Further anchor developments

[thinwater]

... I'm guessing most people would say go by the displacement rather than length....

NO. In fact, ABYC goes by length.

Windage is a much better determinant of rode tension than mass, and windage is more closely related to length than mass. However, the ABYC supporting text does remind the reader that boats that are on the heavy side for their length should go up a size.

See ABYC H-40.

 

[thinwater]

Re. Oversize anchors and stting, the expereiment every anchoring fanatic should try once is to anchor in good firm sand with an oversize Fortress and then with a one-size small Fortess, and then tell use which one held better when the wind changed. It will be the smaller anchor, fully set, not the oversized Fortress with only 1/2 the fluke buried. No question. I have repeated this test.

It is less certain how this applies to what we might call "general purpose" anchors. They are better at resetting than the Fortress and less prone to being grossly oversized. It is something to remember. I feel it is occasionally true and more often not.

I think a point Viking is trying to make is that anchors should not just be sold by the pound. A 35-pound x is not the same as a 35-pound y. If you use high strength steel and thus make an anchor that sets deeper, it's more about area and performance than $/pound.

 

[noelex]

But.., what is the risk of over-sizing? Why are they so adamant about not doing it?

The Viking models have moved the shank attachment point from nearer the centre of the fluke towards the crown. This increases the overhang of the fluke, especially when combined with its the long tapered shape. If reasonable sized models (according to most new generation anchor table sizes) were chosen, a Viking anchor would hit the bow on many boats, damaging the gelcoat.

Compare the attachment of the original Viking rollbar with similar designs from Rocna, Mantus M1, Mansonson Supreme, Sarca etc or the non rollbar Viking model with Mantus M2, Spade, Vulcan, Boss etc and the difference in fluke/shank attachment point is obvious.

Viking have specified very small anchors in their sizing tables. This happens to eliminate the problem inherent in the design. A small Viking anchor (for the boat size) is much less likely to foul the bow.

 

[Neeves]

If you have 2 (almost) identical anchors one made from mild steel and one made from HT steel and both are made to withstand the same tensions then the lighter HT steel based anchor will have a higher hold and set more easily than the identically sized mild steel anchor.

In order to engender strength in the mild steel anchor you will need more steel and everything will be 'bigger' - the steel will need to be thicker - or if you like - the HT steel anchor can be made from thinner steel.

OR

You can make the HT steel anchor smaller such that it gives the same hold as one made from mild steel.

Don't quote me on this but a 10kg HT steel anchor might have the same hold as a 15kg anchor made from mild steel. (It might not be 10kg - but 11kg or 12 kg - depends on the anchor). The only way to find out is to test each of the anchors. Viking have tested each of their anchors - check the hold data. (However - for most anchors only one size has been tested, commonly 15kg, if you read to end of this post you will find that it is invalid to consider that, say, a 10kg anchor will have 2/3 the hold of a 15kg anchor of the same design.)

Don't believe me - go and find a bit of mild steel of 10mm thickness and a piece of mild steel of 5mm thickness and try to push them into hard soil or sand - which is easier. Strength is not relevant here - we are just testing penetration ability. Sheer strength of seabed (and maybe soil) increases with the square of depth.

Look at the thickness of the plate used to make a Mantus M1 15kg fluke and the thickness of the plate to make a 10kg Viking......I choose Mantus in this case because the designs are similar.

This a 15kg Mantus fluke edge to the right and a 10kg Viking fluke to the left. The difference in fluke thickness is obvious. The Viking anchor has a higher hold predominately because the crown (junction of shank and fluke) is more advantageously located - but the thinner fluke simply reinforces the higher hold - design NOT weight.




Windage is a functión of size not weight (though for a given design, say a Benny, then the build characteristics are similar, the maths used to determine layup weight, are similar so weight and length will be related. Engine size usually increases in the same way - but mathematically all very crude.

Interestingly our 38' cat weighs similarly to a 45' Bav (if you strip out the keel) and has a similar windage. There are differences, the Bav mast will be heavier - but the 'dimensions' and statistics are more similar than different.

This, comparing anchors, is easier to understand when looking at a Fortress because you can see design, it is fairly simple. If you can bury all of a Fortress of X^2 cm with your engine in a given seabed then that same engine will bury roughly the same fluke area of a larger Fortress (it will actually be less because the thickness of plate used will increase). So....the bigger Fortress will have more area not buried and a longer shank - which do you think is easier to trip? The one half buried with the bigger lever or the fully buried one with the shorter lever....

With no disrespect - if it were a CQR or a Delta - it may not reset.

A smaller well designed HT anchor can have the same hold, straight line pull, as a larger mild steel anchor - because the smaller anchor buries more deeply. Tests show well buried anchors are less susceptible to tripping as a result of yawing than shallow set anchors. Now whether this is a function of shallow burial or lever arm length - maybe a bit of both. The size of your engine is irrelevant - at most, max revs - your engine will develop a rode tension of the equivalent of, 35 knots.... say. The hold of an anchor, say 10kg HT or 15 kg mild steel, is the same - say 2,000kg. But you anchor may still drag - not because of inadequate hold but because of yawing, chop - some function that reduces the shear strength of the seabed. Recall deep set anchors are less susceptible to yawing....


We have evidence that a light anchor, Fortress, can develop more hold than a heavy anchor, Danforth. The difference in hold is significant. Similarly a HT steel anchor can develop the same hold as a similarly designed mild steel anchor of more weight (and larger physical size).

Its design, not weight. Fortress chose aluminium, part of design.


If you look at hold data do NOT assume that if you double weight you double hold. This is NOT valid. If you double weight you might increase hold by 70% but you will not double hold. The constant is fixed but there is insufficient data for any of our anchors, except Fortress, to determine what the function is. The function for Fortress is, from memory, 83% - but err on the size of caution. The function for cast Bruce in oil rig sizes is around 70%.

Jonathan

 

[sailoppopotamus]

I don't feel Viking anchors are too small. The stated weight might appear small but if you compare the actual fluke length and area to anchors of similar weights offered by other manufacturers, it is much larger. Presumably this is due to the choice of higher grade steel that allows them to get away with thinner construction. I was looking at buying a Viking 10 or 15 for my boat but there was no way either would fit the bow roller, so I bought a Vulcan 12. Turns out, even that doesn't sit very well so I'll have to make changes anyway, so perhaps I was too quick to reject the Viking. For what it's worth, Viking were very helpful over e-mail and even sent me CAD screenshots clarifying various dimensions.

I've spent a lot of time thinking (emphasis on not experimenting) on the question that is raised frequently here on the forum, whether a small well set anchor is preferable to a larger anchor that is not as well dug in. If we accept that holding is a function of how well an anchor is 'set', it follows that an anchor's performance is a function of engine power as stated elsewhere in the thread. I have a sailboat with a puny 16hp engine. When I reverse on the anchor I do so to test its holding, not 'set' it to improve its performance. In full reverse, I think I exert a pull equivalent to around 30kts on the anchor. If it can hold that, then I go to bed with some reassurance that I'm safe, but no guarantee. I've tested that it will hold in 30kts, but whether it can hold up to 50 kts remains to be seen.

 

[Neeves]

The Viking models have moved the shank attachment point from nearer the centre of the fluke towards the crown. This increases the overhang of the fluke, especially when combined with its the long tapered shape. If reasonable sized models (according to most new generation anchor table sizes) were chosen, a Viking anchor would hit the bow on many boats, damaging the gelcoat.

Compare the attachment of the original Viking rollbar with similar designs from Rocna, Mantus M1, Mansonson Supreme, Sarca etc or the non rollbar Viking model with Mantus M2, Spade, Vulcan, Boss etc and the difference in fluke/shank attachment point is obvious.

Viking have specified very small anchors in their sizing tables. This happens to eliminate the problem inherent in the design. A small Viking anchor (for the boat size) is much less likely to foul the bow.

I'm not sure what Noelex actually means but

The crown is the junction of shank and fluke. In terms of definition it does not matter where the crown is, it could be at the heel (Bruce and Fortress) or roughly half way down the length of the fluke, say Spade - but that junction is defined as the crown. As discussed in an earlier thread - ballasted anchors (Delta, Excel, Spade) have their crown roughly half way along the fluke, unballasted anchors have their own near or at the heel, Bruce, Fortress Brittany. If the crown is in another location it will detrimentally impact performance.

Many question my suggestion and comments - and it is healthy to do so.

If you look at this website

XYZ Air Anchor - The most powerful anchor in the world.

You will find an anchor with the crown at the toe. I applaud innovation and time will tell if this works.

This a rough illustration of crown location vs ballast

The anchors on the right all have the crown (that junction where the shank joins the fluke) about 1/3rd forward from the heel. All these anchors have ballast - including Rocna whose toe is composed of a double thickness of steel. From back to front, Excel, Rocna, CQR, Spade, Kobra. The anchors on the left all have the crown at the heel with the Ray, Manson's interpretation of the Bruce, having the crown protruding behind the heel. This latter suggest Peter Bruce know the advantage of a heel located crown and tried to add hold by pushing the crown back. From back to front, Viking, Mantus, Viking, Ray and Fortress




Most people choose anchors on the basis of performance and then look to see if the anchor fits. Many will modify their bow roller or their retrieval technique to accomodate seating on the bow roller - as they prioritise performance. I recall a builder mentioning that when a specific yacht was built the bow arrangement was modified to suit the demands of the owner who wanted an over large anchor - this is exceptional as most of us do not have this flexibility - so we alter our retrieval to suit the 'better' anchor.

Some add a protective plate to protect the bow. An alternative is to stop retrieval before the anchor reaches the bow roller and then seat the anchor by hand and lash the anchor securely - so not relying on the clutch and protecting the gel coat.

Obviously if you anchor weights 40kg - its not quite so easy

Thor, the new model from Viking, has the crown at the rear of the anchor as this engenders maximum hold. Obviously the further aft the crown then the further forward the toe. Anchors are designed to optimise and in the case of Bruce, maximise, hold. If location on your bow roller is more critical than hold - then you might not be using an unballasted Thor. If you want more bang for your buck then Thor offers, as near as you can get, optimum hold (based on Viking's test data) vs weight.

As thinwater mentions It is a step back if anchor development needs to be constrained by bow roller design.

Jonathan

 

[Bouba]

I agree with some of the above.....with newer materials we should talk about size not weight....taken to the extreme a carbon fiber anchor of ten kilos might not fit anywhere on a 10 meter yacht. So...we need a sizing guide that goes by fluke area and shank length

 

[Neeves]

The Viking models have moved the shank attachment point from nearer the centre of the fluke towards the crown. This increases the overhang of the fluke, especially when combined with its the long tapered shape. If reasonable sized models (according to most new generation anchor table sizes) were chosen, a Viking anchor would hit the bow on many boats, damaging the gelcoat.

Compare the attachment of the original Viking rollbar with similar designs from Rocna, Mantus M1, Mansonson Supreme, Sarca etc or the non rollbar Viking model with Mantus M2, Spade, Vulcan, Boss etc and the difference in fluke/shank attachment point is obvious.

Maybe some balance is in order.

This is a Mantus on the bow roller of a yacht. Totally excusable, unless its a Viking.

Jonathan

 

[Sea Pearl 88]

Having been though this with them, that is exactly what they say you shouldn't do - the owner is adamant that a 10 is the right size for a 40' boat.

IMO Viking have terrible marketing, because my reaction was the exact same as yours, and I think it's what most people will do. I think people would be much more inclined to trust them if they made a size 12.5 - then the owner of a 40' boat could buy with confidence that they're right in the middle of its 35' - 45' range.

I ended up trusting them (well, trusting @Neeves really) and getting a 10 for my 40' boat. I'm not going to engage with the anchor debate except to say that, in any case, any NG anchor will have twice as much holding as the Bruce I had before and that held me no bother in a very good gale (although it depends on the holding of course - on other occasions it was not so good, and did not seem to ever reset itself).

So now that you have used the Viking anchor for a while what are your thoughts on it?