Fortress anchor mud setting

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I usually leave the anchor on mud setting when it always sets solidly and reliably _ in mud. However I used it for a short lunch stop on hard sand and it dragged in very gentle winds twice. I put down the Knox and fine. So drying out up a sloping beach and not wishing to be pushed up the beach and get healed I set the Fortress as a stern znchor. When I was dried out l was shocked to find it just turned turtle on the hard sand with me pulling it. I was expecting the efficiency to be less with a mud setting in hard sand but did not expect it not to work at all. Anchoring experts will be aware of this but I was not, as I suspect as some other. It set perfectly on the sand setting.
 
When a Fortress sets it turns on its side resting approximately on one toe, one side of the fluke, its stock and its shackle point - a rather ungainly tripod. Most other anchor set the same way, on their side (minus the stock). In sand, and especially hard sand, the best engagement angle is 30 degrees - which is how most anchors are designed (Fortress at 45 degrees being one of the exceptions). With the fluke at 45 degrees and a hardish sea bed the fluke simply scrape across the surface and simply cannot slice into the seabed.

In really hard sand you need a lower angle than 30 degrees and the only anchor I know of is a Mantus but its engagment angle is 16 degrees and it sacrifices hold for better penetration in a hard seabed. The sacrifice is 50% of the hold of a similarly sized anchor optimised for 30 degrees (I know this as I've modified a Mantus to allow it to engage at 30 degrees). The hard seabed for which Mantus seems designed is an illusion (and buying one is a waste of money) as the number of times people report their anchor has been defeated by a seabed too hard is virtually zero (I know of one example). Viking seems optimised at 26 degrees (and I don't know of an anchor optimised at less than 30 degrees except Viking (and Mantus) - and the manufacturer of Viking believes the anchor develops sufficient hold at this lower angle and retains other beneficial characteristics. I cannot argue with this idea of designing hold to be 'enough' a Rocna, Excel, Spade etc etc has the potential to develop more than enough hold - you will never, ever ,approach the ultimate hold - so having enough (more than enough) and designing other positive characteristics seems sensible.

You can 'copy' this behaviour with a spade (shovel) in hard soil - if you try to dig in hard soil but are also pulling the spade across the surface, as when you set an anchor, the spade at an angle of 45 will simply scrape - the one at 30 degrees has a better chance of engaging - breaking through the surface. Lots of work on this over decades - which is why everyone uses that common 30 degrees (CQR, Danforth, Delta, Bugel, Spade etc etc.

As soon as the fluke can make that initially penetration - you are home and dry - as once the toe engages sufficiently the rest of the fluke will follow - until the anchor sets, locks up.

This is all well known and is in no way a fault of the anchor. Which is why 45 degrees is the setting for mud and 30 degrees the setting for sand.

If you had set the flukes at 30 degrees you would not have had the issue but I'm the first to admit its a real faff altering the fluke angle. For this reason we carry a FX 16 set at 30 degrees and a FX 37 set at 45 degrees. Our anchorages open to the sea (Tasman or Coral Sea) are sand but our rivers tend to be mud (and are the location of oyster farms (mud and oyster farms go together).

Rocna et al will be fine in firm mud but in squishy mud they are as useless as a Fortress set at 45 degrees in hard sand. Most anchor, Excel, Rocna, Spade etc etc rely on a firms seabed to self right - if they land 'upside down' in a soft seabed they cannot self right and will drag for ever in thin mud. (and then you need your Fortress). And in squishy mud you need more surface area, for reliable hold - which is why we carry the big Fortress set at 45 degrees.

Anchors are a compomise, there is no perfect anchor - horses for courses. Don't let complacency set in - your Rocna, Excel, Spade etc etc will let you down in thin mud - been there, done that - tested it and found it out in real life.

There is a school of thought that suggests letting your anchor settle in thin mud will give it time to develop hold (this may or may not be true - I'm not convinced having seen anchor upside down in thin mud - they never, ever, self right). I'd rather use the correct anchor and then me and the crew settle down rather than wait for an anchor to settle (or not).

Jonathan
 
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C08 said:
I usually leave the anchor on mud setting when it always sets solidly and reliably _ in mud. However I used it for a short lunch stop on hard sand and it dragged in very gentle winds twice. I put down the Knox and fine. So drying out up a sloping beach and not wishing to be pushed up the beach and get healed I set the Fortress as a stern znchor. When I was dried out l was shocked to find it just turned turtle on the hard sand with me pulling it. I was expecting the efficiency to be less with a mud setting in hard sand but did not expect it not to work at all. Anchoring experts will be aware of this but I was not, as I suspect as some other. It set perfectly on the sand setting.
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This is right in the instructions. The mud setting is ONLY for soft mud. Not a surprise at all.
 
Neeves said:
When a Fortress sets it turns on its side resting approximately on one toe, one side of the fluke, its stock and its shackle point - a rather ungainly tripod. Most other anchor set the same way, on their side (minus the stock). In sand, and especially hard sand, the best engagement angle is 30 degrees - which is how most anchors are designed (Fortress at 45 degrees being one of the exceptions). With the fluke at 45 degrees and a hardish sea bed the fluke simply scrape across the surface and simply cannot slice into the seabed.

In really hard sand you need a lower angle than 30 degrees and the only anchor I know of is a Mantus but its engagment angle is 16 degrees and it sacrifices hold for better penetration in a hard seabed. The sacrifice is 50% of the hold of a similarly sized anchor optimised for 30 degrees (I know this as I've modified a Mantus to allow it to engage at 30 degrees). The hard seabed for which Mantus seems designed is an illusion (and buying one is a waste of money) as the number of times people report their anchor has been defeated by a seabed too hard is virtually zero (I know of one example). Viking seems optimised at 26 degrees (and I don't know of an anchor optimised at less than 30 degrees except Viking (and Mantus) - and the manufacturer of Viking believes the anchor develops sufficient hold at this lower angle and retains other beneficial characteristics. I cannot argue with this idea of designing hold to be 'enough' a Rocna, Excel, Spade etc etc has the potential to develop more than enough hold - you will never, ever ,approach the ultimate hold - so having enough (more than enough) and designing other positive characteristics seems sensible.

You can 'copy' this behaviour with a spade (shovel) in hard soil - if you try to dig in hard soil but are also pulling the spade across the surface, as when you set an anchor, the spade at an angle of 45 will simply scrape - the one at 30 degrees has a better chance of engaging - breaking through the surface. Lots of work on this over decades - which is why everyone uses that common 30 degrees (CQR, Danforth, Delta, Bugel, Spade etc etc.

As soon as the fluke can make that initially penetration - you are home and dry - as once the toe engages sufficiently the rest of the fluke will follow - until the anchor sets, locks up.

This is all well known and is in no way a fault of the anchor. Which is why 45 degrees is the setting for mud and 30 degrees the setting for sand.

If you had set the flukes at 30 degrees you would not have had the issue but I'm the first to admit its a real faff altering the fluke angle. For this reason we carry a FX 16 set at 30 degrees and a FX 37 set at 45 degrees. Our anchorages open to the sea (Tasman or Coral Sea) are sand but our rivers tend to be mud (and are the location of oyster farms (mud and oyster farms go together).

Rocna et al will be fine in firm mud but in squishy mud they are as useless as a Fortress set at 45 degrees in hard sand. Most anchor, Excel, Rocna, Spade etc etc rely on a firms seabed to self right - if they land 'upside down' in a soft seabed they cannot self right and will drag for ever in thin mud. (and then you need your Fortress). And in squishy mud you need more surface area, for reliable hold - which is why we carry the big Fortress set at 45 degrees.

Anchors are a compomise, there is no perfect anchor - horses for courses. Don't let complacency set in - your Rocna, Excel, Spade etc etc will let you down in thin mud - been there, done that - tested it and found it out in real life.

There is a school of thought that suggests letting your anchor settle in thin mud will give it time to develop hold (this may or may not be true - I'm not convinced having seen anchor upside down in thin mud - they never, ever, self right). I'd rather use the correct anchor and then me and the crew settle down rather than wait for an anchor to settle (or not).

Jonathan
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Thanks for such a detailed analysis, it is a pfaf to reset the Fortress angle from mud to sand so I might get another fortress set up as a mud anchor. The Knox is good.
 
What I find is that very thin sloppy mud, generally has firmer mud under it. Accordingly, I find that whichever anchor I use digs down through the sloppy stuff until it gets a grip in the firmer stuff. Because of that, I don't even think about setting my Fortress to 45°.
 
From the instructions on the Fortress web site:

4. Re-assemble the anchor with the stock going through this other
hole, which should be covered with a sticker that says “Soft Mud
Anchoring only”.

Most people never use that setting. I would only use it If was going to be weathering a major storm in soft mud... which I would try hard to avoid.
 
C08 said:
Thanks for such a detailed analysis, it is a pfaf to reset the Fortress angle from mud to sand so I might get another fortress set up as a mud anchor. The Knox is good.
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If you follow up on this - note that in thin mud the Fortress recommended for your yacht might be a bit small - so go for the next size up. Contrarily I find Fortress sizings a bit big. This is maybe because the smaller anchors, the size smaller than recommended might be perfectly adequate - but they set so deeply they are a devil to retrieve, after a decent blow. If you might be deploying from a dinghy - smaller is easier and once you get to FX 37 they are monsters (or I think so). If you are carrying them assembled - you need somewhere quite large to store them. Being a faff to assemble we carry them assembled and they fit neatly against the locker wall. But many will not have a big locker and you can source, or easily make, brackets to store them assembled on the transom. Lots of compromises.

The size Fortress, the then top man in Fortress, recommended a FX23 - we now carry a FX 16 and a FX 37.

Our FX 37 is set for mud and the FX16 set for sand. We would use the FX 16 predominately deployed from the dinghy. In clean sand in a straight line - its as good as you can get

If you go into the Fortress website you will find reports on their tests a couple of years back in Chesapeake - they tested a whole batch of anchor, most of which were blatantly inadequate in the seabed they chose (they were making a point - successfully) but they also tested 2 sizes of Fortress and even the big Fortress in thin mud did not have a 'buller proof' hold - hence the reason to go 'bigger'. But if you will never experience thin mud - just go for one size.

I don't know if the Lewmar LFX is easier to assemble and change angles - nor know how much it costs. I assume (one should never assume) that it performs as well as the Fortress but it might be cheaper and its assembly might be simpler.

I understand Fortress come on on eBay intermittently in the UK.

Note that the Guardian is a fixed angle, is not anodised, the flukes are not honed and the shank not tapered - but it is cheaper. Also the Guardian only has a circular hole for the shackle, so only takes a shackle pin - which means you need 2 shackles as the eye of the shackle sized for the anchor will be far too large for the appropriate chain - just more compromises!

Finding the appropriate anchor for the seabed, and you often have little idea what the seabed is actually like until you try, is a bit hit and miss. You found out the hard way - and you will not forget :).

We would not sail without our Fortress.

Jonathan
 
Neeves said:
If you follow up on this - note that in thin mud the Fortress recommended for your yacht might be a bit small - so go for the next size up. Contrarily I find Fortress sizings a bit big. This is maybe because the smaller anchors, the size smaller than recommended might be perfectly adequate - but they set so deeply they are a devil to retrieve, after a decent blow. If you might be deploying from a dinghy - smaller is easier and once you get to FX 37 they are monsters (or I think so). If you are carrying them assembled - you need somewhere quite large to store them. Being a faff to assemble we carry them assembled and they fit neatly against the locker wall. But many will not have a big locker and you can source, or easily make, brackets to store them assembled on the transom. Lots of compromises.

The size Fortress, the then top man in Fortress, recommended a FX23 - we now carry a FX 16 and a FX 37.

Our FX 37 is set for mud and the FX16 set for sand. We would use the FX 16 predominately deployed from the dinghy. In clean sand in a straight line - its as good as you can get

If you go into the Fortress website you will find reports on their tests a couple of years back in Chesapeake - they tested a whole batch of anchor, most of which were blatantly inadequate in the seabed they chose (they were making a point - successfully) but they also tested 2 sizes of Fortress and even the big Fortress in thin mud did not have a 'buller proof' hold - hence the reason to go 'bigger'. But if you will never experience thin mud - just go for one size.

I don't know if the Lewmar LFX is easier to assemble and change angles - nor know how much it costs. I assume (one should never assume) that it performs as well as the Fortress but it might be cheaper and its assembly might be simpler.

I understand Fortress come on on eBay intermittently in the UK.

Note that the Guardian is a fixed angle, is not anodised, the flukes are not honed and the shank not tapered - but it is cheaper. Also the Guardian only has a circular hole for the shackle, so only takes a shackle pin - which means you need 2 shackles as the eye of the shackle sized for the anchor will be far too large for the appropriate chain - just more compromises!

Finding the appropriate anchor for the seabed, and you often have little idea what the seabed is actually like until you try, is a bit hit and miss. You found out the hard way - and you will not forget :).

We would not sail without our Fortress.

Jonathan
Click to expand...

Thanks for this and especially the comment on sizing. What is the length and weight of your boat?
 
stuartwineberg said:
Thanks for this and especially the comment on sizing. What is the length and weight of your boat?
Click to expand...

First up

I mention that the Guardian, the cheaper version of the Fortress, is not anodised - I have never heard of anyone mention that this is is an issue. But maybe they don't sell many.

We sail a Lightwave 38 catamaran (38' x 22'6"). F ully laden for a 3 month cruise to Tasmania we weigh around 7t. We have a similar windage to a Bav 45 (I've measured them both). We draw 1m, mini keels (I don't recall but a Bav 45 will draw about 2m and will weigh around 14t in full cruising mode).

It merits mention all our anchors are aluminium, an aluminium Spade A80, aluminium Anchor Right Excel and 2 x Fortress, the 16 and 37. The Spade and Excel steel equivalents weigh 15kg vs 8kg for the aluminium versions. We use a lightweight rode of high tensile 6mm chain, 75m, and we use a bridle with 30m 'arms' of 12mm dynamic climbing rope. We have a spare rode of 15mm x 6mm HT chain + 40m of 12mm 3 ply nylon and can cobble together at least one more rode (we carry spare chain to put round rocks for shore lines).

Jonathan
 
Hi Jonathan, in #3 you say that when a Fortress sets, it turns on it's side. I find that to be an extraordinary statement. Would you like to explain? It's certainly not been my experience.
 
I’m slightly confused by all this Fortress talk. We have a Fortress anchor that we have as a kedge. It was second hand and unused when I bought it 15 years ago. It came with what were described as ‘mud plates’ as an optional extra. It’s in the bottom of the cockpit locker and I’ve never used it!

Have Fortress changed their design? Should I be worried?
 
NormanS said:
Hi Jonathan, in #3 you say that when a Fortress sets, it turns on it's side. I find that to be an extraordinary statement. Would you like to explain? It's certainly not been my experience.
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I'm pleased that you find it extraordinary :) and that you have an enquiring mind.

When a Fortress sets one toe, or the other catches, the anchor slews round, because one toe has caught, then the stock on the side catches and the whole anchor further slews round and lifts the uncaught stock off the seabed. During all this the toe of the anchor and the 'other' fluke are burying and as the anchor further engages the two flukes tend toward centralisation. Unless you actually watch a Fortress setting, again and again - you will not see this. Looking at a set Fortress tells you the end result - not the bit in-between. The idea that a Fortress sits flat on the seabed and sets symmetrically is but a nice idea.

If you think it sets 'flat' and symmetrical. Consider a Fortress lying flat on the sea bed. You apply tension and the anchor moves forward, then the toe catches. For the anchor to remain symmetrical the anchor must be able to balance on the toe ()which is very narrow) and the seabed has to be perfectly even in hardness. A slight difference in texture or hardness and one tow will set more quickly and the whole anchor will fall over, and rest on the angle of the fluke edge and the stock - if you like - its on its side. The stock ensures that the angle part of the fluke edge engages with the seabed.

However the anchor does not always attain symmetry and you will often find, in a set Fortress, that one side of the stock protrudes and that the anchor is still lying at an angle.

This is another reason to use a smaller Fortress. One of the more common complaints of a Fortress is that in a change of tide the anchor can easily self trip. If you consider the common advise (to oversize your anchor) then a big anchor, and a big Fortress is very difficult to set deeply - so to have a half buried Fortress with one side of the stock skying is a recipe for tripping. Undersizing offers you a better chance of burying fluke, crown and stock. Many people carry a Fortress as a storm anchor (because it is so effective in sand) and for a storm anchor people want size (and they also think they want weight - so they use bigger still) - no wonder it self trips when used in application other than a storm

Most anchors a re designed that the fluke penetrates the seabed at about 30 degrees, it does vary between about 25-35 degrees. You will also note that a Rocna, Excel, Kobra, Spade buries the shackle end of the shank and the toe simultaneously and these 2 components bury at roughly the same rate, so the shank buries with the fluke. As the anchor buries and fluke and shank are burying the anchor need pull chain into the seabed - all driven by your engine if you are power setting or wind otherwise. A Fortress will bury all of the fluke before the shank begins to bury. Shanks do not add to holding capacity, except in terns of veering or yawing resistance but they do resist burial. As the shackle buries it 'is lifted' because the seabed resists its burial and the tension angle on the anchor is NOT the scope angle but the shackle angle (you will find this extraordinary as well). But because the Fortress does not bury the shank until all the fluke is buried the tension on a Fortress fluke is the scope angle whereas the tension on a Rocna will be higher, and higher as it buries. A Fortress is hardly perfect (show me an anchor that is perfect) but it is surprisingly effective (Danforth and Ogg knew what they were doing!).

A Fortress is not unusual in setting, on its side, virtually all anchor set on their side, or from their side. They usually set with the shackle on the seabed and the fluke edge on the seabed - as they bury the toe sets more quickly because it presents least resistance and the anchor tends toward lying symmetrically.

John, Mud palms are standard, they are no longer an option, on a Fortress and should be installed permanently - or every time you use it. You must have a very old model. I don't think your experience unusual - I'm sure many carry unused Fortress (which is why there some for sale fairly regularly on eBay). Duncan beat me to it as I was taking too long to polish my script :(

Jonathan
 
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I think the Supermax, sold in the US and I have never seen one), is the only other anchor that allows the fluke angle to be varied (this is fluke angle with relation to seabed). Now joined by the Lewmar LFX. To me this suggests that the market for anchors that work in mud is not large - or we would have other anchors with the ability to vary fluke angle.

We were on the Mekong a couple of years ago and I checked the anchors being used on the river barges - without exception they were almost all Danforth 'types' and were set at 40 degrees. They also carried 'fishermans' which they used when tying up to the river bank (burying one fluke in the river bank)

Jonathan
 
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