Lewmar Epsilon

[down...2 greens]

Dangerous territory I know, but I was hoping for some advice and/or information on the subject of the A-word...

It's for a 34ft AWB of about 5T displacement and a fair bit of windage (high topsides and cockpit enclosure). I'm minded to go Epsilon, but should it be 10 or 16 Kg? The sizing guide at

https://dkutenx65dka0.cloudfront.net/cms/PDFs/841284841285SIZING.pdf

seems a bit vague. I have an electric windlass and 8 mm chain so the only real downside of the larger version is the extra 6 Kg on the bow - irrelevant in practical terms?

I also see from the Lewmar website that only stainless models (with associated comedy price tags) seem to be currently available. Some retailers still seem to have galvanised ones in stock so I think I could track one down, but maybe there's a reason why they have apparently been discontinued?

And finally - I can only find a sizing template for the 6 Kg model on the website - if anyone happens to know where I could find a 10/16 Kg one that would be very handy.

Thanks in advance!

 

[Tranona]

Lewmar sizing is always vague and you are at the margins. I had the same dilemma with a smaller older style boat, but heavier and less windage. I went for a 10kgs and 6mm chain which was already there and almost new along with a new Lofrans Windlass and 6mm gypsy. All well matched, but if the windlass and chain had been 8mm I would probably have gone for a 16kg as the cost of changing the gypsy and chain would have been more than the anchor! In terms of holding power and setting I don't think you would notice any difference in normal use, although possibly in very extreme conditions you might test the 10kgs at its limit. So many variables though difficult to be certain.

Did not realise there was a shortage of Epsilons as I bought mine 2 years ago, but at a guess they may have supplier problems because the finishing and particularly galvanising is not up to the standard it should be.

 

[noelex]

Lewmar anchor sizing tables are optimistic. Unfortunately, if you want to sell anchors to boatbuilders (which is where Lewmar has been enormously successful) you need to recommend small, lightweight anchors. In this way the boatbuilder saves money not only from the smaller anchor, but importantly the smaller anchor winch and bow roller etc.

If the customer complains, the boatbuilder deflects the blame with "we fit the manufacturer’s recommended size".

If you anchor frequently and can comfortably manage the 16 kg then this would be my choice. You will be able to safely anchor in a wider range of substrates and cope with shorter scopes than would be required with the smaller anchor. If you ever experience very strong conditions you will also likely be glad that you had chosen an anchor with close to 60% more maximum holding power (holding power is almost proportional to anchor weight when comparing models of the same design and construction material).

The extra 6kg will likely be a small, or very small (depending on how much chain you have) increase in your total ground tackle weight for a considerable increase in performance.

 

[Neeves]

I'm not afraid of the 'A' word - neither should you be. Your question is totally legitimate.

Given your questions, suggesting lots of doubt, I wonder why you are persisting with a search for an Epsilon. Whilst no-one has bought one and found it to be a lemon, it does have Super High Holding Power (along with Rocna, Spade and Excel) - which suggests it has acceptable hold, the fact you cannot easily buy a galvanised version would prompt me to look at alternatives - there are a decent number of reliable options.. You should not have need to be inconvenienced in buying an anchor - if its any good it should be on shelves

I went to the Sydney International Boat Show, early in August this year - and saw not one Epsilon - and I did specifically look.

Kobra is cheap and gets decent reviews (I question the strength of the shank), Rocna are widely accepted (but collect mud and weed), Spade have steller performance but are both expensive and have appaling galvanising - all proving that anchors are a compromise

But why not the local hero - The Knox Anchor or if you fancy supporting the war effort look at the 'made in Ukraine' - Viking and opt for the Viking 10, which has the performance of its 15kg peers (and highly rated on the Panope spread sheets). In terms of it performance as an anchor it is streets ahead of its nearest 'competitor' and significantly better than all the rest. If you don't like the ideas of a roll bar then Viking's new sibling, Odin, would be an option but they will not be in full sales mode till 2025.

I understand that their, Viking, website is a bit of a disaster - simply contact them by email for clarity. But as I say - there are pretty of acceptable options.



Jonathan

 

[Neeves]

If you anchor frequently and can comfortably manage the 16 kg then this would be my choice. You will be able to safely anchor in a wider range of substrates and cope with shorter scopes than would be required with the smaller anchor. If you ever experience very strong conditions you will also likely be glad that you had chosen an anchor with close to 60% more maximum holding power (holding power is almost proportional to anchor weight when comparing models of the same design and construction material).

I'm not sure why Noelex implies that doubling weight doubles hold. Anchors 'work' on the basis of design and surface area. If you double weight you do not double surface area. Based on testing other anchors an increase of 60% in weight might increase hold by about 30%, maybe less (as there is a need to increase strength, more steel, in proportion to the increased stresses (for example on the shank).

Doubling weight will double volume, not the working surface area - if you are not changing design perameters.

However I am sure Noelex will be able to substantiate his ideas.

Jonathan

 

[doug748]

Dangerous territory I know, but I was hoping for some advice and/or information on the subject of the A-word...

It's for a 34ft AWB of about 5T displacement and a fair bit of windage (high topsides and cockpit enclosure). I'm minded to go Epsilon, but should it be 10 or 16 Kg? The sizing guide at

https://dkutenx65dka0.cloudfront.net/cms/PDFs/841284841285SIZING.pdf

seems a bit vague. I have an electric windlass and 8 mm chain so the only real downside of the larger version is the extra 6 Kg on the bow - irrelevant in practical terms?

I also see from the Lewmar website that only stainless models (with associated comedy price tags) seem to be currently available. Some retailers still seem to have galvanised ones in stock so I think I could track one down, but maybe there's a reason why they have apparently been discontinued?

And finally - I can only find a sizing template for the 6 Kg model on the website - if anyone happens to know where I could find a 10/16 Kg one that would be very handy.

Thanks in advance!

As you say almost no downside to the 16kg model.

However, if you are in the mood for compromise, Jimmy Green are offering 2nd grade Sarca Excels 12.5kg at a good discount:

Clearance Sarca Excel Anchor - Size 2 - 30% OFF

These are well regarded anchors and come out above Epsilons in a number of tests - tho I have an Epsilon myself and have no problem with it.

.

 

[noelex]

Based on testing other anchors an increase of 60% in weight might increase hold by about 30%,

Jonathan

You can look at work done by Professor Knox as just one example. His tests included various sizes of popular anchors.

His conclusion was:

"Within the limits of error, the holding power at a scope of five is proportional to the weight for these types of anchor.". So doubling the weight doubles the ultimate holding power.

For example, in his tests a 6 kg steel Spade had an ultimate holding capacity of 120 kgf and the 15 kg steel Spade had an ultimate holding capacity of 420 kgf (in the substrate where the tests were conducted).

https://static1.squarespace.com/sta...02103d72392/1489319853474/JHK+PBO+article.pdf

He even produced a graph showing the linear relationship between the ultimate holding power and the anchor weight (assuming the same design and construction material).

https://static1.squarespace.com/static/5677c3c19cadb68edf5284f5/t/59fe95608165f5564abae59b/1509856649414/Practical-Boat-Owner-2002.

There is no contradictory evidence that I am aware of that shows "increase of 60% in weight might increase hold by about 30%". Perhaps you could provide links supporting this assertion.

 

[Neeves]

You can look at work done by Professor Knox as just one example. His tests included various sizes of popular anchors.

His conclusion was:

"Within the limits of error, the holding power at a scope of five is proportional to the weight for these types of anchor.". So doubling the weight doubles the ultimate holding power.

For example, in his tests a 6 kg steel Spade had an ultimate holding capacity of 120 kgf and the 15 kg steel Spade had an ultimate holding capacity of 420 kgf (in the substrate where the tests were conducted).

https://static1.squarespace.com/sta...02103d72392/1489319853474/JHK+PBO+article.pdf

He even produced a graph showing the linear relationship between the ultimate holding power and the anchor weight (assuming the same design and construction material).

https://static1.squarespace.com/static/5677c3c19cadb68edf5284f5/t/59fe95608165f5564abae59b/1509856649414/Practical-Boat-Owner-2002.

There is no contradictory evidence that I am aware of that shows "increase of 60% in weight might increase hold by about 30%". Perhaps you could provide links supporting this assertion.

It was you that said an increase of 6kg from 10kg to 16kg would offer a 60% increase in hold. 60% increase in weight will not result in a 60% increase in hold. A 60% increase in surface area will increase hold, a bit less than 60%, but the weight will increase much more than 60%.

You are now saying that an increase in weight of 60% will increase hold by 30% which is a decent rule of thumb, but I'd work to a 25% increase of hold to a 60% increase in weight.

Because weight increases by ^3 and surface area increases ^2 the relationship is not linear and having two point on a graph cannot be extrapolated as you suggest.

I am happy to accept that Epsilon, being a SHHP anchor and will have been tested against another SHHP anchor (and has to be shown to be at least equal in hold to the comparitator) that a 15/16kg Epsilon will have a hold of about 2,000kg in sand (which is the sort of seabed most would prefer to anchor). This roughly equals the hold found by many testers for a 15kg Rocna, Supreme, Excel, Spade. This probably gives a safety factor of about 3 - which is not wildly outside industry norms, (4:1 for chain, 5:1 for shackles).

Hold is not only the the impact of changing surface area but of design and there is insufficient evidence to be dogmatic over your, new idea, of 30% and my 25%.

But when you move down to the 5kg or upto 30kg models - you are extrapolating to much and I err very much on the side of caution and your 30% is, to my mind, too optimistic. There are exceptions and a Fortress being 'two dimensional' will differ from, say, a ballasted Epsilon which is 'three dimensional'.

Jonathan

Maybe I misunderstand.....

Professor Knox defining that the hold of a 15kg Spade is 420kg - lacks any credibility, in any seabed except maybe custard (or soupy mud in Chesapeake Bay). 420kg is well within the real life tension in the rode for a 15kg anchor, on say a 40' yacht - and no-one would buy an anchor of 15kg if its hold was a derisory 420kg. Spade has been tested by a number of reputable organisations and its hold is around 2,000kg for a 15kg version in sand (which was the basis of the seabed, sand used by Professor Knox..

You suggest Prof Knox found a 6kg Spade had a hold of 120kg and a 15kg Spade had hold of 420kg. So the bigger anchor has a hold 3.75 times that of the smaller one (though the hold or both anchors is .... a joke).

So now the situation, according to your email - that increasing the weight by 2.5 times, for Spade, allows the hold to increase by 3.75 times....??? - which makes me wonder where you got your 60%. This contradicts the concept that anchor performance is a function of surface area, not weight.

A 6kg Spade anchor has a surface area of 400cm^2 and the 15kg Spade 800cm^2 - according to the data you provide a 2 times surface area results in a 3.75 times increase in hold - though reiterating - the hold data is a joke.

 

[down...2 greens]

Thanks everyone, excellent food for thought and some very useful suggestions in there as well.

Cheers.

 

[webcraft]

Depending on the substrate, area can be more important than weight. (See 'Fortress')

A 10kg sSpade will hold your boat perfectly in most weather and bottoms, but in soupy mud area is more important than weight.

 

[noelex]

You are now saying that an increase in weight of 60% will increase hold by 30% which is a decent rule of thumb, but I'd work to a 25% increase of hold to a 60% increase in weight.

No, I am not saying this. It is your assertion and your assertion alone that increasing the anchor weight by 60% increases the hold by 30%. See the quote below from post #5.

Based on testing other anchors an increase of 60% in weight might increase hold by about 30%, maybe less (as there is a need to increase strength, more steel, in proportion to the increased stresses (for example on the shank).

Jonathan

I am not sure why you have changed your mind and now feel the right answer is 25% but both numbers are wrong.

The results from Professor Knox show "Within the limits of error, the holding power at a scope of five is proportional to the weight for these types of anchor." This means a 60% increase in weight will result in roughly a 60% increase in holding power.

You cannot just look at the surface area. Factors such the depth of bury make a significant difference to an anchor’s holding power. If only surface area was important we would all be using anchors such as the Manson Boss with its enormous fluke surface area. The Manson Boss is an OK anchor, but not as accomplished as other anchor models with a much smaller surface area, such as the steel Spade.

You still have not posted any evidence to support your claim that increasing the anchor size by 60% results in a 30% or now 25% increase in the ultimate holding power (assuming the design remains the same).

 

[noelex]

So now the situation, according to your email - that increasing the weight by 2.5 times, for Spade, allows the hold to increase by 3.75 times....??? - which makes me wonder where you got your 60%.

The OP is considering an Epsilon anchor of 10kg or 16kg. The 16kg model is 60% heavier than the 10kg model and therefore on average can be expected to have around 60% more ultimate holding ability.

The Spade was just one anchor tested. Professor Knox also measured the holding power of several sizes of Delta, CQR, Bruce, Bruce copy, Manson Supreme and Rocna anchors to form his conclusion that an anchor’s holding power is proportional to its weight for the same design of anchor (in other words, doubling the weight will double the anchor’s holding power), but you are correct that the Spade and many of the other anchors increased in holding power more than this simple formula suggests.

If anything, his conclusion was conservative given the experimental results he measured. You can read the papers he published in the links I posted in post #7.

 

[NormanS]

Am I correct in my recollection that Prof Knox did his tests on a sandy beach, with the tide out, and using a steady and continuous pull?
If so, his results for actual anchoring are largely meaningless.

 

[Zing]

The OP is considering an Epsilon anchor of 10kg or 16kg. The 16kg model is 60% heavier than the 10kg model and therefore on average can be expected to have around 60% more ultimate holding ability.

The Spade was just one anchor tested. Professor Knox also measured the holding power of several sizes of Delta, CQR, Bruce, Bruce copy, Manson Supreme and Rocna anchors to form his conclusion that an anchor’s holding power is proportional to its weight for the same design of anchor (in other words, doubling the weight will double the anchor’s holding power), but you are correct that the Spade and many of the other anchors increased in holding power more than this simple formula suggests.

If anything, his conclusion was conservative given the experimental results he measured. You can read the papers he published in the links I posted in post #7.

Just as an aside comment. It’s a little misleading. I think what he should have said is holding power for a given anchor design is (close to) proportional to surface area as it’s the surface area that gives the holding power, not weight.

 

[noelex]

Just as an aside comment. It’s a little misleading. I think what he should have said is holding power for a given anchor design is proportional to surface area as it’s the surface area that gives the holding power, not weight.

Holding power is not just dependent on surface area. Other factors such as the maximum depth of bury play a significant role.

All the evidence supports the view that the holding power for a particular design is roughly proportional to the weight of the anchor. Professor Knox has done the most work in this area. Most anchor tests do not include anchors of the same design but with different weights, but this is exactly what he did to establish the relationship between holding power and anchor size. His conclusion:
"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).

There is other evidence. You can look at results published by the anchor manufacturers. This is old data from Rocna, showing the anchor manufacturer expects a 20 kg anchor to have double the holding power of the 10 kg model. The 44 lb Rocna model holds 1122 lbs in this substrate the 22 lb model holds 1/2 of this or 561 lbs:


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

Or you can look at the Vryhof results from the tests. These are for very large anchors. Their results indicate doubling the anchor size increases the hold by 92%. Their formula for hold versus anchor weight is:

Ultimate holding capacity = A*(W)0.92 where W is weight and A is constant based on the anchor design and substrate.

 

[Zing]

Holding power is not just dependent on surface area. Other factors such as the maximum depth of bury play a significant role.

All the evidence supports the view that the holding power for a particular design is roughly proportional to the weight of the anchor. Professor Knox has done the most work in this area. Most anchor tests do not include anchors of the same design but with different weights, but this is exactly what he did to establish the relationship between holding power and anchor size.

There is other evidence. You can look at results published by the anchor manufacturers. This is old data from Rocna, showing the anchor manufacturer expects a 20 kg anchor to have double the holding power of the 10 kg model. The 44 lb Rocna model holds 1122 lbs in this substrate the 22 lb model holds 1/2 of this or 561 lbs:


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

Or you can look at the Vryhof results from the tests. These are for very large anchors. Their results indicate doubling the anchor size increases the hold by 92%. Their formula for hold versus anchor weight is:

Ultimate holding capacity = A*(W)0.92 where W is weight and A is constant based on the anchor design and substrate.

I wonder if those figures in the Rocna formula derived from Vryhof or were they empirically calculated?

I can’t see how it would be much different from what I suggested. i.e. if you double the surface area you then double the load capacity and double (approximately) the weight. This is a principle of foundation design for example and anchors work in a similar way.

I appreciate a heavier anchor with the same area will dig deeper, which is an argument for small, heavy anchors, yet we know big and relatively light ones hold better, like the Viking.

 

[Tranona]

I wonder if those figures in the Rocna formula derived from Vryhof or were they empirically calculated?

I can’t see how it would be much different from what I suggested. i.e. if you double the surface area you then double the load capacity and double (approximately) the weight. This is a principle of foundation design for example and anchors work in a similar way.

I appreciate a heavier anchor with the same area will dig deeper, which is an argument for small, heavy anchors, yet we know big and relatively light ones hold better, like the Viking.

There is probably a strong correlation between weight and size, but anchors are traditionally sold by weight because it is easy.

This does not mean it is weight that provides the "hold" as in those instances where the same anchor is made in both steel and aluminium (which is roughly half the weight) the hold is the same.

Weight is so firmly bedded in the consciousness because anchors are sold by weight it is easy to be seduced by weight being the determinant of performance - ignoring the fact that lighter anchors of different design with more effective and larger flukes outperform "traditional" heavy anchors.

 

[Neeves]

Am I correct in my recollection that Prof Knox did his tests on a sandy beach, with the tide out, and using a steady and continuous pull?
If so, his results for actual anchoring are largely meaningless.

He did his tests in the inter tidal zone in pools, with sandy bottoms, when the tide had retreated and the pools provided his test bed. I forget the exact location, but its in the articles, but was on the south side of the River Forth estuary.

Given the results of the hold developed with a 15 kg Spade - you are correct - his tests are meaningless. Spade in a clean sand seabed has been consistently tested for hold by a number of test teams completely independent of each other at 'about' 2,000kg - suggesting that the same anchor has a hold of less than 400kg is a joke and meaningless. Obviously from the very low hold data he developed the sand was unconsolidated and behaved more like soupy mud - and coincidentally the holds he developed for Spade are similar to those developed on Spade in Fortress' Chesapeake mud tests. The other problem with the tests is that he used different rodes and did not test the anchors against each other at the same time in the same sand.

He and his wife devoted much time to the measurements and I have no doubt the measurements are accurate and reflect the conditions for each series of pulls - but the seabeds are simply not typical. I note that Prof Knox published his work in 2002 (and must have done the actual tests much earlier), 4 years before the widely read 2006 West Marine/YM tests - he was not to know his results were questionable.

If you look at the Spade data their small anchors increase weight in proportional to surface area, as the anchors get bigger the weight increases more than surface area - because the anchors need to increase in strength as they get bigger, particularly the shank.

Jonathan

 

[Neeves]

Holding power is not just dependent on surface area. Other factors such as the maximum depth of bury play a significant role.

All the evidence supports the view that the holding power for a particular design is roughly proportional to the weight of the anchor. Professor Knox has done the most work in this area. Most anchor tests do not include anchors of the same design but with different weights, but this is exactly what he did to establish the relationship between holding power and anchor size. His conclusion:
"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).

There is other evidence. You can look at results published by the anchor manufacturers. This is old data from Rocna, showing the anchor manufacturer expects a 20 kg anchor to have double the holding power of the 10 kg model. The 44 lb Rocna model holds 1122 lbs in this substrate the 22 lb model holds 1/2 of this or 561 lbs:


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

Or you can look at the Vryhof results from the tests. These are for very large anchors. Their results indicate doubling the anchor size increases the hold by 92%. Their formula for hold versus anchor weight is:

Ultimate holding capacity = A*(W)0.92 where W is weight and A is constant based on the anchor design and substrate.

This is another example of questionable data.

A 15kg Rocna has been consistently tested to hold 2,000kg in clean sand, in common with Spade, Excel, Epsilon, and Supreme - all of which have been extensively tested and tested against each other at the same time in the same seabed by Voile, YM and Lloyds (or another Classification Society).

To calculate hold, as in the post for 841lbs for a 33lb Rocna anchor means the manufacturer is erring on the side of caution by a factor of at least 2. The data is meaningless as a basis for a discussion on the importance, or otherwise, of design, surface area or weight.

The only consistent and reliable data points are to take an average of the holds developed on a series of anchors in a series of tests in 'similar' sea beds. I know of 2 Voile tests, the one WM/YM tests. Most tests are conducted on 15kg anchors, because they are a common size and relatively easy to handle when testing. However this only produces a comparison of design, not the impact of surface area or weight. As Spade, Excel, Epsilon, Rocna, Supreme, Ultra (and the aluminium versions where relevant) (apologies if I missed some) are all SHHP anchors then each of these designs, different though they maybe, provide similar (2,000kg for a 15kg anchor) and reliable hold.

I'd add Viking/Odin to the list based on my tests - but my tests totally lack the rigour of Lloyds, Voile, YM. If we add to the SHHP anchors then the HHP anchors, 15kg anchor has a hold of 1,000kg we have Delta, CQR, Bruce (and based on my tests and the opinion of a researcher from the US Navy) Mantus.

Until someone tests a 30kg version of these same anchors then sadly, despite it being fun, discussion on whether weight or surface area are the determinants of performance - are academic.

You cannot use the Panope tests - because, important though it may be, he never measured hold. The Panope tests give a subjective, one man's, view. It has some value but omits a critical perameter. You can add in your own value/importance for 'hold' to the Panope spread sheet - but it will not change the location on the spread sheet for Spade, Excel, Epsilon, Rocna, Supreme, Ultra (Viking) - as they all develop the same hold.

Jonathan

 

[noelex]

Jonathan, have a look at the estimated holding power listed on the Viking website. If any figures will convince you these should, given your close association.

The increase in weight from the smallest Viking 5 model to the next size up is 53%, but the estimated holding power jumps by 80%.

The next model up increases in weight by 83%, but the estimated holding power increases by 111%.

The next model up increases in weight by 33%, but the estimated holding power increases by 37%.

The next model up increases in weight by 69%, but the estimated holding power increases by 23%.

The next model up increases in weight by 28% but the estimated holding power increases by 41%.

If we look at the total Viking range the largest anchor is 8 times heavier than the smallest anchor, but the larger anchor has 9 times the estimated holding ability according to the manufacturer.

Frankly I am skeptical of this manufacturer’s figures, particularly as there is no reference to the type of substrate or how these estimates were made, but nevertheless this manufacturer (like the other anchor manufacturers) believes that if you increase in anchor size by doubling the weight the estimated holding power doubles or more than doubles.

Do you have any data or test results or anything at all that supports your contention that if an anchor’s weight is increased by 60% the holding power will only increase by 30% or 25%. If so, could you please post a link.