Fortress scaling plot

[geem]

Fortress produce a great anchor, but they don’t set well (or sometimes at all) in hard substrates and are poor at responding to changes in the direction of pull. Unfortunately, they often develop a high list and break out as they try and rotate. These reasons are why they are a poor primary anchor (although they are an excellent kedge anchor).

Your Spade will work much better in this situation and a 30 kg model is a decent size for your Trintella 44. On my reading this 30 kg Spade is oversized for your 44 foot 32,000 lb yacht. (Spade rate your 30 kg model as suitable for boats up to 65 feet) so perhaps you are member of the BIB (Big Is Better) club without knowing it .

I have never had any trouble setting my oversized Mantus M1 anchor, or before this my identically sized Rocna anchor. The Mantus M1 in particular is invariably the best set anchor in the anchorage . You can see photos in the link below showing this anchor together with the anchors from all the other boats nearby and make up your own mind.

I have used an oversized Rocna or Mantus M1 over 16 years of full time cruising, anchoring almost every day. I often dive to observe how the anchor is performing. These anchors have always "shuffled" ie remained buried and engaged with the seabed when rotating around in response to a change in wind direction. Once again, there are many photos of this happening in the link below.

In short, I don’t believe there is any risk of the issues you have been having with your Fortress anchor if you oversize a good primary anchor. The fact that you have observed a deep setting depth from your relatively large Spade anchor reinforces this view.

Photos of Anchors Setting - Page 111 - Cruisers & Sailing Forums

Hmm, we weigh 40,000lbs most times we have lifted out. I selected the Spade for it's actual weight not the empty weight. We just weighed the rudder. It's 250kg. My 30kg Spade is 19kg with no lead in the tip. Will it make it better if I add 5kg to the tip weight?

 

[thinwater]

I thought anchor threads only ended with the heat death of the universe and then only maybe!

And then only because God got a headache and ended everything, just to kill the thread.

 

[thinwater]

Just so. When perfect Universal equilibrium is attained, there is nothing to suggest it can't kick off all over again.

Wait a second. I think I remember that happening, on some other forum....

 

[Neeves]

Do you have room in the ballast chamber for another 5kg of lead + a layer, say 10mm, of resin to seal the chamber?

Personally I don't think you will notice any difference nor do I think if you used a load cell would you indentify any increased hold. The hold characteristics might change - get worse because the extra weight you will add will be back toward the heel, not in the actual toe (which might improved reliability of setting). I don't see hold increasing because the surface area remains constant.

In any event - have you noticed anything wrong with the Spade over the years - if you are happy why change anything.

The only improvement I would make to a Spade is, I would dispense with the hollow shank and used thin HT steel instead of the fabricated structure. I'd also like a sharper toe - but cannot see how to do that - really you have to add a pointy bit (weld it on). Spade has the bluntest, or one of the bluntest toe, of most anchors - in hard seabeds the recommendation is - sharpen the toe.

Jonathan

 

[Neeves]

If one reason to carry the Fortress is to give security in soft muds - then you need size and you need to accept that the same anchor will set only shallow in other seabeds. The answer if you also want a back up anchor is not to rely on the 'mud sized' Fortress (which will set deeply in sand if you are hit by a Typhoon, Cyclone etc) and source another primary (with a similar hold to your Spade) but of a different design. I don't think weight is an issue for you, but anchors do take up a lot of room.

I'm personally not in favour of demountable anchors - when you want an anchor you want it NOW (not in 30 minutes time when you have found the spanner to tighten the bolts). I have this nagging thought demountable anchors were designed to allow cheap shipping (which hopefully is passed on to the market place). We carried an FX 37, for mud - it was carried assembled, but we had a big bow locker,

A consistent complaint of Fortress after a hurricane etc is that the anchor worked as expected - did not drag etc etc - but simply could not be retrieved. It was buried too deep well beyond the retrieval capabilities of the yacht. I have this thought that Brian Sheehan replaced lost anchors for such reasons under their no question asked warranty - but this might not be correct.

Jonathan

 

[geem]

Do you have room in the ballast chamber for another 5kg of lead + a layer, say 10mm, of resin to seal the chamber?

Personally I don't think you will notice any difference nor do I think if you used a load cell would you indentify any increased hold. The hold characteristics might change - get worse because the extra weight you will add will be back toward the heel, not in the actual toe (which might improved reliability of setting). I don't see hold increasing because the surface area remains constant.

In any event - have you noticed anything wrong with the Spade over the years - if you are happy why change anything.

The only improvement I would make to a Spade is, I would dispense with the hollow shank and used thin HT steel instead of the fabricated structure. I'd also like a sharper toe - but cannot see how to do that - really you have to add a pointy bit (weld it on). Spade has the bluntest, or one of the bluntest toe, of most anchors - in hard seabeds the recommendation is - sharpen the toe.

Jonathan

I have not had a problem with the Spade setting unless there is a reason. Such as coral or rocks. It was really a rhetorical question. The Spade anchor works in my opinion, because the anchor weigh/fluke area combination is correct for my boat/engine combination. We can power set the anchoring in our normal Caribbean anchoring spots such that the anchor buries. I don't know what load this power setting creates, but it's enough foe a good set. The anchor only sets deeper after a blow of 35kts or higher. At this wind speed, the deeper set makes anchor retrieval interesting. Once the windlass has pulled the chain vertically over the anchor, the windlass will often stall out trying to recover thr buried anchor. Its a large powerful windlass. I will be on the helm and my wife operating the windlass. I can see the bow of the boat dip. I tell my wife to stop and I drive forward on tick over to break out the anchor.

 

[Neeves]

I have not had a problem with the Spade setting unless there is a reason. Such as coral or rocks. It was really a rhetorical question. The Spade anchor works in my opinion, because the anchor weigh/fluke area combination is correct for my boat/engine combination. We can power set the anchoring in our normal Caribbean anchoring spots such that the anchor buries. I don't know what load this power setting creates, but it's enough foe a good set. The anchor only sets deeper after a blow of 35kts or higher. At this wind speed, the deeper set makes anchor retrieval interesting. Once the windlass has pulled the chain vertically over the anchor, the windlass will often stall out trying to recover thr buried anchor. Its a large powerful windlass. I will be on the helm and my wife operating the windlass. I can see the bow of the boat dip. I tell my wife to stop and I drive forward on tick over to break out the anchor.

Text book practice.

You have answered your own question - you don't need to add extra ballast.

Some of the equipment for yachts is commonly sized on the basis of yacht length, anchors and chain, come to mind. I suspect engines are also similarly chosen on the basis of a crude HP vs Length equation. Its all a bit crude - but it seems to work.

I know that its not all about HP but the propellor effectiveness as well - - - etc etc.

I'd have said that revving engine(s) to cruising revs for power setting an anchor, not maximum, was about equal to 30 knots of wind so your cut in at 35 knots seems to fit the crude 'equation'.

I'm also of the view that if you power set your anchor in sand and stay in the same anchorage for a decent period of time, many days, that the anchor settles further. The constant movement of the yacht is transmitted by the rode to the anchor and the constant gentle twitching of the anchor reduces shear strength of the seabed - and the anchor settles into the seabed. A bit like the 'toy' using 2 tin cans and storing to establish a communication device. I think Thinwater made mention of a similar phenomena in Chesapeake in mud where the action would be accelerated to a few hours. Tests on very large, permanant moorings - for commercial vessels also 'enjoy' enhanced hold after 'earthquake' tremors.

Jonathan

 

[vyv_cox]

I'm also of the view that if you power set your anchor in sand and stay in the same anchorage for a decent period of time, many days, that the anchor settles further. The constant movement of the yacht is transmitted by the rode to the anchor and the constant gentle twitching of the anchor reduces shear strength of the seabed - and the anchor settles into the seabed. A bit like the 'toy' using 2 tin cans and storing to establish a communication device. I think Thinwater made mention of a similar phenomena in Chesapeake in mud where the action would be accelerated to a few hours. Tests on very large, permanant moorings - for commercial vessels also 'enjoy' enhanced hold after 'earthquake' tremors.

Jonathan

Very many years ago we raced a regatta at Fleetwood, a place of very strong tides that dry to sand for miles. I noticed that a large channel marker buoy had no chain lying on the sand, thus it became submerged at HW. The harbourmaster told me that the concrete weight to which the buoy was attached had sunk into the sand. This happened regularly. In the past they had tried digging them out but the chain was vertical. Apparently the block simply sank into the sand straight down, dragging the chain and sometimes the buoy with it.

 

[geem]

Very many years ago we raced a regatta at Fleetwood, a place of very strong tides that dry to sand for miles. I noticed that a large channel marker buoy had no chain lying on the sand, thus it became submerged at HW. The harbourmaster told me that the concrete weight to which the buoy was attached had sunk into the sand. This happened regularly. In the past they had tried digging them out but the chain was vertical. Apparently the block simply sank into the sand straight down, dragging the chain and sometimes the buoy with it.

I was there last month. Those tides get pretty strong

 

[NormanS]

My anchor is ignorant. It can't tell and therefore doesn't know whether it's being "power set" using an engine (commonly used by motor boats), or if it's merely being pulled in by the windage of the boat.

 

[geem]

My anchor is ignorant. It can't tell and therefore doesn't know whether it's being "power set" using an engine (commonly used by motor boats), or if it's merely being pulled in by the windage of the boat.

I really don't think it makes a huge difference when I anchor in UK waters. The tidal nature of UK waters seems to provide good sand or mud. Maybe some kelp to be avoided but very different to my experience anchoring in none tidal waters where we see lots more hard seabeds with a mixture of hard sand and broken coral. The problem comes when there is little wind to set the anchor and it just lies on the seabed on its side. It doesn't get set ( or not set) until the wind picks up. Only then do you know if the tip is fouled or you have picked the only kelp for miles around. It's not always needed, but power setting removes the doubt

 

[boomerangben]

Just so. When perfect Universal equilibrium is attained, there is nothing to suggest it can't kick off all over again.

That got me thinking…. Does the Starship Enterprise have a Vulcan anchor?

 

[Neeves]

That got me thinking…. Does the Starship Enterprise have a Vulcan anchor?

I was invited on board the Enterprise to identify if I could help then with exactly this problem. Spock showed me around and I suggested they contact Brian Sheehan, who on leaving Fortress joined Dockmate. Brian offered them a better solution which was to install extra thrusters and by using the Dockmate system the vessel could simply be held in geostationary orbit and they then used the teleporters to disembark. As the vessels are powered by a combination of nuclear and solar keeping the whole thing powered up was not an issue. They did not really like the idea of anchor, or anchors, as the vessel is very weight conscious and the extra weight of the anchor plus the rode was an issue.



Jonathan

 

[Tranona]

I really don't think it makes a huge difference when I anchor in UK waters. The tidal nature of UK waters seems to provide good sand or mud. Maybe some kelp to be avoided but very different to my experience anchoring in none tidal waters where we see lots more hard seabeds with a mixture of hard sand and broken coral. The problem comes when there is little wind to set the anchor and it just lies on the seabed on its side. It doesn't get set ( or not set) until the wind picks up. Only then do you know if the tip is fouled or you have picked the only kelp for miles around. It's not always needed, but power setting removes the doubt

Not too different from many places in the Med where the deficiencies of "traditional" anchors and techniques quickly show. Maybe some people need to get out more to appreciate the variety of different situations that need different techniques. anchors may be inanimate objects but they do have different characteristics and behave in different ways in relation to the way they are used.

 

[NormanS]

Not too different from many places in the Med where the deficiencies of "traditional" anchors and techniques quickly show. Maybe some people need to get out more to appreciate the variety of different situations that need different techniques. anchors may be inanimate objects but they do have different characteristics and behave in different ways in relation to the way they are used.

You owe it to us to itemise and explain what you consider to be these "different techniques".

 

[Neeves]

You owe it to us to itemise and explain what you consider to be these "different techniques".

Like others Tranona volunteers his deep knowledge when he has the time and I have found his knowledge reliable. I suspect that if you trawl through his posts, using the YBW search engine, you will find the answer you demand.

Jonathan

 

[Tranona]

You owe it to us to itemise and explain what you consider to be these "different techniques".

Given that you are an avid reader of anchor threads I would assume you have found that out for yourself.

However just to give you a taste. Compare your style of anchoring in your conditions with your boat and its gear with me parking my Bavaria backwards to a quay in the Ionian, with 6m of water shelving to 3m and a seabed consisting of a thin layer of churned up sand sitting on top of an almost solid layer of compacted mud. The role of the anchor is to hold the boat off the quay against the stern warps. The anchor has to be dropped about 30m from the quay, avoiding all the other boats' anchors, get a hold quickly while the boat reverses into a specific gap almost as wide as the boat. Just for extra fun there is a 20 knot crosswind.

Get the message - this is a routine for cruisers and charters who wish to spend the night moored up in front of the taverna. No tide, no choice of finding "good holding" so the engine has to be used for "power setting" and anchor chosen to work in those conditions.

 

[NormanS]

Given that you are an avid reader of anchor threads I would assume you have found that out for yourself.

However just to give you a taste. Compare your style of anchoring in your conditions with your boat and its gear with me parking my Bavaria backwards to a quay in the Ionian, with 6m of water shelving to 3m and a seabed consisting of a thin layer of churned up sand sitting on top of an almost solid layer of compacted mud. The role of the anchor is to hold the boat off the quay against the stern warps. The anchor has to be dropped about 30m from the quay, avoiding all the other boats' anchors, get a hold quickly while the boat reverses into a specific gap almost as wide as the boat. Just for extra fun there is a 20 knot crosswind.

Get the message - this is a routine for cruisers and charters who wish to spend the night moored up in front of the taverna. No tide, no choice of finding "good holding" so the engine has to be used for "power setting" and anchor chosen to work in those conditions.

Thanks for that. It is indeed very different from the anchoring that I do. But look on the bright side, you do have certain advantages:

You know that people habitually anchor there, so you can assume that the seabed is fairly forgiving, or nobody would anchor there.
Your boat is not subject to yawing, and so the direction of pull on the anchor is pretty constant.
You have no tide to worry about, either in terms of a varying depth, or a change in the direction of current.
The fact that the seabed shelves up towards the shore is a benefit. Anchors are much less liable to drag uphill.
Presumably you choose to anchor so that you can "spend the night moored up in front of the taverna".

Each to their own. Our anchoring is more like wild camping, while yours is more like being in a camp site. "Vive la difference".

 

[noelex]

The fact that the seabed shelves up towards the shore is a benefit. Anchors are much less liable to drag uphill.

This is a good point. It is easy to underestimate the effect of the slope of the seabed on the holding ability of an anchor. One simple way is to calculate the "effective scope".

The maths is quite easy. Below is a typical example with an anchor dropped on a section of seabed sloping at 5.7 degrees (10m drop over 100m) with a nominal scope of 5:1.

The effective scope varies from 10 :1 to 3.4 :1 depending on the direction of pull.

 

[AntarcticPilot]

Thanks for that. It is indeed very different from the anchoring that I do. But look on the bright side, you do have certain advantages:

You know that people habitually anchor there, so you can assume that the seabed is fairly forgiving, or nobody would anchor there.
Your boat is not subject to yawing, and so the direction of pull on the anchor is pretty constant.
You have no tide to worry about, either in terms of a varying depth, or a change in the direction of current.
The fact that the seabed shelves up towards the shore is a benefit. Anchors are much less liable to drag uphill.
Presumably you choose to anchor so that you can "spend the night moored up in front of the taverna".

Each to their own. Our anchoring is more like wild camping, while yours is more like being in a camp site. "Vive la difference".

I'm afraid your first assumption is not correct. People use their anchor there because a quay is available for that style of mooring; it's the standard type of mooring in the Mediterranean. In fact, others have often bewailed the problem of poor holding and foul seabeds in such locations!