Mantus rode

[ramblinrod]

Originally Posted by Delfin

Most of the firms I might call...

Well, you'd have to call another firm, because there's a really good chance that with your charming attitude and demeanor, I'd tell you, "Sorry, we're too busy", about 15 seconds into our new customer screening process.

[ramblinrod]

Originally Posted by skipmac

Rod I see you still arguing your position but did not see your response to my post #136 that compared the actual angles between a 7:1 and the 10:1 scope you claim is so much better. Maybe it's hard to argue against real numbers.

Oh, I thought that was adequately answered by another who correctly advised you that there is more to scope than just straight line draw angle.

But my response would have been, "While the straight line angle difference may appear small, with increased scope comes increased catenary, which can contribute significantly to holding.

Should the forces required to pull out this catenary in longer scope be present, then every little bit of lower angle you can maintain on the stock is "ultimately" important to make sure you stay put instead of ending up on the rocks.

[ramblinrod]

Originally Posted by evm1024

You advise in an autocratic way that people should give up good holding in deep water to seek higher scope on a lee shore.

Actually, I have never stated what you claim.

This is about the 100th time you've done this to me in only 2 threads.

It's the name of your game.

That's your problem.

[Dockhead]

Originally Posted by ramblinrod

I'm sorry if I was confused by your posts.

From your post # 19...



From your post # 22...



and



and



From you post # 24...

.



From your post # 41



From you post # 63



PS, I never responded to this at the time, but the issue to be remedied was not that he had adequate scope and moved; the issue was that he foolishly (in my position) land tied so he was broadside to wind and waves. First of all, I wouldn't have likely pulled that silly stunt in the first place, I learned long ago that it is far better to swing on the hook than anchor out and tie to shore (IN GENERAL).

From your post # 64


And then you posted....


From you post # 71



So after a bunch of disparaging remarks about my understanding and anchoring skill, it now this seems like a complete about face on your part, claiming that one should always use more scope than 3:1 if they can. This didn't seem to be the thrust of your message when you were espousing Dashew, apparently your idol, using 2.2:1.

And then you posted,

From your post # 76

Oh I see, we have gone from you should use the amount of scope you need, which you indicated in a prior post could be as much as 8:1, but now you only use as much as you have.

What if all you have is 3:1 but you need 8:1? I guess you are kinda screwed for not carrying 8:1 aren't you?

Then you posted...


Oh what conditions would those be? Certainly not with all catenary remove d by force on the boat pulling out of the rode. My knowledge and experience helps me understand that with more scope, you would have more catenary (if it weren't pulled out) and a better angle if it were. So 2:1 scope kinda sucks in anything but benign conditions. Good way to pull the anchor out of the bottom if the catenary is mostly removed, (which would only require a bit more force than the weight of the chain at that short of scope).

So it appears to me that initially you have been claiming that a short scope, as low as 2.2 is acceptable, a scope of 4:1 is adequate and 10:1 would never be required, . .

You are indeed confused by my posts, deeply.

No where does it say that you never need more scope.

What they say, which you have never yet understood, is that different amounts of scope down to even, yes, 2:1, CAN be enough, depending on the circumstances and, yes, even in a storm.

The main point of what I have been saying, which has always gone right over your head, is that you have to KNOW how much scope you need in a given situation. It requires KNOWLEDGE.



Not just "more is better"; "I will die on 2:1", "Less than 8:1 reduces holding". That is not enough. That is in fact very bad advice. Anchoring in challenging conditions is not indeed "just that simple".

[Dockhead]

And of course, no one took up the challenge of quantifying this question, which is the acid test.


So let's take a few examples.


With bigger boats in deeper water and bigger anchors, less scope is required. So let's take a smaller boat with an average sized anchor, just to make it interesting.


12 meters boat
20kg Spade
80 meters of 8mm chain


In 50 knots of wind, ABYC design load is 1376daN. Static load (what you might get if you have found good shelter and are not yawing and well snubbed) 464daN, dynamic load (some wave action, yawing, snatching) 1021.


In 42 knots of wind, ABYC design load is 971daN. Static load 297; dynamic 653.


So what kind of holding will we get with this anchor in say 8 meters of water?


First of all, we have to know whether there is any catenary or not.


Last link, 3:1 42daN

Last link, 10:1 517daN



OK, so catenary is gone in both cases, by the time we get to dynamic load conditions.


So that leaves us with the pure geometric angulation, which is:


3:1 19.47 degrees
10:1 5.47 degrees


A new generation anchor will have about 95% of its holding power at 5 degrees, and about 40% at 20% (which is probably conservative; the Bruce is supposed to have 50% at 2:1 which is 30 degrees).


In excellent bottom, a 20kg Spade will develop about 2320daN of holding force. In medium bottom, 795.


So in this case, the 10:1 anchor will have 95% * 795 = 755daN of holding power
The 3:1 anchor will have 40% * 2320daN = 928daN of holding power



Obviously 928 is better than 755. It means that in the dynamic load situation at 42 knots, the 3:1 anchor will likely hold, the 10:1 anchor will probably not.


Anyone not too lazy to have a go, can run his own scenarios.


This illustrates that it is foolish to seek out scope at any cost. For example, anchoring off a lee shore, which greatly magnifies dynamic loads and might even put you in the surf, in a storm, and gives you no room to recover in case the anchor drags. Just to achieve more scope.



It is easy to say "always have enough rode to have a high scope", but very often it is impossible to deploy more rode, even if you have it. That is because the best shelter is very often in a place with limited swinging room. The best bottom condition is very often in deeper water.



Therefore, anchoring is just not "just that simple". It requires knowledge and judgement, and often requires anchoring on less scope, even in a storm. Scope is not magic, and is only one tool.




And again, a key issue is anchor SIZE. Once your anchor is big enough, then 40% of its maximum holding (or even 20%) may be all you need in a wide range of conditions. That is how Dashew is able to habitually uses 2:1. He has a 250 pound anchor. If you have an inadequate anchor, then then you will be less able to give up any part of its maximum holding power. You will not be able to shorten scope if you need to. And that is dangerous, because sometimes you can't find the best bottom or the best shelter, without compromising scope. That is the art of anchoring.

[ramblinrod]

Originally Posted by Delfin

(Superfluous and useless banter removed.)

As DH has patiently explained quite a few times, the only point of scope is to increase the angle of rode to shank if and when the rode is lifted off the sea bed.

Actually, it was I who first introduced the concept of catenary and how it can be removed in this thread.

Post # 8.

But catenary is important.

The key point you and others seem to keep missing, is that if the force on the rode is great enough to remove the catenary from 3:1 scope, it may not be sufficient to remove it from 5:1, or 8:1 or 10:1, so if you had that much more scope out you would benefit from it, including the additional shock absorption during variable load.

And if the force on the rode is great enough to remove the catenary from 10:1 scope, it is way better to have that straight line angle on the stock, than that of 9:1, 8:1, 7:1 or anything less, because quite frankly, you don't really know just how good the holding is or just what that angle can be for that bottom and what ever greater force you may experience, before that anchor pulls out.

You can pretend you do. You can lie to your crew that you do. But I know that you know that you really don't.

[ramblinrod]

Originally Posted by Dockhead

And of course, no one took up the challenge of quantifying this question, which is the acid test.


So let's take a few examples.


With bigger boats in deeper water and bigger anchors, less scope is required. So let's take a smaller boat with an average sized anchor, just to make it interesting.


12 meters boat
20kg Spade
80 meters of 8mm chain


In 50 knots of wind, ABYC design load is 1376daN. Static load (what you might get if you have found good shelter and are not yawing and well snubbed) 464daN, dynamic load (some wave action, yawing, snatching) 1021.


In 42 knots of wind, ABYC design load is 971daN. Static load 297; dynamic 653.


So what kind of holding will we get with this anchor in say 8 meters of water?


First of all, we have to know whether there is any catenary or not.


Last link, 3:1 42daN

Last link, 10:1 517daN



OK, so catenary is gone in both cases, by the time we get to dynamic load conditions.


So that leaves us with the pure geometric angulation, which is:


3:1 19.47 degrees
10:1 5.47 degrees


A new generation anchor will have about 95% of its holding power at 5 degrees, and about 40% at 20% (which is probably conservative; the Bruce is supposed to have 50% at 2:1 which is 30 degrees).


In excellent bottom, a 20kg Spade will develop about 2320daN of holding force. In medium bottom, 795.


So in this case, the 10:1 anchor will have 95% * 795 = 755daN of holding power
The 3:1 anchor will have 40% * 2320daN = 928daN of holding power



Obviously 928 is better than 755. It means that in the dynamic load situation at 42 knots, the 3:1 anchor will likely hold, the 10:1 anchor will probably not.


Anyone not too lazy to have a go, can run his own scenarios.


This illustrates that it is foolish to seek out scope at any cost. For example, anchoring off a lee shore, which greatly magnifies dynamic loads and might even put you in the surf, in a storm, and gives you no room to recover in case the anchor drags. Just to achieve more scope.



It is easy to say "always have enough rode to have a high scope", but very often it is impossible to deploy more rode, even if you have it. That is because the best shelter is very often in a place with limited swinging room. The best bottom condition is very often in deeper water.



Therefore, anchoring is just not "just that simple". It requires knowledge and judgement, and often requires anchoring on less scope, even in a storm. Scope is not magic, and is only one tool.




And again, a key issue is anchor SIZE. Once your anchor is big enough, then 40% of its maximum holding (or even 20%) may be all you need in a wide range of conditions. That is how Dashew is able to habitually uses 2:1. He has a 250 pound anchor. If you have an inadequate anchor, then then you will be less able to give up any part of its maximum holding power. You will not be able to shorten scope if you need to. And that is dangerous, because sometimes you can't find the best bottom or the best shelter, without compromising scope. That is the art of anchoring.

I am sorry, but this is the poorest science I have ever seen in my life.

You paint a great picture though.

Anyone can see you just fudged the numbers in an algorithm to support your point.

Using that same algorithm, put both anchors on the same bottom and 10:1 scope wins over 3:1 hands down every time, everything being equal, no mitigating factors.

How the frig are you going to know so precisely what the bottom holding co-efficient is going to be at various places in the anchorage, pull up core samples and send them off to the lab?

Maybe you're going to paint the bottom whatever you want it to be?

Ridiculous!

[Q Xopa]

Originally Posted by ramblinrod

Thanks!

Yes, we provide "Total Yacht Care" service to a number of clients in South Central Ontario for recreational vessels; power and sail.

As part of our boating community service program we conduct DIY maintenance and improvement seminars for various boating groups.

Another part of our program is to offer general advice and information through internet boating forums.

Those seeking valid solutions to their problems seem to appreciate the opportunity.

Unfortunately, a few become belligerent, some to an extreme.

But logic, reasoning, and experience is always on my side, because I just won't post anything I can't support with it.

Here's the rub.
You are supporting your side, with YOUR logic, reasoning and experiences.
You are obviously happy with that which is fine.

However you are stating it is the Correct way and others should follow your advice.

Because many other respected contributors are Incorrect with their logic, reasoning and experiences.

I see most of the other contributors 'offering' their experiences, learnings etc, but not to the point of stating they are correct and others need to follow what they say.

While I agree the collectively accepted wisdom is not always correct and of course maybe later disproved. It is the best answers we have so far.

I think most of us can see that you are quite knowledgable on many boat subjects, however you seem to miscomprehend what some have said and dogedly stick to some of your interpretations and theories to the point where the threads you comment on always seem to follow a downward spiral.

All I can say is hmmmm.

[ramblinrod]

Originally Posted by Dockhead

You are indeed confused by my posts, deeply.

Well then make your position clear, instead of all over the map.

No where does it say that you never need more scope.

Of course not, but clearly you may, and that is what you keep trying to wash over.

What they say, which you have never yet understood, is that different amounts of scope down to even, yes, 2:1, CAN be enough, depending on the circumstances and, yes, even in a storm.

Wrong, I understand the argument, I just don't agree. Of course one can weather a storm safely with 2:1 on a 3 tonne mooring block.

But a standard anchor and chain. BS. You won't know if it was good enough to hold until the morning. If you are where you were, it was, and you got really lucky. If you weren't so lucky, you aren't where you were.

The main point of what I have been saying, which has always gone right over your head, is that you have to KNOW how much scope you need in a given situation. It requires KNOWLEDGE.

Nothing you have said has gone over my head, I just know it to be wrong.

The point is, you can't possibly know how much scope you need. You put out what you think is enough, based on your prior experience under hopefully the same conditions, set your alarms, tell your crew to get some sleep, and hope like hell you stay put.

You are just kidding yourself if you think you "know" precisely what the holding conditions are and forces are going to be. The 3 day weather forecasts are hardly better than throwing darts at a board. Unless you are in the Bahamas, you don't know that you didn't catch on a log and the anchor isn't dug in at all. You just don't "know", because you can't "know".

What you can "know" as I do, is that everything else equal, barring any unusual mitigating factors, if you are going to anchor in a particular spot, more scope is better, and knowingly carrying only 300 ft of rode to anchor in 100 ft of water is unseamanlike, because 3:1 may not be enough, and more would be better if the conditions require.

[Q Xopa]

Originally Posted by ramblinrod

Yes, I absolutely believe you are being rude.

I don't care if someone has sailed around the world 10 times in a battle ship or across a small pond once in a dinghy, if they post something that I know to be wrong, I'll call them on it, and if they post something useful I can learn from, I'll thank them for it.

The fact is, I do have enough experience to know that every single 3:1 scope proponent in this thread really knows damn well they should carry more rode and use more scope when they reach the end of what they've got; they just don't want to admit to others (or themselves) that they are compromising their safety.

Frankly, I don't really give a crap about any kind of skipper who would do this kind of thing, it's the others on their boat that are counting on them to get home safely that I really care about.

One person in this thread called anchoring an art.

I almost fell of my chair.

It's a science, pure and simple; the application of physics to hold a known object in place against variable forces.

And the science tells us, that more scope is better, and 3:1 scope may not be enough to stand up to those forces; so to carry only enough rode for that amount of scope is completely illogical. Bad science.

If anyone wants to practice art, go paint a picture of flowers or something; don't put other peoples lives in harms way needlessly, when you can easily avoid doing so.

600 ft of rope to attach to that chain won't break the bank or the boat.

Don't be a fool.

Im pretty sure that was never what was suggested. I dont think you understood clearly what he posted. Certainly different to what I understood, and apparently many others from the amout of people disagreeing with you.

Of course it is possible we are all incorrect, like you state.

Speaking of rude, although Im sure he doesnt care, 'dont be a fool', could easily fit that definition.

[Q Xopa]

Originally Posted by Dockhead

And of course, no one took up the challenge of quantifying this question, which is the acid test.


So let's take a few examples.


With bigger boats in deeper water and bigger anchors, less scope is required. So let's take a smaller boat with an average sized anchor, just to make it interesting.


12 meters boat
20kg Spade
80 meters of 8mm chain


In 50 knots of wind, ABYC design load is 1376daN. Static load (what you might get if you have found good shelter and are not yawing and well snubbed) 464daN, dynamic load (some wave action, yawing, snatching) 1021.


In 42 knots of wind, ABYC design load is 971daN. Static load 297; dynamic 653.


So what kind of holding will we get with this anchor in say 8 meters of water?


First of all, we have to know whether there is any catenary or not.


Last link, 3:1 42daN

Last link, 10:1 517daN



OK, so catenary is gone in both cases, by the time we get to dynamic load conditions.


So that leaves us with the pure geometric angulation, which is:


3:1 19.47 degrees
10:1 5.47 degrees


A new generation anchor will have about 95% of its holding power at 5 degrees, and about 40% at 20% (which is probably conservative; the Bruce is supposed to have 50% at 2:1 which is 30 degrees).


In excellent bottom, a 20kg Spade will develop about 2320daN of holding force. In medium bottom, 795.


So in this case, the 10:1 anchor will have 95% * 795 = 755daN of holding power
The 3:1 anchor will have 40% * 2320daN = 928daN of holding power



Obviously 928 is better than 755. It means that in the dynamic load situation at 42 knots, the 3:1 anchor will likely hold, the 10:1 anchor will probably not.


Anyone not too lazy to have a go, can run his own scenarios.


This illustrates that it is foolish to seek out scope at any cost. For example, anchoring off a lee shore, which greatly magnifies dynamic loads and might even put you in the surf, in a storm, and gives you no room to recover in case the anchor drags. Just to achieve more scope.



It is easy to say "always have enough rode to have a high scope", but very often it is impossible to deploy more rode, even if you have it. That is because the best shelter is very often in a place with limited swinging room. The best bottom condition is very often in deeper water.



Therefore, anchoring is just not "just that simple". It requires knowledge and judgement, and often requires anchoring on less scope, even in a storm. Scope is not magic, and is only one tool.




And again, a key issue is anchor SIZE. Once your anchor is big enough, then 40% of its maximum holding (or even 20%) may be all you need in a wide range of conditions. That is how Dashew is able to habitually uses 2:1. He has a 250 pound anchor. If you have an inadequate anchor, then then you will be less able to give up any part of its maximum holding power. You will not be able to shorten scope if you need to. And that is dangerous, because sometimes you can't find the best bottom or the best shelter, without compromising scope. That is the art of anchoring.

As usual, brilliantly constructed post.
Thanks for yours, and other posters efforts. I have learnt a lot from your posts and this thread.

[ramblinrod]

Originally Posted by Q Xopa

Here's the rub.
You are supporting your side, with YOUR logic, reasoning and experiences.
You are obviously happy with that which is fine.

However you are stating it is the Correct way and others should follow your advice.

Because many other respected contributors are Incorrect with their logic, reasoning and experiences.

I see most of the other contributors 'offering' their experiences, learnings etc, but not to the point of stating they are correct and others need to follow what they say.

While I agree the collectively accepted wisdom is not always correct and of course maybe later disproved. It is the best answers we have so far.

I think most of us can see that you are quite knowledgable on many boat subjects, however you seem to miscomprehend what some have said and dogedly stick to some of your interpretations and theories to the point where the threads you comment on always seem to follow a downward spiral.

All I can say is hmmmm.

I disagree.

I believe I am just standing behind my convictions supporting them with facts, logic, reasoning, and practical examples.

I don't believe I miscomprehended anything anyone has posted.

I understood it all perfectly well.

Some of the things that some people posted were just wrong.

The collective wisdom is that the general rule for anchoring is that for a temporary anchor use 3:1, overnight fair conditions, 5:1, and storm conditions, 8:1 scope or better.

That a few are claiming that 3:1 is good enough for storm conditions in 100 ft of water, well I'm sorry, that is not collective wisdom. It may be a set of circumstances that ended turning out favourably, but what if it didn't. What if I'm correct, and they were just lucky, and the next time, not so much?

In my opinion that is just false hope and blind faith, that could very well hurt someone if they accept it as true, and use that as their general rule instead.

I fully admit that I am not likely to roll over and accept something someone or even a group claims is correct when I know it to be false.

So if anyone wishes me to not stand my ground, all they have to do is discontinue challenging the ground I stand on, unless they can actually incorporate something of merit into their challenge, that I can accept as new ground to stand on, and I'll be glad to.

I enjoy learning new things; I don't enjoy discarding facts for fiction, so I am not likely to ever do it.

[ramblinrod]

Originally Posted by Q Xopa

Im pretty sure that was never what was suggested. I dont think you understood clearly what he posted. Certainly different to what I understood, and apparently many others from the amout of people disagreeing with you.

Of course it is possible we are all incorrect, like you state.

Speaking of rude, although Im sure he doesnt care, 'dont be a fool', could easily fit that definition.

I know I understood exactly what was posted.

I just didn't agree with it.

You guys believe what you want.

I've done everything I can to help.

[Dockhead]

Originally Posted by ramblinrod

. . . Using that same algorithm, put both anchors on the same bottom and 10:1 scope wins over 3:1 hands down every time, everything being equal, no mitigating factors.

That's not the question. If you have swinging room and chain for 10:1, you will be more secure than on 3:1. Every idiot knows that. Whether "more" means "meaningfully more" or "usefully more", however, is a completely different question. Just "more" is meaningless.



And it gets interesting when you don't have swinging room, and you have a choice between a worse bottom (or worse shelter) and more scope, or better shelter and better bottom, and less scope. That's where the rubber meets the road.



By the way, a very common situation, because good shelter is often found in tight places, and good bottom is often found in deep water.


In such cases, you'd better have a clue.

Originally Posted by ramblinrod

.How the frig are you going to know so precisely what the bottom holding co-efficient is going to be at various places in the anchorage, pull up core samples and send them off to the lab?. . .

A good sailor with knowledge and experience, knows very well where to find what bottom, and recognizes very well, what kind of bottom he is dealing with, as soon as he starts to back down on the anchor.


And if you don't know for sure, there are cases when you had better have a good guess, because your lifte may depend on it -- may depend on making the right choice between two sub-optimal places to anchor.

[Dockhead]

What Rod has been saying over and over and over again, is that “more is better”. And it’s true – more scope is better for holding.


However, Rod does not seem to understand the concept of “materiality”. We don’t need “better”, if it’s not usefully better. We also don’t need “better”, if the betterness is insignificant. “More is better” is a lazy and, in fact, incorrect approach to the problem.


Insignificant betterness is like the difference between 7:1 and 10:1 scope. Rod says 10:1 is “way better” than 7:1. Well, it’s not. It’s not even measurably better. A good anchor has the same holding power at 8.21 degrees as it does at 5.74 degrees, within fractions of a percent.
"If you have a decent anchor, seven to one scope is all you will ever need. Letting out more will just make your boat sail around more and result in higher loads on the system." https://www.morganscloud.com/2014/01...t-2-technique/


It might not matter if there were no cost to laying out more chain. But there is cost. First of all, you might not be able to. Second, bigger swinging circle increases the risk of fouling, and might increase loads on the system, and might increase the risk of swinging into an obstacle. Therefore, you can’t just dumbly follow “more is better”. More may actually be worse, and at some point will definitely be worse, when you consider the tradeoffs.

Useless betterness is another concept which Rod fails to understand. My anchor, a 100 pound Spade, can produce over 7 tonnes of holding power in excellent bottom. 40% of that – what I get at 3:1 scope – is 2.8 tonnes. So 3:1 in excellent bottom is more than enough to hold my boat even in 50 knots of wind, even according to the worst-case ABYC design standard, and even in shallow water. In conditions which will not exceed Force 8, more than 3:1 scope does not give any useful betterness. 3:1 scope in that case gives a few wind forces of reserve holding power.

It would be entirely different if I were using a 55 pound Delta (what my boat was delivered with). So you can’t talk about scope, without talking about the anchor. You can’t call sailors “foolish” or “unseamanlike” because they use 3:1 scope in some situation, without knowing what kind of anchor they have and what kind of bottom that anchor is set in, and what the alternatives were. One size does not fit all. What is foolish is trying to apply a simple rule, which does not consider a dozen other important factors, to all anchoring situations.


Everything is always a tradeoff. All else is never equal. Therefore, knowing that more scope is better is useless knowledge, in fact worse than useless, because it encourages lazy habits of mind which can lead one into error. You have to know how much better it is, in any given situation, in order to make correct choices, when there are tradeoffs involved, and there always are.