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What is breaking strain: ground tackle


LadyG

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Hi guys, when I was matching my ground tackle, warp, chain and anchor, I am limited by practicality of handling and launching the ground tackle.

I came up with a figure of 6800kg breaking strain which is fine to match the tackle, but I don't have an understanding of "breaking strain"

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2 minutes ago, LadyG said:

Hi guys, when I was matching my ground tackle, warp, chain and anchor, I am limited by practicality of handling and launching the ground tackle.

I came up with a figure of 6800kg breaking strain which is fine to match the tackle, but I don't have an understanding of "breaking strain"

 Breaking Strain is the amount of load put into a chain or other type of equipment required to  cause it to fail (or break) - another way of saying Breaking Point. 

 

HTH

 

Howard

 

  

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Yes, well how is it related to SWL, where presumably "snatch/jerking is less relevant.

How does an engineer determine what ground tackle to use on a warship for example, when a windlass is available and pretty much unlimited resources are available..

Perhaps @Alan de Enfield could advise if he thinks I can handle an 11.5kg Mantus and 10m of 10mm chain. :) plus warp ?

Edited by LadyG
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2 minutes ago, LadyG said:

Yes, well how is it related to SWL, where presumably "snatch/jerking is less relevant.

How does an engineer determine what ground tackle to use on a warship for example, when a windlass is available and pretty much unlimited resources are available..

Perhaps @Alan de Enfield could advise if he thinks I can handle an 11.5kg Mantus and 10m of 10mm chain. :) plus anchor ?

SWL is usually one sixth of the breaking strain. 

 

Howard

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Your chain will weigh circa 2 Kg per metre, so if anchored in 10m of water (assuming 30m of rope warp as well) you are going to need to lift 30KG. Not easy. If in 3ft of water, then if you can drive forward over the anchor to retrieve it, then it is doable. 

I am not really sure what the question is. If it's about an NB, then deploying an anchor is likely to be in an emergency, to being able to drive over the anchor to retrieve it will not be an option ...so best to cut the rope.

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17 minutes ago, Dr Bob said:

Your chain will weigh circa 2 Kg per metre, so if anchored in 10m of water (assuming 30m of rope warp as well) you are going to need to lift 30KG. Not easy. If in 3ft of water, then if you can drive forward over the anchor to retrieve it, then it is doable. 

I am not really sure what the question is. If it's about an NB, then deploying an anchor is likely to be in an emergency, to being able to drive over the anchor to retrieve it will not be an option ...so best to cut the rope.

Holy smokes, Robin, I'll be attaching  a big fat bouy to the bitter end rather than leaving it for the fishes, anyway let's hope I'm never tested.

Yes I am thinking narrowboat: swollen river, being sucked towards a massive weir, engine splutter, cough, silence!

The attachment point would be the weakest link, and that can be sorted.......... to six times 6800kg, I guess. 

My boat is likely to submarine at this rate!

Edited by LadyG
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1 hour ago, LadyG said:

Hi guys, when I was matching my ground tackle, warp, chain and anchor, I am limited by practicality of handling and launching the ground tackle.

I came up with a figure of 6800kg breaking strain which is fine to match the tackle, but I don't have an understanding of "breaking strain"

As the maths teacher used to say "please show your workings".

 

How did you come up with 6.8 tonnes ?

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9 minutes ago, Alan de Enfield said:

As the maths teacher used to say "please show your workings".

 

How did you come up with 6.8 tonnes ?

      total=
Ground tackle     break load
11.5 Mantus     6800
10mm chain     6893
18mm anchorplait     5800
Green pin 10mm[11mm pin]     6000
It's some time since I did this, I used available and comparable figures from the manufacturers      

I got the figures from the original sources as much as I could, the breaking strain was available for all the apparatus, I assume it was kgs, needless to say, I did not take a note at the time.

https://jimmygreen.com/galvanised-shackles/34088-galvanised-shackles-certified-green-pin?search_query=green+pin&results=299

Edited by LadyG
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1 hour ago, LadyG said:

Hi guys, when I was matching my ground tackle, warp, chain and anchor, I am limited by practicality of handling and launching the ground tackle. 

I came up with a figure of 6800kg breaking strain which is fine to match the tackle, but I don't have an understanding of "breaking strain"

Launching the Ground tackle suggests throwing it in, but when i did my Boatmaster Licence training, we were taught never to throw an anchor, but to lower it into thre water with the chain and rope neathly piled on the deck so that it will not foul on ther boat, or worse your feet/legs as it goes in, and being a 72 ft passenger boat we had a big anchor.

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3 minutes ago, LadyG said:
      total=
Ground tackle     break load
11.5 Mantus     6800
10mm chain     6893
18mm anchorplait     5800
Green pin 10mm[11mm pin]     6000
It's some time since I did this, I used available and comparable figures from the manufacturers      

I got the figures from the original sources as much as I could, the breaking strain was available for all the apparatus, I assume it was kgs, needless to say, I did not take a note at the time.

Ahhh...……………….you have chosen some ground-tackle, looked at its 'breaking point' and decided that is the figure you want, so are now looking for a boat to 'match' ?

 

It may be better to start with the boat you want to 'stop' and work out the ground tackle from that.

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2 minutes ago, David Schweizer said:

Launching the Ground tackle suggests throwing it in, but when i did my Boatmaster Licence training, we were taught never to throw an anchor, but to lower it into thre water with the chain and rope neathly piled on the deck so that it will not foul on ther boat, or worse your feet/legs as it goes in, and being a 72 ft passenger boat we had a big anchor.

pffff .............. try anchoring a 76 footer under sail,  50 metres of chain laid out on deck, .............. preparation is the key.

There will only 10m of chain, which should be OK, and the rope can be lightly tied with rotten string, I can;t remember the nautical term,

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19 minutes ago, Alan de Enfield said:

Ahhh...……………….you have chosen some ground-tackle, looked at its 'breaking point' and decided that is the figure you want, so are now looking for a boat to 'match' ?

 

It may be better to start with the boat you want to 'stop' and work out the ground tackle from that.

I did start with a 50ft narrowboat, and my 33m of 18 mm anchorplait, and researched the best anchor for setting in an emergency.

I compared breaking strains once I had the ground tackle "assembled" , breaking strain was available for all four components, anchor, shackle, chain, rope.

 I probably can't handle a bigger anchor and chain given the limited launching facilities of a narrowboat.  

Also we are talking marine mortgage if we step up to a 30kg anchor, 20m of 12mm chain and 30 m of 24mm anchorplait. I think if it ever comes to that, it's air sea rescue territory :)

I think one has to get the anchor in the water as soon as there is a danger of "going over the weir", and before the boat is accelerating

f=ma.

Edited by LadyG
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29 minutes ago, David Schweizer said:

Launching the Ground tackle suggests throwing it in, but when i did my Boatmaster Licence training, we were taught never to throw an anchor, but to lower it into thre water with the chain and rope neathly piled on the deck so that it will not foul on ther boat, or worse your feet/legs as it goes in, and being a 72 ft passenger boat we had a big anchor.

Do they make em that small? ?

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Me thinks you are worrying too much!

I know you have done some lumpy water stuff so know the difficulties in setting an anchor. I would think more about the type of anchor needed and then rely on 10mm chain, as anything bigger will just be too heavy and 50M+ of octoplait.

It is very difficult to set an anchor by just throwing it overboard and hoping for the best. There is a technique to anchoring and it is possible to get it right 90% of the time if anchoring over a decent sea bed, but you need to drop the anchor to the sea bed at the right speed and then reverse to pull the rope/chain out and pull at the the right rate so the point digs in and the anchor sets. To hope that you will set an anchor by chucking it overboard with all its chain is very wishfull thinking. The best type of anchor for this type of deployment is going to be the wrong shape to store in the bow or stern. Then there is the question of which end to put it at. Sods law says it will be the wrong end.

Actual anchoring experience and advice for canal boat is a scarce as rocking horse shit as no one does it....or anchors are rarely deployed. I would love to hear some experiences of trying to deploy anchors in an emergency and what worked/didnt work.

Edited by Dr Bob
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I have selected the 11.4kg Mantus as it can be dismantled for storage, it also has top rating with setting first time, and assembled, it is not too awkward.

When I was a bairn I used to cross the Gareloch to Helensburgh for fish 'n chips in my pram dinghy, and put an anchor balanced on the bow, which "self deployed" when you pushed the boat out from the shore, I was thinking along those lines, the anchor would be on the bow, the chain in the well deck, the warp in the well deck.

I never mentioned throwing it in the water, it would be sitting on the bow deck ready for action.

Edited by LadyG
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Static load of a boat will depend on shape, wind speed and to a lesser extent weight.

Shock-loads on anchors are regularly in excess of 3x static loads.

 

Very little research (non ?) has been made on canal boats anchoring - well its not something they do is it ?

 

Trying to extract meaningful figures from 'lumpy water boat' anchor tests should give some indication - but - it is purely speculation and no 'warranty given or implied'.

 

A 12 tonne yacht in a 30knt wind will exert a static load of about 1200 kgs, the 'snatch load' (as waves hit-and-lift) will be something like 4000kg

 

If you 'spec your tackle' at 6000kg you should be OK with that on most NB's

 

This is all pretty meaningless if the anchor doesn't 'set'.

The latest generation anchors (Mantus, Manson, Fortress) are the best 'all-rounders' and will set quickly in most 'ground'.

 

I went for the 30kg Mantus, (£600) but with hindsight would now go with the Fortress FX55 or FX85 (weighing 14 & 21 kgs respectively)

 

Motor Boat Monthly Magazine tested many different anchors - the Fortress FX37 (10kg) was set and tried to pull it out using a boat with a 375hp engine, at 5000lbs (2300kgs) 'pull' it wouldn't shift, was holding the boat and the test terminated.

 

During Yachting Monthly's anchor tests they highlighted the 10kg (weight) Fortress as 'the best' and achieving over 3000kgs before it stated to bend (that is equivalent to the loads on a 40 foot sailing yacht in a force 10 Hurricane).

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20 minutes ago, Tumshie said:

While I greatly appreciate that this really is a very technical subject - Can we not just ask what other folks have and what do they use it for? And then just go with the one that fits best. :huh:

And just as important as the gear you eventually chose after weighing up all the various advice, you need to work out how you are going to use it. If you are very close to a weir, by the time you have realised that you should have an anchor down it may well be too late and it is probably not going to help, and if you are well away from the weir however, , you may find it better to put the anchor just touching the bottom and use its drag to help you ferry glide to the side. In other words, give the whole subject plenty of thought, not just the equipment.  If you are in a situation where you need to jettison the anchor, unless it is safe and practical, don't concern yourself about anchor recovery. Anchors are cheap, fingers and limbs are not.

 

It may also be worth saying that the incidents of people getting into trouble on weirs are very uncommon, and while it is useful to prepare as much as you can, it is not worth worrying the subject to death!?

 

Howard

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32 minutes ago, howardang said:

It may also be worth saying that the incidents of people getting into trouble on weirs are very uncommon, and while it is useful to prepare as much as you can, it is not worth worrying the subject to death

That is true - but in the last 4 years I have been present at 2 such incidents.

 

One went over the weir as the boat was rolled under the Dolphins, the second one* got his anchor down (Danforth) which would not set properly but slowed him down enough to give us chance to get a line aboard and tow him away - we were about 100 yards from the Dolphins by the time we got him secured - Brown trouser time all round.

 

* Was Cromwell weir where 10 soldiers lost their lives when they (their boat) went over the weir.

 

I try to work on the principle "better to have and not to need, than need and not have".

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The highly experienced contributors to this thread don’t need telling, but for the less experienced who may be reading it, when choosing an anchor’s weight, it’s not whether you can manage to lift it to deploy it, it’s whether you can recover it. Since you don’t have a winch on a narrowboat, even when it’s straight up and down, if it’s covered in river weed it’s a quite incredible effort to get it back.

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2 hours ago, LadyG said:

pffff .............. try anchoring a 76 footer under sail,  50 metres of chain laid out on deck, .............. preparation is the key.

There will only 10m of chain, which should be OK, and the rope can be lightly tied with rotten string, I can;t remember the nautical term,

What has that got to do with canals, or any non tidal rivers?

 

 

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I would approach the OP's  problem from an energy perspective.  Assuming the best/worst case of anchor sets immediately how  much energy do I have to absorb.  That is determined by the speed and the mass of your boat when the anchor grabs.

 

Most of it will be sbsorbed by the octoplait stretching, so how much strain energy will octoplait accept in a given length.  Does that stretch the rope enough to break it?  If not the gear is strong enough.

 

I have anchored a narrowboat, but it was deliberate, not emerrgency brake stuff.  In the Avon at Pill above the M5 bridge.  That was OK.  Getting the gear back was hard.  If you have successfully stopped in extremis getting the hook back would be a bonus, but there will be time for that after solving the root problem. 

N

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1 hour ago, mrsmelly said:

Do they make em that small? ?

Of course they do , as you well know.  As indicated to LadyG, this is a Canal Forum and the maximuim length on most canals is 72ft. As it happens my licence entitled me to captain any passenger carrying boat much larger than the one we were operating.

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12 minutes ago, David Schweizer said:

Of course they do , as you well know.  As indicated to LadyG, this is a Canal Forum and the maximuim length on most canals is 72ft. As it happens my licence entitled me to captain any passenger carrying boat much larger than the one we were operating.

It must have been an old style licence then? They have been significantly updated since.  The ones we have now from the MCA are very specific. Mine allows for twin screws but only a maximum of 500 passengers. The boat I took it on is 86 feet length 16 feet air draught and 20 foot beam two decks and seating for 172 with twin screws. I was also tested greatly on my knowledge of the Trent twixt the humber and Nottingham and over an hour questioned on the boat, its watertight compartments, fire fighting capabilities etc then an hours drive to show capabilities in wind, flow and manouvering.  Another boatmaster licence I hold is the standard narrowboat licence which is probably what you mean? Even these now are more onerous than the first I took in 2000 which was a doddle. the old were blue the ones now issued by MCA are red much like a passport. My licence also has to be renewed every three years and not just rubber stamped, a medical and firefighting and first aid courses again as part of the test. Funnily enough the first aid part has been downgraded now from 3 to 1 day course.

Edited by mrsmelly
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2 hours ago, Tumshie said:

While I greatly appreciate that this really is a very technical subject - Can we not just ask what other folks have and what do they use it for? And then just go with the one that fits best. :huh:

We bought an anchor to do the ship canal just after we bought the boat

 

It has never been in the water since 2003

 

Richard 

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