How should I anchor?

[Fascadale]

Happy New Year everyone and thanks for all the excellent advice.

In the OP the hypothetical question described the haphazard collection of anchoring gear on my own boat. I have often wondered how I would best deploy it in more challenging conditions. So having carefully read all the advice, and with the gear on my boat I would......................

..........................lie to one rode, with the Manson Supreme at the end of it. I am not confident that any of the other three, the Fisherman, the CQR or the Bruce, all on short chains but longish ropes, have the holding power to merit being on a rode of their own in strong to very strong winds.

So eggs in one basket. I would lay out all 50ms of the 8mm chain plus ten or so metres of the 16mm multi plait giving me a scope of about 7:1. My existing nylon snubber would give me about another 5 ms as well as giving me some extra shock absorption.

I would dismantle the number three rode and shackle the Fisherman and Bruce to the main rode about 5 metres in front of the Manson. ( we do have some dive gear onboard ) Hope fully these anchors might give some extra holding; they would, to an extent, act as a chum/kellet and they would add friction to the rode going some way hopefully to minimising movement in the main anchor. I would also be very tempted to take the advice to use the chain from the no 3 rode as an extra angel/chum on the main rode.

As also advised I would keep the number 2, CQR rode as a back up ( the yacht in the Vathi storm was forced to cut her primary rode at the bitter end)

I’m slightly surprised there has been so little discussion of strategies to minimise “sailing to the anchor” and thus snatching from wider angles thereby shaking loose the anchor.

In my hypothetical situation and with the equipment to hand I think I would hang the unused rope from rode 3 in loops over the bow along with a couple of buckets. That might dampen the yawing a bit.

After that it it would be anchor watches, preparation of Plan B, lashing everything down, minimising windage, engine on if things got even worse and of course, a cup of tea.

Equipment I would like to have: a riding sail, unfortunately I can no longer find the video of the late and great “Piotaskipper’s” double sail. I would want to copy that. I would also want a better but dismountable no. 2 anchor so as to equip myself for V anchoring, a “Viking 20” looks the business. I think I shall also be making myself a two legged “storm snubber” as shown in this article, Safety at Sea: Surviving a Powerful Storm in the Med And I shall be visiting my local climbing wall. Light weight high tensile chain does sound good but with limited funds………………

And finally I do apologise if this thread has been a rehash of many of the other anchoring threads I have read over the last years but heyho, after 50 years sailing over 50K nms I still have questions to ask and there is still plenty for me to learn. Happy New Year from Scotland.

 

[NormanS]

Happy New Year everyone and thanks for all the excellent advice.

In the OP the hypothetical question described the haphazard collection of anchoring gear on my own boat. I have often wondered how I would best deploy it in more challenging conditions. So having carefully read all the advice, and with the gear on my boat I would......................

..........................lie to one rode, with the Manson Supreme at the end of it. I am not confident that any of the other three, the Fisherman, the CQR or the Bruce, all on short chains but longish ropes, have the holding power to merit being on a rode of their own in strong to very strong winds.

So eggs in one basket. I would lay out all 50ms of the 8mm chain plus ten or so metres of the 16mm multi plait giving me a scope of about 7:1. My existing nylon snubber would give me about another 5 ms as well as giving me some extra shock absorption.

I would dismantle the number three rode and shackle the Fisherman and Bruce to the main rode about 5 metres in front of the Manson. ( we do have some dive gear onboard ) Hope fully these anchors might give some extra holding; they would, to an extent, act as a chum/kellet and they would add friction to the rode going some way hopefully to minimising movement in the main anchor. I would also be very tempted to take the advice to use the chain from the no 3 rode as an extra angel/chum on the main rode.

As also advised I would keep the number 2, CQR rode as a back up ( the yacht in the Vathi storm was forced to cut her primary rode at the bitter end)

I’m slightly surprised there has been so little discussion of strategies to minimise “sailing to the anchor” and thus snatching from wider angles thereby shaking loose the anchor.

In my hypothetical situation and with the equipment to hand I think I would hang the unused rope from rode 3 in loops over the bow along with a couple of buckets. That might dampen the yawing a bit.

After that it it would be anchor watches, preparation of Plan B, lashing everything down, minimising windage, engine on if things got even worse and of course, a cup of tea.

Equipment I would like to have: a riding sail, unfortunately I can no longer find the video of the late and great “Piotaskipper’s” double sail. I would want to copy that. I would also want a better but dismountable no. 2 anchor so as to equip myself for V anchoring, a “Viking 20” looks the business. I think I shall also be making myself a two legged “storm snubber” as shown in this article, Safety at Sea: Surviving a Powerful Storm in the Med And I shall be visiting my local climbing wall. Light weight high tensile chain does sound good but with limited funds………………

And finally I do apologise if this thread has been a rehash of many of the other anchoring threads I have read over the last years but heyho, after 50 years sailing over 50K nms I still have questions to ask and there is still plenty for me to learn. Happy New Year from Scotland.

I have, and occasionally use a twin riding sail, but then having a ketch, it's easy to rig such a sail, and also a ketch doesn't yaw about all over the place anyway. Best of both worlds.

 

[Neeves]

I have, and occasionally use a twin riding sail, but then having a ketch, it's easy to rig such a sail, and also a ketch doesn't yaw about all over the place anyway. Best of both worlds.

Many people still swear by, and are happy with decent sized, Bruce, CQRs, Deltas. I'd include genuine Danforth but I don't think they are common outside America, or its colonies. So - excluding Danforth - Delta, CQRs and Bruce (all genuine) are available very cheaply - you cannot give them away. They would make excellent second anchors to be deployed on a spare rode in a 'V' to dampen yawing. A better choice would be Fortress (and UK members mention fairly frequently that they come up on eBay- because they store flat (of flattish) or dismount and they are easier to deploy from a dinghy. When the Epsilon is eventually released in the UK I can envisage even more of my selected group of anchors coming available.

Of your policies in the above post 101 - I'd use your rode as a rode, not dismantle and deploy the Bruce as a second anchor in a 'V' - if the Bruce is of the same sort of size as your Supreme (see para 1 above). This will reduce veering and veering is believed to be a major cause of anchors dragging. If you are veering then a good snubber will mitigate the snatches - as you say, visit the climbing gyms. If they offer you 2 ropes, take them - if you deploy 2 rodes you will benefit from 2 snubbers and the climbing rope will be more elastic than anything else you already have. I have not used a riding sail (difficult to rig on a catamaran without a back stay) so cannot comment but the few to use them, NormanS, offer positive reports.

Jonathan

 

[Neeves]

What a refreshing idea, except that Fortress would say something similar. A recommendation based on design not weight. Another perpetuated myth being questioned:

That anchors must be heavy.

Jonathan

 

[JumbleDuck]

What a refreshing idea, except that Fortress would say something similar. A recommendation based on design not weight. Another perpetuated myth being questioned:

I remember when Fortress came out, years ago, being very impressed at how much they were said to hold ber unit weight, compared to te Danforth. Then I check and found that the holding powers quoted per unit size were just about the same as for a Danforth. Concludion: for that design at least it's the size that matters, not the weight.

I have a Fortress as my kedge, but have never used it.

 

[geem]

One thing that nobody has considered is timing. If you are going to lay to two anchors then presumably you will use the dinghy to set a second anchor. If you have a small inflatable dingy and egg whisk type engine, you will need to set the anchor before waves build up and wind builds up or you increase the risk of capsize and the task becomes untenable. In this situation setting a second anchor that is light will make the task easier. In addition a rope only rode also makes the task far easier. We use aluminium anchors with no chain when setting from the dinghy. We have not had unacceptable chafe issues on the all rope rode yet, but we have never had to deal with wind speeds at anchor above 50kts?. We have set a second anchor in wind blowing 40kts using our 3.8m hard dinghy and powerful 15hp engine without too much difficulty, albeit rather damp?

 

[noelex]

I have never understood the logic behind using a half-buried large anchor to get the amount of holding of a well-designed right-sized fully buried anchor.

The logic is a “half buried large anchor” will bury further and therefore develop more holding power if the wind picks up.

A small anchor that has buried to its maximum depth has reached its ultimate holding power for that substrate.

 

[NormanS]

One thing that nobody has considered is timing. If you are going to lay to two anchors then presumably you will use the dinghy to set a second anchor. If you have a small inflatable dingy and egg whisk type engine, you will need to set the anchor before waves build up and wind builds up or you increase the risk of capsize and the task becomes untenable. In this situation setting a second anchor that is light will make the task easier. In addition a rope only rode also makes the task far easier. We use aluminium anchors with no chain when setting from the dinghy. We have not had unacceptable chafe issues on the all rope rode yet, but we have never had to deal with wind speeds at anchor above 50kts?. We have set a second anchor in wind blowing 40kts using our 3.8m hard dinghy and powerful 15hp engine without too much difficulty, albeit rather damp?

With our present boat, we have laid out second anchors, both by dinghy and from parent boat. If it's done early enough, while conditions are benign, we would always use the dinghy. If conditions have already deteriorated, it's not difficult to do it from the yacht. We would aim to finish up with two anchors on roughly the same length of rode, and set at about 40° apart. It's a case of carefully arranging everything on deck, making absolutely sure that the second rode (mostly rope) is free to run. Drive ahead under engine, going off to the side until approximately as far ahead as the first anchor, and then let the second one go.
I appreciate that this requires some judgement, and spatial awareness, and for that reason is not as easy as deployment from the dinghy. I always rig a buoyed tripping line to the second anchor. Two reasons: one is simply that it gives a good indication of where the anchor is in relation to the yacht. The other reason is that if for some reason, it becomes essential to leave the anchorage urgently, the second anchor can be simply slipped, allowing all concentration on retrieving the first one.
Our previous 60ft boat used anchors of 140 lbs, so laying out a second anchor by dinghy, would have been challenging.
On one never to be forgotten occasion, and a long time ago, we rode out a three day gale lying to two 140 lb anchors, both on chain, one of 16mm, the other of 18mm. That was OK until on the the final night, the wind had completely died away and the boat had rotated, twisting the rodes. Since that experience, the second rode has always been mainly rope, with just a relatively short length of chain connected to the anchor. Happy anchoring!

 

[Neeves]

The logic is a “half buried large anchor” will bury further and therefore develop more holding power if the wind picks up.

A small anchor that has buried to its maximum depth has reached its ultimate holding power for that substrate.

To set a small anchor, being used as a primary (noting that the 'small; anchor is the size recommended by the manufacturer of the anchor for that size of yacht) to its maximum depth from a yacht, with engine power or wind is basically - a totally unrealistic idea (and lacks any concept of 'logic'). A 15kg anchor will develop a hold of 2,000kg in a fairly common sand seabed - who has an engine (or how strong does the wind need be) to develop a tension in the rode of 2,000kg. So if you set the anchor sized for the yacht you will never be anywhere near the maximum hold. If the wind picks up it will set more deeply (as will the larger anchor) but if the tension in the rode is 1,000kg (which would scare most people witless if the recommended anchor is 15kg) then the 15kg anchor will not be set to its maximum hold of 2,000kg - and neither would the larger anchor (whose maximum hold might be, say 3,000kg).

There is no evidence that a large anchor, of say a 3,000kg maximum hold is any more safe that a smaller anchor (whose maximum hold is 2,000kg) which is also set to 1,000kg of tension. Some say that in difficult seabeds the larger anchor is 'better' but never are able to produce any data to substantiate the idea or even to describe the seabed that is 'difficult'.

It would be logical if you had this imaginary anchor of 3,000kg hold to carry the appropriate chain - after all the logic is that the bigger anchor will develop more hold - no-one who uses a larger anchor mentions that they use larger chain - which seems to contradict the idea that the hold will be higher.

Jonathan

 

[Neeves]

One thing that nobody has considered is timing. If you are going to lay to two anchors then presumably you will use the dinghy to set a second anchor. If you have a small inflatable dingy and egg whisk type engine, you will need to set the anchor before waves build up and wind builds up or you increase the risk of capsize and the task becomes untenable. In this situation setting a second anchor that is light will make the task easier. In addition a rope only rode also makes the task far easier. We use aluminium anchors with no chain when setting from the dinghy. We have not had unacceptable chafe issues on the all rope rode yet, but we have never had to deal with wind speeds at anchor above 50kts?. We have set a second anchor in wind blowing 40kts using our 3.8m hard dinghy and powerful 15hp engine without too much difficulty, albeit rather damp?

We would set a second anchor if the forecast wind is going to exceed 35 knots in the anchorage, but would want to achieve this at the time of the forecast (or soon after) not when the wind has developed. Sometimes of course we deploy a second anchor and the wind is never more than benign. Its relatively easy to accurately set a second anchor from the yacht (rather than the dinghy) as long as you have saved the location of the first anchor on a chartplotter. You can then set the second anchor with some, or complete, accuracy.

All our anchors are aluminium and all are of roughly the same size and weight (8kg) (and thus similar hold). If it fitted on our bow roller the all steel Viking 10, which would offer a similar hold would be a couple of kg heavier. Our second rode is 15m of high tensile 6mm chain (same chain as the rode and same strength as the 8mm it replaced) and 40m of 3 ply nylon. 6mm chain, or 15m of it is easy to deploy by hand from a dinghy. Our dinghy is a Foldabote which we find very comfortable in chop as it flexes in chop whereas the fibreglass one it replaced would 'slam' into waves.

I suspect if you, Geem, only deploy your second all rope rode in winds over 40 knots (not for us - our OB is a 2 stroke petrol driven egg whisk) then when you tension the rode up - its all off the seabed and abrasion will simply not be an issue.

Jonathan

 

[geem]

We would set a second anchor if the forecast wind is going to exceed 35 knots in the anchorage, but would want to achieve this at the time of the forecast (or soon after) not when the wind has developed. Sometimes of course we deploy a second anchor and the wind is never more than benign. Its relatively easy to accurately set a second anchor from the yacht (rather than the dinghy) as long as you have saved the location of the first anchor on a chartplotter. You can then set the second anchor with some, or complete, accuracy.

All our anchors are aluminium and all are of roughly the same size and weight (8kg) (and thus similar hold). If it fitted on our bow roller the all steel Viking 10, which would offer a similar hold would be a couple of kg heavier. Our second rode is 15m of high tensile 6mm chain (same chain as the rode and same strength as the 8mm it replaced) and 40m of 3 ply nylon. 6mm chain, or 15m of it is easy to deploy by hand from a dinghy. Our dinghy is a Foldabote which we find very comfortable in chop as it flexes in chop whereas the fibreglass one it replaced would 'slam' into waves.

I suspect if you, Geem, only deploy your second all rope rode in winds over 40 knots (not for us - our OB is a 2 stroke petrol driven egg whisk) then when you tension the rode up - its all off the seabed and abrasion will simply not be an issue.

Jonathan

I think our dinghy is a different animal. We can make long trips in rough conditions in our dinghy. No problem to motor across a 2 mile wide bay in 20kts of wind with 1.5nm of fetch. She will run into the sea and stay bone dry. In flat water it will do over 20kts, two up.

We have a reel of 300ft of 18mm nylon braid on braid as our rode for the second anchor. We have never used all of it but maybe 200ft. The aluminium anchor sets well on very long scope and if you have it why not use it. I just drive away from the yacht and my wife lets the line run out. I drop the anchor carefully to make sure it doesn't tangle with the rode then we winch the line tight from the yacht or if the wind is howling, simple motor towards the anchor a little

 

[JumbleDuck]

I have never understood the logic behind using a half-buried large anchor to get the amount of holding of a well-designed right-sized fully buried anchor.

Perhaps because the large one can hold even more if the wind gets up and it digs in more while the small one is at its limit?

 

[Lucy52]

Perhaps because the large one can hold even more if the wind gets up and it digs in more while the small one is at its limit?

But, how can it hold more than the UTS of the chain, assuming the small anchor can hold at least that much?

Daring to trespass on an anchor thread.

 

[JumbleDuck]

But, how can it hold more than the UTS of the chain, assuming the small anchor can hold at least that much?

Daring to trespass on an anchor thread.

Fair question, but let's turn it the other way round ... what's the point of having an anchor with less holding power than the UTS of your chain?

 

[NormanS]

But, how can it hold more than the UTS of the chain, assuming the small anchor can hold at least that much?

Daring to trespass on an anchor thread.

You don't often hear reports of chain breaking, but cases of anchors dragging are not unusual.

 

[Neeves]

You don't often hear reports of chain breaking, but cases of anchors dragging are not unusual.

Anchors do not drag because their Ultimate Holding Capacity (UHC) is too low (or exceeded). The hold of a 15kg Delta in sand is around 1,000kgs (which is 25% higher than the WLL of an 8mm chain and much lower than its Proof Test of 1,500kg. If there was a tension in the rode of 1,000kg something else would fail, bow fitting. Delta and Rocna both drag at much less than their UTC - so UTC (or its inadequacy) - the only piece of quantitative data we have is NOT the reason for anchors dragging. The only factoid we do have is that Rocna et al drag less often than a Delta or CQR thus hold (Rocna would have a UTC of 2,000kg) seems to relate to drag frequency.

If you power set a 15kg Delta, a 15kg Spade or a 30kg Rocna with a 20hp engine then the hold developed for each anchor will be exactly the same - say 200kg. If the wind picks up the Spade and Rocna will both increase hold to, say 300kg - this increase depends on the windage of the yacht not size of anchor. Show me the data that confirms the 30kg Rocna is better and tell me why the Spade and Rocna will, statistically out perform the Delta. Finally tell me why the Viking that will weight less than the Spade, say 10kg and has a similar UTS to the Spade will not perform similarly to the Spade.

I own a steel Spade (15kg), an aluminium Spade (8kg) of the same size. I own a steel Excel (15kg) and an aluminium Excel (8kg) of the same size and a FX 16 which has a slightly larger fluke areas than the Spade and Excel. I cannot tell the difference between the aluminium and steel versions and their UTS is similar. Blindfold if I set the Fortress it is indistinguishable to the Spades or Excels. Tell me why I'd be more secure with bigger anchors. I also have a FX 37. If I set the FX 16 and the FX 37 to the same (high) tension I can bury the FX16 but the FX 37 sits with its stock and crown protruding from the seabed - just ready to self trip in a change of tide or wind and the chain gets under the stock.

Someone will note that I will deploy 2 anchors in a 'V' in stronger winds - anchoring in a 'V' reduces the impact of veering - commonly caused in many anchorages due to the characteristics of wind and the and local geography (nothing to do with the yacht). Veering may be a major contributor to dragging - tell me why a single large anchor set to the same tension as each of 2 smaller anchors (aligned to the veer of the wind) is a better option.

Note - People lose anchors, for a variety of reasons, consequently you should be carrying 2 anchors - the spare should be of a size to replace the primary (especially if you are going 'off piste'). Tell me why I really should be discarding my 8kg aluminium wardrobe and replacing it with a 30kg steel version and carrying 2 of them, one as my primary and one as my spare. Tell me why I will be more comfortable and safer when the wind veers back and forth through 30 degrees (but the average wind direction is constant) and I am at one anchor.......

Jonathan

 

[NormanS]

Anchors do not drag because their Ultimate Holding Capacity (UHC) is too low (or exceeded). The hold of a 15kg Delta in sand is around 1,000kgs (which is 25% higher than the WLL of an 8mm chain and much lower than its Proof Test of 1,500kg. If there was a tension in the rode of 1,000kg something else would fail, bow fitting. Delta and Rocna both drag at much less than their UTC - so UTC (or its inadequacy) - the only piece of quantitative data we have is NOT the reason for anchors dragging. The only factoid we do have is that Rocna et al drag less often than a Delta or CQR thus hold (Rocna would have a UTC of 2,000kg) seems to relate to drag frequency.

If you power set a 15kg Delta, a 15kg Spade or a 30kg Rocna with a 20hp engine then the hold developed for each anchor will be exactly the same - say 200kg. If the wind picks up the Spade and Rocna will both increase hold to, say 300kg - this increase depends on the windage of the yacht not size of anchor. Show me the data that confirms the 30kg Rocna is better and tell me why the Spade and Rocna will, statistically out perform the Delta. Finally tell me why the Viking that will weight less than the Spade, say 10kg and has a similar UTS to the Spade will not perform similarly to the Spade.

I own a steel Spade (15kg), an aluminium Spade (8kg) of the same size. I own a steel Excel (15kg) and an aluminium Excel (8kg) of the same size and a FX 16 which has a slightly larger fluke areas than the Spade and Excel. I cannot tell the difference between the aluminium and steel versions and their UTS is similar. Blindfold if I set the Fortress it is indistinguishable to the Spades or Excels. Tell me why I'd be more secure with bigger anchors. I also have a FX 37. If I set the FX 16 and the FX 37 to the same (high) tension I can bury the FX16 but the FX 37 sits with its stock and crown protruding from the seabed - just ready to self trip in a change of tide or wind and the chain gets under the stock.

Someone will note that I will deploy 2 anchors in a 'V' in stronger winds - anchoring in a 'V' reduces the impact of veering - commonly caused in many anchorages due to the characteristics of wind and the and local geography (nothing to do with the yacht). Veering may be a major contributor to dragging - tell me why a single large anchor set to the same tension as each of 2 smaller anchors (aligned to the veer of the wind) is a better option.

Note - People lose anchors, for a variety of reasons, consequently you should be carrying 2 anchors - the spare should be of a size to replace the primary (especially if you are going 'off piste'). Tell me why I really should be discarding my 8kg aluminium wardrobe and replacing it with a 30kg steel version and carrying 2 of them, one as my primary and one as my spare. Tell me why I will be more comfortable and safer when the wind veers back and forth through 30 degrees (but the average wind direction is constant) and I am at one anchor.......

Jonathan

Why is all that long story addressed to me? ? All I said was that you hear more of anchors dragging, than you do of chain breaking. Are you saying now that anchors never drag?

 

[Neeves]

Why is all that long story addressed to me? ? All I said was that you hear more of anchors dragging, than you do of chain breaking. Are you saying now that anchors never drag?

Norman,

Don't be so sensitive.

There was no criticism of you, at all - not an iota.

You simply offered an introduction to allow comparison of the Ultimate hold of an anchor and the specifications/characteristic of chain. In the case of the anchor and chain the data, all of which is well accepted and available from a number of independent sources show that chain is well over strength, compared to the hold of an appropriate anchor (which agrees with what you said). Also that the Ultimate hold of an anchor bears little direct relationship to the tensions at which anchors drag as the ultimate holds of anchors, as measured when measuring 'holding capacity', are far beyond the tensions that people will ever experience. Consequently the idea of a big anchor has to be justified by something other than hold - as hold of an anchor (as measured) is far in excess of what is needed. Larger anchors MIGHT be safer but repetitively quoting they have higher hold is simply not directly relevant - and in the absence of anything else the mantra is based on gut feel (or people feel sorry for anchor makers and want their, the anchor makers, pensions funds increased - maybe altruism is not dead!)

Personally I don't think a big anchor is necessary - that is based on practical experience. People who rely on big anchors actually have the same experience as me - their anchors don't drag. However that is a false positive as they never compare (its very difficult to compare) their experience with use of a smaller anchor in the same place at the same time.

Interestingly the back ground to the development of the spread sheets for chain vs vessel size and anchor size (defined in kgs) and vessel size are derived the same way (decades of historic usage). If the Rocna spread sheets were wrong - Rocna/Spade/Anchor Right/Lewmar would amend them (as all the manufacturers have roughly similar spread sheets). The religious fervour for large anchors comes from the 'private', sector and a very small part of the private sector, not the boat building industry, not from insurance companies, not from the Classification Societies, not from the marine rescue organisations. No-one from this small sector has been able to justify their mantra - except, repetition, gut feel and 'I say so'.

Jonathan

 

[NormanS]

Norman,

Don't be so sensitive.

There was no criticism of you, at all - not an iota.

You simply offered an introduction to allow comparison of the Ultimate hold of an anchor and the specifications/characteristic of chain. In the case of the anchor and chain the data, all of which is well accepted and available from a number of independent sources show that chain is well over strength, compared to the hold of an appropriate anchor (which agrees with what you said). Also that the Ultimate hold of an anchor bears little direct relationship to the tensions at which anchors drag as the ultimate holds of anchors, as measured when measuring 'holding capacity', are far beyond the tensions that people will ever experience. Consequently the idea of a big anchor has to be justified by something other than hold - as hold of an anchor (as measured) is far in excess of what is needed. Larger anchors MIGHT be safer but repetitively quoting they have higher hold is simply not directly relevant - and in the absence of anything else the mantra is based on gut feel (or people feel sorry for anchor makers and want their, the anchor makers, pensions funds increased - maybe altruism is not dead!)

Personally I don't think a big anchor is necessary - that is based on practical experience. People who rely on big anchors actually have the same experience as me - their anchors don't drag. However that is a false positive as they never compare (its very difficult to compare) their experience with use of a smaller anchor in the same place at the same time.

Interestingly the back ground to the development of the spread sheets for chain vs vessel size and anchor size (defined in kgs) and vessel size are derived the same way (decades of historic usage). If the Rocna spread sheets were wrong - Rocna/Spade/Anchor Right/Lewmar would amend them (as all the manufacturers have roughly similar spread sheets). The religious fervour for large anchors comes from the 'private', sector and a very small part of the private sector, not the boat building industry, not from insurance companies, not from the Classification Societies, not from the marine rescue organisations. No-one from this small sector has been able to justify their mantra - except, repetition, gut feel and 'I say so'.

Jonathan

That's all very well, but spreadsheets don't anchor boats. The worrying fact remains that on occasion, boats do drag, even at times with fashionable anchors. Maybe it would be useful research to delve into the reasons why.
My own opinion, unsubstantiated by detailed scientific research, is that anchors of any weight or design, function best on appropriate seabed. Maybe more emphasis should be on this. In our own case we anchor on a variety of seabeds.
Anchoring on sand in clear water, it is very easy to ensure that the anchor is dropped onto a good clear patch. In deep water, and in less than clear water, probably on a variety of muddy bottoms, it is much more difficult. I use a fishfinder, which gives a clear, and amazingly detailed picture of the seabed. It shows if there are potential obstructions or clumps of weed etc. As the transducer is pretty far forward, it is showing a picture of the seabed not far from vertically under the bow roller. I would strongly recommend the use of a suitable Fishfinder.
As I say, my own feeling is that selecting anchoring place, is probably more important than selecting anchor design.

 

[geem]

That's all very well, but spreadsheets don't anchor boats. The worrying fact remains that on occasion, boats do drag, even at times with fashionable anchors. Maybe it would be useful research to delve into the reasons why.
My own opinion, unsubstantiated by detailed scientific research, is that anchors of any weight or design, function best on appropriate seabed. Maybe more emphasis should be on this. In our own case we anchor on a variety of seabeds.
Anchoring on sand in clear water, it is very easy to ensure that the anchor is dropped onto a good clear patch. In deep water, and in less than clear water, probably on a variety of muddy bottoms, it is much more difficult. I use a fishfinder, which gives a clear, and amazingly detailed picture of the seabed. It shows if there are potential obstructions or clumps of weed etc. As the transducer is pretty far forward, it is showing a picture of the seabed not far from vertically under the bow roller. I would strongly recommend the use of a suitable Fishfinder.
As I say, my own feeling is that selecting anchoring place, is probably more important than selecting anchor design.

My experience of anchoring is that they all perform reasonably well once properly set. The difficult issue is getting anchors to set in hard packed sand, weed, coral rubble, sand/rock, etc. I think the biggest gain in recent anchor design has been the improved setting ability of NG anchors. We see people trying to anchor with CQRs and Bruce anchors,etc in the Caribbean and having several goes before they achieve a set. We see NG anchor equipped boats that routinely achieve a set first time and sometimes it may take a second attempt. It rarely takes more attempts than this. This is a huge step change.
In a 50kt squall in Falmouth Harbour, Antigua a couple of years ago, no boats dragged. The holding in the bay can be variable but following a few days of squalls of 30kts, everybody's anchors had set well. Does ultimate hold matter? It does but setting ability is far more important for me