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Anchor for the Thames

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I'll soon be taking a trip up the Thames from Brentford to Oxford on a 70' narrowboat. The boat currently has no anchor so I need to establish exactly what I need in terms of anchor weight, size and length of chain and warp length.

 

I've been in touch with an anchor supplier to ask this question after providing the same info and they suggested the following options:

 

20kg Brittany anchor, 10m of 8mm chain and 20m warp

or

16kg Brittany anchor, 9m 10mm chain and 20m warp

 

Both options weigh a total of around 35kg although I'm erring towards option 2 as a 16kg anchor might be easier to pick up and manoeuvre overboard than the 20kg version.

 

The supplier did suggest I got a second opinion hence this post but all thoughts welcome!

 

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If you do a search for anchor on the forum you will see a lot of discussion and conflicting opinions. The root problem is that the experience for actually deploying an anchor on a fast flowing river from a narrowboat, or wide beam in an emergency is very low. There just isn't enough real world knowledge to give much reliable advice. What does exist is for sea going vessels and this doesn't necessarily translate to inland craft. Buy the biggest heaviest anchor and longest heaviest chain and warp you can afford and pick up. Tie the end of the warp to something solid on the boat. Not the T stud at the bow as this can just be ripped off by the force of the boat coming on to the anchor. You've then got the best chance that it will work in an emergency.

 

Now someone will come along and say this is completely wrong and they may be right. I've never deployed an anchor inland for real. Chances are they won't have either! 😀

Jen

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At least 20kg, imho, and as much chain as you can, ideally the length of the boat? Then twice as much rope, and think about how to deploy the anchor in an emergency. If the anchor is at the bow, and you are alone at the stern, it won’t be much use, and if your crew member(s) can’t pick up the anchor, that’s no use either...

Do make sure one end of the rope is attached to the boat, very securely! As Jen says, it’s a subject fraught with disagreement.

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It's a bummer.

I spent ages researching the issue many years ago  and bought the right amount of chain and warp.

Never had to use it in anger - and thats for several decades on the River

Used it to moor for lunch stops and the silly thing just dragged. Blurry heavy to recover as well

In an emergency the stream has probably pushed you into the bank before the anchor has taken a hold.

There's very little flow at the moment - and it won't be long before the lockies will get the sandbags out and only worh the locks when they're full (of boats that is)

 

However - you should have an anchor.....

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25 minutes ago, OldGoat said:

Used it to moor for lunch stops and the silly thing just dragged. Blurry heavy to recover as well

 

That just confirms two points :

 

1) The anchor was not the correct size or design to suit the boat.

2) It shows that you need to practice anchoring, you cannot just 'throw it overboard' and expect it to work.

 

 

Anchoring is a skill that has to be developed and that only only be done with practice, the correct anchor & chain will assist, but relying on a 10kg Danforth anchor with 5 metres of chain is a potential 'killer'.

 

There are a number of threads on the forum where people with experience have contributed years of knowledge to be told "its different on the inland waterways" AND yes it is, you need a far better and bigger anchor that is going to take the load of a 20 tonne boat and bring it to an immediate stop, and then not drag rather than a 10 tonne boat that is already stopped and you are lowering the anchor in a controlled way, if it doesn't set you have another go and another go.

 

If you are deploying your anchor on a NB it is an emergency situation, the anchor needs to deploy, set and not drag, 1st time, everytime.

 

Start with this old post :

 

Scroll up to the 1st post and read on from there.

 

 

'But what if I cannot retrieve it" yes you can, you use the engine to retrieve it.

Edited by Alan de Enfield
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When I remember, I use an anchor buoy. This is attached to the "other" or bottom end of the anchor (I am sure there is a proper techincal term) via a rope and shackle. When you want to depart you motor forwards, pick up the buoy, and then either pull, or tie off and motor forward, to break the anchor out of the river bed. I did find it easier to lift this way rather than pulling on the chain. Also worth remembering that in deep water the chain can weigh as much as the anchor

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30 minutes ago, Scholar Gypsy said:

When I remember, I use an anchor buoy. This is attached to the "other" or bottom end of the anchor (I am sure there is a proper techincal term) via a rope and shackle. When you want to depart you motor forwards, pick up the buoy, and then either pull, or tie off and motor forward, to break the anchor out of the river bed. I did find it easier to lift this way rather than pulling on the chain. Also worth remembering that in deep water the chain can weigh as much as the anchor

But you still have to be able to lift the weight from the bottom to the top. I have never had to do it but I guess that getting it from the water onto the deck is not easy, especial;y foredeck. (We did once have to pick up a person, fit, healthy, male, but getting him from the water into the boat was quite a struggle. Similar experience when I fell into the eater at a marina and several strong people had to work rather hard to get me out - I could not haul myself with all the weight of wet cloths).

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32 minutes ago, Scholar Gypsy said:

When I remember, I use an anchor buoy. This is attached to the "other" or bottom end of the anchor (I am sure there is a proper techincal term) via a rope and shackle. When you want to depart you motor forwards, pick up the buoy, and then either pull, or tie off and motor forward, to break the anchor out of the river bed. I did find it easier to lift this way rather than pulling on the chain. Also worth remembering that in deep water the chain can weigh as much as the anchor

 

10mm anchor chain weighs 2.3kgs per metre which is why it is so much better to use chain than 'rope', the weight holds the anchor down and ensures the pull is horizontal rather than vertical.

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2 hours ago, Mike Todd said:

But you still have to be able to lift the weight from the bottom to the top. I have never had to do it but I guess that getting it from the water onto the deck is not easy, especial;y foredeck. (We did once have to pick up a person, fit, healthy, male, but getting him from the water into the boat was quite a struggle. Similar experience when I fell into the eater at a marina and several strong people had to work rather hard to get me out - I could not haul myself with all the weight of wet cloths).

Yes, that's true. My point is a buoy makes it easier to get the anchor out of the mud etc.

 

And one can just lift it until it is at or just above water level, tie it off to the T stud, pull the chain on board, and leave the anchor there (ie on the outside of the hull) until things calm down!

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2 hours ago, Mike Todd said:

But you still have to be able to lift the weight from the bottom to the top. I have never had to do it but I guess that getting it from the water onto the deck is not easy, especial;y foredeck. (We did once have to pick up a person, fit, healthy, male, but getting him from the water into the boat was quite a struggle. Similar experience when I fell into the eater at a marina and several strong people had to work rather hard to get me out - I could not haul myself with all the weight of wet cloths).

I imagine if you had a 200lb anchor wrapped in wellies and wet 'woolies' it would be difficult to lift on board as well, however most folks will be lifting a 30-50lb metal anchor which is not that difficult. You will only recover the anchor if the engine is running, you motor up to the anchor position recovering the chain as you go so you are never listing much more than 2 or 3 metres (8kg ?) of chain, once you are over the anchor, tie the chain off and keep going, the boat breaks-out the anchor, you can then simply lift it the 2 or 3 metres back onto the boat.

 

It really isn't as difficult as some folks would like to make it - if it was, we wouldn't anchor up almost every day.

 

Your anchor will weigh less than a gas cylinder (13kg size) less than a toilet cassette (22kgs) and less than a bag of coal (20kg)

Edited by Alan de Enfield

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11 minutes ago, Scholar Gypsy said:

Yes, that's true. My point is a buoy makes it easier to get the anchor out of the mud etc.

 

And one can just lift it until it is at or just above water level, tie it off to the T stud, pull the chain on board, and leave the anchor there (ie on the outside of the hull) until things calm down!

Sorry Simon, but the last thing an inexperienced canal boater needs to be encumbered with is an anchor buoy. They can be a PITA at times offshore never mind in the panic of an emergency on the cut! 

 

If the anchor has been deployed successfully and the panic has diminished it can be treated as sacrificial if it can't be retrieved without causing a hernia!

 

Howard

 

 

Edited by howardang
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3 minutes ago, howardang said:

Sorry Simon, but the last thing an inexperienced canal boater needs to be encumbered with is an anchor buoy. They can be a PITA at times offshore never mind in the panic of an emergency on the cut! 

 

If the anchor has been deployed successfully and the panic has diminished it can be treated as sacrificial if it can't be retrieved without causing a hernia!

 

Howard

 

 

That's a fair point, I was proposing a controlled anchoring and in quite deep water.  

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20 hours ago, Alan de Enfield said:

  You will only recover the anchor if the engine is running, 

Or when someone comes to tow you home, If you need to anchor on the Thames is probably because the prop has stopped turning for some reason.

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Had to drop the anchor on the Severn, somewhere below Worcester, a couple of years ago when the engine on the hire boat overheated. 

I was the assumed "expert" as I have my own boat. Another crew member threw the anchor into the water while I attended to the engine.

After a while I noticed we were moving downstream. He had dropped the anchor until it touched the bottom and tied the warp off at that length so the anchor couldn't bite.

Fortunately the river was low and after about 30 mins we were on our way again.

An anchor has to lay on the bottom and if it has a good few meters of chain laid down as well it should hold.

I guess the real need is if you are being swept towards a weir.

Edited by dixi188
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On 16/07/2020 at 14:48, Scholar Gypsy said:

When I remember, I use an anchor buoy. This is attached to the "other" or bottom end of the anchor (I am sure there is a proper techincal term) via a rope and shackle. When you want to depart you motor forwards, pick up the buoy, and then either pull, or tie off and motor forward, to break the anchor out of the river bed. I did find it easier to lift this way rather than pulling on the chain. Also worth remembering that in deep water the chain can weigh as much as the anchor

Tripping line attached to the tripping ring at the crown of the anchor.    Lots of experience of anchoring........with ships and yachts in the coast, never once inland though have anchored a 90,000mt ship in the Thames Estuary! 
 

I would recommend a 20kg Danforth with 10m of chain and 20m of rope.   When on rivers I use a floor mat on the cabin roof to place the anchor close to the helmsman, the other end needs to be made fast at the bow, with the rope/chain combo going outside of all obstructions on the boat.   Never had to use in anger, but if you do you need it close at hand and able to deploy without it snagging on anything on your boat.   
 

 

it’s the weight of the anchor and chain that keeps you from drifting, not just the anchor itself.   With chain only you need min 3 x the depth of water, rope at least 5 x depth of water.   

Edited by Dharl
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A secondhand anchor and chain available here. Should prevent your boat drifting even before it is deployed as your entire boat will become a mud weight on the bottom.

Jen 😁

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You'll have to imagine your own sound effects here.   After the my 20kg anchor goes,"plooush", the 10m of chain goes "gggggrrrr", the 20m of rope goes "wzzzz"  I dont want to hear a tiny "plop" as the securing shackle drops into the water..

My question is: what' strength does the anchor's final anchoring point need to be, where should it be and how do you attach it?   

I'm planning to sit my anchor and warp etc on a purpose made cradle on the roof at the front, when cruising the upper Thames, with the  warp routed neatly down the front of the cabin to an eye ring on the well deck that's an emergency, last stop back-up anchor point.  You'd normally tie off the anchor with the tee stud once enough chain or warp had been deployed so the  isn't the main securing ring - just one in case all hell breaks loose and there isn't time or whatever to tie off beforehand.  

 I'm picturing this as a lifting eye ring tucked away in the corner of the well deck.   A grot standard M12 bolt shears at about 4.8tonnes and Calando weighs 17 tonnes.   Whilst the anchor point won't need to take the full weight of the boat, I don't know what the snatch forces would produce if she's in , say, a 7 knot stream and the anchor bites.   

A big fat plate beneath the ring under the well deck should stop any nonsense but don't know how to get under the well deck or whether it's safe to surface weld on  due to internal insulation etc.

Any advice welcome

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2 hours ago, Cal Ando said:

You'll have to imagine your own sound effects here.   After the my 20kg anchor goes,"plooush", the 10m of chain goes "gggggrrrr", the 20m of rope goes "wzzzz"  I dont want to hear a tiny "plop" as the securing shackle drops into the water..

My question is: what' strength does the anchor's final anchoring point need to be, where should it be and how do you attach it?   

I'm planning to sit my anchor and warp etc on a purpose made cradle on the roof at the front, when cruising the upper Thames, with the  warp routed neatly down the front of the cabin to an eye ring on the well deck that's an emergency, last stop back-up anchor point.  You'd normally tie off the anchor with the tee stud once enough chain or warp had been deployed so the  isn't the main securing ring - just one in case all hell breaks loose and there isn't time or whatever to tie off beforehand.  

 I'm picturing this as a lifting eye ring tucked away in the corner of the well deck.   A grot standard M12 bolt shears at about 4.8tonnes and Calando weighs 17 tonnes.   Whilst the anchor point won't need to take the full weight of the boat, I don't know what the snatch forces would produce if she's in , say, a 7 knot stream and the anchor bites.   

A big fat plate beneath the ring under the well deck should stop any nonsense but don't know how to get under the well deck or whether it's safe to surface weld on  due to internal insulation etc.

Any advice welcome

Whatever you do decide on, double the dimensions of the steelwork you fit. The well deck is a good option, what is under it?

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3 hours ago, Cal Ando said:

   Whilst the anchor point won't need to take the full weight of the boat, I don't know what the snatch forces would produce if she's in , say, a 7 knot stream and the anchor bites.   

 

Any advice welcome

What is the breaking strain of you rope would that give before the ring

 

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18 minutes ago, Stilllearning said:

Whatever you do decide on, double the dimensions of the steelwork you fit. The well deck is a good option, what is under it?

Like the blind fawn - no eyed-deer.   Almost certainly the water tank but unless its a weird bespoke shape, probably not where I want to put the ring.  (right by the gunnel and right in front of the cabin bulkhead.

BUT I now know the force of my boat being stopped is:  1/2mV*V/d    (1/2 M Vsquared / distance over which force acts)

where m is the mass of the boat, V is its speed and d is the distance taken to stop from its travelling speed to 0 (i,e, snatch distance)

m = 17,000 kg, V = 7 knots = 3.6m/s (YIKES) and d = 4m allowing for anchor movement when biting, rope stretch etc

THUS force = 27,540 Newtons which = 2,808 kg or about 3 tonnes

 

Thus in theory, any chinese steel M12 bolt from Lidl which would be rated at 4 tonnes should be adequate.

 

If my estimate of 4m  stopping distance is inaccurate and it's 2 m, then this is double the force so would need M16 to be safe

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As a strong point attachment I have passed the rope through one of the well deck scuppers to tie a loop around the hull side. Should be plenty strong enough. The risk might be that the sharpish edge of the 6mm steel side would cut the rope. Never actually tried deploying the anchor. I used it because it was already there. 

There are limited places to put in a nice big ring bolt on my and many other boats. The well deck has a stainless water tank immediately underneath. Other steelwork forms part of the gas locker and putting a ring bolt through that below the level of the gas cylinder valves could lead to arguments during a BSS inspection. I really should fit one at some point. Probably the top of the gas locker would be the best spot. 

Jen

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2 hours ago, ditchcrawler said:

What is the breaking strain of you rope would that give before the ring

 

OK, you've ruined everything now haven't you!   I'm using 16mm hemp so even using the 2D2 formula for breaking strain this would only be 512kg (2 x 16 x 16) or describing it another way "ping!" if 4 tonnes is stuffed on it.   I think the minimum rope size to hold 4 tonnes would be 44mm dia or 10mm hauser.   If you had 100 ft of 44mm hemp you probably wouldn't need an anchor if you could manage to heave that lot over the side!

Back to the drawing board.   I'll just stay on the K&A (although you need an anchor sometimes on the K

ennet section

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Just now, Cal Ando said:

OK, you've ruined everything now haven't you!   I'm using 16mm hemp so even using the 2D2 formula for breaking strain this would only be 512kg (2 x 16 x 16) or describing it another way "ping!" if 4 tonnes is stuffed on it.   I think the minimum rope size to hold 4 tonnes would be 44mm dia or 10mm hauser.   If you had 100 ft of 44mm hemp you probably wouldn't need an anchor if you could manage to heave that lot over the side!

Back to the drawing board.   I'll just stay on the K&A (although you need an anchor sometimes on the K

ennet section

 

When anchoring you should be using 100% chain anyway - much less space taken up as you ony need 3 to 5 times depth instead of 10x depth with rope.

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56 minutes ago, Cal Ando said:

Like the blind fawn - no eyed-deer.   Almost certainly the water tank but unless its a weird bespoke shape, probably not where I want to put the ring.  (right by the gunnel and right in front of the cabin bulkhead.

BUT I now know the force of my boat being stopped is:  1/2mV*V/d    (1/2 M Vsquared / distance over which force acts)

where m is the mass of the boat, V is its speed and d is the distance taken to stop from its travelling speed to 0 (i,e, snatch distance)

m = 17,000 kg, V = 7 knots = 3.6m/s (YIKES) and d = 4m allowing for anchor movement when biting, rope stretch etc

THUS force = 27,540 Newtons which = 2,808 kg or about 3 tonnes

 

Thus in theory, any chinese steel M12 bolt from Lidl which would be rated at 4 tonnes should be adequate.

 

If my estimate of 4m  stopping distance is inaccurate and it's 2 m, then this is double the force so would need M16 to be safe

I wouldn't be out on a river running at 7Kts in a Narrowboat, but I'm a wimp.

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43 minutes ago, Jen-in-Wellies said:

As a strong point attachment I have passed the rope through one of the well deck scuppers to tie a loop around the hull side. Should be plenty strong enough. The risk might be that the sharpish edge of the 6mm steel side would cut the rope.

Jen

As usual, Jen, you've provided a great solution.   Many thanks. 

I'll chuck a chain and shackle round the scuppers and attach the warp to that.   Now whats the breaking strain of the shackle?.....

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