Reversing the engine when digging in the anchor – how much anchor load does this correspond to?

[jordanbasset]

Again my posts are based on real life experience but hey that counts for $h1t here.

PW.

Okay are you telling us in the real world you just use chain with no anchor on it?
Or do you use a chain with an anchor on it?
If the former that would be real world experience. If the latter then you make the point others are making, or at least you are unable to say in the real world the anchor made no difference

 

[vyv_cox]

It must be 10 years since I bothered to contribute to one of these pointless threads. Following up on a 'chain does the holding' thread then, I pulled my 65 metre, 8 mm chain along the unsurfaced boatyard in Greece. I am long since retired, certainly could not be described as muscular and not too much overweight. I found it easy to pull one end of a loop of chain and was able with a bit of effort to pull it in a straight line.
How much can I pull? Not more than 50 kg I suspect. Would not take a lot of wind blowing on my boat to exceed that.

 

[Stemar]

All I'm going to say on the subject is that I've sat out some fairly boisterous weather on a mixed rode. Not gales in a 24 footer, thank you very much, but definitely on the bumpy side.

It doesn't take that much wind to pull an all chain rode off the bottom, and when that happens, a mixed rode and all chain are no different. In fact, a mixed rode will do better, as the rope will stretch when the boat tugs on it, absorbing the shock and reducing the peak load on the anchor. If I had enough rope out - and I would in a blow, I wouldn't need a snubber, because the rope would do the job. I've heard arguments that make sense to me that the only time one should use all chain is on coral or a similar bottom that eats rope.

 

[Neeves]

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

Have you tried removing your anchor and just deploying the chain?

Do let us know the result, please.

- W

He seems to be basing his comments on 'being in command of small ships' - nothing to do with leisure vessels. I am not aware that small ships use a mixed rodes though I have seen commercial vessels using wire as the rode, worked off a drum. The Classification Societies are quite comfortable with wire rodes.

My interpretation.

Characteristically his, Pilot Wolf's, posts lack any numerical data, so we don't know what small means, but a small commercial ship could be 20,000t, or 1,000t, and will not use anchors like ours. He implies he is a certificated commercial skipper, a Master, of small ships as he says he has been 'in command'. He gives no indication of ever having anchored a leisure craft sized vessel. His comments are largely anecdotal in relation to our practices and have no relationship to our experiences where we expect our anchor to offer security - well beyond winds during which commercial vessels would retreive their anchors, motor offshore and wait until conditions become less harsh. His comments on (commercial) anchors not offering the hold of our anchors might have validity (for commercial practices) as their ground tackle is not designed to offer security during Gales and certainly not Storms - though even then - though the anchors might not be as reliable as ours they and the chain would be adequate - in combination - to 30 knots.

I conclude that his comments offer no, not an iota, of relevant knowledge to us (except don't anchor downwind of large commercial vessels when Gales or Storms are forecast).

Whether he is offering his time as some from of entertainment - I cannot judge. But given this Forum is established to help leisure yachtsmen and women - and if he is a qualified Master - he must be bored.

However I would pick up Thinwaters comment, no wonder he is the Technical Editor of a prestigious American sailing magazine:

Don't feed the trolls

Sorry Mathias - your thread has been hijacked.

Stay safe, take care

Jonathan

 

[vyv_cox]

Have you tried removing your anchor and just deploying the chain?

Do let us know the result, please.

- W

I have actually been in this unfortunate situation. We were anchored in a bay in Ibitha, wind force 2-3, when my original swivel failed (account on my website, stress corrosion cracking). At the time we were in shallow water so probably had 20 - 25 metres of chain deployed. We heard the bang when the swivel failed and the boat immediately started to drift backwards. The chain did almost nothing to hold us.

 

[gordmac]

It is not the chain or the anchor that holds you it is the chain and anchor!

 

[gordmac]

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.

Very few non technical (and some who should know better!) Seem to understand units and dimensions, I don't suppose they really need to! I have used the SI system all my working life except a bit of design to American standards, slug anyone!
Sadly you buy stuff in kilogrammes rather than Newtons and kg weight although not SI seems to have become the norm, kp would be more sensible but next to nobody would understand why I suspect.

 

[Poignard]

 

[PilotWolf]

He seems to be basing his comments on 'being in command of small ships' - nothing to do with leisure vessels. I am not aware that small ships use a mixed rodes though I have seen commercial vessels using wire as the rode, worked off a drum. The Classification Societies are quite comfortable with wire rodes.

My interpretation.

Characteristically his, Pilot Wolf's, posts lack any numerical data, so we don't know what small means, but a small commercial ship could be 20,000t, or 1,000t, and will not use anchors like ours. He implies he is a certificated commercial skipper, a Master, of small ships as he says he has been 'in command'. He gives no indication of ever having anchored a leisure craft sized vessel. His comments are largely anecdotal in relation to our practices and have no relationship to our experiences where we expect our anchor to offer security - well beyond winds during which commercial vessels would retreive their anchors, motor offshore and wait until conditions become less harsh. His comments on (commercial) anchors not offering the hold of our anchors might have validity (for commercial practices) as their ground tackle is not designed to offer security during Gales and certainly not Storms - though even then - though the anchors might not be as reliable as ours they and the chain would be adequate - in combination - to 30 knots.

I conclude that his comments offer no, not an iota, of relevant knowledge to us (except don't anchor downwind of large commercial vessels when Gales or Storms are forecast).

Whether he is offering his time as some from of entertainment - I cannot judge. But given this Forum is established to help leisure yachtsmen and women - and if he is a qualified Master - he must be bored.

However I would pick up Thinwaters comment, no wonder he is the Technical Editor of a prestigious American sailing magazine:

Don't feed the trolls

Sorry Mathias - your thread has been hijacked.

Stay safe, take care

Jonathan

So ridiculing me has no value given my experience doesn't relate to your toys?!

As you've also chosen to ignore I can count on 1 yes ONE hand the number of times I have had an anchor and chain drag in maybe 30 years but guess I'm not doing it right.

Bored? Sometimes, sometimes maybe helping, mostly amused at the crap posted here...

PW

 

[geem]

So ridiculing me has no value given my experience doesn't relate to your toys?!

As you've also chosen to ignore I can count on 1 yes ONE hand the number of times I have had an anchor and chain drag in maybe 30 years but guess I'm not doing it right.

Bored? Sometimes, sometimes maybe helping, mostly amused at the crap posted here...

PW

Slagging off people for no reason with a wealth of experience in lesuire craft ( it's Practical Boat owner not Practical ship owner) will not win you many friends. You assume because you have 30 years working on a ship that that qualifies you to talk with knowledge about anchoring boats. Clearly it doesn't. Your lack of knowledge is alarming

 

[thinwater]

Not my expert.

Wrong type of bridge.

Again my posts are based on real life experience but hey that counts for $h1t here.

PW.

Moving on...

If a key question is whether an anchor becomes exposed in a tidal change, what factors will keep the anchor engage?

1. Modern design
2. Chain (buffers the turn)
3. Setting a second anchor in a V
4. Riding sail
5. Other

Discuss. Certainly the first 3 help.

 

[DanTribe]

To quote Charlie Brown

"Oh good grief!"

 

[MathiasW]

If the ansatz is reasonable to work out the load on the anchor caused by the engine as f = ? p / v, then I can apply the same principle to work out the load caused by a head-on tidal stream. Only head-on, not from the side!

I do the same procedure as before, but now with engine with full thrust forward. ? and v may be slightly different, but p will be the same.

Then I use the - Bernoulli ? law - of quadratic dependency of the resistance in a laminal flow to scale this force / load to the speed of the tidal current, v_c. This gives me the anchor load due to the tidal current as f_c = ? p / v (v_c/v)^2.

As said, only an approximation for when the tidal stream is coming head on. Normally, wind and tide will mean the vessel is at an angle for both of them, meaning windage area is enlarged, as well as the under-water hull. This will mean the anchor load to the tidal stream will normally be larger than what I have estimated above. It'll make for a factor 2, 3, 4?

Anyway, just toying around with the concept.

 

[NormanS]

Ye Gods! I hadn't realised that I was so clever. I've always managed to anchor, nearly always successfully, while calculating the requisite anchor, chain, and suitable anchoring position, in my head. ?

 

[PilotWolf]

Slagging off people for no reason with a wealth of experience in lesuire craft ( it's Practical Boat owner not Practical ship owner) will not win you many friends. You assume because you have 30 years working on a ship that that qualifies you to talk with knowledge about anchoring boats. Clearly it doesn't. Your lack of knowledge is alarming

Wasn't aware I'd slagged anyone off? I have friends here and there, I'm not looking to solicit any here.

But for the record I started at the bottom and worked my way up so my experience includes leisure and small craft too in those 30 years you assume are on a ship.

Boat? Ship? Both the captain and I of the last I was aboard used both terms, he is probably 15-20 years more experienced than I.

You have no idea of my level of knowledge - the MCA and USCG does, both are satisfied it is sufficient.

PW

 

[webcraft]

Wasn't aware I'd slagged anyone off? I have friends here and there, I'm not looking to solicit any here.

But for the record I started at the bottom and worked my way up so my experience includes leisure and small craft too in those 30 years you assume are on a ship.

Boat? Ship? Both the captain and I of the last I was aboard used both terms, he is probably 15-20 years more experienced than I.

You have no idea of my level of knowledge - the MCA and USCG does, both are satisfied it is sufficient.

PW

We have a very good idea of the level of your knowledge when it comes to safely anchoring leisure craft.

It is quite obvious that it is shockingly deficient.


- W

 

[PilotWolf]

We have a very good idea of the level of your knowledge when it comes to safely anchoring leisure craft.

It is quite obvious that it is shockingly deficient.


- W

Nope you don't . But keep digging (that anchor).

PW

 

[Richard10002]

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

I think we all know who the "random guy on a forum" is .

He seems significantly unwilling to provide any evidence for what he says, and has not answered my question, despite my asking it twice.

Personally, having sailed on ocean going ships several decades ago, and been yachting until not too long ago, I think he is talking bolleaux, but would be happy to change my opinion if he could support what he says.

 

[geem]

I think we all know who the "random guy on a forum" is .

He seems significantly unwilling to provide any evidence for what he says, and has not answered my question, despite my asking it twice.

Personally, having sailed on ocean going ships several decades ago, and been yachting until not too long ago, I think he is talking bolleaux, but would be happy to change my opinion if he could support what he says.

Yep, not one jot of evidence to support his childish argument.

 

[PilotWolf]

We have a very good idea of the level of your knowledge when it comes to safely anchoring leisure craft.

It is quite obvious that it is shockingly deficient.


- W

Unfortunately or maybe otherwise you don't.

PW