Anchors, is one big one better than 2 small ones

[KellysEye]

The anchor should be the size designed for the weight of your boat. We carried a 45lb CQR as the main anchor, a medium sized fortress as a second anchor and a monster Fortess as a storm anchor. Anchoring is basicaly about chain rather than the anchor, there is a myth that one length will handle anything. In five metres of water it should be ten times depth. In ten metres 7x depth, 20 metres 5 x depth, 30 metres 3X depth. The aim is that the catenary of the chain holds the boat and doesn't pull on the anchor, it's a last resort. We carried 290 feet of chain knowing we would sometimes be anchoring in deep water, we also carried chain for the other two anchors. This advice has been in the Royal Navy ratings training book for a century plus.

 

[Neeves]

Anchor makers or Boat manufacturers ?

I had not thought of that one, but both, good point.

Conachair makes the point that 2 sizes bigger is for serious cruisers - I'm not disagreeing (well not much) but to sell a 'serious cruising yacht' without a serious anchor - if that's the verdict looks, questionable?

 

[Conachair]

I do not see that long distance blue water cruisers have a need any greater to a debate on anchor choice than someone in the UK.

Jonathan

I was saying the exact opposite. The Morgans cloud link and many of the bib posts on the cf thread came from a long distance cruising perspective, your idea that everyone has a bigger anchor than specified by manufacturers possibly doesn't hold anywhere near as true for the majority of boats.

edit - bit strong, maybe not "everyone"

 

[Sybarite]

There has been a recent debate over the value of carrying one big anchor to use in preference to two smaller anchors when conditions get tough.

Jonathan

Two naval architects whom I respect take this point of view: Steve Dashew and Michel Joubert. Also the Rocna guys said that if you moor with two anchors, there is a risk that the weight will be on one, which will slip, and then the weight will transfer to the other which will also then slip.

 

[Rum_Pirate]

Two naval architects whom I respect take this point of view: Steve Dashew and Michel Joubert. Also the Rocna guys said that if you moor with two anchors, there is a risk that the weight will be on one, which will slip, and then the weight will transfer to the other which will also then slip.

Is that with the anchors set in line (Ie one behind the other and the rear anchor attached to the front one) in comparison to the layout in post #4 ?

 

[Tradewinds]

Two naval architects whom I respect take this point of view: Steve Dashew and Michel Joubert. Also the Rocna guys said that if you moor with two anchors, there is a risk that the weight will be on one, which will slip, and then the weight will transfer to the other which will also then slip.

But there's big and then there's BIG . . .

2 sizes up on my recommended Sarca size is 36kgs (nearly 80lbs)

 

[KellysEye]

>Also the Rocna guys said that if you moor with two anchors, there is a risk that the weight will be on one, which will slip, and then the weight will transfer to the other which will also then slip.

We have used two anchors many times a CQR and a Fortress each at 45 degrees to the bows. Never had a problem with slipping but that could go back to what I said that the amount of chain is more important than the anchors.

 

[TQA]

I am in my 11th year of living on the hook mostly in the Caribbean. I use a single 60lb CQR on all chain in my current 44ft boat.

On the previous 38ft boat it was a 45lb CQR. In the 90s you used to see some boats trying to use two small anchors but now it is almost always a single anchor.

The only time I would lay a second anchor would be high wind situation where I was expecting a major windshift. EG the Bahamas with a cold front. I would adjust the rodes so I was only laying to one. One thing that concerns me is the difficulty in dealing with the second anchor if you have to get out in a hurry. On most boats the anchor windlass setup makes it difficult to lift the second anchor without some major rejigging which is to be avoided at 3am in the rain with a big squall blowing through and people dragging in front of you.

So IMO one big one is better.

 

[NormanS]

We cruise in and around the NW coast of Scotland, and the Outer Isles, in a 36ft ketch. We tend not to use many of the limited, though increasing, yacht facilities, so anchoring is the norm. We normally use a 20kg (genuine) Bruce, on 10mm chain. We also have a (genuine) 20kg Danforth, with 10m of 11mm chain / 64m of nylon. We also have a 20kg fabricated Fisherman.

The area is well blessed with sheltered anchorages. By which I mean, sheltered from the sea, shelter from the wind is much more difficult, so sometimes anchoring can be quite challenging. We have had sustained winds of 60+ knots on several occasions, and once a blow of 75 knots. To me, the most important things are choosing a suitable anchorage for the expected conditions, and then choosing, or finding a suitable bottom. I have found that for the latter, a fish-finder is an excellent tool.

I'm not sure how my anchors and chain compare with the recommendations, but I do notice a lot of similar sized boats with both lighter anchors and chains. We normally lie to one anchor, but if conditions are severe, I am quite happy to motor ahead, and out to one side, and drop a second anchor. I find then, that although the boat still ranges about, the angle of pull to the anchors is reduced. Co-incidentally, I intend to do some experimenting with a twin "anchor sail", this year, which may cut down the amount of ranging about.

We have, for the last several years, left our boat, anchored unattended, in a couple of sheltered locations in the Outer Isles for periods of four weeks. For this we arrange a Bahamian Moor, which we have found very successful.

To the people who say that they cannot handle a big enough anchor to suit their size of boat, I would say, "Get a smaller boat".

 

[oldbilbo]

We are biased, we have a cat that allows us into places....We are wimps and scurry into the best shelter we can find, we tie to trees, rocks and set 2 anchors.... Basically we try not to challenge..... So our 2 anchors, say, are supplemented by other devices, warps ashore, anchors dragging under the bow etc.

I hear and echo.... and Conachair.... and others. FWIW, I've been a cat enthusiast most of my days and 'when my ship ( ticket! ) comes in' I'll certainly go find me a big Outremer. Meanwhile, I go in the boat I have....

So anchoring becomes more complex the more one does of it.

When I taught this stuff a while ago, I held that one needed more than one anchor on board - in case of loss, stranding/kedging - probably of different types for different substrates, and that the primary anchor should unquestionably be well up to the likely job. I held the view that the primary anchor should be the heaviest one could manage on the foredeck.

It is noted that merchant and naval practice down the ages has always been to have more than one anchor, and both techniques and circumstances for deployment have kept professional pundits occupied, in the journals of e.g. the Nautical Institute forever and a day. ( 'viz. Harland's 'Seamanship in the Age of Sail' )

I seem to recall newbies asking "What's the smallest anchor I can get away with on my boat", and that would often be similar to what the anchor makers recommended. Interestingly, boat builders would often supply something smaller. A couple of years later, the same -once newbie would be back asking "What's the biggest anchor I can reasonably carry..." In between, one surmised a degree of 'on-the-job experience'. My conclusion was that it is always the skipper's ( owner's ) responsibility to get such decisions right, and the boat builder's profit-and-loss account should not be the determining factor.

The view that BOTH primary anchor systems ( that includes the provision of wholly-adequate chain and rode ) should be capable of doing the anticipated job is one I share. I certainly would be uncomfortable with the idea of shipping two modest-sized anchors, neither one of which is, alone, really capable of holding the boat in a reasonable blow.

 

[Neeves]

The suggestion is not to use modest sized anchors but anchors that are of a size recommended for the boat, if the yacht has high windage, is heavy displacement or is borderline then the suggestion is to go the next size up. The BIB suggestion is that the recommended sized anchors are too small by 2 sizes. Thus if Rocna are suggesting a 25kg anchor (and this is based on your taking windage or displacment into account, for your yacht then you should really be using an anchor of 40kg.

Many of the 'historic' recommendations, much quoted, were based on use of a CQR and Bruce. It does not surprise me that the idea developed to go 2 sizes bigger. Weight mattered as in many seabeds these anchors did not work too well and it has been said many times that the larger Bruce is much more efficient in larger sizes. I am not suggesting that the 'older men' of the sea were not cautious. In the last 10 years we have seen a number of much more efficient anchors develop - but despite the fact they are better - the same recommendations still come through of BIB (which seems to contradict every article I have ever read on new gen anchors, and also suggest we have all, or me at least, been conned).

My Opening Post was to suggest might having 2 new gen anchors (or more) of a recommended size be adequate (rather than BIB). I'm not necessarily suggesting they be used at 30 degrees to each, but they might (stops veering and veering results in snatch loads, I'm not suggesting setting in tandem, but it is possible, I'm not suggesting a Bahamian moor, but it is possible, I'm not suggesting one could swap one anchor for another if the first does not work as well as desired in a specific seabed, but the opportunity is there.

I'm not even suggesting the 40kg anchor might not work - the question is - is the 40 kg anchor necessary, might the 2 (recommended sized anchors) offer something missing from 'all the eggs in one basket'. I might reiterate my suggestions have been roundly condemned as 'stupid', for which Conachair can confirm, and my stupidity met with little support.

The suggestion of 2 anchors is contingent on them both being of a size for the yacht and both being new gen and both having their own rode and that the rodes are both adequate One might be all chain, one might be chain and nylon. I would actually be suggesting at least one further anchor, so maybe Supreme, Spade and Fortress.

And whereas one could carry 2 x 40kg anchors, when the recommended sized anchor was 25kg I can think of a few problems, like where to store the second anchor and how do you manage to deploy, change etc. It is possible, many do deploy 40kg anchors (another use for the halyard winch etc - but is it necessary is it a bit OTT?

But importantly how many actually have an anchor 2 sizes 2 big, so are putting their money where their posts are, and how many have dragged with a recommended sizes new gen anchor. If new gen anchors of the correct size do drag, relatively frequently, then there is a clear and unequivocal case to go larger. I do not recall hearing of many new gen anchors dragging, they will drag - but usually for reasons that might make a bigger new gen anchor drag anyway.

People who have quoted their experiences on the thread so far do not seem to be using overly large anchors but do seem to have endured some trying conditions.

Jonathan

 

[NormanS]

You keep on quoting "recommended size". So what's the recommended size for my 36ft ketch, which is really only 34ft, with a sticky-out bow roller? And who is it recommended by? And do they have more experience of my boat and my anchorages than I have?

As I have alluded to previously, anchoring can never be an exact science, and depends on a huge extent, on the particular bottom where the anchor lands.

 

[Neeves]

NormanS, Of course I do not have a recommended anchor size for you, but Lewmar, Spade and Manson do (have a chart). They usually say - if you are bordeline, go one size up; if you have high windage; go one size up; if you have heavy displacement, go one size up. Some of the charts cross reference weight and length.

Having made you decision, based on the anchor makers, the suggestion is it is 2 sizes too small. From your post I 'feel' you have gone up in size anyway - did you go up 2 sizes? Did you go up in size as a result of nasty experiences? Or just gut feel (and there is nothing wrong with gut feel). Are you using a new gen anchor? If you are using a CQR, Bruce, Bugel - I'd be saying go 2 sizes up - its the 2 sizes up new gen I am querying.

 

[Rossynant]

Of course I do not have a recommended anchor size for you, but Lewmar, Spade and Manson do (have a chart).

Well, they do. So what?
Lewmar table suggest for my boat (30') CQR of 20 or 25 pound. How this translates to reality? Boat was to Lloyd specks - came equipped with CQR - 35 pound... And another one (for kedge, a size lighter) So what is the "size recommended"
and by whom?

 

[Neeves]

I note that most respondents are carrying old styles, predominately CQRs and some are larger than suggested - which fully supports Coanachair's comments on the recommendations of Dashew and Moitessier et al. The original post was focussed at new gen anchors.

The only person to reply and define having a new gen anchor is Tradewinds, who seems happy with recommended size and expressed some incredulity at going 2 sizes larger. Do I get the impression that new gen anchors (apart from mention of Fortress) have simply not penetrated the UK (or members of YBW)? If this is the case, of few owning and using new gen anchors, then I'm on a hiding to nothing hoping to receive comment.

Jonathan

 

[oldbilbo]

Thinking through the excellent stuff published by Alain Fraysse, with that delivered to the Cruising Association by John Barry, it occurs that focusing on 'weight' of anchor might be a tad misleading. Surely what matters is the weight/volume/physical-resistance-to-disturbance of the lump of seabed that the anchor is trying to displace?

And surely that is - in any specific spot - a function of the 'effective projected surface area' of the relevant anchor's fluke(s) or blade? A larger surface area of anchor is trying to shift a larger weight/volume of seabed than would be the case with a small anchor.....? Hence the relative effectiveness of the lightweight aluminium Fortress anchor, once it is buried and set.

Sure, the shape of an anchor's blade will have some effect on how the lump of sand/mud/clay is displaced, or not, but it seems to me that a larger lump of seabed will better resist being moved aside than a small lump.

Is 'weight' a misleading metric? Should it instead be 'area' that we compare? Some manufacturers - e.g. Rocna, Spade - indicate the surface area of each model. It seems they consider 'comparative surface area' to be significant.

And as for '2 steps larger', it is clear from inspection of the various charts/tables that there is no standardisation of what constitutes a 'step'. For example, The Lewmar Delta anchor jumps from 10kg to 16kg ( +60% ), then on to 20kg ( +25% ). There's another large jump of ( + 60% ) between the 25kg model and the next larger at 40kg. The Kobra anchor, in contrast, has models at 10kg, 12kg, 14kg, 20kg.....

With the Delta, then, a '2 step' increase from the popular 10kg size doubles the weight to 20kg. and almost doubles the cost. With a Kobra, a '2 step' increase over 10kg takes one to 14kg, with an approximate one-third increase in cost. Confusion...? You bet.

 

[Neeves]

Oldbilbo,

I agree totally with the idea we should be looking more toward surface area than weight, some manufacturers quote SA and reading the background to the design of specific manufacturers many highlight SA. The biggest problem is that many anchor makers do not quote SA, thus it is impossible to compare (without access to a complete range of each anchor). I took the easy option by considering that most new gen anchors, for a given weight, across a cross section of reports seem to have 'similar' holding capacities and if surface area is proportional to holding capacity and new gen anchors of similar weights have similar holding capacities then they have similar surface areas (Fortress excluded!). Basically I have taken the 2 x Voile et Voileurs tests the infamous West Marine 2006 in YM test and a few others and used them as a basis.

It would be interesting to learn how many others believe in surface area, but possibly that's a new thread.

Its really crude, but I can think of no other way. I also looked at what Classification Societies say/do and they class the Supreme, Fortress, Excel (Australian equivalent testing) and Rocna as SHHP (in terms of holding capacity) and SHHP is twice HHP and Delta, CQR, Bugel are rated HHP. Many people would consider Spade, Kobra etc, my original list) along with Supreme, Excel etc - so I've lumped them altogether. Fortress is difficult to categorise but basically for a similar SA it has about half the weight, so an 8kg Fortress is about the same as a 16kg Excel (the Fortress is slightly bigger in SA). VetV seems to find the alloy Spade with the same Holding Capacity as the steel Spade of the same size, steel has twice the weight of the alloy.

But I'm trying to avoid discussions on the merits of one anchor over another (for obvious reasons). So my listing choice is crude.

Why 2 sizes bigger, the original thesis was proposed by Morgan's Cloud and in the debate, I recall, were specifically applying their discussion with reference to their own Rocna anchor (interestingly they carry 2 anchors, 2 bow rollers, the second is a Spade). In the image on their website they actually show the bow of a yacht with old gen anchors, but they note the discussion is limited to new gen. Basically I am taking Morgan's Cloud thesis, 2 steps larger, based on Rocna sizing, and then applying that size differential across the crude list of anchors.

I thus took the Rocna as the bench mark and used 2 sizes bigger, which for a 25kg anchor is 40kg. If it were a 20kg Rocna, 2 sizes bigger is 33kg and for a 33kg Rocna 55kg. For a Spade this tends toward 3 sizes bigger.

I checked American pricing and a 2 x 25kg Rocnas cost the same as one 40kg Rocna and similarly 2 x 25kg Spades are the same as 1 x 40kg Spade (or as near as makes no difference). I actually found this surprising as I had thought that the bigger anchors would be, relatively, cheaper. I'd not suggest buying 2 x Rocnas, I suggest, say, one Rocna and say one Spade (and also 1 x Fortress).

The thesis is based on the idea that the smaller new gen (of the size recommended for a yacht by the anchor maker) will drag under very strong winds and that to obviate this problem the answer is to carry one larger anchor. I simply ask is it actually necessary, do recommended sized new gen anchors have a propensity to drag under very strong winds, and if so might carrying another (recommended sized) new gen anchor that can be deployed when conditions demand be a sensible alternative option. I'm thinking that one larger anchor should well hold but does not offer the option to carry different designs (for different seabeds) (unless you carry 2 rather large anchors) and in the event you need to abandon one anchor what to do? So part of the issue is - do people who 'oversize' carry a second anchor and if so is it also oversize. My thought is the second anchor should be 'as good' as the first, so same size also new gen.

I apologise if my original post was not sufficiently succinct.

Jonathan

 

[Neeves]

Oldbilbo,

Interestingly I do not recall Alain Freysse, to whom you rightly refer, suggesting BIB, but I might have that wrong.

Jonathan

 

[Conachair]

......

Having made you decision, based on the anchor makers, the suggestion is it is 2 sizes too small. .......

I think that is mistaken. The "2 sizes up" seems to come from the likes of Morgans Cloud, Dashew et al, writing about what works for them long distance, not suggesting what others to carry. Different feel to the statement.

Also, outside of the world girders there doesn't seem to be much, if any, interest in going 2 sizes up. Neither on the forums or from looking around marinas. Maybe a cautious up one size.
-----------------
Q. Does anyone on the forum feel going up 2 sizes from manufacturers spec is necessary? (for "normal" weekend, fortnight in the summer cruising)

 

[NormanS]

If and when I put out a second anchor, which is not often, I invariably rig a tripping line and buoy. This is primarily to show me the approx position of the second anchor, but also means that if I had to change position in a hurry, I would just slip the second anchor, for later retrieval. I wouldn't abandon an anchor.