Why has the market not embraced alloy anchors?

[Neeves]

So ideally the primary and kedge anchors would be very different models. A Mantus, Rocna or steel Spade are typical premium primary anchors (although there are many other choices), and an aluminium Fortress or Guardian is used as kedge. The biggest dilemma concerns what happens if the primary anchor is lost. In an ideal world a spare primary anchor would be carried, but some boats accept, I think often reasonably, that the kedge anchor can be used with caution as a primary anchor until a replacement primary can be found. Much depends on the remoteness of the cruising grounds, time away from marinas, and the practicalities of retrieving a stuck primary anchor.

So still in denial

Please provide any information you have on the hold of Mantus.

Your credibility looks questionable yet you still want to attack an anchor you have never used, aluminium Spade yet continue to champion Mantus that you have used that has no performance data you can quote. It obviously has a defect - that low fluke seabed angle - yet you are unable to even attempt, in the face of evidence from, amongst others, the US Navy - that a low angle produces a low hold.

Mantus has the hold of a similarly weighted Delta and should not and cannot merit comparing, favourably, with a Rocna or, even, and aluminium Spade.

I have used all of these anchors and tested all of them.

By modification of Mantus it can be made as good as a Rocna - which is what Viking has done - but as is - its not worth the hype

Jonathan

 

[dgadee]

Back to the Vulcan. I took photos of it newly set but unfortunately can't get them from the camera onto something from which to post. Under full reverse power in sand around half of the arch shows, with the blade and shackle well covered. The other day I was sheltering from a F6/7 (no waves) and the entire anchor dug itself in. Nothing to be seen.

I also thought yesterday I had set in sand but when I looked via a snorkel it was seagrass in bloom. Plenty came up on the anchor. And last night I set again in seagrass and full reverse once again held. I think the correct technique may be to wait until the boat settles, use just a little power and then slowly increase to full power. Hold that for a good 10 seconds, then full power again. Doing that seems to get the vulcan below the seagrass. Whether it will hold as firmly as in sand is another thing.

The discussion of fortresses not holding on a large shift in direction is not comforting. I have an fx11 as a kedge and an fx16 as a spare bower anchor. Still not sure how best to deploy these.

I also have a Kobra, but I presume if I lose my Vulcan I will also lose my 60m of chain.

 

[noelex]

Back to the Vulcan. I took photos of it newly set but unfortunately can't get them from the camera onto something from which to post. Under full reverse power in sand around half of the arch shows, with the blade and shackle well covered. The other day I was sheltering from a F6/7 (no waves) and the entire anchor dug itself in. Nothing to be seen.

That sounds excellent. If you can retrieve the photos in future, I would love to see them.

I think the correct technique may be to wait until the boat settles, use just a little power and then slowly increase to full power. Hold that for a good 10 seconds, then full power again. Doing that seems to get the vulcan below the seagrass. Whether it will hold as firmly as in sand is another thing.

That is a good technique. New generation anchors are normally very tolerant of a bad technique. In most substrates they set so well you have to do something very stupid to have a bad result. However, in difficult substrates good technique does play a role.

In weed it is important not to put any force on the anchor until you have laid out a reasonable scope. If the anchor slides along the bottom before a reasonable amount of rode is deployed, the anchor will not dig in because of the short scope, and the tip will become clogged with weed reducing the chance of the anchor digging in when a suitable scope is reached. So try and avoid any force on the anchor until you have 3:1 scope.

When applying the setting force try to have a progressive and steady increase in the force. A sudden large force before the anchor has started to dig in will once again drag the anchor along the weed and risk clogging the fluke.

The discussion of fortresses not holding on a large shift in direction is not comforting. I have an fx11 as a kedge and an fx16 as a spare bower anchor. Still not sure how best to deploy these.

If you have the chance try to observe the Fortress underwater when the direction of force changes. You will find frequently the Fortress develops a very large list with very little of its flukes in contact with the substrate. Often it will subsequently dig in and set in the new direction, but I find the behaviour quite disconcerting to watch. A gust at the wrong time when the anchor has little grip will see the anchor sliding along the seabed. Moving anchors, particularly light weight anchors have a tough time digging in when rapidly sliding along the bottom.

Contrast this with your other anchors that will generally remain well buried and “shuffle” around to the new direction with only a slight list, maintaining reasonable grip throughout the transition.

However, while the Fortress has a weakness in this area, it has many other great properties such as very light weight and fantastic grip in soft substrates. As a kedge anchor it is great, but use some caution if using it as a primary anchor. Fortress suggest deploying two anchors if there is a risk of a significant change in the direction of pull.

I also have a Kobra, but I presume if I lose my Vulcan I will also lose my 60m of chain.

In some circumstances, all the chain can be lost, but it is more common to be able cut and retain most of the chain (as a last resort) if the anchor or chain is caught. Chain can be easily cut with a hacksaw.

The Kobra can be used without chain. The emphasis on using the Fortress without chain is mostly because of the advantage of the very light weight is lost if a lot of chain is used.

All models of anchor will set slightly better (in most circumstances) with some chain close to anchor, but the difference is not huge and most designs remain usable without any chain. Slightly more care is needed when setting the anchor and it important to understand that without the chafe protection of chain there is a risk of cutting the rode. This risk is very dependent on the type of substrate, but even in uniform sand or mud substrates there are often patches of debris (unfortunately often man made rubbish) or isolated rocks that can potentially cut through line. This risk in many locations is small but it something to take into account especially without and chain close to the anchor on the part of rode that will always be in contact with the seabed.

If the rode is cut, without any anchor attached the drag will be very rapid and there is more danger of not regaining control before damage occurs. So The dangers of a cut rode are more severe than a “normal” dragging incident.

 

[Neeves]

dgoadee,

If you can dig the photos out - a picture is worth a thousand words.

I find Fortress may over specify their anchors. The issue is - if the anchor is 'too' small it can set too deeply and is very difficult to retrieve. Fortress have had to be abandoned simply because they were set so deeply - usually after a strong wind effect - but a small anchor would suffer the same issues.

I have this idea that they have set their anchor size charts a bit 'big' to ensure anchors can be retrieved relatively easily. A shallow set Fortress may trip and may not subsequently re-set. A deep set Fortress may simply not move.

The size recommended for our yacht was a FX 23 - I found we could not really deep set it and we have swapped it for a FX 16, set at 30 degrees. The FGX 16 (and the FX 23) are bit small for squishy mud so we also carry a FX 37 set at 45 degrees.

If there is to be no wind shift a Fortress will not trip.

I, and many other, find Fortress totally reliable, use it frequently - and if you are careful with forecast - have never experienced it tripping.

As with any anchor - they are a compromise.

Jonathan

 

[prof pat pending]

Whilst using 3D printing will enable the verification & validation of anchor design it certainly won't decrease unit cost and is unlikely to yield the best ultimate strength characteristics.

3D is a great fast prototyping method but is slow and costly for volume manufacturing, especially if you are using metals which will require sintering afterwards (furnace or laser). Also, the grain structure of the metal (notice I didn't mention alloys of steel, aluminium or other metals ) won't be present. The presence and direction of the grain structure of metals is often key to design and their strength/characteristics in use.

Sorry to come back to such an old post, but you’re at least ten years out of date I’m afraid.

Many modern additive manufacturing machines (aka 3D printers) are capable of 99.97% dense metal parts in numerous materials. Steels (even 316), Titanium, Aluminium alloys (including metal matrix composite (may as well get really fancy)), Nickel super Alloys, various precious metals, (need I go on?) are an everyday thing now.
The benefits of additive manufacturing in weight and complexity CAN outweigh the cost in the right place, Aerospace, medical, military and motorsport applications are common. It’s even breaking into low volume automotive, every BMW i8 roadster has a couple of additive metal parts. Michelin make all of the metal inserts that put the grooves in their tyres using 3D printers, they even invested into a company to manufacture the machines to make their parts. Every General Electric leap aircraft engine has fuel nozzles that used to be 12 assembled parts that were replaced with a single 3D printed part, they passed 30,000 units earlier this year. They even managed a 3D printed helicopter turbine engine that considerably reduced the part count and assembly time

I have to agree that we’re some way off anchors being viable though