring the extra roughly 50% maximium holding power a 15kg anchor has over 10kg model of the same design will enable you to use shorter scopes and/or poorer substrates. Contrary to Jonathan’s assertion, this does not mean you have to always, or even commonly, use a shorter scope (or seek out poorer substrates) than you would with a 10kg anchor, but the ability to safely do so opens up anchoring opportunities that would otherwise be unavailable.

Around 50% greater maximum holding ability for 5kg or a 5% increase in your total ground tackle weight (assuming 60m of 8mm chain). This is a bargain in my view, but as always it your boat so it your choice.

Danger of repeating myself, but post 141 goes through the same process - and I chose a 10kg. So we are in agreement in that it satisfies my needs - I will never have to anchor in 50 knots of wind. Where I think we are still apart is your assertion that within the parameters used I would not be able to access any of the additional 50% holding power of the larger size, simply because my boat is not capable of applying the load required. Of course in the unlikely event that I could shed 10 years of age and decide to sail off in the way my boat was designed for I would fit a larger anchor and chain.

BTW Jonatan gives some real world figures on loads in post#136.

 

[noelex]

Of course in the unlikely event that I could shed 10 years of age and decide to sail off in the way my boat was designed for I would fit a larger anchor and chain.

 

[Tranona]

In all the years I've sailed ... I've never had call to use a 'snubber' other than a short rope to avoid chain grating on the stemhead.

Agreed I do not live aboard or cruise Carib' etc ... just an ordinary boater ...

If you can find a copy of PBO June 2002 there is a good article about a GH31 like mine riding out a summer depression in a shallow loch in the Outer Hebrides. Anchor was a 35lb CQR with a 25lb behind it in tandem on 60m 3/8" chain. Even with a chum the catenary disappeared at around 30 knots of wind so to reduce snatching 10m of 16mm 3 strand nylon was added as a snubber. The writer calculated the forces involved using formulae from Prof Knox. At 60knots the force is 680kgs, and an estimate of the extra shock load of the chain as 240kgs, so a range of between 650-900kgs. Note this is well below the ultimate holding power of a typical modern 15kgs (or even 10kgs) anchor. If 10m rope is added it will absorb more than 1000kgs if stretched 25%. The result is that the rope will offset the loss of catenary at higher windspeeds and particularly snatch loads.

The depression took nearly 24 hours to pass and local weather stations recorded gusts in the high 50s/low 60s and on board in the mid 40s, as many as 20 in one hour. So the snubber made a contribution once wind speeds exceeded 30 knots.

The writer reports some evidence of dragging (from Decca plots) which probably shows the limit of the CQR.

Given that the ultimate holding power of my 10kgs Epsilon is greater than a 35lb CQR, I would like to think that it would have performed equally well, although the lower level of catenary of my 6mm chain would mean that the snubber would have more work to do!

 

[Refueler]

Hi T ... where do I say not to use or not any benefit ?

I only comment because a few members repeatedly throw 'snubbers' into the arena ...

As to riding out weather .... I'm a coward !! I prefer to either ride it by being offshore .... or find a bolthole to shelter in ...

 

[doug748]

Of course in the unlikely event that I could shed 10 years of age and decide to sail off in the way my boat was designed for I would fit a larger anchor and chain.

So would I, we got there in the end.

.

 

[Refueler]

If the latest Business Deal can be finalised and successful ... in one year - I could be thinking of shutting up shop and disappearing to distant horizons on suitable boat !

Oh sh** - was I dreaming again ??

 

[Refueler]

If the latest Business Deal can be finalised and successful ... in one year - I could be thinking of shutting up shop and disappearing to distant horizons on suitable boat !

Oh sh** - was I dreaming again ??

I do have ideas to do more with the 38 though ....

 

[Zing]

So would I, we got there in the end.

.

Like turning a supertanker

 

[Tranona]

Like turning a supertanker

Actually if you read my posts on the subject absolutely nothing has changed . I have always stated when discussing the choice of anchor for my boat that my choice for my current pattern of sailing was a 10kg Epsilon, but if I changed where and how I sailed - for example going long term cruising I would probably choose a 15kg Epsilon. Nothing controversial about that - exactly what the consensus advice says. The boat will be heavier (it is already toward the top end of the 10kg recommendation) and will have even greater windage because I would at least refit the davits and solar or more likely build an arch for solar, and there is at least an expectation that at some point I would be anchoring in far more extreme conditions than pootling along the south coast in fine summer weather and anchoring maybe 40 times a year as I have done for the last few years.

Your categoric statement in post#21 represents exactly the opposite of my analytical approach.

My objection to your view is that a larger anchor is NOT automatically "better" than the one recommended by the maker for a particular boat.

 

[Neeves]

If you can find a copy of PBO June 2002 there is a good article about a GH31 like mine riding out a summer depression in a shallow loch in the Outer Hebrides. Anchor was a 35lb CQR with a 25lb behind it in tandem on 60m 3/8" chain. Even with a chum the catenary disappeared at around 30 knots of wind so to reduce snatching 10m of 16mm 3 strand nylon was added as a snubber. The writer calculated the forces involved using formulae from Prof Knox. At 60knots the force is 680kgs, and an estimate of the extra shock load of the chain as 240kgs, so a range of between 650-900kgs. Note this is well below the ultimate holding power of a typical modern 15kgs (or even 10kgs) anchor. If 10m rope is added it will absorb more than 1000kgs if stretched 25%. The result is that the rope will offset the loss of catenary at higher windspeeds and particularly snatch loads.

The depression took nearly 24 hours to pass and local weather stations recorded gusts in the high 50s/low 60s and on board in the mid 40s, as many as 20 in one hour. So the snubber made a contribution once wind speeds exceeded 30 knots.

The writer reports some evidence of dragging (from Decca plots) which probably shows the limit of the CQR.

Given that the ultimate holding power of my 10kgs Epsilon is greater than a 35lb CQR, I would like to think that it would have performed equally well, although the lower level of catenary of my 6mm chain would mean that the snubber would have more work to do!

If these are the conditions for which you plan then you need to extend your thinking.

650-900kg of tension is beyond the WLL of G30 8mm chain - so you need to scrap the existing chain and use G40 chain (and G40 is marginal) or move up in size, from 8mm, to 10mm. 10mm chain will need a new gypsy or new windlass. The chain, 8mm x G30, will not start to distort until beyond 1,500kg so you can ignore that consideration.

But if you want to introduce your own safety margin, working at the limits of WLL might not be sensible then you might want to think of G40 10mm (and get the new gypsy or windlass). I have a suspicion you should look at the specification of the windlass anyway.

You can mitigate the snatch loads by using a snubber, or snubbers if you can devise a bridle, and I'd then suggest you look at this article:

Adjustable Snubber Bridle and Chain Hook - Practical Sailor

or send me a PM and I'll send you a series of PDFs

If you already use a snubber, yacht length, or better longer, then carry a spare - they age with use and can fail, we have broken 2. You can extend life by using a bigger (diameter) snubber - but then you sacrifice stretch.

Most chain hooks, available in chandlers, are going to stress the link to which they are attached and you should source chain hooks from the lifting industry that do not damage chain.

I can send you PDFs on the damage that poorly designed hooks, most of them in chandlers, can cause.

If you use snubbers the snatch loads melt away, tensions are reduced - and you don't need a bigger anchor. However if you are extending your geography to places you don't know then veering winds will become common place and an ability to anchor in a fork or 'V' will manage the veering - which will demand use of a second, primary, anchor and a second snubber (or mixed rode).

This is an article that prompted much of my work on snubbers and chain hooks - it makes sobering reading.

Safety at Sea: Surviving a Powerful Storm in the Med | Cruising World

Just look at the picture of the author looking at the chain hook he destroyed - you don't want to go there.


Final thought: To harp on about bigger anchors without considering the full implications is ignorance and complacency at its worst. The rode is a complete package, and the anchor is only one part of the package. If you repetitively suggest a bigger anchor without pointing out you should be looking at chain specification (and using snubbers) simply means you have not thought through the details and your thoughts on anchors could ALSO, and very likely, be incorrect. There is no point in suggesting the anchor needs to hold more - if it makes the chain, shackles, snubber, windlass, chain hook etc - the weak links

Jonathan

 

[Refueler]

If the anchor you have does the job you ask of it ... then what's problem ?

OK - so if you decide to go off world girdling and expect times of extreme anchoring - then up the size to give peace of mind.

Seems there's a lot of strong wind being blown on this thread ...

 

[Neeves]

If the anchor you have does the job you ask of it ... then what's problem ?

OK - so if you decide to go off world girdling and expect times of extreme anchoring - then up the size to give peace of mind.

Seems there's a lot of strong wind being blown on this thread ...

Interestingly many people, when Super High Holding Power (SHHP) anchors became available and the message had sunk in bought the same weight of Rocna, Spade, Excel, Supreme etc to replace their HHP CQR, Delta, Bruce etc.

Surprise, surprise. .... It would certainly do the job required.

And advantageously be more reliable to deploy

I'm the first to agree if buying a bigger and 'better' anchor gives you peace of mind it is very difficult, let me re-phrase that, a waste of time to argue with emotion using data to offer an alternative view. As this and other threads underline anchors and anchoring are an emotive issue - and anchor makers do nothing to dispel the fears (why would they?)

Despite data being quoted in posts - virtually no-one takes a blind bit of notice and no-one offers any data to support their choice of 'bigger is better' - their choice is based on subjective comments.

Jonathan

 

[GHA]

OK - so if you decide to go off world girdling and expect times of extreme anchoring - then up the size to give peace of mind.

Seems there's a lot of strong wind being blown on this thread ...

Out in the real world there's much more than just that, though feeling a bit better is a very valid thing 3am with huge gusts
World girdling you're into only having probabilities to guess at. You'll have a very real chance of having to deal with conditions well beyond those which the anchor sizing charts are based on. Very high chance the bottom will be a lot less than ideal, good chance you'll end up with less scope than you'd like. And as mentioned in post 118 at least 1 manufacturer said going up a size than their charts for long distance cruising is a good idea. So many unknowns & going up a size really has no downside,
What the vast majority of cruisers don't do is pay any attention at all to some angry blokes ranting on social media about personal opinions
All of which is irrelevant to very nearly everyone on here

 

[Neeves]

I am not sure why an older version of Panope’s results have been posted. This the current version. While no testing protocol is perfect,

View attachment 178234

Now I'm not sure why Noelex chose this spread sheet

But he does mention that big anchors are useful in difficult seabeds, though never defines what a difficult sea bed might be. Similarly he never defines why your choice, recall he only allows one choice for your primary, might be the best in mud, cobblestones and weed

But the Panope tests cover a range of seabeds and if you want a restricted anchor quiver (and agree with Noelex ideas - one primary anchor only) then the Viking Anchor should be top of your list. Viking is 15% ahead of any other anchor (and also happens to be a product of Ukraine). In fact Viking is better than any other anchor tested, in every of the various seabeds used for the tests.

So....if you want to go 'bigger' then go for the anchor that's the best .... everywhere and then you don't need to worry about any 'difficult seabeds'.

And in an anchorage demanding use of a short scope - a decent snubber answers that - elasticity replaces catenary (except you can have the elasticity down your sidedeck(s).



Jonathan

I'd endorse a Viking Anchor - except it would not fit on our bow roller. I could test it but it was very difficult to use it 'every day' - hence my caution. I like the idea of an anchor using high tensile steels of various plate thicknesses to optimise weight without sacrificing strength (same steel as used in the crumple zones of Mercedes and passenger protection in military vehicles). I suspect Viking/Ukraine have other priorities but a 'non roll bar' anchor should be an obvious development.

J.

 

[doug748]

......Despite data being quoted in posts - virtually no-one takes a blind bit of notice and no-one offers any data to support their choice of 'bigger is better' - their choice is based on subjective comments.

Jonathan

The only thing we do know with a fair degree of confidence is that bigger anchors have higher hold, I agree much of the rest is subjective.

.

 

[Zing]

Now I'm not sure why Noelex chose this spread sheet

But he does mention that big anchors are useful in difficult seabeds, though never defines what a difficult sea bed might be. Similarly he never defines why your choice, recall he only allows one choice for your primary, might be the best in mud, cobblestones and weed

But the Panope tests cover a range of seabeds and if you want a restricted anchor quiver (and agree with Noelex ideas - one primary anchor only) then the Viking Anchor should be top of your list. Viking is 15% ahead of any other anchor (and also happens to be a product of Ukraine). In fact Viking is better than any other anchor tested, in every of the various seabeds used for the tests.

So....if you want to go 'bigger' then go for the anchor that's the best .... everywhere and then you don't need to worry about any 'difficult seabeds'.

And in an anchorage demanding use of a short scope - a decent snubber answers that - elasticity replaces catenary (except you can have the elasticity down your sidedeck(s).



Jonathan

I'd endorse a Viking Anchor - except it would not fit on our bow roller. I could test it but it was very difficult to use it 'every day' - hence my caution. I like the idea of an anchor using high tensile steels of various plate thicknesses to optimise weight without sacrificing strength (same steel as used in the crumple zones of Mercedes and passenger protection in military vehicles). I suspect Viking/Ukraine have other priorities but a 'non roll bar' anchor should be an obvious development.

J.

By endorsing a Viking anchor you are another (like Tranona in a few of his comments) making a reluctant admission of the bigger is better argument.

Viking won the performance test, mostly because they are the biggest anchor in the test. They are also a typical NG anchor and of superior shape to the older style anchors. In the test they are matched to the other anchors in weight approximately, but this is not really a valid measure of comparison, because the Viking is made of extra high tensile steel and is made using thinner plate than seen in more conventional steel anchors. This makes them much lighter for a given surface area, so the anchor tested is actually a bigger anchor than the comparably shaped steel competitors.

 

[westernman]

I have a 75lb CQR as the main anchor on my boat.
My boat is 51ft LOD, 67ft LOA (tip of bow sprit to stern) and about 32 tonnes.

If I look at the Rocna sizing chart, I should have a 88lb Rocna. But I have one size down.

CQR is not a new gen anchor, and if I was buying a new anchor I would not get an 88lb CQR.

However, it has never let me down.
Even in a full gale in a bay with the beach behind me (when the only other boat in the bay dragged and ended up on the beach).

So, basically, don't get too worked up over size, nor design. They almost all work reasonably well.

 

[Neeves]

I meant to send this as a reply to GHA, post 154. But the technology to send it defeated me, then. I found another way, always happy to support GHA's posts.

Now the graph does not answer GHA's example of being forced to deploy at 3:1 under arduous conditions - but hopefully you can make the extrapolations.

Under normal conditions your yacht is subject to wind and your windage results in tension in the rode. That tension is magnified when your yacht reacts to the tension, and the variation in direction of the wind causing the yacht, to 'sail' at anchor. As the yacht moves it develops momentum which if the rode is short - may develop snatch loads.

All of this movement means the yacht is energised and your rode, anchor and wherever the rode is secured on the bow, needs to accept this energy.

The graphs simply illustrate how that energy is managed (but ignores the simple fact that your anchor 'absorbs' some of the energy - it moves (to a greater or lesser extent).

With an all chain rode, sadly very common, the tension straightens the rode, the catenary disappears (never completely) but the ability to accept tension disappears surprisingly quickly, even at 5:1 with 30m x 10mm of chain deployed.

Contrarily 10m of 10mm nylon works and works and works (until it fails, 10mm nylon - fails at about 1.5t when new),

Basically nylon and chain offer the same performance up to about 300kg of tension (about the tension developed when you power set with a 30hp engine at full revs or about 30 knots of wind). Beyond 300kg of tension the chain rode has reached its limit but the nylon will absorb the snatch loads, until it fails.

In real life you will be unlikely to have only a 10m x 10mm nylon rode. But have the 2 in combination you have a winner (especially for those anchorage with the ill defined holding) where you are stuck with a 3:1 scope.

But double your chances - have a 20m snubber (and that Viking Anchor on Noelex' spread sheet (thanks mate!)



We use 8kg anchors, sometimes singly, sometimes in a 'V' - the anchors are equivalent to their 15kg siblings. We would commonly try to anchor at 5:1 with 6mm chain. Our snubbers, a bridle (its a cat, 38' x 22'6" beam 7t)) can be extended to 30m is 10mm kermantle, a fancy braided nylon. If at 3:1 (or 5:1) we replace 'lost' or the absence of catenary with nylon. You can check - nylon is cheaper than chain, nylon is lighter than chain, nylon works more effectively that chain - its downside is abrasion (which is easy to manage).

By endorsing a Viking anchor you are another (like Tranona in a few of his comments) making a reluctant admission of the bigger is better argument.

Viking won the performance test, mostly because they are the biggest anchor in the test. They are also a typical NG anchor and of superior shape to the older style anchors. In the test they are matched to the other anchors in weight approximately, but this is not really a valid measure of comparison, because the Viking is made of extra high tensile steel and is made using thinner plate than seen in more conventional steel anchors. This makes them much lighter for a given surface area, so the anchor tested is actually a bigger anchor than the comparably shaped steel competitors.

Bigger almost without exception refers to weight, the outsiders are Fortress and the aluminium Excel and Spade. In terms of Viking it is not only that they use 'lighter' steel but they also use thinner steel. The thinner steel has less resistance when penetrating the seabed in those 'difficult seabeds' of which we hear much. Viking are pandering to the weight disciples and using it to advantage. The reality is that I've been testing a 10kg Viking version, vs my 8kg Aluminium Excel and 15kg steel Excel, its a similar size, area, to my Aluminium Excel and the same size as my 15kg Excel - so I'm comparing like with like - its the Panope tests that are 'wrong'. I'm not comparing a bigger anchor at all - though when I pick up the steel Excel in one hand and the Viking in the other - I can tell you, blind fold, which seems to be 'bigger'.

I don't have the long term experience with the Viking, I have to deploy by hand, which is not an issue - but hand retrieval is a pain.

I repeatedly say - its design not weight - and YOU are agreeing with ME. Pity you live so far away - we could enjoy sharing a decent bottle of Shiraz!

Jonathan

 

[Neeves]

This is a picture of my Viking 10, 10kg vs my steel Excel No 4 15kg.

I specifically wanted an anchor that would be comparable in performance to the Excel and steel Spade (also 15kg). The difference in surface area is actually not great. The toe of the Excel is solid steel back to the 'e' of 'ex' on the right hand side of the Excel. The big difference is that the crown (joint of shank and fluke) on the Viking is well to the heel of the fluke whereas on the Excel is roughly 'amidships'. The location of the crown, amongst other characteristics, dictates hold. For Bruce the crown extends behind the heel and for Fortress it is at the heel.

I paint my anchors with any paint I have left over so that they are easier to see underwater,

Jonathan