Why has the market not embraced alloy anchors?

[Zing]

In poor holding there is no evidence that a bigger anchor will be any better than a smaller one.

You can't surely intend to say that? The reason why the Fortress works well in poor holding is because it is very big. Bigger area = bigger grip, all else being equal.

 

[geem]

+1

In good holding that 15kg Rocna should be good for about 2t hold. I, and I am sure Vyv (and most others), never, ever expect the tension in our rode to be 2t. In poor holding there is no evidence that a bigger anchor will be any better than a smaller one. In thin mud you would be better off with an anchor better suited to thin mud as tests suggest you would need a really big anchor, in Vyv's case a 45kg steel anchor, to develop dependable hold.

Strangely - for all the doubters - aluminium alloy, Fortress (slightly oversized), offers the best hold in thin mud.

If you were to use a steel 'equivalent' you would need a Danforth of around 20/25kg, rather than a Fortress of 8/12kg - I know which I would rather deploy. The Fortress might be more expensive - but to me its worth it (it has nothing to do with 'saving' weight (though cumulatively it helps) - its simply easier and safer).

It is slightly contradictory that without exception people say alloy anchors are more (and they imply 'too') expensive but go off and buy an anchor at least one size, sometime 2 sizes (and in the extreme - double the weight) of the anchor recommended. Oddly prices rise with size. And as Vyv says:

"I suggest you have indulged in overkill for no useful purpose."

That overindulgence cost extra money - for no useful purpose

One day someone will produce categorical and robust evidence that a larger anchor, than that recommended, does offer available and useful extra hold - until that happens - its all about gut feel.

But a Rocna, or Excel or Spade is better 'by design' not weight - bigger is not better, better (design) is betterer.

And if its not weight, why not aluminium alloy - if it is available in a betterer design - noting if you read the complete thread - Spade appear to have upgraded the shank of the alloy Spade. They have been listening - if slow to react.

Jonathan

The Spade seems to get its abilty to set quickly from the lead weighted tip placing a high proportion of its weight over the pointy end. Its not a particularly large anchor for its weight. Compare it to a Mantus and its tiny. If you were to replace the lead with tungsten (50% heavier than lead) the anchor would still be the same size but it would have even more weight over the tip. I suspect this would be a good thing rather than a bad thing since more weight over the sharp end would aid penetration into a difficult seabed. Once set I dont think it matters if the anchor is made of lightweight material. The shape keeps it digging once its set. Its just that initial set that can be difficult in less than perfect bottoms.
How do you think the aluminium version of the same size Spade would perform compared to the tungsten tipped Spade?

 

[grumpy_o_g]

You can't surely intend to say that? The reason why the Fortress works well in poor holding is because it is very big. Bigger area = bigger grip, all else being equal.

Thank you - I was starting wonder where everyone was anchoring. My worry about holding (and I sail lots of different boats as crew so lots of different set ups) is about the bottom (the holding ground) more than anything else. I do check the cleat(s) and fairleads and the chain/rode and shackles if I can (and I'm really nervous on a new to me boat if i can't see if the bitter end has been secured) but I've never worried about the anchor breaking, even when using a Fortress in mud.

As for alloy anchors the choice of alloys would be to reduce corrosion, reduce weight, improve cosmetics, etc. You wouldn't gain anything in terms of ease of manufacture nor from cost). So Aluminium alloys to reduce weight - and they already exist of course. Stainless steel alloys to improve looks and corrosion resistance - but they also exist. I'm not aware of a titanium alloy anchor but it would be VERY expensive.

 

[Neeves]

I think you, completely, misunderstand.

The hold of an anchor is solely dependent on the windage of the yacht and tension in the rode. It does not matter how big your anchor is the hold will be the same for the same yacht, same tension. Being bigger does not magically allow the bigger anchor to develop more hold.

In a good holding bottom a 15kg Rocna, a 15kg steel Excel or a 8kg alloy Excel, or any other NG anchor has an ultimate hold of around 2t. On a 35' yacht the tension in your chain might be around 500/750kg - max - nowhere near the ultimate hold of the anchor. If you were to measure the actual hold with a load cell it might be say 750kg (which is pretty excessive). If you have an anchor, same design, twice the size the hold will still be 750kg. The bigger anchor might have an ultimate hold of 3t - but unless the wind develops to, say 100 knots, you will never, ever approach that ultimate limit.

Swap the NG anchor, say a Rocna, for a Fortress and the hold developed will be exactly the same, 750kg - the fact its ultimate hold is higher is irrelevant.

In thin soupy mud tests suggest, because the hold is poor, you do need greater area (but its design not area that allows Fortress to excel in thin soupy mud) (a Danforth off the same area will hold less) - but there is no evidence you can extrapolate this to a good holding bottom - simply because you can develop the 'required' hold with a smaller anchor in a good holding bottom - the shear strength of the seabed is sufficient for a smaller anchor to be reliable.

Now - there maybe other seabeds where a larger anchor is 'better' than a smaller one - but no-one has come up with any evidence, at all, to support the idea. As, I think GHA said, its like speaking to a talking clock. Lots of gut feel - not a shred of evidence. Repeatedly ask why a big anchor will hold at short scope - and you will not get an answer (but the same nonsense is continually repeated). Ask why a big anchor is safer, or better, and no-one has any evidence.

Now it could be magic that tensioning your rode to 500kg on a recommended sized anchor 'only' develops 500kg of hold but on an oversized anchor develops a hold of 750kg - but I'd like to see evidence and I'd like to see it quantified - currently people seem happy to spend extra for an illusion of security, but unhappy to spend the same amount on an alloy anchor (for a variety of reasons)


On big anchors - because the bigger anchor, under the same tension, will not dive as deeply as a smaller anchor the bigger anchor will be in a part of the seabed with a lower shear strength, compared to the smaller model. Shear strength increases with the square of depth. Additionally most NG anchors bury chain when they set. Take Noelex advise and dive on your anchor and you will find that as the chain moves the anchor twitches. Others have noticed this. A twitching anchor will reduce the shear strength of the seabed in immediate proximity to the anchor. However an anchor that has dived deeply and buried more chain twitches less than a shallow set anchor

Which might be more reliable a deep set anchor or a shallow set anchor? Which might be more reliable an anchor with buried chain or one whose chain is thrashing the seabed, and shackle.

People on this forum have identified that an anchor twitches with chain movement. People on this forum have identified that some chain can be buried (and I've checked the level of twitching for shallow set and deep set anchors)


So tell me - unless you exceed the ultimate hold, 2t, of a recommended sized (15kg) anchor for a 35' yacht, please explain why a 30kg anchor, same design, is better.

And 'it stands to reason' cuts no ice with me.

Jonathan

 

[Neeves]

I'm not aware of a titanium alloy anchor but it would be VERY expensive.

I can assure you they do exist

Jonathan

 

[thinwater]

I think the whole point of threads like this is to boost forum traffic:ambivalence:! That said...

Steel Anchor = 35 pounds.
3/8" Chain = 350-500 pounds.

Are we missing the forest for the trees? I think so. The difference in anchor weight is that of 10-15 feet of chain. Yes, a lighter anchor is easier to handle as a kedge, but on a roller, not so much. Even hoisting, by the time you add 20 feet of chain, we're probably only saving 20% of that. Only 2-3% of total ground tackle weight savings. Small change.

So the real question is, what rode is used with a lightweight anchor? Not chain. In the case of a Fortress kedge, I would argue that no chain is a valid alternative, and I've done enough anchor testing to be pretty sure of that (I used a Fortress to secure the boat while dragging other anchors, hundreds of times). A chafe resistant leader is an option.

As for the main anchor, I will leave the topic open. To start, I've used both all-chain and nearly-all-rope both extensively. I believe which is better depends on both the boat and the location.

 

[Neeves]

Too simplistic.

We carry 4 anchors, we save around 35kg, were we to carry those same anchors in steel. Our rode weighs 0.8kg/m. Our weight saving is over 50% of our rode (total rode 75m (plus 15m (same) chain on spare rode)

3 anchors are 8kg, one anchor 12kg, our cat 38' x 7t (normal big windage).

Why 4 anchors, all of which can be used as the primary.

We might lose an anchor

Anchorages encompasses good clean sand, thin mud, weed and stones.

Weather might cover a Storm warning once a month and a Gale warning once per week.

We, including my wife (who is rather diminutive) can hand deploy, and retrieve, easily, any of the anchors from the bow or dinghy (hung on transom - chain of spare rode, 12kg, in milk crate).

A 3 month cruise might cover 3,000nm and anchoring every night, unless we are on overnight passage.

Money, for aluminium alloy, is not a major issue - anchors are cheap insurance (we also insure with Pants). It is important we can both handle the ground tackle in any situation.

We have lost an anchor, once (retrieved later), we have had windlass failure (solenoids sticking), we have lent anchors, twice in 20 years, visiting yachts - did not carry any spare anchors (bizarre). We do hand deploy (our rivers are exclusively mud). We do anchor sometime in a 'V' (especially for exposed anchorages, that face the Southern Ocean, and for those Storm warnings).

We could carry heavier chain, we could use steel anchors - aluminium anchors are cheaper that chiropractors and offer the exact same performance. The nearest chiropractor to Port Davey, SW Tasmania - is a long way when you need one

Jonathan

 

[NormanS]

Jonathan, I don't want to reproduce the whole of your long post #124, but at some point in it you declare that a Danforth of the same area as a Fortress, will develop a lesser hold. Having firsthand experience of both these anchors, I can't imagine why this should be so, and certainly not in my experience. OK, the Fortress is finer finished than the Danforth, and is arguably more eye-catching, but does the mud care? In fact, the Danforth has a slight initial advantage, simply because it's heavier, therefore the blade tips will be slightly keener to dig in. Both anchors, once buried, will have exactly the same holding capacity.

As you know, I have changed from a Danforth to a Fortress, but that was simply for ease of handling on deck or dinghy, and nothing to do with holding capacity.

 

[NormanS]

The Spade seems to get its abilty to set quickly from the lead weighted tip placing a high proportion of its weight over the pointy end. Its not a particularly large anchor for its weight. Compare it to a Mantus and its tiny. If you were to replace the lead with tungsten (50% heavier than lead) the anchor would still be the same size but it would have even more weight over the tip. I suspect this would be a good thing rather than a bad thing since more weight over the sharp end would aid penetration into a difficult seabed. Once set I dont think it matters if the anchor is made of lightweight material. The shape keeps it digging once its set. Its just that initial set that can be difficult in less than perfect bottoms.
How do you think the aluminium version of the same size Spade would perform compared to the tungsten tipped Spade?

If you really want an anchor where you are guaranteed to have 50% of its total weight pressing directly down on the tip, get a









Fisherman.

 

[Neeves]

Jonathan, I don't want to reproduce the whole of your long post #124, but at some point in it you declare that a Danforth of the same area as a Fortress, will develop a lesser hold. Having firsthand experience of both these anchors, I can't imagine why this should be so, and certainly not in my experience. OK, the Fortress is finer finished than the Danforth, and is arguably more eye-catching, but does the mud care? In fact, the Danforth has a slight initial advantage, simply because it's heavier, therefore the blade tips will be slightly keener to dig in. Both anchors, once buried, will have exactly the same holding capacity.

As you know, I have changed from a Danforth to a Fortress, but that was simply for ease of handling on deck or dinghy, and nothing to do with holding capacity.

You are correct - it about surface area - but also how that area is presented to the seabed and the consistency of the seabed.

I only quote the Fortress Chesapeake soft mud tests - and that is the result they achieved. I was privy to all the test data and don't think they tried to influence the results. The 2 anchors are not identical, Fortress is 'better' engineered. Danforth, of course, cannot alter the fluke angle - which is critical, factorially so, in soft seabeds (and in very hard seabeds). It is not only fluke area - but how the fluke is presented to the seabed.

Hold is a function of sine of angle of fluke/seabed.

But a large angle, Fortress 45 degrees, may not engage at all in a medium hard (common sand) seabed and would be a complete disaster in a very hard seabed. 30 degrees is a universal angle, but is not optimised for soft mud. In a very hard seabed the acknowledged remedy is sharpen the toe and use a shallow angle (but the reduced angle compromise hold (that sine of angle).

To exaggerate:

A fluke that is horizontal to the seabed will cut through like a knife in butter. A fluke at 90 degrees to the seabed will be like a brick wall - now imagine angles in between.

So a fluke with a low angle to the seabed will have low hold, but a fluke with a high angle might simply not penetrate and just bounce along the surface.

Oil rig anchors can have variable fluke angles. Danforth can be made with specific fluke angles. Only Fortress and Supermax offer us the leisure sailor the opportunity to alter the angle. Most of our anchors take the middle ground - and are generally acceptable.

Is this too brief?

Jonathan

edit - in good clean sand both fluke would be at 30 degrees and I might expect the Fortress to have a higher hold, but I don't think you (or I) would detect the difference. In softer seabeds the Fortress would have 'increased' hold - if you altered the fluke angle - and you would notice (or you would if the wind got up!) But in very thin mud even a Fortress would not offer a decent night's sleep -unless it was oversized (next size up). Area does count. This is why we now carry a FX16 at 30 degrees for sand and a FX37 set at 45 degrees for thin mud (and we have a number of anchorages where the mud is thin, or soupy).

 

[dom]

The hold of an anchor is solely dependent on the windage of the yacht and tension in the rode............

And 'it stands to reason' cuts no ice with me.

Jonathan

Good post. It's refreshing to see someone carefully explore the boundary between science and folklore in an area so dominated by the latter. :encouragement:

 

[vyv_cox]

If you really want an anchor where you are guaranteed to have 50% of its total weight pressing directly down on the tip, get a









Fisherman.

I don't think that is actually the case. The Spade has 50 % of its weight acting on the tip. I am not sure there is a definitive design of a Fisherman anchor but most that I see have a heavy shank that lies on the bottom, whereas the thickness of metal at the fluke is considerably less. My guess is that there is more weight at the shackle than at the tip. Which does not stop it from penetrating weed quite effectively.

 

[geem]

If you really want an anchor where you are guaranteed to have 50% of its total weight pressing directly down on the tip, get a

I dont need to, I have a Spade. It already has that. A Fisherman is fine in rock but carp in just about anything else. Good over here on Hurricane season to hook in to the mangroves when its blowing 100kts but otherwise rarely seen or needed

 

[NormanS]

You are correct - it about surface area - but also how that area is presented to the seabed and the consistency of the seabed.

I only quote the Fortress Chesapeake soft mud tests - and that is the result they achieved. I was privy to all the test data and don't think they tried to influence the results. The 2 anchors are not identical, Fortress is 'better' engineered. Danforth, of course, cannot alter the fluke angle - which is critical, factorially so, in soft seabeds (and in very hard seabeds). It is not only fluke area - but how the fluke is presented to the seabed.

Hold is a function of sine of angle of fluke/seabed.

But a large angle, Fortress 45 degrees, may not engage at all in a medium hard (common sand) seabed and would be a complete disaster in a very hard seabed. 30 degrees is a universal angle, but is not optimised for soft mud. In a very hard seabed the acknowledged remedy is sharpen the toe and use a shallow angle (but the reduced angle compromise hold (that sine of angle).

To exaggerate:

A fluke that is horizontal to the seabed will cut through like a knife in butter. A fluke at 90 degrees to the seabed will be like a brick wall - now imagine angles in between.

So a fluke with a low angle to the seabed will have low hold, but a fluke with a high angle might simply not penetrate and just bounce along the surface.

Oil rig anchors can have variable fluke angles. Danforth can be made with specific fluke angles. Only Fortress and Supermax offer us the leisure sailor the opportunity to alter the angle. Most of our anchors take the middle ground - and are generally acceptable.

Is this too brief?

Jonathan

edit - in good clean sand both fluke would be at 30 degrees and I might expect the Fortress to have a higher hold, but I don't think you (or I) would detect the difference. In softer seabeds the Fortress would have 'increased' hold - if you altered the fluke angle - and you would notice (or you would if the wind got up!) But in very thin mud even a Fortress would not offer a decent night's sleep -unless it was oversized (next size up). Area does count. This is why we now carry a FX16 at 30 degrees for sand and a FX37 set at 45 degrees for thin mud (and we have a number of anchorages where the mud is thin, or soupy).

My experience of really soft mud doesn't include that of Chesapeake Bay. We do have anchorages which have soft mud, although I'm not sure how you quantify the "softness". My own experience suggests that lurking just beneath the surface of our soft mud, there are firmer and firmer muds. Once the anchor has fallen through the real soupy stuff, it has to be able to get a proper grip in the real mud further down. For that reason, if not for downright lazyness, I have never even contemplated changing the angle of the flukes. Maybe when the next generation of New Generation anchors is unveiled, we'll get anchors which automatically change their fluke angles to suit the conditions in which they find themselves being required to perform? In the meantime, I am content that in changing from a Danforth to a Fortress of approximately identical dimensions, the hold is also identical. Frankly, I cannot see how it could be otherwise.

 

[NormanS]

Good post. It's refreshing to see someone carefully explore the boundary between science and folklore in an area so dominated by the latter. :encouragement:

That demonstrates the difference between "hold" and "potential hold".

 

[Neeves]

To improve a Spade

Simple high tensile steel shank, or duplex stainless cut from plate (they seem to have already converted to a 7075 alloy for the aluminium version).

Sharpen up the toe of all versions

Seal the lead in the toe of the aluminium version, with a welded plate over the pocket/ballast chamber.

Cast steel into the toe of the steel version - it is inevitable steel anchors will need to be regalvanised - though in America (I understand) they have recently offered a old for new replacement - which seems too good to be true.

Tungsten in the toe - a sharper toe would have a similar effect and tungsten a devil to cast

Great design, largely stood the test of time, ripe for some (more) improvements.

Jonathan

 

[Neeves]

My experience of really soft mud doesn't include that of Chesapeake Bay. We do have anchorages which have soft mud, although I'm not sure how you quantify the "softness". My own experience suggests that lurking just beneath the surface of our soft mud, there are firmer and firmer muds. Once the anchor has fallen through the real soupy stuff, it has to be able to get a proper grip in the real mud further down. For that reason, if not for downright lazyness, I have never even contemplated changing the angle of the flukes. Maybe when the next generation of New Generation anchors is unveiled, we'll get anchors which automatically change their fluke angles to suit the conditions in which they find themselves being required to perform? In the meantime, I am content that in changing from a Danforth to a Fortress of approximately identical dimensions, the hold is also identical. Frankly, I cannot see how it could be otherwise.

Sorry Norman, Your query was valid, I was a bit lax with the detail in my post.

We have anchored twice where a Fortress at 45 degrees was the only sensible answer. The first time we did not have the Fortress deployed, unforecast frontal system, and were driven slowly backwards in winds, measured at the masthead, of 55 knots. We had the engines running, in neutral, but the Excel eventually bit - as we were driven out of the mud into firmer seabed. The second time the Excel would not hold the tension under power setting and as a Storm was forecast we set the Fortress at 45 degrees - and the wind did not materialise.

I too cannot be bothered with changing the fluke angle - and we now have 2 x Fortress. I think the FX23, the size recommended for our cat, is too big for sand but too small for thin mud, hence FX16 (30 degrees) and FX37 (45 degrees).

Jonathan

 

[dom]

Somewhat tangentially: about 10 years ago I contacted Spade as their 20kg, while just within their selection criteria, seemed a bit light and I thought their 30kg would add a sensible safety margin.

Spade immediately advised 20kg, I was stuck on 30kg, they told me I knew more about racing than anchoring, I dithered! Their arguments included comments along the lines of Neeves that a better-set anchor would be preferable as conditions toughened, than a less well-set bigger one - the key being whether the fully-set anchor would be man enough for its ultimate job.

Unconvinced, I bought a 20kg for the main anchor, and a 30kg as a backup/switch-over in tougher conditions. Or as I suspected, the 20kg proved too tiddly.

10 years later the 20kg has never ever missed a beat, to my amazement and the amusement of Spade technicians.

Meanwhile, the 30kg sits in my garage as the back-up anchor is now an easier to stow Danforth :ambivalence:

 

[Zing]

I think you, completely, misunderstand.

The hold of an anchor is solely dependent on the windage of the yacht and tension in the rode. It does not matter how big your anchor is the hold will be the same for the same yacht, same tension. Being bigger does not magically allow the bigger anchor to develop more hold.....
....So tell me - unless you exceed the ultimate hold, 2t, of a recommended sized (15kg) anchor for a 35' yacht, please explain why a 30kg anchor, same design, is better.

And 'it stands to reason' cuts no ice with me.

Jonathan

It needs to be assumed that the rode strength and boat cleats are strong enough to cope with the loads imposed on them. That given, the holding power of a given design of anchor, which is properly dug in is proportional to its surface area. It is analogous to the foundation design for a building.

A different question is what force is exerted on that anchor and that basically depends on the wind strength and windage of the boat.

So, the circumstance when a bigger anchor is better is when the ground has not the strength to hold a given anchor and the boat drags, In this weaker ground a bigger anchor will hold it and prevent dragging. It is not relevant to consider when the ground's holding capacity is so good that it approaches the ground tackle's load limits as then a small anchor may be adequate.

There is no limit to how bad the ground can get and no guarantee of being certain you are anchored in optimally strong ground so a bigger anchor will always give you a bigger margin of safety against dragging.

 

[Neeves]

Tell that to the 'buy bigger' brigade!

Interestingly Spade's recommended sizes (of anchors v yacht length) are on the light side, compared with Manson, CMP/Rocna and Anchor Right. Despite the rhetoric of 'better hold' the NG anchor sizing charts and that of Delta/CQR and Bruce are as close to identical as possible. Only Spade suggest smaller anchors compared to the 'old gen' anchors.

Our 15kg steel Spade and 8kg alloy Spade are Spade's recommended sized anchors for a 38' cat. I forget how they designate the steel version (?80) but the aluminium alloy version is the A80.

Jonathan