Displacement to Anchor Weight Ratio

[rw58ph]

Here is a site that you can play with as to weight, rode, wind, displacement abd bottom. http://alain.fraysse.free.fr/sail/rode/rode.htm The bottom type, type of rode and scope a big factor as to how anchors perform.

According to the site the Eagle which is 40 tons, 58 ft long with a high air draft, requires and anchor, that is 90+ lbs, all chain rode and scope of 5 times with a fair bottom. Another anchor test showed the 5 time scope, 20 degrees. Any increase of the scope above 5 showed little increase/results. Also the anchoring between the East Coast, thin/shallow water and the PNW, fat/deep water is quite different. It took me a long time to understand, why east coast could anchor with a light anchor short rope length and little chain.

I did a comparison of the newer fast a anchor sets, most have sharp the fluke edges, sharp the flukes point is and the angle of the fluke. As to holding power the area and mass are factors. I am modifying our 70 lbs Forjord, navy type, by increasing the area of the fluke, which increases the weight and sharpen the flukes edges and point. The above site shows our anchor for the PNW should be 90+ lbs, all chain and 300 ft. If you want to talk anchors go to Trawler Forum Trawler Forum As anchoring is a big topic.

Anyway play with the factors/variables.

[TacomaSailor]

Originally Posted by Sharki127

The thread took a turn towards fluke type anchors which are frowned upon as primaries.

I guess I missed that warning?

Discouraged?

By whom
Why?
When?

I don't use my FX-55 very often 'cause it digs in so deep it is a PITA to retrieve.

[JonJo]

Originally Posted by TacomaSailor

I guess I missed that warning?

Discouraged?

By whom
Why?
When?

I don't use my FX-55 very often 'cause it digs in so deep it is a PITA to retrieve.

+1

We only use an FX 23 and do not use it as a primary only because it does not fit on our bow roller. We would need major expense to allow us to fit a Fortress but being so light its not an issue as we, me, wife, grandchildren aged 10 years can deploy by hand. When we have tested it deployed by hand we have found it holds well in most seabed types commonly found in Australian water, river and estuarine muds and sand, including hard packed (it is frowned upon here to anchor in weed beds). It sets quickly and if there has been any strong wind it is, as suggested, a PITA to breakout by hand. It sets well in thin or sparse weed. If the wind veers though 90 degrees the anchor simply swivels round - and does not as suggested by some breakout and never re-set. This latter seems to be one of those phurphies constantly repeated by those with tunnel vision to the excellence of one design over all else and whose anchor choice is so perfect their anchors never have faults.

If we were to sustain a Gale or Storm we would have no fears whatsoever in using a Fortress as part of our anchor strategy and would not leave home waters without one.

I have never seen any credible source (in fact no source at all) suggesting fluke anchors should not be used as a primary. There are too many Fortress sitting on the bows of boats - and they cannot be there for decoration as they can only be considered an item of outstanding beauty by the manufacturer

Jonathan

[Fortress]

Originally Posted by JonJo

There are too many Fortress sitting on the bows of boats - and they cannot be there for decoration as they can only be considered an item of outstanding beauty by the manufacturer

Jonathan

Jonathan,

Well, you would not be the first to suggest that our anchor "has a face that only a mother could love."

I am presently in Amsterdam exhibiting at the Marine Equipment Trade Show (METS) and a builder from Turkey made this same hurtful comment, as in "no customer wants an anchor that big and ugly on their bow….they want a beautiful stainless steel ornament……a trophy!"

I countered with an emphatic plea to consider the holding power capability, which he was aware of since he already owned one (he was with our Turkish distributor), but he replied, "Nobody cares, they want beauty on the bow!"

Right across from me at this show is the CMP Global stand, and they have a huge stainless steel Rocna anchor rotating around, reminding me of what some apparently think anchor beauty is….

[44'cruisingcat]

Originally Posted by Sharki127

I should have specified that the Displacement/Anchor Weight Ratio applies to the primary anchor. The thread took a turn towards fluke type anchors which are frowned upon as primaries.

Also, the Displacement to Anchor weight ratio should not be confused with the Debt to Assets Ratio which is also abbreviated D/A.

So, what's your D/A?

Ours is around 300:1.

[Coops]

I will retell this story. Bloke comes into the chandlery where I worked on the Gold Coast. he proceeds to moan and groan about the fact that the powder coating is coming off of his anchor. I asked him why he had it powdercoated and he said that it looked ugly as it was. He wanted to know if I agreed with him that his powdercoating should have lasted longer than two years.

He had a Riviera motor cruiser, the boats you buy when you know nothing about boats as they are referred to lovingly here.

Coops.

[44'cruisingcat]

Should have sold him a stainless steel one!

[JonJo]

Beauty is only skin deep, as any mother will tell you - with spouses and anchors you want something/someone on which you can rely, something/someone that will hold on 'come hell or high water'.

When the anchor is under the water then beauty counts for very little - its performance that counts - and a Fortress looks and is 'the business'.

Jonathan

[noelex 77]

Originally Posted by JonJo

If the wind veers though 90 degrees the anchor simply swivels round - and does not as suggested by some breakout and never re-set. This latter seems to be one of those phurphies constantly repeated by those with tunnel vision to the excellence of one design over all else and whose anchor choice is so perfect their anchors never have faults.

I have observed a Fortress breaking out, or at least becoming very unstable with a change of direction of pull on many occasions. It does not happen on every rotation, but other good designs will not do this at all if well set.

On most occasions the anchor will reset, and the owner is unaware that anything has happened, but not always. Hence the reason why the commonly repeated warning about Fortress (and Danforth anchors) in conditions where the direction of pull may change. It is not some great conspiracy, just people relaying their experience.

I took some photos a while ago of a beach test. They are not very well done and I don't think beach tests are very accurate, but it does show the sort of thing I see diving. The Fortress sometime develops a very high list during rotation. If the long stock hits some deeper harder substrate it pivots the anchor out. If the the rotation continues from the photograph the Fortress will completely break out, or just about completely break out.

Fortress are great anchors. They will do what no other anchor will do, but you do need to aware of their Achilles heel.

[JonJo]

Originally Posted by noelex 77

I have observed a Fortress breaking out, or at least becoming very unstable with a change of direction of pull on many occasions. It does not happen on every rotation, but other good designs will not do this at all if well set.

On most occasions the anchor will reset, and the owner is unaware that anything has happened, but not always. Hence the reason why the commonly repeated warning about Fortress (and Danforth anchors) in conditions where the direction of pull may change. It is not some great conspiracy, just people relaying their experience.

I took some photos a while ago of a beach test. They are not very well done and I don't think beach tests are very accurate, but it does show the sort of thing I see diving. The Fortress sometime develops a very high list during rotation. If the long stock hits some deeper harder substrate it pivots the anchor out. If the the rotation continues from the photograph the Fortress will completely break out, or just about completely break out.

Fortress are great anchors. They will do what no other anchor will do, but you do need to aware of their Achilles heel.

2 factors -

This really does not look like a well set anchor.

What would be more convincing of your thesis would be other anchors set to the same level of pull, you will need a load cell and recorder for this, and then they similarly pulled sideways. I think you will find when poorly set on a beach - they will all tip over, pull out and if the fluke is not clogged - reset

All this demonstrates is that a Fortress if poorly set on a beach might tip sideways when loaded at an angle to the set direction. I have done exactly the same thing with other anchors - but I do not try to show them as indicative, of anything.

Fortunately I have done the test in real life - and your beach experiment is not reproducible under water when the anchor has been properly set and used by a yacht.

You will find that anchors that clog (with say weed or cloying mud) when loaded at an angle to set the direction will pull out and simply not re-set (unless or until the clogged fluke is cleared).



Jonathan

[noelex 77]

Originally Posted by JonJo

Fortunately I have done the test in real life - and your beach experiment is not reproducible under water when the anchor has been properly set and used by a yacht.

I have seen this underwater many times. So I guess we will have to agree to disagree on this one.

Originally Posted by JonJo

You will find that anchors that clog (with say weed or cloying mud) when loaded at an angle to set the direction will pull out and simply not re-set (unless or until the clogged fluke is cleared).

It is not very common for a dragging anchor to reset, it is certainly not something you want to put much hope in.
The secret is to keep them set. The good anchors do this remarkably well. They swivel, (or perhaps shuffle is a better verb) around. They do develop a slight list, but don't break out. They barely move rotating around their centre. It is an area of anchor performance that should be studied more.

[congo]

Re: Displacement to anchor weight ratio
Quote:
Originally Posted by JonJo
Fortunately I have done the test in real life - and your beach experiment is not reproducible under water when the anchor has been properly set and used by a yacht.


Noelex wrote:

I have seen this underwater many times. So I guess we will have to agree to disagree on this one.
__________________

looking back over many threads in this forum, I think you all very lucky to have a Noelex supplying so much information from diving, we would never be none the wiser without it. really does defy arguing.
Never the less argue we shall, good anchors you say such as you are describing shuffle around rather than break out is rubbish, I have seen a couple of incidences whereas your anchor design has been sitting on a beach at high tide still clogged from when it broke out, I will try and find a photo from last Christmas.
Regards Rex.

[noelex 77]

Originally Posted by congo

I have seen a couple of incidences whereas your anchor design has been sitting on a beach at high tide still clogged from when it broke out, I will try and find a photo from last Christmas.

I presume by "your anchor design" you mean the Rocna I own rather than my Fortress, or CQR (although sadly I cannot claim influence on any of the designs )

Any anchor can drag. When turning around they all develop at least a slight list and they are a bit more vulnerable at this stage, especially if not set well (or at all), but a good anchor of adequate holding power for the substrate and conditions, set well, will simply rotate around its centre. The anchor breaking out is a situation that carries some risk. To ideally set an anchor needs a slow steady increase in force and this is not always supplied by Mother Nature. So one of the characteristics of a good bower anchor is the ability to remain set while reorienting to the new direction. Not all anchors do this equally.

When anchors drag they rarely reset and yes when an anchor has dragged a reasonable distance it can pick up debris. This is why, especially in weedy areas you want an anchor that sets reliably in a very short distance. This is a major improvement of the good new generation anchors that can usually set in in a metre or so.

[JonJo]

Every time I see a roll barred concave anchor being lifted in areas of cloying mud, heavy clay or weed the anchor breaks the surface full of seabed. Sometimes it takes the owners a considerable period of time to clear the clod using a power wash and digging at it with a broom handle. This is not an issue in clean sand.

This might not be an issue with Mantus as it has a very wide fluke and roll bar and has less restriction to passage of seabed though the constricted area. it is not an issue with Spade and Ultra as there is no restriction nor compression (compression occurs under the toe).

Mud, heavy clay, weed bottoms are not unusual.

I fail to see given the very considerable effort needed to clear such material how the anchor will reset should it break free The argument that a well set anchor does not break free sounds like marketing fluff to me. Having conducted tests I can assure you anchors do break free but if tests are conducted with clogged concave roll barred anchors they sometimes do not reset.

Perhaps this is the Achilles heal of concave roll bar anchors that owners, having spent so much money, do not care to share with other cruisers. Shame on them.

Jonathan

[Delancey]

Regarding concave roll bar anchors collecting debris and getting jambed up, see the abstract in the attached image. Obviously, with the roll bar aft of the shank this maybe doesn't matter so much, or maybe it does.

Either way it makes a case for the Mantus fluke with the flat spot, and a case against the other concave styles that have the shank located right in the middle of the single peak pressure zone that comes with not having a flat spot.

Think of a Ronco or Mason Supreme with a V-shaped fluke that puts the shank right at the intersection of tangents of the angled fluke surfaces.