Brittany Anchors

[hylass]

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If you look at some of the french sites you will see that the FOB does have the stamp of approval from one of the official shipping agencies, unfortunately can't remember which one.


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The French site is: http://www.fob.fr/menu.lasso?locate=fobhp and the anchor is “Agréée ancre à haut pouvoir de tenue par le Bureau Véritas. » Which doesn’t mean anything, in all test without exception, it has had one of the lowest holding power..


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It does not have the long bar that Fortress and Danforth anchors seem to have.”


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And THERE is the reason of the Problem.. this “long bar” is not there for “decoration” purpose.. but to avoid (or delay) the “Corkscrewing” behaviour common to all “Flat” anchors.. it is an UNSTABLE anchor and under strong pulls, it will suddenly corkscrew and break free at the most unwanted time.. (see again the curve of the Britany..)

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a couple of cruisers I know have used it all around the world and have been more than happy


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I can’t believe that.. Did they have it as a main anchor or did they use it a secondary anchor that they have used only a couple of time in settled weather??

 

[Roberto]

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a couple of cruisers I know have used it all around the world and have been more than happy


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I can’t believe that.. Did they have it as a main anchor or did they use it a secondary anchor that they have used only a couple of time in settled weather??

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I meant they were very happy in using it in the same way I wish to use mine: as a kedge (so maybe rather tertiary anchor /forums/images/graemlins/wink.gif, a light weight anchor with just a few meters of chain, easier to be handled in the dinghy, or as a lunch anchor when bringing out of the anchor locker tens of metres of chain of the main (heavy) anchor would be an unnecessary waste of time

I do not expect it to hold in a hurricane, just to help make life easier when the main big steel anchor is not necessary

sometimes I happen to anchor in only 10/15kt winds.. /forums/images/graemlins/grin.gif

 

[vyv_cox]

As others have said, the flat design anchors cannot be relied upon for general anchoring. I have a Fortress as a second anchor and it never fails to drag when the tide turns or wind changes direction. It undoubtedly will hold well in the right kind of bottom by virtue of its surface area.

IMHO the ability to re-bed is of far greater importance than the maximum pull that the anchor can resist. Few of us would be sitting around at anchor taking the kind of loads given in your table, which represent wind speeds verging on the ridiculous! However, all of us need to be sure that the anchor will remain in the bottom when the tide turns in the night.

 

[wiggy]

Possibly the worst anchor ever, mine is regulrly used to stop the car rolling on the drive and is far bettrer at this than keeping a boat attached to one particular spot of seabed

 

[poter]

Befor you finally buy a new anchor, just have a look at the Rocnor, I know Craige Smith has replied on here without pushing his own product, but I certainly think you should at least have a look at this new design.

Rocna

The site is very persuasive, & I am looking at buying one for my Dufour.

Good luck with whatever you finally decide on. /forums/images/graemlins/wink.gif
poter

 

[hylass]

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I am looking at buying one ROCNA for my Dufour.


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There is one, brand new, for sale on:
FOR SALE


http://www.ssca.org/sscabb/index.php?action=vthread&forum=4&topic=2940

 

[blackbeard]

Hi to Hylas
Reference the curve you show for the Britany anchor: this shows, as far as I can see, the anchor breaking out repeatedly and then re-bedding, in each case holding up to slightly less than 200 daN (not bad for 3.3 kg anchor?) or have I got this wrong?
and presumably if 100 daN (or proportionately more from a heavier anchor) was thought adequate this would be OK - under the conditions of test of course?
As opposed to my little Bruceoid where I suspect the friction of the chain on the sea bed did more than the anchor in some cases ...
I would fit an nice big Spade or Oceane, really I would, if only I could think of some way of stowing it so that it was ready for instant use ... not only my anchor locker, but also the stemhead and foredeck, are really unhelpful in this respect.

 

[blackbeard]

I do love anchor threads! never fail to produce a divergence of opinion. So the Britany is the best thing since sliced bread, or scrap iron, similarly smaller sizes of Bruce. I wonder what to make of all this?
Is the key not so much the anchor, as how we use it, and what we expect of it? for instance we probably wouldn't expect a Danforth type to cope with a major change in wind direction, but if we don't intend staying in one place for long, maybe that's not so important. And some people make sure that the anchor is well dug in, others don't bother.

 

[craigsmith]

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Hi to Hylas
Reference the curve you show for the Britany anchor: this shows, as far as I can see, the anchor breaking out repeatedly and then re-bedding, in each case holding up to slightly less than 200 daN (not bad for 3.3 kg anchor?) or have I got this wrong?
and presumably if 100 daN (or proportionately more from a heavier anchor) was thought adequate this would be OK - under the conditions of test of course?
As opposed to my little Bruceoid where I suspect the friction of the chain on the sea bed did more than the anchor in some cases ...

[/ QUOTE ]Blackbeard,

You are correct that it shows the anchor breaking out and re-setting regularly. This alone is a problem, as it clearly does not remain embedded while it drags. In practice your boat will gather speed while the resistance is down low, reducing the chance that it will re-set at all.

200daN (approx equal to Kg force) is quite bad for a 3.3Kg anchor. It depends on the bottom of course but in the course of our testing we have measured our 10Kg anchors holding up over 1000 Kg (1 tonne).

Proportionately you would then expect a 3.3Kg equivalent to hold up over ~ 300 Kg, BUT it is not proportionate, to address your assumption that it is. As you increase the weight of any given anchor type, the weight increases out of proportion to the physical size. For example our Rocna 10 has a fluke area of 717cm², but the 20 at 1174cm² is not double, although the design is identical.

In other words the expectation of 300 Kg max above is actually too low. Something for 3.3Kg proportionate with our figures would be ~ 450 Kg, so you see how 200 is actually terrible, assuming it is in "good holding" (hard sand / clay).

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I do love anchor threads! never fail to produce a divergence of opinion. So the Britany is the best thing since sliced bread, or scrap iron, similarly smaller sizes of Bruce. I wonder what to make of all this?

[/ QUOTE ]Sort the wheat from the chaff and make what you will from the wheat. As I touched on in my earlier post, people must specify what situations and applications they have in mind when they debate anchors.

The key is to identify what you need and research the available products until you find the one that meets your requirements. One reality that should become clear is that there is no reason today to compromise on major areas of performance by using the "traditional" anchor types, and types such as the Britany should not even be on your list.

I am sure Hylas will agree /forums/images/graemlins/smirk.gif

 

[trouville]

Better still carry enough anchors for bottems!! Even my small boat carries a fisherman, bruce(awful but works??) and the very very best a Britany!!!

I almost forgot i have two grappnels one large and one small (in case my bike falls overboard)

I think any boat need a minimum weight of anchor small ones just dont hold or hold but wont reset. Over 25lbs they mostly will reset (though Britanys just hold!!)

I agree not just the French but "others" drop the anchor the dump the chain on top and leave!!
I always stop then drop the hook when it gets to the bottem i give some reverse and feed the chain out then dig it in,perhaps thats why ive only draged(very slowly) in places where thats common
I used to support the CQR and use a 35LB one, then i began to use my kedge my 25LB Britany as it was lighter and easier to handel on deck.

Slowly i left it down even when i knew i would be in the anchorge for a week or more,and after some freights with bad conditions where i wished id laid the CQR when the Britany held I begn to trust my Britany more and more untill i could sleep even in very bad anchorages never had a problem!!

When it has draged so have many other boats with many different anchors my Britanys aways been holding me in safe ground even after dreadful conditions

I have to say the same was true of my CQR except when in mud weed the the weed has stopped it resetting propely but it just dragged faster than i would have liked!! But once got in and droped in a nive clear patch of sand/mud it held as well as my Britany!!

 

[hylass]

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I am sure Hylas will agree /forums/images/graemlins/smirk.gif

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I was thinking that question was adressed to me??

But I wouldn't have done a better answer Craig, You are absolutely perfect.. Thanks.. /forums/images/graemlins/laugh.gif

Best Regards

Alain
SWORD Anchor

 

[blackbeard]

Hi Craig
Thanks for your detailed reply. Just one point that bothers me - and by now we are probably more into physics than into anchoring, so this is me arguing for the sake of it maybe. Anyway, you say:
"Proportionately you would then expect a 3.3Kg equivalent to hold up over ~ 300 Kg, BUT it is not proportionate, to address your assumption that it is. As you increase the weight of any given anchor type, the weight increases out of proportion to the physical size. For example our Rocna 10 has a fluke area of 717cm², but the 20 at 1174cm² is not double, although the design is identical."
Assuming, as I've been told (can't remember where) that the holding power of an anchor is proportional to the weight of the sea bed which would be shifted should the anchor move, and further assuming that this will be proportional to the fluke area multiplied by the depth below sea bed of the flukes,
and assuming that if proportions are maintained for various sizes of anchor (ie they are all the same shape, just different sizes)
then linear dimensions are proportional to the one-third power (cube root) of the anchor mass, and the fluke area to the square of this, thus proportional to the two-thirds power of the anchor mass.
The mass of sea bed which would shift should the anchor move is proportional to the fluke area multiplied by depth below sea bed, the latter being proportional to the anchor linear dimensions
so we have holding power proportional to anchor mass ^ 2/3 multiplied by anchor mass ^ 1/3, ie directly proportional to anchor mass
all other factors being equal which they never are, for instance if the anchor is on mud, the mud may become more firmly compacted with depth.
Sorry for the ramble. Generally posts on this topic support the idea that size and weight matter a lot (in anchors) suggesting that for a given type the holding power is at least proportional to weight.
regards, Mike

 

[craigsmith]

Your math doesn't take into account the angle of the fluke to the direction of movement, or the flow of the mud/sand past the fluke. I haven't ever bothered working anything like that out properly; to make a worthwhile model you would need to use a computer and create simulations for the anchor in question. Particularly with sand you need to consider a combination of particle physics and fluid dynamics. My head hurts thinking about it. We are more interested in what feedback we get from the real world.

If you simplify things and say that holding power is directly related to fluke size (which it isn't because of some of the factors you mention, plus the fact that larger flukes dig deeper and tend to encounter different substrata) then you have something more practical. It is about right to say that every square centimeter of increased blade area gives a proportionate increase in holding resistance; if 100cm² holds 100Kg, then 200cm² will hold around 200Kg.

My point is that if you take any given anchor design and scale it, when you have doubled the mass you have nowhere near doubled the fluke area. Go to our website and study our sizing chart, which lists both weights and blade areas for all our anchors from 4Kg up to 110Kg.

Size matters, weight is less important and only relevant at all to setting not holding. Size is not directly proportionate to weight but of course it is related. There's probably an equation and the one constant is the density of the steel (when you scale the size you don't scale the density; if you did, then the size would be directly proportionate).

Furthermore, larger boats do not need directly proportionately larger anchors. Fun this eh /forums/images/graemlins/tongue.gif

The reason for my point in my other post was to use our emperical data from testing and just illustrate that 200daN for a 3.3Kg anchor is not particularly good.

You can draw other interesting conclusions, such as the fact that a "holding power per unit of weight" measure (this is one that magazine tests love) is unfair if there is a large range of mass involved.

 

[hylass]

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If you simplify things and say that holding power is directly related to fluke size (which it isn't because of some of the factors you mention,
Size matters....

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Yes Size matters, but the overall design too...

See below two curves of two diferent anchors of about the same size, tested under the same conditions..

Interesting??

 

[blackbeard]

Thanks
Interesting!