Modern Day Anchors

[downunder]

Originally Posted by noelex 77

My primary anchor is a 55kg Rocna. The shank is about 20mm thick steel and I cannot imagine bending it with my boat no matter what grade of steel was used in its manufacture, but its a NZ version so presumably 800 Mpa.

You shouldn't be going anywhere with a 55kg.

[noelex 77]

Originally Posted by JonJo

Noelex and I seldom agree

Let's both agree jet skis are annoying in a deserted anchorage

[noelex 77]

Originally Posted by downunder

You shouldn't be going anywhere with a 55kg.

That's the idea, but I have managed to drag it once

[Visarend]

Do scope and weight matter more than design? (Apart from poor designs)

30 yrs ago I had a 25' plywood boat, which under Mistral blows up to 30-40 kts (no lee shore, of course) always dragged its 6 kg Bruce with 15 m of 8 mm chain plus rope. It only stopped dragging when I upsized to a 15 kh CQR with only 2 m of 12 mm chain and plenty of rope.

Thereafter, I built my 40' rather heavyish cutter (8,5 tons) and had many sleepless nights trying to stick to recommended (by manufacurers and French laws) anchor sizes of different makes. Again, upsizing to a 34 kg Britanny (adopted in France by SNMS rescue teams) and 60 m of 10 mm chain did the job.

Having dived to check the anchor under load in heavy Mistral blows, I understand that a heavy anchor can plough the weed more easily than a lighter one, and that spiked tips can (not always) find a grip in critical rocky bottoms.

I have no experience with modern designs, though. Probably the suggestions of Olesargesas ( weight + modern design) makes sense.

[JonJo]

Originally Posted by noelex 77

Let's both agree jet skis are annoying in a deserted anchorage

They are annoying

[Olesargesas]

Visarend

For me scope and all chain definately matters, minimum scope ever used for me is x3 and doubles sometines triples in some instances in a blow depending on how big and the tide range, when usually I can find resonable depth water of 2.5m at low, with good holding.

[downunder]

A quick google search for a Brittany anchor.

Britany Anchor - 18,15

Seems like a Britany is similar to a Danforth/Fortress and whilst excellent for holding in one direction does not like wind veering whilst your anchor weight 34kg looks good if less than Nolex's 55kg Rocna.

That the rescue organisations recommend it they most likely would use it for kedging not for long term anchoring as a cruiser does.

Following minimum legal anchor requirements of countries can be greatly inadequate speaking for Australian recreational boating laws.

[JonJo]

We should not be anchoring in coral - damage should therefore be minimal

We have anchors specifically designed for retrieval from rock, the slotted, SARCA, Boss and Supreme.

Bad luck plays a role - but anchors are not designed to be retrieved by brute force (from rock or coral - or sand and mud). Anchors are designed to work in sand, mud, clay (but not rock or coral - except those with slotted shanks). To suggest an anchor is at fault because it fails in an environment for which it is not designed, looks unfair(?). You would not take a saloon car over a wet muddy field (even to test an anchor) - tractors a specifically designed for this. Why suddenly are Fortress meant to work in an environment for which they were never designed. One might think that an anchors that bends might eventually be retrieved but an anchor with no 'give', high tensile shank, will result in either damage to the yacht or abandonment of the anchor - but it is no fault of the anchor.

So heads you lose, tails you do not win.

More interesting are the failures, by bending, of anchors in the environment for which they are designed.

[JonJo]

Originally Posted by Olesargesas

JonJo

I thought the Supreme was Gr.350

The Supreme shank is, min 800 MPa (but I think the quote is hyperbole, and wrong). They historically quoted Bis 80 and more recently quote min 800 MPa. My knowledge suggests its impossible to gal min 800 MPa steel (the heat of gal destroys the Hi tensile props). So, as its topical, cut them a bit of slack and assume they still use ASTM 514a (but no longer from Oz - too expensive). Mine is around Bis 80 standard, and I'm assuming they would not dare emulate one of tbeir competitor.

[JonJo]

[QUOTE=noelex

My primary anchor is a 55kg Rocna. The shank is about 20mm thick steel and I cannot imagine bending it with my boat no matter what grade of steel was used in its manufacture, but its a NZ version so presumably 800 Mpa.[/QUOTE]

Depends where and when your anchor was bought as to whether its a genuine NZ model. The 55kg Chinese and 55kg NZ models look identical (fabricated flukes, both). Once ties were cut with the NZ manufacturer, end 2008, then 55kg models in NZ would look the same from whichever source. American HT sales continued until back end 2009. Some Rocnas sold in Oz in 2009 have been replaced, FOC.

A Fortress FX 23 has a 24mm wide shank, 4mm wider than your Rocna. If your is a NZ model it will be indestructible. Many anchors, unbranded, will be made from 250 MPa steel - and it might not matter how thick the shank, they will bend, or the shank would need to be so thick the shank would be too heavy and too thick to penetrate the seabed.

Hence the question - how many people know what steel is used in the shank of their anchor - strength can vary by almost 4 times.

[Visarend]

Jonjo

I partially agree, but the assumption "To suggest an anchor is at fault because it fails in an environment for which it is not designed, looks unfair(?)" looks a bit too theoretical to me.
In fact, when cruising, some of us find almost invariably the same type of bottom (sand, or thick mud); others, as in my case have to do with what they find: sometimes mud, sometimes rocky, Posidonia over sand, gravel (horror!), etc. It is true that no anchor covers all the types, so we need a good allrounder: what is the best allrounder in your experience?

[noelex 77]

Originally Posted by JonJo

A Fortress FX 23 has a 24mm wide shank, 4mm wider than your Rocna. If your is a NZ model it will be indestructible.

The Fortress anchor is completely different design. The shank is aluminium not steel and is tapered. My FX 37 tapers from 25.8mm thick aluminium at the head to 13.3mm at the end (I just measured it).
The Rocna shank is also much deeper than the Fortress.

Even if my (much bigger)Rocna shank was mild steel it would be many times the strength of the shank on my FX37.
Fortress shanks do bend occasionally. I know some boats that have done so. Usually one bends in the anchor tests conducted from time to time by the magazines.

The Fortress guarantee is excellent however. They will replace the bent part at no charge.
You don't have to send the anchor back to them.

[Jim Cate]

GEtting back to the cheap Bruce knock-off anchors... the low price is possible because these anchors are a simple one-piece casting. The genuine Bruce jobs were cast of some sort of high tensile steel and heat treated to improve toughness (IIRC). The copies vary both in shape and in the quality of the casting. I'm not aware that any are heat treated post casting. Some are appallingly poor and have a history of failure. There are apocryphal reports of some shattering when dropped on concrete, but I dunno about that one!

I have never seen a bent shank on a genuine Bruce, but I managed to bend a fluke on a 20 Kg model that I had. It was fouled on an abandoned mooring block in Twofold Bay NSW, and I managed to lift the whole shebang up near the surface so that I could get a line under the block and free the anchor. One fluke was slightly bent, so I took it to an engineering shop in Hobart. They thought their 60 ton press could put it right, but after 30 minutes of cursing they admitted defeat. It continued to serve despite its flaw... who knows if its holding power was altered. I could tell no difference!

Cheers

Jim

[congo]

Great to see a cease fire, but be cautious as there are still plenty of land mines in anchor discussions. Thank you Olesargesas, for opening this thread, and sharing your experience with a great first post as to why you decided on an Excel.
Cotemar Wrote:
Olesargesas,
Welcome aboard the CF.
Interesting first post.
We had a member here refered to as Olesarge in the Sarca Excel thread, but he was not very nice. Here’s hoping you’re the nice one

Lots of Australia cruisers like those Sarca Excel anchors
Cotomer welcome to this thread, there was another Cotemar on the Excel thread, he was a moderator, and you, are much nicer than he.

Moving on, if want security in an anchor strength design then do your research, below, this is the proof test proceedure we go through for testing anchor shank and fluke strength, these tests are done by an authuorized testing facility, in this case Robertsons. http://www.cruisersforum.com/forums/...ifting-company

As we are a certified super high Holding power anchor builders, we have no choice but to spend the dollars to obtain S/H/H/Power certification so as our anchors can be used on all types of boats-vessels under Marine survey.

This means independant strict proof testing for the anchors construction, then metal strength, plus field testing to obtain prooven holding power per kilo of anchor weigth.

There is no room for shonky testing as there are at least three survey officers present checking of every procedure, even though all of our anchors have been taken to yield and in most cases produced up to four times more than the test required, there are still no guarantees you won’t bend a shank. But a certified anchor is the best starting point.

But beware, this testing is only compulsory for anchors of fifty kilos and up, if your anchor of choice, and the company cannot disclose type of steel, same testing of their smaller anchors with proof of test certs then move on, some companies that have achieved certification of the larger anchors then spruce their whole range are certified as S/H/H/Power, is this case ask them to show you proof.

It is also your right to ask them to produce the type of steel used in all anchor sizes, if they cannot, or will not disclose this info then again move on. Steel type and test certs for both our anchor designs can be found on our web site.

Don’t be fooled by just by high holding power figures because the fluke area is so huge, especially on some new anchor types, the cross sectional and metal strength of the shank has to be enormous regardless of steel type, further the fluke plate thickness is also just as important, the leverage applied by wide holding areas will in the short term come to fruition and you will have not only bent shanks but flukes, you will be the looser unless you do your homework .

Regards Rex.

[JonJo]

Originally Posted by noelex 77

The Fortress anchor is completely different design. The shank is aluminium not steel and is tapered. My FX 37 tapers from 25.8mm thick aluminium at the head to 13.3mm at the end (I just measured it).
The Rocna shank is also much deeper than the Fortress.

Even if my (much bigger)Rocna shank was mild steel it would be many times the strength of the shank on my FX37.
Fortress shanks do bend occasionally. I know some boats that have done so. Usually one bends in the anchor tests conducted from time to time by the magazines.

The Fortress guarantee is excellent however. They will replace the bent part at no charge.
You don't have to send the anchor back to them.

Sorry Noelex, I am overly guilty of simplification.

But the metal does not matter, the tensile strength does. A 250 MPa steel has the same strength as a 250 MPa alloy (and marine grade alloys are stronger than mild steel and stainless 316 (though mild steel is hardly a technical term)

The strength of a metal beam is the square of thickness x width - so thickness is much more important than width. Stress, or load, increases linearly along the length of a lever, so the middle of a lever has half the load of the end, so it is on the end that the greatest load is imposed (hence quoting the thickness of the 'plate' at the end). (and this is why anchor shanks get wider, and in the case of Fortress and Spade thicker, toward the fluke). If your shank was mild steel, 250 MPa - I think it might bend before your Fortress alloy, because the square of 20mm = 400 and the square of 25.8 = 665 (but depends on the other dimensions).

But another point of agreement - the Fortress guarantee is unsurpassed, lifetime free replacement of any part that fails - no questions asked. Advantageously as you might be able to straighten the bent component you end up with an emergency spare. But if I was going to be out of touch of DHL or FedEx, I might think of carrying a spare shank anyway. This is a win win for owners - if you bend the shank of a Rocna, you need a new Rocna. Bend the shank of a Fortress and you should be able to bend it back until the replacement arrives. Interestingly Fortress advise that most claims are for 'enthusiastic' retrieval rather than bending when in 'service' as an anchor.