PilotWolf
Well-known member
As everyone seems to like the internet here is the first I found.
I can count the number of times I've had an anchor drag (using my original post 'way'), on one hand and in some pretty horrendous weather.
W.
Reversing the engine when digging in the anchor – how much anchor load does this correspond to?
- Thread starter MathiasW
- Start date
- Status
As everyone seems to like the internet here is the first I found.
I can count the number of times I've had an anchor drag (using my original post 'way'), on one hand and in some pretty horrendous weather.
W.
thinwater
Well-known member
Yeah, I've wondered about that. It is one of the examples of English changing, in this case, for the worse, since it reduces clarity.
From OED:
dynamometer
noun
- An instrument which measures the power output of an engine.
‘First, under the testing conditions described, it is not possible for the dynamometer to measure the locomotive's maximum drawbar pull.’
Wiki dynamometer
But other sources witch things up to follow common misusage, which over time becomes correct:
From Websters:
Definition of dynamometer
1 : an instrument for measuring mechanical force
2 : an apparatus for measuring mechanical power (as of an engine)
The problem with saying you will use a strain gauge or load cell is that technically, these are only the sensing element of the scale. I think the most correct common refference is probably a hanging scale (even if it is horizontal) or crane scale.
---
So yeah, get a cheap hanging scale from Amazon. You can get something accurate but not very durable for $75-$150.
thinwater
Well-known member
Your expert really should get another job (maybe political oppinion writeing--that's a logic- and fact-free zone). Obviously, the anchors at the end of a suspension bridge, for example, are unimportant. I wonder why they waste all that money on them. Getting them into bed rock and all that. So silly.
PilotWolf
Well-known member
Not my expert.
Wrong type of bridge.
Again my posts are based on real life experience but hey that counts for $h1t here.
PW.
MathiasW
Active member
Excellent! Quoting somebody saying something misleading and then taking the wrong interpretation does not make it more true...
The clip is mostly correct in what it is saying. But they are misleading in what they are saying when they claim the anchor holds the chain and the chain is holding the ship. This is true if interpreted as the load is passed on from ship via chain to anchor. But it is not true to invert this statement and say the anchor does not hold the ship.
Other than that, a nice video explaining how the chain absorbs energy as it gets raised. This is particularly important for absorbing shock loads.
Zing
Well-known member
PilotWolf
Well-known member
Excellent! Quoting somebody saying something misleading and then taking the wrong interpretation does not make it more true...
The clip is mostly correct in what it is saying. But they are misleading in what they are saying when they claim the anchor holds the chain and the chain is holding the ship. This is true if interpreted as the load is passed on from ship via chain to anchor. But it is not true to invert this statement and say the anchor does not hold the ship.
Other than that, a nice video explaining how the chain absorbs energy as it gets raised. This is particularly important for absorbing shock loads.
I will pass your views on to the captains in my GF's rather large cruise line for their opinions.
PW
MathiasW
Active member
Again, I would love to see your experiment in real life to do away with this silly anchor and "anchor" without it, just using the chain. I mean, an anchor is such a big nuisance, isn't it. It gets entangled in stuff every so often, it is so heavy to handle. If I could have its weight in beer cans, wouldn't this be so much better?
So, please make this experiment and let us know!
PilotWolf
Well-known member
MathiasW
Active member
You said the anchor is not holding the vessel. So, the anchor is not needed then, is it.
And do not tell me it is there to hold the chain, because if it is, then the chain will act as a bridge to connect the load seen on the vessel to the anchor. Or why do you think the anchor needs to hold the chain in the first place? Just the chain itself is perfectly happy to rest on the seabed, if it wasn't for the vessel to pull at it and drag it across. It does not drag, as it passes on the load to the anchor. So, you need to look at it as a complete system that passes on loads from one end to another. Like a tug of war kind of thing. You would not say there that your opponent is only there to keep the tug line in place. He is tugging you across the line if you are not careful!
And this has NOTHING to do with the weight of the chain.
But you are not alone in this view. I was in a German forum the other day, and somebody there had a very similar argument to yours. And he said this is the way it is still taught at maritime universities.
Well, if that is the case, then too bad, they teach it all wrong and should lose their jobs...
Richard10002
Well-known member
As above, are you saying that a ships anchor is never so taut that the chain is all off the bottom?
gordmac
Well-known member
Thanks. Where is kp used? Don't think I have come across that one (I am a mechanical engineer).Indeed, it was in Newton - ever so slightly embarrassing.
kp is kilo pont, which is the same numerical value as kg on Earth, but just a unit of force and weight, rather than mass. The numerical factor between kp and N is 9.81, the gravitational acceleration on Earth.
MathiasW
Active member
I think it is not really used a lot. It used to be a unit in Europe, or Germany at least, but then with SI units the Newton took over. Some strange folks like me use it when we are working in units where people with no technical background would wrongly use the unit kg, which is referring to a mass, not a force, as kp does. kp is just nice in that it has the same numerical value as kg, on Earth that is...
So, if you were to say the tension of your rope is 1000 kg, I would correct you - being teacher's son and of many irritating habits - to 1000 kp...
Other than the numerical equivalence to kg, there is not a huge benefit in using it. And worse, it can make you trip over units as it did in my case in the original post.
Interestingly, there is an analogy for the imperial units. Almost everybody is using lbs to describe tensions, but if you are strict, you would use lbs only for mass and lbf for force. It is even wrongly printed on my bicycle tires...
Hardly anybody knows or cares about it, is my impression. Thinwater had alluded to it earlier, though.
Last edited:
PilotWolf
Well-known member
OK.
I'll stick with the consensus of maritime academics and practical experience over some random guy on a yachtie forum but thanks for your opinion and experiments.
PW
Neeves
Well-known member
I stand to be corrected but I think that is what you said here
My interpretation of your post was that the chain offers the hold, not the anchor. If the anchor is not offering the hold - as asked - why use it? Anchors are not cheap, they detract from yacht performance, they are not very pretty (unless you are an anchor maker or own an Ultra) and they are hazard if you run into another yacht at the start line of a race (or anywhere else). If you believe in your statements possibly you can explain why every yacht and Mo Bo you see has an anchor on the bow roller - I assume everyone is wrong .......... except you. Strangely most Maritime bureaucracies and Classification Societies demand that an anchor, or 2 or 3, is carried, and despite the fact that anchors detract from performance - all race authorities demand yachts carry an anchor or 2.
Sadly PW - the world and the leisure boating community seem to be against you. But all credit to you to air your beliefs in the face of evidence. We will at least know of the credibility of your ideas and can treat your ideas appropriately when you post on YBW. I encourage you to keep posting, YBW offers opportunity for people to express their views, controversial or not, and it is educational to know how others think and the beliefs they hold.
Just out of interest PW, if its not an impertinence - what do you sail, what ground tackle do you carry.
Final comment - Mathias is, or was (we all need to retire at some stage), an academic - he is not 'some random guy' on a forum. Thinwater is Technical Editor at Practical Sailor - he, similarly, is not 'some random guy' on a forum. Most of the contributors to this thread have decades of experience of anchoring in diverse locations round the world - they too are not 'random guys' on a forum.
Jonathan
Last edited:
MathiasW
Active member
Upon watching the video clip again - they are clearly wrong when stating that it is the chain that holds the ship, not the anchor. I do not know what authority the voice over of that clip claims to have.... and why one should believe him.
As to maritime academics, I cannot judge what they really teach, but what I could imagine is that they are saying the anchor holds the chain in place and the chain holds the ship in place. That statement is not ideal, but ok-ish, if interpreted as saying the load needs to pass from ship to anchor.
But it would be wrong to invert this statement by then concluding that the anchor does not hold the ship in place. That is definitely a different statement from the above.
But I rest my case now - may the force be with you!
a random guy
PilotWolf
Well-known member
Got to love an anchor thread.
I don't sail anything as can't be doing with all that flappy stuff. But have been in command of small ships and witnessed biggish ship (90k ton) procedures.
But I promise not to laugh at your antics if trying to anchor alongside me. Hell I'll even put the rescue boat afloat to save your ass if needed.
You/they are all random to me as is the YouTube video - hence posted it was the first I found in a search.
How about getting into using thrusters whilst anchored? Do they affect the holding? What about tenders alongside - do they add to the needed holding needed?
PW
I don't sail anything as can't be doing with all that flappy stuff. But have been in command of small ships and witnessed biggish ship (90k ton) procedures.
But I promise not to laugh at your antics if trying to anchor alongside me. Hell I'll even put the rescue boat afloat to save your ass if needed.
You/they are all random to me as is the YouTube video - hence posted it was the first I found in a search.
How about getting into using thrusters whilst anchored? Do they affect the holding? What about tenders alongside - do they add to the needed holding needed?
PW
Neeves
Well-known member
I wonder if the skipper of the Pasha Bulker was a disciple of the holding capacity of the chain used by commercial vessels.
Commercial ground tackle is not designed to hold commercial vessels in adverse conditions. The ground tackle is demanded to allow commercial vessels to wait outside a port/discharge facility in 'benign' conditions. These conditions are clearly defined in ALL publication of ALL Classification Societies that In strong winds commercial vessels are recommended to retrieve their ground tackle. Off Australia's east coast commercial vessels are directed, there is no choice, to vacate the anchorage and steam (?) in open seas until the conditions abate. This restriction is fairly recent, since the beaching of the Pasha Bulker, and now we know the reasons - a childish belief in efficacy of the holding capacity of chain.
Beggars belief.
Statements being made without any experience, without any technical basis, not an iota of quantitative data.
Just some idle and dangerous ramblings.
Jonathan
Commercial ground tackle is not designed to hold commercial vessels in adverse conditions. The ground tackle is demanded to allow commercial vessels to wait outside a port/discharge facility in 'benign' conditions. These conditions are clearly defined in ALL publication of ALL Classification Societies that In strong winds commercial vessels are recommended to retrieve their ground tackle. Off Australia's east coast commercial vessels are directed, there is no choice, to vacate the anchorage and steam (?) in open seas until the conditions abate. This restriction is fairly recent, since the beaching of the Pasha Bulker, and now we know the reasons - a childish belief in efficacy of the holding capacity of chain.
Beggars belief.
Statements being made without any experience, without any technical basis, not an iota of quantitative data.
Just some idle and dangerous ramblings.
Jonathan
PilotWolf
Well-known member
webcraft
Well-known member
Have you tried removing your anchor and just deploying the chain?
Do let us know the result, please.
- W
- Status