Why has the market not embraced alloy anchors?

[JumbleDuck]

"it is important to note that we do not recommend the use of an aluminium anchor as a main anchor."

Shall we look at the whole quote?

2 – Does the aluminium SPADE have the same holding as the steel version of the same size?

Holding power of an anchor has very little relation to its weight. Holding power has a much closer relation to the size, and the shape, of the effective surface area of the anchor’s blade. Because each model of our anchors will have the same effective surface area, whether made of steel or of aluminium, each anchor will have the same holding power. Several independent tests, by nautical magazines have confirmed that our aluminium anchors hold with exactly the same power as the steel version of the same size although it is important to note that we do not recommend the use of an aluminium anchor as a main anchor.​

“This is true; the model in steel will dig in slightly more readily than the equivalent aluminium version. “

Oooh, let's look at the full version of that too

4 – Does the lighter weight of an aluminium SPADE mean that it will not penetrate as well as a steel version of the same size?

This is true; the model in steel will dig in slightly more readily than the equivalent aluminium version. However, due to its superior design (which gives 50% of the weight on the tip), an aluminium SPADE will have better penetration qualities than most other types of steel anchor of equivalent size (which, because of the materials, will be twice the weight of the aluminium SPADE). And we remind you that once set; the aluminium SPADE will have the same holding power as the steel SPADE. Both will be far superior to other types of anchor of equivalent size.​

I think Spade should be congratulated for this honestly when advertising their products

What they say is, to paraphrase, that the aluminium one holds exactly as well as the steel one, and penetrates almost as well. They do not explain why they don't recommend aluminium for the main anchor.

 

[moomba]

One would presume that aluminum anchors with galvanized or stainless steel chain in a marine environment could cause an issue.
https://www.bssa.org.uk/topics.php?article=89

Also I would presume that Aluminum would be more adverse to issue than harder steel.
Steel and Aluminum. Even with the possibility of corrosion, steel is harder than aluminum. Most spinnable tempers and alloys of aluminum dent, ding or scratch more easily as compared to steel. Steel is strong and less likely to warp, deform or bend under weight, force or heat.
https://www.wenzelmetalspinning.com/steel-vs-aluminum.html

 

[ghostlymoron]

I shudder at the thought of this!!

In the mid sixties. my Dad and I were members of Hullbridge YC on the River Crouch. I was around 10 years old.

One sunny mid-week afternoon, one of our fellow club members went out by himself, for a relaxing spot of therapeutic line fishing, just inside Clements Creek.

Lovely!!

For reasons he couldn't later explain, however, he decided to swing his anchor around his head with the intention of, in your words, "casting it".

I don't recall precisely how it happened, but things went horribly wrong.

The fluke of his anchor whacked him a direct hit in his right eye, before dropping just over the gunwale.

He lay down on the cockpit sole, by himself, covered in blood.

No vhf, no cell phone, and it was midweek, so it was several hours before he was eventually spotted, and rescued, by a passing boat.

He lost the eye.

Sadly, this is a 100% genuine story: please take extreme care.

In fact, personally, I can't think of even one compelling reason why I'd ever want to swing an anchor around my head.

I was just saying I could if I wished to emphasise how light it is not that I would actually consider doing it. I have swung it underarm and let it go.

 

[noelex]

JumbleDuck, without a windlass the aluminium Spade is an attractive option so I can understand your enthusiasm. I think this may be an excellent choice for your vessel and cruising ground. The aluminium Spade is a good anchor in a lightweight package. Ideal for your vessel.

However, everything on yacht is a compromise and I think you are deluding yourself if you do not recognise the quotes from Spade that indicate that even the manufacturer reluctantly acknowledges that the aluminium version has a performance trade off.

Personally, I am a little skeptical of manufacturer’s claims so I can perhaps sympathise with you dismissing their recommendation not to use the aluminium version as a primary anchor, but look at the results of the large independent 2009 anchor test, and the other evidence before making up your mind.

 

[CAPTAIN FANTASTIC]

Does anybody have any pictures of Aluminium Anchors that have been damaged in any way? (bent, deformed);

 

[moomba]

Does anybody have any pictures of Aluminium Anchors that have been damaged in any way? (bent, deformed);

It is well documented that Aluminum is more pliable and bends easier to hardened steel, one would assume that a trapped anchor under a rock or coral head being Aluminum may bend easier and potential snap , to that of a hardened steel anchor which potential will move the rock under heavy load
Interesting video series , watch it through
https://www.youtube.com/watch?v=WQeznHmxB9s

 

[JumbleDuck]

One would presume that aluminum anchors with galvanized or stainless steel chain in a marine environment could cause an issue.
https://www.bssa.org.uk/topics.php?article=89

On the other hand, since aluminium is right next to zinc in that table, the pair will make a very weak galvanic cell. Any exposed steel or cast iron will suffer worse ...

JHowever, everything on yacht is a compromise and I think you are deluding yourself if you do not recognise the quotes from Spade that indicate that even the manufacturer reluctantly acknowledges that the aluminium version has a performance trade off.

The manufacturer says that holding power is exactly the same and that setting speed is only slight less, and still much better than older types of anchor.

 

[thinwater]

One would presume that aluminum anchors with galvanized or stainless steel chain in a marine environment could cause an issue.
https://www.bssa.org.uk/topics.php?article=89

Also I would presume that Aluminum would be more adverse to issue than harder steel.
Steel and Aluminum. Even with the possibility of corrosion, steel is harder than aluminum. Most spinnable tempers and alloys of aluminum dent, ding or scratch more easily as compared to steel. Steel is strong and less likely to warp, deform or bend under weight, force or heat.
https://www.wenzelmetalspinning.com/steel-vs-aluminum.html

I think we may be going to far with this one.

1. The Fortress has been out there for a long time, and corrosion is NOT one of it's failings. They hold up very well.
2. Aluminum alloys and zinc galvinizing are actually quite close on the galvanic scale. For example, aluminum anodes and zinc anodes are effectively interchangeable. I could evaluate the specific alloy, but it will be close. Also remember that they are anodized.
3. Steel is more wear resistant. But the galv wears off and then they rust. This is probably sort of tie. Again, this has not been an issue and would not be a deciding factor.

As for bending and strength, it depends on the alloy AND the design; in general the designer will compensate, and the difference in strength with high-strength alloys is not that great. You can't say anything about strength without engineering analysis of the specific construction.

---

I've used both, but I'd rather listen than comment directly at this time.

 

[moomba]

I think we may be going to far with this one.

1. The Fortress has been out there for a long time, and corrosion is NOT one of it's failings. They hold up very well.
2. Aluminum alloys and zinc galvinizing are actually quite close on the galvanic scale. For example, aluminum anodes and zinc anodes are effectively interchangeable. I could evaluate the specific alloy, but it will be close. Also remember that they are anodized.
3. Steel is more wear resistant. But the galv wears off and then they rust. This is probably sort of tie. Again, this has not been an issue.

As for bending and strength, it depends on the alloy AND the design; in general the designer will compensate, and the difference in strength with high-strength alloys is not that great. You can't say anything without engineering analysis of the specific construction.

luminium and stainless steel together also appears to be a bi-metallic corrosion risk, from the 'nobility' table.
With this combination the affect of relative surface area on corrosion is important.

A large area of 'cathode' relative to 'anode' will accelerate the anodic corrosion. Although aluminium is anodic to stainless steel, large relative surface areas of aluminium to stainless steel can be acceptable, dependant on local conditions.
To complete the cell, a conductive liquid must bridge the contact metals.
The more electrically conductive the liquid is, the greater the danger of corrosion. Seawater or salt laden moist air is more of a risk than contact with rain water or towns water.

In testing I agree that Aluminium and Stainless steel would be ok , but we are dealing with Salt water , and salinity in Water varies around the world ,The deep salinity within the Mediterranean Sea is between 38 and 39 psu and in the North sea The salinity averages between 34 to 35, so does the composition of the water with other chemicals present, Just saying
People like to test in nice dry environments wit hall the best tech .

 

[Kukri]

It’s simple. Cost. I expect to lose an anchor occasionally. That’s why I have more than one.

 

[Lon nan Gruagach]

With the experience of a sum total of 1 aloominum anchor....
It has had to be welded at least twice, but didnt ever break.
Strength to weight ratio aloominum beats steel hands down
To bring this particular specimen back up to "weight" it has a lead filled pocket in it.....

Allloy... try the "well actually all metal is an alloy" argument at your local 'hood where the cars have pretty lights underneath and the drivers war rather a lot of gold.....

 

[noelex]

I expect to lose an anchor occasionally. That’s why I have more than one.

Good advice.

Better anchors set in a shorter distance, which I think greatly reduces (but unfortunately does not completely eliminate) the chance of the anchor becoming fouled.

Have a look at my Mantus anchor in this photo. You can see from the marks in the sand that it has set within less than a metre. An excellent performance, but this is not unusual for this model of anchor.

There is not a high chance the anchor will become caught on debris in this short distance. Softer substrates will extend the setting distance for all anchors, but an anchor that sets as quickly as possible is very helpful and will reduce the chance of becoming fouled.

So the good news is better anchors will become fouled less often, but of course the heartache if they are lost is greater .

 

[Kukri]

Very good point, which I accept.

 

[doug748]

What a swizzle.
20 years of rows about anchors and it turns out the Danforth was best all along.

 

[NormanS]

Good advice.

Better anchors set in a shorter distance, which I think greatly reduces (but unfortunately does not completely eliminate) the chance of the anchor becoming fouled.

Have a look at my Mantus anchor in this photo. You can see from the marks in the sand that it has set within roughly a metre. An excellent performance, but this is not unusual for this model of anchor.

There is not a high chance the anchor will become caught on debris in this short distance. Softer substrates will extend the setting distance for all anchors, but an anchor that sets as quickly as possible is very helpful and will reduce the chance of becoming fouled.

So the good news is better anchors will become fouled less often, but of course the heartache if they are lost is greater .

Noelex, the clean sand that most of your anchor photos, like the one above, presumably mean that when you lift your anchor, by the time it reaches the surface, it is spotless and you won't need a deckwash hose. Some of our anchorages are like that, but more often they are thick sticky mud. If/when I know there's bad weather coming, I would always choose mud, rather than sand, in the belief based on my own experience, that mud will give much greater holding, irrespective of the particular make of anchor. Would you, or indeed anyone, care to comment.

My main anchor is a genuine Bruce (made of some kind of alloy of steel), and my second anchor is a Fortress ( made of some kind of alloy of aluminium). (for pedants).

 

[Neeves]

Tensile strength of aluminium alloy, for convenience I will now call it alloy, can be as good (or as high) as virtually any high tensile steel used in anchor production. Alloy might not be quite as high as 800 MPa, but its not far off. The fact its not used is down to cost and its difficult to work with. A common alloy used is 7075 - and it is used in the shank, sometimes slightly beefed up to bring to the same strength as 800 MPa steel. Fortress overcome the strength issue in a slightly different way - a lifetime guarantee on all and any part - no questions asked. The fact they give this guarantee, almost uniquely, seems to suggest failure of any of the components is rare.

Some alloys are not brilliant in terms of corrosion resistance in seawater, this has not stopped thousands, 10s of thousands of aluminium vessels being made and used - corrosion does not deter their usage. An anchor can of course be anodised. Equally thousands use Fortress - no-one complains of corrosion and the Guardian is not anodised and equally no-one complains. I have seen countless steel anchors where they have been either badly galvanised or are old and they are rusting well. In the Med painted anchors are common, some of these have been painted because the gal is now inadequate. I have never seen an alloy anchor suffering from corrosion (except the exception of one or two examples where the corrosion is lead/alloy ( and this is soluble). Again Fortress' guarantee suggests that corrosion is not an issue. Our alloy Excel has lead in the toe, the pocket is sealed, alloy welded to seal the lead - it cannot corrode.

I have seen alloy anchors with a bent shank (Spade - which might be the reason they do not recommend its application as a primary anchor - why they persist with their expensive shank production method when 7075 would be as good, if not much better, beats me). However I have seen galvanised anchors with bent toes, torn toes and bent shanks. You can bend any anchor if you try hard enough.

I cannot tell the difference in setting speeds not hold between our steel Excel and the alloy version (same physical size) and the steel Spade and the alloy Spade (same physical size). Tests and reports do not seem to indicate one is worse than the other. Spade seem to agree, thank you JD for the complete, rather than biased and edited, quote. In virtually every test a Fortress will out perform a Danforth, of the same size.


To me - there seems a huge amount of mis-information being bandied about with little attempt to verify what is posted (par for the course). JD provides technical evidence - and people still want to argue with him. People will quote poor corrosion resistance - apparently suggesting its worse than raw steel (conveniently forgetting anodising and the huge numbers of tinnies being used). People quote 'poor' tensile strength, forgetting that all modern aircraft are all alloy - and that they use high tensile alloys and good engineering.

Sadly high tensile alloys, even the medium tensile 7075 is expensive (compared to cheaper alloys). it is difficult to work the HT alloys, water jet cutting, limited used of heat and this is a deterrent. But at the end of the day a well engineered alloy anchor will be more expensive than the steel version. There are weldable HT alloys, but there are even stronger alloys - and when you build today's aircraft weight is critical - and engineering solutions (other than welding) are common (and confidential - I've asked to no effect ).

BUT you could make an alloy Rocna with equal characteristics but half the weight - tomorrow (or today if you have time). 5083 alloy, good corrosion resistance, can be welded (used to build alloy vessels) is freely available, usage is well known. 7075 has been around for 70 odd years, well known, high strength a bit pricey - easily available (needs water jet cutting). There are stronger alloys - usage well known, pricey,

I guess an answer that comes through - aluminium anchors are too expensive, compared to their steel brothers, and these is an unhealthy lack of knowledge of technical characteristics of the stronger alloys. Weight might be halved - but costs are simply too high for this to be of interest to most. The fundamental issue appears to be - a misunderstanding off characteristics (and all the misunderstanding are negative), too expensive and little enthusiasm for the lighter weight.

Lewmar with their alloy Fortress look alike may achieve lower costs (or higher margins for themselves and the retailer) by sourcing in China. China is a major source of the newer higher tensile alloys, used in aerospace. But to increase market size - Lewmar, and the other manufacturers, have a huge conservative market, as someone pointed out, to educate if they want alloy to become 'more' mainstream.

Jonathan

 

[noelex]

Noelex, the clean sand that most of your anchor photos, like the one above, presumably mean that when you lift your anchor, by the time it reaches the surface, it is spotless and you won't need a deckwash hose. Some of our anchorages are like that, but more often they are thick sticky mud. If/when I know there's bad weather coming, I would always choose mud, rather than sand, in the belief based on my own experience, that mud will give much greater holding, irrespective of the particular make of anchor. Would you, or indeed anyone, care to comment.

Yes, I agree wholeheartedly Norman.

Most mud, especially the thick sticky mud you describe, is the ideal substrate. Nearly all anchor designs work well in this type of bottom. It provides excellent holding. If you have a choice, heading for an anchorage with this substrate if bad weather is forecast it is ideal. I wish this was always possible.

 

[Neeves]

Noelex,

I'm glad you are here - you still have been unable to confirm why an anchor setting with a low fluke/seabed angle can develop as good a hold as one setting at a higher angle. One reason your anchor is 'well set' - its in the low shear strength upper surface of the seabed - and thus has a low hold. It might appear 'well set' but it has the same hold as a similarly sized Delta - and the market have voted with its wallet and largely rejected Delta.

I assume you cannot respond - and hope I might forget.

Your 50kg anchor has roughly the same hold as a 25kg steel Spade (or Rocna) or (to get back to the thread) a hold similar to a 12.5kg alloy Spade or 12.5kg alloy Excel (and maybe the FX37) - which possibly puts it all into context.

Cost is an issue, but so is weight. A 50kg Delta, a 50kg Mantus (25kg Rocna) - or a 12.5kg alloy Spade or Fortress?

Jonathan

 

[Dull Spark]

I am astonished at the complexity of answers to this question.

The "market" being referred to is not clear to me, but in the marine market, the requirements for an anchor are mainly structural, with weight being secondary. (If I want to reduce the weight at the bow, I just don't fill the water tank. Job done.)

If the market being referred to is floatplanes or flying boats, then in addition to structural requirements, weight is very definitely a constraint. Perhaps those guys have embraced it?

So why would any one of us "require" an aluminium alloy anchor? (Why not "require uranium instead of lead in the nose?)

Is it a solution looking for a question?

 

[Neeves]

Dull Spark,

Why would you carry any extra weight - if it was unnecessary, especially in the bow.

I'm amazed your water tanks are in the bow.

Try deploying a second anchor from a dinghy (many, here, profess to do this) - which is easier call it safer - a steel anchor or one the same size but half the weight. Once you get to around a 35' yacht - hand deployed steel anchors in challenging weather is not quite that easy.

A Minn has mentioned - he carries a spare (or spares) anchor. Why not carry a, or 2, spare 10kg anchors than a spare 20kg (or 2) anchors. I know - keep it in the bilges - have you ever tried to carry a 20kg anchor from the bilge to the bow and attach and deploy? On Clipper yachts, bigger anchors but lots more crew, they have a whole section of training to retrieve a steel anchor from the bilges so as to deploy.

Jonathan