Big anchors

[Supertramp]

Can you prove that and can a sue you if I follow your recommendation on oversizing my next anchor and end up wrecked??

Of course I am being obtuse. The whole issue with anchoring is the multiple unknowns and the compromises we are willing to make as users. I would suggest having a two or maybe even three anchors of the correct size rather than one oversized. May I ask if your kedge and or spare is oversized?. If it isn’t, then your argument falls flat since in my book losing your bower is a significant risk to a live aboard.

My kedge anchors are smaller than my main (which is oversized) but not massively undersized. I am UK coastal cruising for relatively short trips. I agree with you that for liveaboards carrying a full sized kedge makes sense.

I want a reliable main anchor for routine use in all conditions, without having to deploy multiple anchors routinely. I want a kedge to provide a back up but also better holding than the main in specific, awkward substrates. Hence a Fortress or Brittany (or Danforth...).

Also three full sized main anchors with their rodes, especially if all chain, is a serious amount of kit, hard to justify for my kind of sailing. I'm not strong enough to move it all around for a start! You are right that everyone finds their choices and compromises.

 

[noelex]

Only if you can fully set it in the difficult substrate. If it's only partly penetrating the difficult substrate due to broken coral debris, as is very common in the Caribbean.

I agree coral rubble is a difficult substrate and it appears reasonably common from my limited anchoring experience in the Caribbean.

I think even all those promoting the "small is adequate” mantra have conceeded that a large anchor will have a higher ultimate holding power in any particular substrate than a smaller anchor of the same design and construction material. In difficult substrates this is where this extra ultimate holding power can be particuarly beneficial.

There is an exception that proves the rule, and that exception is in rock. In smooth rock and rock boulders large anchors have no ultimate holding advantage. In gravelly and pebbley substrates the normal rules still apply and larger anchors have a higher ultimate holding ability than smaller anchors of the same design and construction materials.

You can see photos of different anchors in these types of substrates including some in rock, gravel and pebbles. Click the link below and make up your own mind:
Photos of Anchors Setting - Page 57 - Cruisers & Sailing Forums

You can also look up the excellent tests conducted by Panope. He has tested large and small versions of anchors in pebbly substrates.

Coral rubble is a mixture of larger boulders and pebble sized bits of dead broken coral. The dead coral is generally considerably lighter than rock it so may not behave in exactly the same manner, but I am expecting that when anchoring amongst patches of large coral boulders there will not be any advantage from a larger anchor. If anchoring in coral rubble consisting of pebble sized pieces I expect the larger anchor will have a higher ultimate holding ability. Time will tell if these predictions are accurate in the Caribbean.

 

[geem]

My kedge anchors are smaller than my main (which is oversized) but not massively undersized. I am UK coastal cruising for relatively short trips. I agree with you that for liveaboards carrying a full sized kedge makes sense.

I want a reliable main anchor for routine use in all conditions, without having to deploy multiple anchors routinely. I want a kedge to provide a back up but also better holding than the main in specific, awkward substrates. Hence a Fortress or Brittany (or Danforth...).

Also three full sized main anchors with their rodes, especially if all chain, is a serious amount of kit, hard to justify for my kind of sailing. I'm not strong enough to move it all around for a start! You are right that everyone finds their choices and compromises.

We carry a normal sized, 30kg Spade as the main anchor. A 10kg aluminium Danforth type anchor and huge Fortress Fx55. Just as important is what you are going to attach it to. We carry two short lengths of chain, circa 5 or 6 metres each. These attache to either 50 metres of 25mm anchorplait or 100 metres of 19mm nylon braid on braid. Both are super stretchy, particularly the braid on braid being thinner

 

[noelex]

The 2006 YM/Sail/West Marine tests were carried out in three very different seabeds, one selected because it was poor. The concave anchors (only Rocna, Spade and Manson were in production then) plus Fortress held well in all of them. From memory the Rocna and Mantis did not quite make 5000 lbs in the poor one but otherwise all held at above this figure. All were 15 or 16 kg models except Fortress, which was proportionately too big in error.

Anchor pull tests are valuable, but nearly all have been conducted in good substrates that are very uniform. Alternative results would be helpful. For example, testing in weed would be invaluable, but this it is difficult due the irregular nature of the seabed.

You can have a look at the many photos I have taken of anchors underwater or look to Panope’s video results for an idea how various different models perform in more difficult seabeds, but some maximum holding power tests would be valuable.

The extensive 2006 study you mention was probably the largest anchor test and looked at four different sites. The Mantus was not tested (it was not around then). The three best performing anchors were the steel Spade, Rocna and Fortress. The 15kg steel Spade generated 2500 kg of holding power at three of the four locations, but only 250 kg of holding power at the fourth location. The Rocna generated 2500 kg of holding power at two of the locations, 1300 kg at the third and 750 kg of holding power at the fourth. The physically larger Fortress generated 2500kg at three locations and 750 kg at the fourth.

The Fortress is a great anchor, but it does not do well in difficult substrates (apart from very soupy mud) and the strong results suggest no locations were particularly difficult.

The only comprehensive static pull tests that have considered a difficult substrate were the Fortress tests in very soupy mud. The test results were very inconsistent, showing the problems of conducting this type of test in less than perfect substrates. The Fortress and Danforth did best, as you would expect. These anchors excel in this type substrate. All models suffered a significant reduction in ultimate holding ability here (it must have been very soupy mud). This shows how much reduction in holding power that anchors can suffer when the substrate varies. Even the Fortress FX-37 at 32° only achieved 451 kg. Setting the fluke angle to 45° improved this to 845 kg, but it is still well below the 2500 kg measured in more conventional substrates (at 32°).

The substrate is very important and will have a significant impact on the holding ability of your anchor. If you are expecting 2500 kg holding power all the time from a 15kg anchor (as some posts in this thread suggest) you will be disappointed.

 

[geem]

Anchor pull tests are valuable, but nearly all have been conducted in good substrates that are very uniform. Alternative results would be helpful. For example, testing in weed would be invaluable, but this it is difficult due the irregular nature of the seabed.

You can have a look at the many photos I have taken of anchors underwater or look to Panope’s video results for an idea how various different models perform in more difficult seabeds, but some maximum holding power tests would be valuable.

The extensive 2006 study you mention was probably the largest anchor test and looked at four different sites. The Mantus was not tested (it was not around then). The three best performing anchors were the steel Spade, Rocna and Fortress. The 15kg steel Spade generated 2500 kg of holding power at three of the four locations, but only 250 kg of holding power at the fourth location. The Rocna generated 2500 kg of holding power at two of the locations, 1300 kg at the third and 750 kg of holding power at the fourth. The physically larger Fortress generated 2500kg at three locations and 750 kg at the fourth.

The Fortress is a great anchor, but it does not do well in difficult substrates (apart from very soupy mud) and the strong results suggest no locations were particularly difficult.

The only comprehensive static pull tests that have considered a difficult substrate were the Fortress tests in very soupy mud. The test results were very inconsistent, showing the problems of conducting this type of test in less than perfect substrates. The Fortress and Danforth did best, as you would expect. These anchors excel in this type substrate. All models suffered a significant reduction in ultimate holding ability here (it must have been very soupy mud). This shows how much reduction in holding power that anchors can suffer when the substrate varies. Even the Fortress FX-37 at 32° only achieved 451 kg. Setting the fluke angle to 45° improved this to 845 kg, but it is still well below the 2500 kg measured in more conventional substrates (at 32°).

The substrate is very important and will have a significant impact on the holding ability of your anchor. If you are expecting 2500 kg holding power all the time from a 15kg anchor (as some posts in this thread suggest) you will be disappointed.

What we are lacking is definition of 'difficult substrate'. There must hundreds of variations. Some will be hard to penetrate. Some will be so muddy that penetration won't be the problem. Both ends of the spectrum and a whole lot in between. I can see that in soupy mud, a large anchor surface area will have more hold. At the other end of the spectrum, I don't think so. If you take the analogy of pushing a nail through leather compared to pushing a pin through, you can imagine how a smaller, sharper anchor may penetrate a hard surface better than a larger blunt tipped anchor. An anchor designed to perform well in hard surfaces and or weed won't do well in soupy mud. You can imagine thst in hard seabeds, if you can get a get deep set, you will likely achieve a good hold. First you have to set. I don't see the advantage here of an oversized anchor

 

[thinwater]

A kedge is smaller and lighter for a reason. It is a tool, typically rowed out, either for moving a boat or as a second anchor, commonly to limit swing. Generally anything more than 20 pounds is no longer a kedge for a yachtsman, since he cannot handle it from a dinghy by himself, it is a second anchor. It is not a spare bower. Nothing wrong with a spare bower, but it is not a kedge.

This is why a Fortress is so popular as a kedge in the US. With a rope rode, it serves this purpose handily.

As for live-aboard, I would think you would have 3 anchors. If the large bower is lost, then the kedge can be used with the spare in a two anchor rig until a replacement is secured. Or the 3rd anchor is either bower or storm sized.

Kedge (from OED)

verb
verb: kedge; 3rd person present: kedges; past tense: kedged; past participle: kedged; gerund or present participle: kedging

1. (with reference to a ship or boat) move by hauling in a hawser attached to a small anchor dropped at some distance.
   "I kedged the dinghy to the port"
   

noun
noun: kedge; plural noun: kedges; noun: kedge anchor; plural noun: kedge anchors

1. a small anchor used to reposition a ship or boat by having the anchor's hawser hauled in.
   

Origin

 

[geem]

A kedge is smaller and lighter for a reason. It is a tool, typically rowed out, either for moving a boat or as a second anchor, commonly to limit swing. Generally anything more than 20 pounds is no longer a kedge for a yachtsman, since he cannot handle it from a dinghy by himself, it is a second anchor. It is not a spare bower. Nothing wrong with a spare bower, but it is not a kedge.

This is why a Fortress is so popular as a kedge in the US. With a rope rode, it serves this purpose handily.

As for live-aboard, I would think you would have 3 anchors. If the large bower is lost, then the kedge can be used with the spare in a two anchor rig until a replacement is secured. Or the 3rd anchor is either bower or storm sized.

Kedge (from OED)

verb
verb: kedge; 3rd person present: kedges; past tense: kedged; past participle: kedged; gerund or present participle: kedging

1. (with reference to a ship or boat) move by hauling in a hawser attached to a small anchor dropped at some distance.
   "I kedged the dinghy to the port"
   

noun
noun: kedge; plural noun: kedges; noun: kedge anchor; plural noun: kedge anchors

1. a small anchor used to reposition a ship or boat by having the anchor's hawser hauled in.
   

Origin

You have just described my set up

 

[Neeves]

The substrate is very important and will have a significant impact on the holding ability of your anchor. If you are expecting 2500 kg holding power all the time from a 15kg anchor (as some posts in this thread suggest) you will be disappointed.

You consistently miss the point.

No-one expects their anchor to have a hold of 2,500kg - because they cannot access that hold. Most people would be happy with 1,000kg hold - beyond that we are talking about hurricane conditions and given access to forecasts you will be somewhere else or have made other arrangements to secure your yacht (mangroves, trees, marina, shore lines, deploy the Fortress etc etc. and move out of the way of yachts upwind).

To me a powerful item of data is

Most people actually use anchors of the recommended size, many still use old gen anchors.

Reports of new gen anchors dragging are like hens teeth. They do drag but commonly for good reason, they are clogged or picked up some trash. In the last, almost, 20 years since the 2006 report there have been no consistent reports from members here that their anchor has dragged and no-one has reported here that they find their new gen anchor undersized. Not one single report. Some years ago I initiated a thread on new gen anchors dragging - nothing in that thread indicated that, other than operator error or bad luck, new gen anchors were inadequate. Some of course were oversized - but the majority believed the spreadsheets.

When yacht owners report on storm anchoring, or anchoring in storms, never is the size of the anchor mentioned in a way to suggest bigger is better. Reports exclusively focus on other topics, snubbers, other yachts dragging - size of anchor is simply not a topic of discussion.

If the spread sheets were wrong and consistently wrong - we and insurance companies would know.

Add the absence of reports of dragging of new gen anchors to the test data and you have a very powerful argument to buy what the anchor maker recommends - knowing that they will have hedged their bets.

Now.....new gen anchors do drag - that's why Morgans Cloud removed their recommendation for Rocna (and Supreme). They removed their recommendation because the anchor clogged, not because it was undersized. MC made no beef about size, no mention that the misfortune would not have occurred if the anchor had been bigger. Arguably it was the wrong anchor in that seabed (as they have no restriction on use of an Excel nor Spade - and no mention of oversize).

We have powerful data from a number of members with documented reports of use of their anchors - none have come up on this thread saying

I'm glad I bought an oversized anchor.


There are a number of people reading this thread

How many of you have dragged with a new gen anchor?

How many of you feel your anchor is undersized?

Jonathan

 

[noelex]

Can you prove that and can a sue you if I follow your recommendation on oversizing my next anchor and end up wrecked??

. Wouldn’t it be great if the anchor manufacturers offered such a warranty. I think some of those manufacturers suggesting ridiculously small anchor models would rapidly change their mind .

I don’t want to suggest that fitting the largest anchor you can comfortably manage, even if this is well oversized means you will never drag. The extra ultimate holding ability will make you more secure, but anchoring can never be 100% reliable. By fitting the best equipment, which includes the best anchor design with the largest anchor you can comfortably manage, you can significantly increase your chances of staying put, but there are no guarantees. The better gear will also enable you to explore anchorages with more difficult substrates or in locations when shorter scopes (than otherwise would be desirable) are required. This is the most significant advantage, but common sense and judgment is still needed.

May I ask if your kedge and or spare is oversized?. If it isn’t, then your argument falls flat since in my book losing your bower is a significant risk to a live aboard.

It is a good point about the spare anchor. You should give some thought to what you would do if the primary anchor needs to be cut away. My spare anchor is the same as my primary anchor and is of course oversized. The above is the ideal set up and is justifiable in my case because I anchor most days of the year and like to explore remote areas. If you are always sailing waters where marine stores are readily available, especially if there are a multitude of marinas or mooring buoys and/or warm clear water where the anchor could be readily recovered, then the expense of this ideal set up is perhaps not justified. The most important factor is the performance of your primary anchor, as this is what you will be using 99+% of the time.

If you need to frequently use two anchors in stronger wind (I don’t), unfortunately you need to carry a minimium of four anchors if you want to cover when you need to cut away two anchors.

My kedge anchor is the recommended sized Fortress This is not oversized. I don’t think the primary and kedge anchors should be sized in the same way. There is an advantage to a kedge as small as feasible as this can then be easily be deployed from the dinghy or even swimming (with a float to support the anchor). In my case, it is most commonly used as a stern anchor to keep the bow aligned into the swell and in this role the holding power is not critical, but I would not say no if someone wants to donate a larger Fortress .

 

[noelex]

An anchor designed to perform well in hard surfaces and or weed won't do well in soupy mud.

Sure, but we need to consider anchors of the same design and construction material. Here I thought we had agreed the obvious, that a larger anchor will always have a higher ultimate holding ability in any particular substrate than a smaller anchor.

Even Jonathan has posted that it would be really illogical to argue differently:

No-one, in any of the posts is denying that a bigger anchor, of the same or even similar design does not have a higher hold than a smaller anchor. It would be really illogical to argue such.

 

[Neeves]

Sure, but we need to consider anchors of the same design and construction material. Here I thought we had agreed the obvious, that a larger anchor will always have a higher ultimate holding ability in any particular substrate than a smaller anchor.

Even Jonathan has posted that it would be really illogical to argue differently:

Possibly then we could also agree that for any particular design, whether or not it is good for hard sand, soft sand or soupy mud then if the anchor is of the recommended size, for the yacht and the seabed, it will be impossible to use the full potential hold of that anchor - negating the need for a bigger one.

I dislike the use of the word kedge, a personal issue as a kedge anchor is not considered as a primary.

However if you carry a Fortress as a kedge then it will commonly be 'smaller'. As Fortress clearly demonstrated in their Chesapeake mud tests physical size is everything and soupy mud is the one seabed where a large anchor is demanded. If you use a Fortress of a size recommended for sand it will be grossly undersized for soupy mud and in fact will simply not hold in a typical strong wind event on the Chesapeake. For this reason we carry a FX55 for soupy mud. We also carry other anchors that can be all used as a primary, all alloy, all 8kgs (for a yacht with the windage of a Bav 45).

It simply seems good seaman ship and prudent to carry anchors that are 'spare' - you simply don't know if or when you might lose one - and even though you can see it - the anchor might not be retrievable, safely. The number of shark attacks in the Whitsundays would be a guaranteed deterrent. We have only personal evidence of the problems of not carrying a sensible spare:

A cruising coupled begged a loan of a spare anchor (anything) having lost their, only, anchor. There were no convenient chandlers and they found sailing one on deck arduous and needed some sleep. We were more than happy to oblige, we were pinned to a small bay as a forecast Storm rolled past, - and swore, to ourselves, we would never be in that situation.


We did lose an anchor once, In mud. No chance to see it. We carry a reef anchor, a sort of grapnel with bendable wire flukes. We needed to deploy a second primary (to secure Josepheline)_ so that we could trawl in the dinghy across the seabed with the grapnel to find the lost primary. It took half a day to find and retrieve the primary. It was an interesting exercise as we found the chain - but you cannot lift a rode length of chain in a small dinghy - the rode (with anchor) is simply too heavy

(even more difficult if you are trying to lift an oversized steel anchor with matching chain).

Jonathan. 2k

 

[Neeves]

I think even all those promoting the "small is adequate” mantra have conceeded that a large anchor will have a higher ultimate holding power in any particular substrate than a smaller anchor of the same design and construction material. In difficult substrates this is where this extra ultimate holding power can be particuarly beneficial.

You keep repeating this - you keep forgetting to provide the data supporting your ideas.

How is this 'extra holding power' accessed and be beneficial.

I have anchors with a holding capacity of 2,000kg - I am never likely to need more than 600kg of holding power. I have, roughly, 60% of the hold of my anchors in reserve. Precisely how am I going to find the extra hold beneficial of an overly big anchor when I cannot access the hold of my existing anchor.

You keep mentioning 'difficult seabeds' and now conjure up coral rubble - which you freely admit you are not familiar with...? As an instant expert - please define 'coral rubble'

Beggars belief - promoting a concept without a shred of evidence.

Jonathan

 

[geem]

Sure, but we need to consider anchors of the same design and construction material. Here I thought we had agreed the obvious, that a larger anchor will always have a higher ultimate holding ability in any particular substrate than a smaller anchor.

We agree that a bigger anchor will have higher potential hold, assuming you can access that hold. You only access that additional holding capacity if you can set it. If it is not fully set, then it may not provide anymore holding power than a smaller anchor of the same design that is fully set.
That was what I said in post#1

 

[Supertramp]

Isn't the core question whether a part set (in sub optimal substrate) oversize anchor holds better than the correctly sized one? It's about relative holding part set in poor conditions.

It will depend on the substrate but it is the real world we operate in. If true, then a massive argument for over sizing.

 

[boomerangben]

Isn't the core question whether a part set (in sub optimal substrate) oversize anchor holds better than the correctly sized one? It's about relative holding part set in poor conditions.

It will depend on the substrate but it is the real world we operate in. If true, then a massive argument for over sizing.

I agree that is the hypothesis and one worth pursuing, but until it is held up by facts, it remains a hypothesis. Opinions are being expressed as facts and that is, IMO as questionable as anchoring in poor holding.

 

[Neeves]

There are a number of people reading this thread

How many of you have dragged with a new gen anchor?

How many of you feel your anchor is undersized?

Jonathan

Not many replies yet.....so no-one has dragged using a new gen anchor and you are all happy with the size...??

Jonathan

 

[noelex]

Possibly then we could also agree that for any particular design, whether or not it is good for hard sand, soft sand or soupy mud then if the anchor is of the recommended size, for the yacht and the seabed, it will be impossible to use the full potential hold of that anchor - negating the need for a bigger one.

No, this is wrong.

If, for example, you look at the results of the extensive 2006 anchor test that Vyv raised, a 15kg Spade recorded an average holding power of 2500 kg in three locations, but in the fourth it only held on average 250 kg. This would not be enough for most cruising boats of the size that might consider this sized anchor. A larger Spade with its higher ultimate holding power would be required to anchor safely at this location for stronger wind.

 

[vyv_cox]

No, this is wrong.

If, for example, you look at the results of the extensive 2006 anchor test that Vyv raised, a 15kg Spade recorded an average holding power of 2500 kg in three locations, but in the fourth it only held on average 250 kg. This would not be enough for most cruising boats of the size that might consider this sized anchor. A larger Spade with its higher ultimate holding power would be required to anchor safely at this location for stronger wind.

The reality is that you cannot predict whether this is correct or not. There are many reasons why anchors may not develop their full holding power and size is only one of them. The Chesapeake Bay tests showed that increasing the size of most anchors made no difference - they still dragged.

In the real world we reverse hard to test the anchor holding. If it drags we try again somewhere else.

Minor correction to your earlier post. There were three locations, as I said. They recorded results from the first twice. I am not sure why as I know they carried out dozens of tests in each location on every anchor.

 

[noelex]

Isn't the core question whether a part set (in sub optimal substrate) oversize anchor holds better than the correctly sized one? It's about relative holding part set in poor conditions.

It will depend on the substrate but it is the real world we operate in. If true, then a massive argument for over sizing.

Not only is this true, it is freely agreed upon even by those that argue that small anchors are adequate.

Look at the results in post #29 again. In this substrate a 6kg Spade only reached an UHC (ultimate holding capacity) of 120 kg. The 15 kg Spade increased this to 420 kg. Jonathan has suggested he would be happy with 600 kg for his vessel. It would need around 20-25kg Spade to achieve this holding power in the test substrate and the Spade was the best performing anchor in this test.

 

[Tranona]

Isn't the core question whether a part set (in sub optimal substrate) oversize anchor holds better than the correctly sized one? It's about relative holding part set in poor conditions.

It will depend on the substrate but it is the real world we operate in. If true, then a massive argument for over sizing.

Precisely the kind of data I have asked for several times. The measure is hold achieved against load applied. So if I set my anchor using my engine I am applying between 250-300kgs. The size of anchor is irrelevant - the hold will be the same. This will continue as the load increases (the wind gets up) until the anchor drags - and both anchors will behave the same. The question then is whether the larger anchor will hold for higher loads.

It seems to be accepted that dragging is now rare, and when it does happen it is more likely to be because of the nature of the substrate , too little scope, poorly set etc rather than limitations of the ultimate holding capacity of the anchor