If you like to know the anchor load and minimal chain length... here is the tool to do it...

geem said:
You forget that there are a huge number of people with little experience of anchoring. We have witnessed some appalling anchoring practises recently. Some of these people may benefit from understanding a little more about how it works. It's not aimed at the vastly experienced sailor who anchors regularly in conditions that the average marina berth holder who never consider anchoring in
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No, I am well aware that there are many people sailing, with little experience of anchoring. Making it seem more complicated than it really is, merely puts people off, and prevents them from learning by doing.
 
NormanS said:
No, I am well aware that there are many people sailing, with little experience of anchoring. Making it seem more complicated than it really is, merely puts people off, and prevents them from learning by doing.
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So the guy near me a couple of weeks ago who dragged four times is learning? It didn't seem so.
I think he needed a bit of a lesson in the theory as the 'doing' wasn't working
 
NormanS said:
No, I am well aware that there are many people sailing, with little experience of anchoring. Making it seem more complicated than it really is, merely puts people off, and prevents them from learning by doing.
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Let me correct. Prevents them from learning by doing it wrong. The idea, like school is to shorten the learning curve by pointing out things they cannot see, explaining errors they can see but don't understand, and helping them side step unnecesary errors. I have helped a few boats off shoals that learned by doing it wrong.

I assume you attended school. Same thing here. But in this case, attendance is not mandatory.

---

Another possibility is that these guys are just having fun in their studies. As for puting people off anchoring, I think just the opposite is more likely. This generation values instruction.
 
geem said:
So the guy near me a couple of weeks ago who dragged four times is learning? It didn't seem so.
I think he needed a bit of a lesson in the theory as the 'doing' wasn't working
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I'm sure he was learning. Presumably he didn't drag after the fourth time. ?
Do you seriously believe that putting a whole lot of fairly nebulous numbers into a calculation app would have helped him? Anyway, if folk like it, fine. It's just not for me.
 
NormanS said:
I'm sure he was learning. Presumably he didn't drag after the fourth time. ?
Do you seriously believe that putting a whole lot of fairly nebulous numbers into a calculation app would have helped him? Anyway, if folk like it, fine. It's just not for me.
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He left after the fourth time.
So presumably your not a scientist then ?
 
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Wing Mark said:
I don't think this adds very much to knowing that the length of chain and depth of water dictates the angle of the anchor, and that you need some kind snubber if there's any motion?
Since the app doesn't tell us how it's getting the numbers, we don't know if the assumptions are relevant on the day.
We put i n a rough guess for the swell or vessel speed in the chop, it comes back with a snubber stretch to 0.1%.
Guesses in, garbage out.

Most people find chains work well in shallow water?

Do people really want or need an ap to tell them the motion of the boat is bad so they need to either let more rode out, use a better snubber or find somewhere better to park?
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Well, there is indeed a lot of garbage in and garbage out on forums like this...

If you care to read the documentation, you'll find a link to my long treaty on the mathematics and modelling of anchor chains:

Catenary Anchor Chain Length - Die Kettenkurve - Fun Facts - SAN

It is all described there, what this app is based on. But yes, it takes time to digest all that, and in days like these many people are not patient enough anymore.

If people find chains work well for them in shallow water, then that is fine. Fact is that the chain physics dictates that a chain prefers to live in deeper water. Only there can it unfold its full potential. You'll find it hard to argue against physics. But even that has become fashionable these days...

For me, I do not necessarily need the precise numbers. But knowing the chain physics does help me to take the correct decision where to anchor and where not, and how. After all, at most sailing schools, they do not teach about anchoring. And sure, if you have 30 years experience, you may not need that. But why should every generation have to wait for 30 years before they know it all? Understanding the physics of the chain and possibly an app to play around and learn about the physics during playing, that does not sound so bad to me.

Cheers, Mathias
 
pandos said:
does that include the nerve of commercial operators getting free research and feedback on this forum?
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Commercial operation? What do you mean? This is a free tool, so where is the commerce, please???? I have spent far in excess of 1000 hours on this topic and if this were a commercial operation, my business would have long gone belly up.

My motivation is to help folks anchor more safely. Some appreciate this, others do not. But frankly, I fail to understand why some are trying to piss down my back for trying to help others!
 
Sandy said:
What about swell? I've anchored in a F8 in a flat sea!
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Swell is hard to model. What I am doing is to estimate the kinetic energy a vessel gets after getting hit by swell (or a gust for that matter). This energy then needs to be absorbed by the chain and snubber, and that is what I calculate. In order to calculate the kinetic energy I need to know the weight of the vessel and how fast at anchor the vessel is. Hence the "Vessel velocity" entry. I will change that one to be more precise as "Vessel velocity @ anchor".

Cheers, Mathias
 
Tradewinds said:
Apologies but you have taken my comments the wrong way. As I said - it's just not for me, even if free to use. Neeves likes it and so will many others. It's a forum - we're allowed to comment (on some subjects nowadays :rolleyes:). I pay for a few apps and use a lot of free ones too. Good luck with yours but it's of little interest to me.
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okido, thanks. Mathias
 
thinwater said:
I tried some numbers. On the "basic" setting the results were non-sense, about 5-10 times too high. On the "expert" setting they agree reasonably well with what I have measured. However, the swell effect is tricky, and I feel it would be easier for most people to try a cheap scale, as Neeves suggested; that way they will actually believe the number.

The range is huge, depending on the snubber, depth, wave exposure, and other factors, and that is the value of calculators. No one wants to be out there at 50 knots or more (I did that twice in severe thunderstorms and I didn't like it--never again)! I did confirm that with a good snubber, the storm values agreed with force ~ V^2, so I don't need to do it again. With a short snubber or all chain, snatching will begin at some speed, often 30-35 knots, so force may go up considerably more than V^2 in that case, in most tests several times more.
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Thanks for this feedback. You do not mention which numbers were too high in Basic Mode? Anchor loads? Or snubber stretches? The latter depend on the quality of the snubber.

For a monohull with average properties my Basic Mode is based on measurements of the windage area / anchor load done by the late Robert Smith. For other vessel types I have added a fudge factor to the windage area.

Cheers, Mathias
 
thinwater said:
How do you allow for variations in yawing characteristics? That can increase load 50% or even more. My initial testing used a boat used a boat on a bridle that did not yaw. I then added yawing later. hobby horsing can also be a factor in exposed areas that shelve rapidly. Very dangerous.
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You need to enter a larger vessel in Basic Mode to simulate this, or increase your calculated / measured windage area in Expert Mode somewhat, remembering that the wind load is proportional to windage area. So increase windage area by 50%. Should you have gotten the windage area by measurements, then putting this in the Expert Mode is all that is needed.
 
Skylark said:
Was that comment really necessary? You could have ignored it or simply said “thank you for your feedback” and moved on. Your response says more about you than it does about the poster giving feedback.

If you ask for feedback, you must be prepared to accept negative comments, it’s pretty poor form to insult people for giving what you’ve requested.
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I am prepared for critical comments, but if I consider a comment as very rude or inappropriate, I return in the same currency. And yes, this does say something about me - I am not shying away. And I am very ok with that. Incidentally, contrary to what you are suggesting, though, I did not ask for rude, inappropriate or useless comments.

As said before, I have spent a lot of work on this topic, hoping that it will help some other folks so that they do not have to go through a long and potentially dangerous and costly learning curve. In the past I have received enthusiastic feedback from somebody anchoring already for 30 years who said my explanations have been an eye opener for him and he will do things differently from now on. Another person said after 30 years of anchoring in deeper water, and not following the advice handed down by his father to anchor as shallow as possible, he now understands why his choice had been the right one.

That is the kind of feedback that keeps me going in this work.

Useless feedback is, i.e., to come back saying, it does not work, without providing any details. Or dismissing things in a minute and wanting to be spoon fed with information. Acquiring knowledge is always hard work.

And yes, experienced sailors can dismiss all this as being not relevant. Or they do not like the electronics. But that is beside the point. It is for those who do not have the experience, or those who do, but simply want to continue to learn. The next generation will sail very differently to what it was like 30 years ago, and suggesting to them to continue to anchor like mankind has always done, simply will not fly.

Cheers, Mathias
 
MathiasW said:
Swell is hard to model. What I am doing is to estimate the kinetic energy a vessel gets after getting hit by swell (or a gust for that matter). This energy then needs to be absorbed by the chain and snubber, and that is what I calculate. In order to calculate the kinetic energy I need to know the weight of the vessel and how fast at anchor the vessel is. Hence the "Vessel velocity" entry. I will change that one to be more precise as "Vessel velocity @ anchor".

Cheers, Mathias
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Please explain how I would get a figure for "vessel velocity" at anchor?
 
thinwater said:
Let me correct. Prevents them from learning by doing it wrong. The idea, like school is to shorten the learning curve by pointing out things they cannot see, explaining errors they can see but don't understand, and helping them side step unnecesary errors. I have helped a few boats off shoals that learned by doing it wrong.

I assume you attended school. Same thing here. But in this case, attendance is not mandatory.

---

Another possibility is that these guys are just having fun in their studies. As for puting people off anchoring, I think just the opposite is more likely. This generation values instruction.
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First rule of seamanship, and lots of other things in life: Never assume anything.
 
Skylark said:
There’s a bit of a common theme with the OP here. Why be so rude just because other people don’t share your views?
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Who's being rude? The OP has spent a huge amount of time developing a calculation that may be useful to the less experienced sailor in trying to understand the basics of anchoring and snubbers. To have his work described as technobabble is uncalled for. How would you feel if you had invested time and effort and has some of the less than complimentary comments on this thread?
 
NormanS said:
Please explain how I would get a figure for "vessel velocity" at anchor?
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Sure! It is not precise, as Jonathan already hinted at, but if you have your chart plotter running at anchor for a while and watch the Speed over Ground arrows pointing here and there in all directions, then watch for how large the velocity gets when the vessel is moving away from the anchor. Mathematically, it is the velocity component pointing away from the anchor that matters. Not pointing towards it, neither sideway. Only the velocity component really stretching the chain is what matters.

This figure may only be accurate to some 50%, so add some margin to what you see. Better to be on the safe side.

Cheers, Mathias
 
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