Don't drag your anchor!

[RichMac]

Following the healthy debate over my navigation video - I've decided to post the anchoring video I did a few months ago.
Once again I've mentioned the RYA, obviously a big mistake. Sorry, but it can't be helped now!

Anchoring is important, the best of us get it wrong sometimes, and it's very difficult for new sailors. Maybe this video will help.

 

[vyv_cox]

Not bad, a bit too long IMHO. Mostly opinion though, not many actual figures.

When I bought my Rocna their advice was that sizing was for any conceivable conditions, no need to go bigger.

Agree about RYA, the advice on their website is years out of date. I have twice offered to assist with updating it - no reply.

 

[sarabande]

"Bigger is better at cutting through weed". No, it's the design that enables an anchor to cut through weed or dig into sand or mud. Mass and larger dimensions are but two variables in the design.

The forum's consensus over thousands of hours of debate is that different sea beds need different anchors .

"Experienced skippers go for one or two sizes bigger". That's nonsense and you cannot, I bet, substantiate or verify that highly subjective statement. Experienced skippers use the parameters of different designs and select according to their perceived area of use. Racing skippers stow anchors below, not on the bow.

Your example of a 10 ton boat choosing an anchor 10 to 15 kg bigger makes me wonder about the basis of that claim. The Rocna fitment table for a 10 tonne boat of 12m length suggests a 20kg Rocna. The experienced Rocna designers suggest that a 33kg anchor is adequate for a 16m boat of 18tonnes. All that your suggestion of going two sizes larger achieves is to make it a damn sight more difficult and dangerous to handle the anchor especially in bouncy conditions, with the potential disadvantage of the anchor digging in so firmly that it is very difficult, even impossible to break out.

We have a huge resource of technical and real-life experience on this forum about anchoring. Frankly I find your videos patronising and so subjective and full of inaccuracies and generalisations that I cannot rely consistently on what you say. Which is a pity, bcs you are clearly a very nice chap with your heart in the right place, and have done a lot of interesting sailing. Your communication style is dated, and the last video needs, desperately needs, diagrams and charts to back up your claims, not stock footage of boats whose mooring kit breaks through exceptional circumstances. Otherwise beginners are going to rush round anchorages with anchors that are 50% oversize and needing chain size increases to match the mass and holding parameters of the anchor, and that will lead to control problems including not being able to drop and engage an anchor swiftly.

You might find it advantageous to spend a month or so looking through our extensive archive of anchor threads to find out why I am so concerned at the subjective and unsubstantiated material you put out.

 

[NormanS]

It seems slightly odd to have someone pontificating about anchoring and the sizing and type of anchor, whose boat promptly drags ashore, when the wind gets up overnight.

 

[RichardS]

It seems to me, admittedly based on only 12 years anchoring in the Med, is that the single biggest reason for dragging is letting out too little scope.

3:1 or less is fine until the wind gets up but then the problems start .... and if that happens to be in the middle of the night and everyone is asleep then all hell breaks loose.

Richard

 

[noelex]

Well worth watching.

 

[RJJ]

I don't agree that having dragged disqualifies anyone from offering advice. I have yet to drag but it only takes one big blow in sub-optimal holding. Hands up who's perfect?

I don't agree that anyone offering their advice, for free, for consumption, should be attacked for their presentation. I deal with that sort of tedium at work, where people get paid for it.

I do agree that people should qualify their advice by observing where there are different perspectives and advising people to see the whole picture. OP's vid could do more to emphasise this. But I am unsure that the advice to go up a size is "wrong" or that it necessarily causes problems ceteris paribus. At worst it seems like unnecessary spondoolies and risk of pulled muscles if manhandling cos the windlass failed. The extra kg on the end of the chain doesn't seem to affect the breaking load of the system or the ability of the windlass to lift it.

 

[V1701]

I'd maybe consider going one size bigger if the next size up wasn't a lot bigger/heavier than the recommended size. Surely an anchor that's way bigger/heavier than a manufacturer's recommended size would be more difficult to set properly...

 

[Neeves]

I'd maybe consider going one size bigger if the next size up wasn't a lot bigger/heavier than the recommended size. Surely an anchor that's way bigger/heavier than a manufacturer's recommended size would be more difficult to set properly...

Precisely.

The hold is developed by the tension in the rode and that tension is developed by the windage and movement of the yacht. If the tension in the rode is 300kg - that's the hold of the anchor whether big or small. Most 15kg modern anchor will develop a maximum hold, in a nice clean seabed, of around 2,000kg - no yacht for which that anchor is specified is every going to develop a tension of 2,000kg in the rode (my guess is the bow roller will collapse first).

You will find some people, including members here, who will counter this and say

'What about anchoring in difficult seabeds'

They are never, ever, able to elaborate as to which 'difficult' seabeds the same size larger anchor will work more effectively then a small version. The comments is based on gut feel - nothing more - and if it were possible to prove a bigger one was safer - there would be data.

Now there are exceptions, well know exceptions. Most anchors will not work in sloshy mud and I imagine (from the data) that if you increased size factorially - say 5 or 10 times bigger - most anchors would work - the answer is to use an anchor designed for mud, namely a Fortress (and bigger is recommended (next size up). But anchors are a compromise and if you use a big Fortress in hard sand it will be difficult to set, deeply, the stock will stand proud of the seabed - and it will be prone to tripping in a change of tide or wind (because of this issue, and lots of testing, we carry an FX16 and a FX37 though the recommended anchor is a FX23).. The Fortress is not unique - an oversize Mantus that is not deep set has wings at the heel, holds the roll bar, that are often not buried and like a Fortress stock could cause the anchor to trip.

Anchors work by design, or don't work through lack of design, if your anchor does not work in a specific seabed - you need an anchor of a different design. There are lots of anchors that have been proved through testing, the classic test was the 2006 SAIL magazine test, repeated in YM (there have been many more tests subsequently), and through usage in real life subsequently and some new ones have joined the list: Rocna, Supreme, Spade, Fortress, Excel, Ultra. None of these anchors are perfect, they cost too much, they are not distributed very well, etc etc. Oddly there are anchors that have not been tested Mantus, Vulcan - buyer beware. But you do not need to buy an untested anchor there is one, or 2, for everyone.

I reiterate - if your anchor does not work in a specific seabed and is sized correctly - you have the wrong anchor - try another one (surely you carry more than one anchor?! and your other anchor is a different 'style' but of a weight to be your primary.)

This is another way to assess an anchor:

An Inquiry into Anchor Angles - Practical Sailor

These issues, on fluke angle, are all documented by the US Navy, in PhD thesis, by the oil rig anchor makers and from learned books, and from independent (unpublished as yet) testing. You don't need to buy an anchor that has not been tested or the results unpublished.

Thinwater and I firmly believe that yawing and hobby horsing are major contributors to anchors dragging - but we have been unable to develop a test to prove this. I have noted, and mentioned on other threads, that if you touch an anchor when set it vibrates and a vibrating anchor reduces the shear strength of the seabed in immediate proximity to the fluke. A snubber seems to reduce the frequency of vibration.

There is still much work to do in 'defining' anchor performance - comments based on gut feel and the common and repeated repetition of these 'gut feel' comments simply build into the fear factor - for no justification. So until someone proves conclusively that 'Bigger is Better' I for one stick to the size recommended by the anchor manufacturer. I am unwilling to contribute to the anchor maker's or designer's pension fund, unnecessarily, and I'll save my money - and save the money for anyone else who cares to read and follow links. Everything I say is based on testing - not gut feel. So when someone says 'Bigger is Better' - or any other unsubstantiated claim - ask for the data.

Jonathan

 

[RichMac]

"Experienced skippers go for one or two sizes bigger". That's nonsense and you cannot, I bet, substantiate or verify that highly subjective statement. Experienced skippers use the parameters of different designs and select according to their perceived area of use. Racing skippers stow anchors below, not on the bow

Delta has recommended down to 10 Kg for a 40 ft yacht, experienced skippers definitely go bigger! Your suggestion of choosing the right anchor for the conditions isn't practical over 40 ft, it's simply too hard to change, and we don't know what the bottom is anyway. In Thailand, I used to change anchors, and had the right one for the storm in Kata beach. Now with a bigger yacht, I only use the oversize Rocna.

I see I was criticised for dragging anchor myself, but they're missing the point. If you go to a wide range of anchorages, you will eventually encounter a combination of wind and bottom type that overloads the best of anchors. That's why I recommend a bigger anchor if your gear can handle it, it greatly reduces (but not eliminates) the chances of dragging.

I'm grateful to receive constructive criticism of my amateur presentation, but not the suggestion that I shouldn't make the video at all. I don't agree that people would be better informed by endless trawling of the various forums, not everyone has the time, and it's hard to sort the wheat from the chaff.

This anchoring video has now been viewed almost 120,000 times, and I'm happy if I've played a small part in improving the general standard of anchoring. My video is far from perfect, I am hoping it will inspire someone to make a more professional and informed version, Youtube has become a powerful training medium.

 

[Neeves]

I'd like you to define why a bigger anchor of the same design can cope better in the same seabed.

I don't accept that at 40' you cannot use a different anchor - that's why people have twin bow rollers. Weight is not an issue - you can source aluminium anchors - and if you accept (which many don't) that its design not weight - then the aluminium will work as well as steel. I know the aluminium and steel versions return similar hold - I've measured them

We have used both aluminium and steel and the steel versions now sit in my workshop and the aluminium versions are used exclusively. So unlike others - we have used and measured and can compare.

We are 38' cat with 22' beam and weigh in at, full cruising weight, 7t. We have the windage of a 45' AWB - I've measured it.

I would not criticise your efforts (I know how much effort goes into filming and ediiting) - except you repeat, without qualification., mantras that are not accepted by many. YouTube (and forum) can be valuable - except when it repeats questionable ideas which can be taken by many as accepted truths - and then repeated (as you have done with the bigger anchor concept). However when you quantify the idea - and add it to the video - I will be more than happy. I will quite happily accept I have been wrong - when someone can demonstrate the error of my ways . The disadvantge of YouTube and Forum is that the information enjoys minimal vetting and the loudest voice and most repeat mantra usually wins especially when supported by good photography and good editing.

The biggest danger is - because its on YouTube or has some gorgeous photos - it must be right.

Jonthan

 

[RupertW]

Delta has recommended down to 10 Kg for a 40 ft yacht, experienced skippers definitely go bigger! Your suggestion of choosing the right anchor for the conditions isn't practical over 40 ft, it's simply too hard to change, and we don't know what the bottom is anyway. In Thailand, I used to change anchors, and had the right one for the storm in Kata beach. Now with a bigger yacht, I only use the oversize Rocna.

I see I was criticised for dragging anchor myself, but they're missing the point. If you go to a wide range of anchorages, you will eventually encounter a combination of wind and bottom type that overloads the best of anchors. That's why I recommend a bigger anchor if your gear can handle it, it greatly reduces (but not eliminates) the chances of dragging.

I'm grateful to receive constructive criticism of my amateur presentation, but not the suggestion that I shouldn't make the video at all. I don't agree that people would be better informed by endless trawling of the various forums, not everyone has the time, and it's hard to sort the wheat from the chaff.

This anchoring video has now been viewed almost 120,000 times, and I'm happy if I've played a small part in improving the general standard of anchoring. My video is far from perfect, I am hoping it will inspire someone to make a more professional and informed version, Youtube has become a powerful training medium.

Well that’s 120,000 people who have been misled by well meaning but sloppy thinking. I lost you when you started explaining your belief in catenary - clearly you have never observed your anchor chain in heavy conditions but was already disappointed at your equally misguided but common belief that when you move up to an NG anchor you need to make it much heavier than the one which worked so often before. If NG anchors only work if you make them so heavy that a sphere of that weight would work you aren’t really advertising their effectiveness.

 

[RichMac]

I'd like you to define why a bigger anchor of the same design can cope better in the same seabed.

Look at the quoted loads for any anchor (on an ideal bottom), the loads always increase with size. I've never seen any tests of different sizes of the same anchor, but I'm sure that it would show the same proportion, except that I think (no evidence) that heavier anchors are better at digging thru weed or into a hard bottom.

The racing yacht or those with hand-launched anchors have an incentive for lighter equipment. The offshore cruising yacht is much more interested in security than saving a few Kg or $.

If you sail long-term over a wide range of places, you will inevitably have a number of anchor-dragging situations, whether due to extreme weather, difficult bottoms, or both. As a sailor who is on anchor every night, I'm keen to reduce the % chance of failure. The unfortunate charter boat with a "recommended" Delta will drag frequently. My oversize Rocna will be better than most, but not infallible.

My incident in Greece was extreme weather, several people were killed on land, and many yachts badly damaged. At 3am when the storm hit, my 33Kg Rocna dragged back and we wedged on the rocks by our rudder. The recommended 25Kg anchor would have dragged a bit further, maybe with serious damage. If I'd bought the next size up, maybe we would have stopped short of the rocks and saved a terrifying night.

The modern production monohulls have no room for 2 anchors, so we tend to buy the anchor with the best reputation. If I was building a yacht, I would certainly fit wide-spaced rollers for 2 anchors, it would be nice to have a choice to suit the bottom.

 

[Neeves]

All anchors are compromise, there is no perfect anchor.

Morgan's Cloud removed their recommendation for Rocna (and by association Supreme and maybe the Super SARCA anchors) subsequent to a number of vessels dragging and ending up on beaches. Most people here dutifully ignore the implied advice. Morgans Cloud retired their Rocna and use a Spade.

Practical Sailor conducted some tests:

Anchor Resetting Tests - Practical Sailor

looking at a 90 degree veers and a 180 degree change of wind direction and found that a well set Rocna/Supreme could be made to drag relatively easily and the anchor would not re-set until such time that the anchor 'self cleaned'. So in a sticky mud or an anchorage with only a little weed, but enough to bind, the anchors would drag a considerable distance before they self clean (if they self clean at all)..

People here know that a Rocna and Supreme both carry mud - they see it every time they retrieve from a muddy or weed bottom (or any cloying bottom) - and have need to spend time cleaning the fluke. I can well believe people don't read Practical Sailor nor fund Morgans Cloud - but to ignore the evidence before your eyes on the fluke of your anchor and be unable to extrapolate the difficulty of cleaning your anchor to its performance under water - were it to drag - ...... I worry and fret (because people do become complacent - I know, I'm guilty)

Size has nothing to do with it - except a large anchor would not be set so deeply, might drag earlier and might self clean more easily.

All of this, and many of the comments underline - don't be complacent, your anchor IS a compromise - set your anchor alarm (which we often do not do) - and if the weather looks questionable have your second anchor and rode ready on the bow, to hand deploy. n(we do do this - its easier than setting an anchor alarm, a crate of rode and 1 anchor). You are much better to be thought of as a wimp (or simply cautious) than end up on a beach.


Frankly I don't believe a modern production yacht does not have room for a second, full sized anchor. Brackets to hold anchors on the transom are freely available and you could store a knock down Spade or Fortress in the bilges.

The Balts have been storing anchors on their transoms for decades and if you extend your geography to Patagonia you will find all sorts of novel arrange,ents for second, third or fourth anchor storage.

Know how: Expanding your Anchoring Repertoire

the the first picture is on the Baltic and is fairly typical the other pictures are all monohulls and some quite small, the smallest (with the laundry basket with lines stored inside) came from Malta, Patagonian pictures, Punta Arenas

Jonathan

 

[noelex]

The concept of anchor holding power vs size is often presented in a very misleading way on this forum.

Strangely, more sensible things are sometimes said in magazines, perhaps because the editor does not permit nonsense to be published:

"A final argument could be suggested that bigger anchors will work better. This is valid and roughly twice the weight will produce twice the hold" (Jonathan Neeves Cruising Helmsmen magazine November 2015).

For experimental results you can look at the work done by Prof Knox. His conclusions are:


"The maximum holding of an anchor, as recommended by manufacturers, is proportional to its weight. This is precisely what I found by direct experiment" (Prof Knox PBO magazine August 2002).

You can see for both the tested Delta and Bruce:

Or you can look at the results from the Vryhof tests. Their results indicate doubling the anchor size will result in an anchor with 1.92 x the ultimate holding power. These are almost the same results as Professor Knox’s. Certainly there is no doubt that increasing anchor size increases the anchor’s ultimate holding ability.

Or you can look at results published by the anchor manufacturers. The table below is from Rocna. Rocna are suggesting users will find almost the same results as Professor Knox did with his experimental data. Again, certainly there is no doubt that increasing anchor size increases the anchor’s ultimate holding ability:

Holding
Power(lbs) .......Weight (lbs)
229 .................... 9
331 .....................13
561 .....................22
841 .....................33
1122 ...................44
1402 ...................55
1861 ...................73
2244 ...................88
3085 ...................121
3927 ...................154
6196 ...................243

If you compare two otherwise identical anchors where one anchor is larger than the other, the larger anchor will have higher ultimate holding capacity. It is really that simple.

 

[zoidberg]

If you compare two otherwise identical anchors where one anchor is larger than the other, the larger anchor will have higher ultimate holding capacity. It is really that simple.

While I wouldn't dare to quibble with 'noelex's excellent generalisation - for I follow the principle myself - might I offer the thought that 'weight' and 'size' is but a substitute proxy for the volume of the seabed which is engaged by the anchor. It follows then that perhaps the crucial factor is the effective surface area of anchor presented to that seabed.

In support of that, I offer the very high 'holding capacity' achieved by the very lightweight Fortress anchors, once embedded. And the heavier genuine 'Danforth'.

 

[Neeves]

Noelex,

I'm not quite sure what your point is.

I don't think anyone ever disputes the idea that for 2 anchors of the same design the bigger one has the higher POTENTIAL hold. Anchors do NOT scale perfectly and if you double size, weight, you do NOT double hold - but this is not really relevant.

The hold of an anchor used by a yacht owner is dictated by the windage of the yacht (or the power developed by its motor(s), transferred to tension in the chain. If the yacht develops a tension in the chain then the bigger anchor, say twice the size of the smaller one, of the same design, (and, for the sake of argument has twice the ULTIMATE hold) will have exactly the same hold as the small anchor. If the tension doubles, the hold will be exactly the same in the big anchor AND the small anchor. The two 'holds' will remain the same until the smaller anchor's Ultimate hold is exceeded (and it will then drag).

The idea that a big anchor, somehow, magically develops more hold than the small one is a fantasy

As I mentioned early on in the thread in the SAIL/West Marine tests (and in subsequent tests) 15kg modern and good anchors, Ultra, Spade, Excel, Supreme, Rocna etc all return Ultimate Holding Capacity of 'about' 2,000kg in a nice sand seabed. In other seabeds you will achieve better or less good results. A yacht, of a size for which a 15kg anchors is recommended will exceed the WLL of his chain by 3 times and will probably damage the bow roller (or many bow rollers I see) with a 2t rode tension. Simply speaking the ULTIMATE hold is factorially greater than anything the yacht will experience.

The idea that a big anchor 'magically' develops more hold than the small one is a fantasy. As with most fantasies it is not real.

Now in thin mud most anchors will simply not perform - at all and this illustrates that choosing an anchor design that performs well in the seabed is key - and as Zoidberg mentions - Fortress stands head and shoulder above its peers And especially thin mud (and offers very reliable hold in clean sand). So horses for courses - in thin mud - use a Fortress (its factorially better than anything else)

Interestingly if you average Spade/Rocna and Excel and then average CQR/Bruce and Delta and plot the recommended vessel size against anchor weight - you will find 2 identical lines. Basically those older anchors which have about half the hold of the newer anchors are recommended for the same size vessels as are recommended by the newer anchors. Given the newer ones have twice the hold - safety factors have been doubled.

Now Noelex, your point was?

Jonathan

 

[doug748]

I'd maybe consider going one size bigger if the next size up wasn't a lot bigger/heavier than the recommended size....

Yes, for small boats there is a special consideration. I can bring up my 10kg/8mm anchor/chain from 30 mts by hand but an extra 5kg might well defeat me and a winch would be necessary. Manual winches are slow and, singlehanded, you really need to have the gear aboard quickly.
Going up two sizes to 20kg would certainly justify an electric winch.

In both cases the smaller anchor avoids extra expense, weight, complication and general buggeration. Though of course your chosen tackle still has to be capable of doing what you expect of it.

.

 

[Neeves]

Look at the quoted loads for any anchor (on an ideal bottom), the loads always increase with size. I've never seen any tests of different sizes of the same anchor, but I'm sure that it would show the same proportion, except that I think (no evidence) that heavier anchors are better at digging thru weed or into a hard bottom.

The recommendation for the US and UK Navies for a hard seabed is - sharpen the toe (which presumably also means use an anchor that already has a sharp toe). A sharp toe can also be a negative - as it can pierce shells and impale object buried in the seabed. Anchor with fouled toes -.....drag (

Which is one reason to power set - you hope the tension from the power set is higher than any tension developed by windage and the power set is thus higher than anything that will happen and the anchor will not move (unless you veer . )

Jonathan

 

[V1701]

Yes, for small boats there is a special consideration. I can bring up my 10kg/8mm anchor/chain from 30 mts by hand but an extra 5kg might well defeat me and a winch would be necessary. Manual winches are slow and, singlehanded, you really need to have the gear aboard quickly.
Going up two sizes to 20kg would certainly justify an electric winch.

In both cases the smaller anchor avoids extra expense, weight, complication and general buggeration. Though of course your chosen tackle still has to be capable of doing what you expect of it.

Yes same for me, i.e. no windlass and adding weight to the bow is something I really need to avoid if at all possible. BUT my thinking is that going too big probably means I'm going to find it difficult to set properly and if I can't set it properly it's ultimate holding power is an irrelevance. Therefore I'd be more inclined to opt for an anchor that's at or only slightly over that recommended for my boat's size. I was erring towards a Mantus, then a Rocna, now maybe a Spade or should I consider a Fortress, all because I'm not happy with the CQR I currently have and now my head hurts...