Mantus rode

[Dockhead]

Originally Posted by ramblinrod

The impression I received from your posts, is that when I was recommending 10:1 scope for storm conditions, you were contradicting this and attempting to justify and even recommend using much less, including down to 3:1.

If you meant something different, I think you need to be much clearer, especially when you could be endangering people's lives, who may follow advice.

I think it was pretty clear to anyone who read with any care, that I never said that.


In storm conditions, you should use as much rode as you have, up to the limit of swinging circle. But the limit of swinging circle is not trivial. If you are hanging on 100 meters of chain, you have to be sure that if the wind shifts, you won't be swung into the shore. This problem increases by pi times the square of your rode length.

Originally Posted by ramblinrod

Let me make sure my position on this subject is abundantly clear...

1. "The force required to pull the catenary from chain, increases proportionally with scope."

This is false. You can use Alain's spreadsheet (see: Forces) to calculate various scenarios and see for yourself. You get practically no benefit from scope beyond 8:1.

Originally Posted by ramblinrod

2. "The greater the catenary, the more horizontal the force on the anchor is to the seabed."

False again. Where do you get this stuff? The "horizontalness" of the force on the anchor is called "angulation". As long as even one link of the chain is still lying on the seabed, angulation is zero, and all the force is horizontal. You can get zero angulation with even 2:1 scope, under some conditions.

Originally Posted by ramblinrod

3. "The more horizontal the force on the anchor, the greater the holding power, and the less likely the dragging."

And yet again false. Holding power of an anchor is absolutely the same as long as angulation is 0, without regard to catenary or "horizontal force", and is almost the same up to 10 degrees. More catenary does almost nothing once angulation is below 10 degrees and absolutely nothing below 0, other than motion damping, but we are talking about holding.

Originally Posted by ramblinrod

4. "Therefore 10:1 scope is vastly superior to 3:1 scope, in all cases, everything else being equal."

False. So a perfect 100% score for misunderstanding how anchors work.



If you will play around with Alain's calculator with different scenarios, you will see that 10:1 is never materially better than 8:1 under any circumstances. 8:1 will be significantly better than 5:1 in only a limited range of conditions. Under a limited range of conditions, 3:1 will provide equal holding (that is, maximum possible holding from the anchor), to 8:1 (or 10:1 or 20:1 or whatever).





Don't believe me. Plug in your parameters here: Forces





I do have to compliment Rod, sincerely, for formulating his theses in a completely clear and objectively verifiable form. That is a real achievement, and it really advances the discussion, which has now actually become kind of interesting for the first time.

[ramblinrod]

Originally Posted by evm1024

This post is simply not accurate.

Rod, you have never ever anchored out with a 10:1 scope. You have never been anywhere near where Dockhead anchors out. And you would be better served if you had a healthy respect for your limited experience and knowledge.

I disagree.

I believe my post you referenced #67, was spot on.

You are incorrect. I have anchored with 10:1 scope, many times, in anticipation of bad storms.

I have never sailed outside North America, and have never claimed to sail near Dockhead. In my opinion this is completely irrelevant, as the laws of physics are identical around the globe. Additionally, I have sailed in conditions similar to those described, though not as remote and not as far North, two factors which have little bearing, other than risk of ice, and outside support. If one does not rely on outside support, that leaves ice, which I don't believe has a significant bearing on the amount of scope one needs, other than when frozen in and no anchor is required to stay put (which I don't recommend in a production fibreglass boat).

Actually, I have a very healthy respect for the experience that I have, which has kept me, loved ones, and other sailors safe, for a long time. I believe this experience is substantial compared to most sailors, and especially newbies, who may be considering "advice" received on the internet.

[skipmac]

Originally Posted by ramblinrod

4. "Therefore 10:1 scope is vastly superior to 3:1 scope, in all cases, everything else being equal."

To pick one point from your list, this is completely incorrect for several reasons.

First, look at the basic geometry of the angles. Once you get past 7:1 the additional change in the angle of pull, even looking at the ideal, perfectly straight line rode is extremely negligible. Here is the math.

Scope - angle rode to anchor in degrees

3:1 - 19.5
4:1 - 14.5
5:1 - 11.5
6:1 - 9.5
7:1 - 8.2
8:1 - 7.2
9:1 - 6.3
10:1 - 5.7

So from 7 to 10 scope ratio the change in pull on the anchor decreases by 2.5 degrees. That is negligible and the effect on anchor holding would close enough to zero to be ignored. All you are doing by increasing scope to 10:1 is increasing your swinging radius with all the previously stated problems that incurs.

So an argument might be made for increasing scope to 7:1 in shallow water but that means you ignore the effects of depth, chain weight and the resulting catenary, etc when anchoring in deeper water. However 10:1 would be worse in almost any situation I can imagine.

[Dockhead]

Originally Posted by skipmac

To pick one point from your list, this is completely incorrect for several reasons.

First, look at the basic geometry of the angles. Once you get past 7:1 the additional change in the angle of pull, even looking at the ideal, perfectly straight line rode is extremely negligible. Here is the math.

Scope - angle rode to anchor in degrees

3:1 - 19.5
4:1 - 14.5
5:1 - 11.5
6:1 - 9.5
7:1 - 8.2
8:1 - 7.2
9:1 - 6.3
10:1 - 5.7

So from 7 to 10 scope ratio the change in pull on the anchor decreases by 2.5 degrees. That is negligible and the effect on anchor holding would close enough to zero to be ignored. All you are doing by increasing scope to 10:1 is increasing your swinging radius with all the previously stated problems that incurs.

So an argument might be made for increasing scope to 7:1 in shallow water but that means you ignore the effects of depth, chain weight and the resulting catenary, etc when anchoring in deeper water. However 10:1 would be worse in almost any situation I can imagine.

For clarity, and Skipmac will forgive me, I hope, for interpreting his post --


these are the angles without considering catenary at all. So what you would get with say a Dyneema rode.



Chain will be different because it will sag, and part of it will lie on the seabed up to the amount of force which causes the last link to rise.


Here is what it looks like for 100 meters of 12mm chain in 30 meters of water:





Up to 450daN of force (about a normal force for a 50' boat in 50 knots of wind), there is zero angulation. Then the angulation increases up to about 8.75% by 900daN of force. That's slightly less than what you would get with 7:1 on a rope rode.

[skipmac]

Originally Posted by Dockhead

For clarity, and Skipmac will forgive me, I hope, for interpreting his post --


these are the angles without considering catenary at all. So what you would get with say a Dyneema rode.



Chain will be different because it will sag, and part of it will lie on the seabed up to the amount of force which causes the last link to rise.


Here is what it looks like for 100 meters of 12mm chain in 30 meters of water:


Attachment 187924


Up to 450daN of force (about a normal force for a 50' boat in 50 knots of wind), there is zero angulation. Then the angulation increases up to about 8.75% by 900daN of force. That's slightly less than what you would get with 7:1 on a rope rode.

Please. In this situation all the clarification that can be brought is not only helpful but it seems necessary.

I did mention the angles calculated were based on the ideal, perfectly straight rode which is of course is impossible but I think stating it in those terms might have been to subtle.

Clearly the chain weight and resulting catenary is of course significant and more so when anchored in deeper water.

[evm1024]

Originally Posted by ramblinrod

I disagree.

I believe my post you referenced #67, was spot on.

You are incorrect. I have anchored with 10:1 scope, many times, in anticipation of bad storms.

I have never sailed outside North America, and have never claimed to sail near Dockhead. In my opinion this is completely irrelevant, as the laws of physics are identical around the globe. Additionally, I have sailed in conditions similar to those described, though not as remote and not as far North, two factors which have little bearing, other than risk of ice, and outside support. If one does not rely on outside support, that leaves ice, which I don't believe has a significant bearing on the amount of scope one needs, other than when frozen in and no anchor is required to stay put (which I don't recommend in a production fibreglass boat).

Actually, I have a very healthy respect for the experience that I have, which has kept me, loved ones, and other sailors safe, for a long time. I believe this experience is substantial compared to most sailors, and especially newbies, who may be considering "advice" received on the internet.

How much chain do you have on your boat? How much line if any?

You have made assertions and by sharing your actual rode length we may all learn from you.

As for conditions - topology, bathymetry and meteorology play a great role. Place makes a big difference.

How much chain do you have. Show us you practice what you preach.

[ramblinrod]

Originally Posted by ramblinrod
The impression I received from your posts, is that when I was recommending 10:1 scope for storm conditions, you were contradicting this and attempting to justify and even recommend using much less, including down to 3:1.

If you meant something different, I think you need to be much clearer, especially when you could be endangering people's lives, who may follow your advice.

( Dockhead) I think it was pretty clear to anyone who read with any care, that I never said that.

Well, I guess you're wrong. I certainly understood your position to be that 3:1 was acceptable and any more, was just not necessary.

If you meant what you are now claiming to have meant, I believe you should have been much clearer, like...

"The more scope the better."

If you then wished to qualify this, you could do so very simply, by stating something like...

"However, the benefit of increasing scope is a case of diminishing returns."

(This should already be quite obvious to any reasonable person who knows anything about anchoring, and really goes without saying.)

...and if you wished to qualify it further...

"Obviously, the amount of scope that may be practically used, depends on the length of rode carried and the amount of swing room available."

(Again, I believe this should be abundantly obvious to anyone having any business anchoring, and really goes without saying for this audience.)

...and if you wished to qualify it further yet...

"Obviously, sometimes, other factors may come into play with respect to anchoring, such as the vessel size and shape, anticipated wind direction and speed, wind protection available, bottom contour, bottom material, proximity of obstructions and other vessels, etc., etc., etc. (ad infinitum)."

Note that none of these qualifiers, invalidate the general primary premise (which it appeared to me, you were attempting to do).

To me, this is clear, doesn't require reading and comprehending some relevant, and most irrelevant, information contained in multiple pages, riddled with erroneous information, to get to the crux of your position.

Personally, I believe you would be well served to stop trying to over-complicate, simple issues.

(Dockhead) In storm conditions, you should use as much rode as you have, up to the limit of swinging circle. But the limit of swinging circle is not trivial. If you are hanging on 100 meters of chain, you have to be sure that if the wind shifts, you won't be swung into the shore. This problem increases by pi times the square of your rode length.

Thank you for this.

I think the first sentence is important to the understanding of your position.

This has been my position from well before the start of this thread, and I hope I made this abundantly clear.

Now that you have changed your position, or made it clearer, we are in total agreement on this.

Originally Posted by ramblinrod

Let me make sure my position on this subject is abundantly clear...

1. "The force required to pull the catenary from chain, increases proportionally with scope."

(Dockhead)This is false. You can use Alain's spreadsheet (see: Forces) to calculate various scenarios and see for yourself. You get practically no benefit from scope beyond 8:1.

My mistake, I accidentally used the "word" proportionally (again ;-). Thank you for identifying the error I fully admit to making, which I will now correct as follows...

1. "The force required to pull the catenary from chain, increases scope."

Interestingly, the link you posted to support your claim is invalid.

The subject is clearly the relationship between tension on the rode, and catenary. Your referenced article, defines the tension put on the rode, by various forces against the boat.

These are two different things. I was referring to the effect of the force, and your rebuttal was related to the cause of the force.

Quote:
Originally Posted by ramblinrod
2. "The greater the catenary, the more horizontal the force on the anchor is to the seabed."

False again. Where do you get this stuff?

Nope. This is true. I get it from applying basic geometry.

Every rode, despite the scope and tensile force applied, will have some catenary. When no tensile forces is applied, the catenary is greatest. As the tensile force increases, the catenary is reduced, to the point of rode breakage (which will occur before absolutely all catenary can be removed).

Originally Posted by ramblinrod
3. "The more horizontal the force on the anchor, the greater the holding power, and the less likely the dragging."

(Dockhead) And yet again false. Holding power of an anchor is absolutely the same as long as angulation is 0, without regard to catenary or "horizontal force", and is almost the same up to 10 degrees. More catenary does almost nothing once angulation is below 10 degrees and absolutely nothing below 0, other than motion damping, but we are talking about holding.

No, not false. I believe your response is simply another attempt to overcomplicate. By "angulation" I believe you mean the angle of draw on the anchor stock. It is true, that this is the primary angle of concern that will be directly related to holding power (as I have stated previously in this thread).

I disagree that the holding power of an anchor is almost the same, when this angle is 10 degrees, as compared to 0 degrees, based on my experience conducting anchor setting and holding demonstrations, and my experience with anchor holding on various vessels, and just basic geometry.

For what it is worth, motion damping has a lot to do with holding power. This makes the difference between static load and shock load. Lots of catenary means lots of damping, and little catenary means little damping. More damping (hence more catenary) is better for holding (within limits of course).

Once the rudder stock draw angle is 0, more catenary will have little effect, unless this additional catenary provides sufficient damping, for the shock loading effect on the rode to be taken up, before the draw angle is increased.

Sorry to get so complicated folks, but sometimes it takes a complicated response to rebut an overly complicated contradiction.

Originally Posted by ramblinrod
4. "Therefore 10:1 scope is vastly superior to 3:1 scope, in all cases, everything else being equal."

False. So a perfect 100% score for misunderstanding how anchors work.

If you will play around with Alain's calculator with different scenarios, you will see that 10:1 is never materially better than 8:1 under any circumstances. 8:1 will be significantly better than 5:1 in only a limited range of conditions. Under a limited range of conditions, 3:1 will provide equal holding (that is, maximum possible holding from the anchor), to 8:1 (or 10:1 or 20:1 or whatever).

Don't believe me. Plug in your parameters here: Forces

Incorrect. I believe my premise is accurate, where ever there is room to safely apply 10:1 scope, which is implied, and everything else being equal.

I do not care to use the linked calculator, as I believe it has nothing to do with catenary, but merely the force applied to the boat, (and hence the tensile force to the rode at the bow roller) under various conditions.

If one desires they may play around with a true catenary shape calculator, such as this one.

SNIP, superfluous banter removed.

Well, as best I understand it, you are now claiming pretty much total agreement with my post # 8, some 68 posts prior.

[hpeer]

Back to the OP. Here is how I think about it. Every time I anchor, which is a lot, I put down my anchor, and then some chain, and if really, really pressed 100’ of rode. So I’m carrying a big hunk of anchor on the bow which I use 100% of the time, the some heavy chain, of which I use about half, and the ride is light. So I rationalize that by carrying a really big anchor I don’t need as much weight in chain.

What I have exactly is of no importance, it’s drastically different that what you would or should use. I’m just pointing out some logic. My extra heavy anchor off sets additional chain.

And because someone will ask: 44’ center cockpit, 20 tons, i anchor for 6 months a year, Caribbean, 125# Mantus, 200’ 3/8” HD chain, 100’ of 1” 8 plait flat braid. And then, I have 900’ of 7/8” double braid under the bed. So I figure I could ‘anchor’ in close to 1,000’. Not that I’d ever want to try that. Just saying.

[evm1024]

Originally Posted by Delfin

The most obvious type of libel/slander is to assert that someone said something they most definitely did not in order to make them look stupid, and DH never claimed what you state above. He simply said what cruisers with actual experience, rather than a well worn copy of Royce's on their desks, can attest to - with a proper anchor, chain and technique, 3:1 scope is just fine about 99.5% of the time, with the .5% handled as need be. In other words, you've either lost your reading glasses and can be forgiven because you're clueless what people are writing, or are lying to make a point no one with practical experience thinks makes sense.t

Really Rod, for someone who seems to so desperately want to be taken seriously, your opinions and way of making your points only leads to the exact opposite, which is why people with year's of experience think half of what you write is complete rubbish.

This bears repeating - most obvious type of libel/slander.

[Janet H]

Originally Posted by ramblinrod

Don't have time to respond to your comments, but I declare them invalid.

Originally Posted by evm1024

This bears repeating - most obvious type of libel/slander.

This thread has been closed for a cooling off period and a fair warning from the site team:

1. It's fine to disagree but it's completely unacceptable to hurl personal insults. State your own viewpoint and move along, please.

2. Here are the definitions of libel and slander.

Libel is an untrue defamatory statement that is made in writing.
Slander is an untrue defamatory statement that is spoken orally.

Slander is simply not applicable in this (written) venue.
Personally held opinion is not by definition libellous when stated as such.

[weavis]

People.

We the admin and mods love to hear your thoughts. We dont like the fighting.

Fighting is off the menu.

Please continue.

[evm1024]

Great, nice to be back.

We all hold opinions and we all can read. Some of us keep more up to date in our technical knowledge than others. This is normal.

Some of us anchor around our local area and others of us go out to the ends of the earth. Successfully anchoring in Greenland or the Antarctic requires a level of knowledge and skill that few of us possess. I bow down to their understanding.

All may post their opinions here and have those opinions discussed without fighting. In order to come to some evaluation of the value of a persons opinions I think that it is fair game to ask the poster what ground tackle that they have selected for their own boat. This gives an indication of what the poster thinks is "right" for their boat in the areas they plan on anchoring in.

I'll go first. I currently have a 15 tonne boat 50' long. The rode is 275' of 5/16" G70 chain with a Crosby 7/16" G-209A shackle to an 85 pound Mantus anchor. Stored below is 250' of 5/8" nylon and 100' of 5/16" HT chain. I will be buying a 105# Mantus anchor and another 275' of chain (in case we need to ditch the main chain). I'm not counting the 33# bruce that came with the boat....

OK, your turn.

So Rod, you have strong opinions on what constitutes good ground tackle. What are you using on your boat? How much rode, what kind of rode, what anchor, any other anchors?

Over to you.

[ramblinrod]

So Rod, you have strong opinions on what constitutes good ground tackle.

Over to you.

Yes, I do have strong opinions, based on my education, training, and experience, which is quite substantial.

If you had developed a history of respectful discourse with me, I might be inclined to oblige your request.

Unfortunately, you have not, so I respectfully decline.

[evm1024]

Originally Posted by ramblinrod

Yes, I do have strong opinions, based on my education, training, and experience, which is quite substantial.

If you had developed a history of respectful discourse with me, I might be inclined to oblige your request.

Unfortunately, you have not, so I respectfully decline.

That is fair enough. I know we have had our moments where we do not get along as well as we could.

I suppose my question was really do you still use a Bruce and CQR with both on the bow? And if so do you have enough rode on each for 10:1 in your common cruising grounds worst case anchoring situation.

[skipmac]

Originally Posted by evm1024

That is fair enough. I know we have had our moments where we do not get along as well as we could.

I suppose my question was really do you still use a Bruce and CQR with both on the bow? And if so do you have enough rode on each for 10:1 in your common cruising grounds worst case anchoring situation.

Since he claims to have anchored at least twice in 50' (although in one case he claimed on too short a scope so we will only count one) then he must carry at least 500' of rode.