Anchors

[mayalld]

By far the most important criteria is to get one that can be readily handled by yourself or your crew, no point in having, the best anchor in the world if you can't lift it..

 

And no point having an anchor that won't do the job.

 

If the bigest anchor that you can handle is half the size of the anchor you need, there is no point having that one, because it won't be up to the job.

 

Work out what size you need, then work out a means of deploying it.

[blodger]

And no point having an anchor that won't do the job.

 

If the bigest anchor that you can handle is half the size of the anchor you need, there is no point having that one, because it won't be up to the job.

 

Work out what size you need, then work out a means of deploying it.

 

However, as has been said one less than the optimum will be OK for most uses/needs so is better than none!!

[mayalld]

However, as has been said one less than the optimum will be OK for most uses/needs so is better than none!!

 

Less than the optimum may suffice for some uses.

 

So, if the calc says 50kg, and you decide that you can't deploy more than 25kg, you then need to calculate what waterways and conditions that will suffice for, and stay off the waters where it isn't adequate.

 

Just saying "get the biggest you can handle", without recognising that this will mean that you need to limit where you go is foolhardy in the extreme.

[blodger]

Less than the optimum may suffice for some uses.

 

So, if the calc says 50kg, and you decide that you can't deploy more than 25kg, you then need to calculate what waterways and conditions that will suffice for, and stay off the waters where it isn't adequate.

 

Just saying "get the biggest you can handle", without recognising that this will mean that you need to limit where you go is foolhardy in the extreme.

Agreed

[carlt]

Less than the optimum may suffice for some uses.

 

So, if the calc says 50kg, and you decide that you can't deploy more than 25kg, you then need to calculate what waterways and conditions that will suffice for, and stay off the waters where it isn't adequate.

 

Just saying "get the biggest you can handle", without recognising that this will mean that you need to limit where you go is foolhardy in the extreme.

No narrowboat needs a 50kg anchor so this is a ridiculous statement.

 

I have 8 anchors, on my boat and only one of them weighs more than 30kg, despite it displacing 26 tons.

 

If you can handle an anchor of 20kg then there is one available for pretty much all situations a narrowboat will find itself in.

 

If you should find that some bizarre set of circumstances require a 50kg anchor then 2x25kgs will hold as well, if not better.

 

If you can't handle 20kg then I would find crew that can.

[mayalld]

No narrowboat needs a 50kg anchor so this is a ridiculous statement.

 

I have 8 anchors, on my boat and only one of them weighs more than 30kg, despite it displacing 26 tons.

 

If you can handle an anchor of 20kg then there is one available for pretty much all situations a narrowboat will find itself in.

 

If you should find that some bizarre set of circumstances require a 50kg anchor then 2x25kgs will hold as well, if not better.

 

If you can't handle 20kg then I would find crew that can.

 

I don't suggest that there is a narrowboat that needs a 50kg anchor.

 

What I do suggest is that for any given narrowboat and cruising range, it can be calculated what anchor/anchors will be adequate.

 

I then suggest that, when selecting an anchor/anchors, they MUST be at least as good as one of the possibilities thrown up by the calculations. Simply deciding to select something smaller than any of the options that the calculations suggest is utterly pointless, and potentially dangerous.

[carlt]

I don't suggest that there is a narrowboat that needs a 50kg anchor.

 

What I do suggest is that for any given narrowboat and cruising range, it can be calculated what anchor/anchors will be adequate.

 

I then suggest that, when selecting an anchor/anchors, they MUST be at least as good as one of the possibilities thrown up by the calculations. Simply deciding to select something smaller than any of the options that the calculations suggest is utterly pointless, and potentially dangerous.

Could you provide a link to these calculations, for narrowboats?

 

You seem fixated on size (ooer) but, depending on the river bed, a 15kg anchor, of one type, will hold better than a 50kg anchor of another.

 

What I also said holds true, too. If you can only handle an anchor that is half the weight, these mythical calculations throw up, then have 2 anchors ready to deploy.

 

If you can handle 25kg then this...

The heaviest you can handle.

 

I'd go with 25kg with 10m of chain (10mm links) and 20m of 16mm of 3 strand nylon rope.

....will cover pretty much any circumstances.

[mayalld]

Could you provide a link to these calculations, for narrowboats?

 

You seem fixated on size (ooer) but, depending on the river bed, a 15kg anchor, of one type, will hold better than a 50kg anchor of another.

 

I found them when we sized our anchor, and could probably find them again.

 

I am more than happy to accept that size isn't the only thing when it comes to anchors.

 

However, it is possible to say (for example) that for a 60' narrowboat on non tidal rivers, no more than A metres deep, running at not more than B knots;

• One 25kg anchor of type X
  
• Two 15kg anchors of type X
  
• One 20kg anchor of type Y
  
• One 15kg anchor of type Z
  

 

Will be adequate.

 

In such a case, deciding that you can manage a 10kg type X is bog all use.

[carlt]

I found them when we sized our anchor, and could probably find them again.

 

I am more than happy to accept that size isn't the only thing when it comes to anchors.

 

However, it is possible to say (for example) that for a 60' narrowboat on non tidal rivers, no more than A metres deep, running at not more than B knots;

• One 25kg anchor of type X
  
• Two 15kg anchors of type X
  
• One 20kg anchor of type Y
  
• One 15kg anchor of type Z
  

 

Will be adequate.

 

In such a case, deciding that you can manage a 10kg type X is bog all use.

But 2 10kg anchors of type Y woud do the same, if not better, job as "One 20kg anchor of type Y"

[mayalld]

But 2 10kg anchors of type Y woud do the same, if not better, job as "One 20kg anchor of type Y"

 

Accepted!

 

There will always be more than one way of satisfying the requirements, but that isn't the advice that some people are peddling on this thread.

[Keeping Up]

I think this is a rather useful table - from the IWA Thames Tideway Handbook, as referenced by the Port of London Authority:

 

[RLWP]

I think this is a rather useful table - from the IWA Thames Tideway Handbook, as referenced by the Port of London Authority:

 

 

It's a very elegant table to be sure. What on earth does it mean?

 

Richard

[Keeping Up]

It's a very elegant table to be sure. What on earth does it mean?

 

Richard

It shows the recommended weight of anchor on the Thames Tideway for different size of boats. I don't see why it shouldn't apply equally to any river waters where the speed of flow is similar - unless the bottom is known to be of a markedly different composiution to Thames mud.

 

The "CQR" and "Fisherman" are types of anchor (see Wikipedia for their descriptions and pictures) - unfortunately I don't know how to compare a Danforth anchor with them, which is what most narrowboats carry, but I'd guess it falls somewhere between the two. Maybe someone else here knows better.

 

The other two columns are, I think, self-explanatory

[FadeToScarlet]

No narrowboat needs a 50kg anchor so this is a ridiculous statement.

 

I have 8 anchors, on my boat and only one of them weighs more than 30kg, despite it displacing 26 tons.

 

If you can handle an anchor of 20kg then there is one available for pretty much all situations a narrowboat will find itself in.

 

If you should find that some bizarre set of circumstances require a 50kg anchor then 2x25kgs will hold as well, if not better.

 

If you can't handle 20kg then I would find crew that can.

 

Isn't it also the case that you can increase the length (and therefore weight) of chain warp attached to the anchor, which means the anchor itself can be smaller? I think I read it in PBO or something.

 

That way, even if there was a situation where the anchor required was heavier than the crew could handle, you'd still have enough holding power.

[RLWP]

It shows the recommended weight of anchor on the Thames Tideway for different size of boats. I don't see why it shouldn't apply equally to any river waters where the speed of flow is similar - unless the bottom is known to be of a markedly different composiution to Thames mud.

 

The "CQR" and "Fisherman" are types of anchor (see Wikipedia for their descriptions and pictures) - unfortunately I don't know how to compare a Danforth anchor with them, which is what most narrowboats carry, but I'd guess it falls somewhere between the two. Maybe someone else here knows better.

 

The other two columns are, I think, self-explanatory

 

Thanks Allan, that helps.

 

What we need now is a table to determine how long a length of warp you need for different waterways - Avon, Severn, Thames, MSC and so on.

 

Richard

 

Cherwell?

[Dalesman]

Thanks Allan, that helps.

 

What we need now is a table to determine how long a length of warp you need for different waterways - Avon, Severn, Thames, MSC and so on.

 

Richard

 

Cherwell?

Now to get back to the original question. How deep is the River Thames?

 

In the estuary the charted depth (which can for most general purposes be considered as the depth at low water) is about 20 metres at its deepest . To get the depth of water at Mean High Water Springs (MHWS) you can add about 5 metres to that depth. At Mean High Water Neaps (MHWN) you only need to add about 4 metres.

 

Opposite Southend the charted depth is about 11 metres. Add about 5.7 metres to get the depth of water at MHWS and 4.8 metres at MHWN.

 

At Tilbury the charted depth is about 9.8 metres. Add about 6.4 metres to get the depth of water at MHWS and 5.4 metres at MHWN.

 

At Woolwich the charted depth is about 6.5 metres. Add about 7.0 metres to get the depth of water at MHWS and 5.9 metres at MHWN.

 

At London Bridge the charted depth is about 1.8 metres. Add about 7.1 metres to get the depth of water at MHWS and 5.9 metres at MHWN.

 

At Westminster Bridge the charted depth is about 1.9 metres. Add about 6.8 metres to get the depth of water at MHWS and 5.6 metres at MHWN.

 

At Hammersmith Bridge the charted depth is about 1.4 metres. Add about 5.7 metres to get the depth of water at MHWS and 4.6 metres at MHWN.

 

At Richmond the charted depth is about 1.0 metre. Add about 4.9 metres to get the depth of water at MHWS and 3.7metres at MHWN.

 

On the navigable section of the Non-tidal Thames (Teddington to Lechlade) the depths range from about 3.0 metres to 0.9 metres. The depth of water is controlled by the Environment Agency (EA) by adjusting the height of the weirs. The EA also endeavour to maintain a minimum dredged depth on the non-tidal River. It is not a constant depth: it varies depending on the section of river:

 

Fairway

Depth

 

Teddington - Staines Bridge

2.0m

 

Staines Bridge - Windsor Bridge

1.7m

 

Windsor Bridge - Reading Bridge

1.3m

 

Reading Bridge - Folly Bridge

1.2m

 

Folly Bridge - Lechlade

0.9m

 

 

All the figures quoted for both the tidal and non-tidal Thames are approx as the riverbed is constantly changing and it does not take into account rainfall and other weather effects or surge tides in the North Sea.

 

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[howardang]

Thanks Allan, that helps.

 

What we need now is a table to determine how long a length of warp you need for different waterways - Avon, Severn, Thames, MSC and so on.

 

Richard

 

Cherwell?

You don't really need a table for that. The rule of thumb minimum length of anchor warp is around 4 times the maximum deprth you may expect to have to anchor in for an all chain set up , or at least 6 times if using rope warps with a short length of chain. There is no maximum length - it's up to you.

 

Howard

[RLWP]

You don't really need a table for that. The rule of thumb minimum length of anchor warp is around 4 times the maximum deprth you may expect to have to anchor in for an all chain set up , or at least 6 times if using rope warps with a short length of chain. There is no maximum length - it's up to you.

 

Howard

 

I'll turn that one around then. What depth of water do you expect to have to anchor in?

 

Richard

Edited March 16, 2010 by RLWP

[Dalesman]

Thanks Allan, that helps.

 

What we need now is a table to determine how long a length of warp you need for different waterways - Avon, Severn, Thames, MSC and so on.

 

Richard

 

Cherwell?

The MSC is dredged to 28 feet, the River Weaver is only about 10 ft or less,while the Seven up stream of Gloucester is also only about 10 feet and the Avon is even less, except of course in flood conditions like in 2007..!!

Edited March 16, 2010 by Dalesman

[Keeping Up]

More useful figuires Dalesman (unless you're going on the Cherwell)

 

Ideally you need your warp to be 5 times the depth of the water, but I understand that you can reduce this figure to 3 times if you have mainly heavy chain rather than rope. On that basis, given that I have 20 metres of heavy chain (weighing about 50 Kg) and 10 metres of rope, I reckon I could safely anchor in about 9 metres of water - which just about covers me for everything upstream of Limehouse (I don't plan on going in the other direction).

 

Someone who was staying on the non-tidal Thames would need 15 metres of rope, or 9 metres of heavy chain - or better still a combination of the two.

[RLWP]

All this confirms my suspicion that we have enough warp and chain to anchor off Penzance

 

Richard

 

(about 200 feet)

[Naughty Cal]

Using the anchor correctly is also another point to think about. Just dumping it overboard isnt going to help you no matter how much chain or rope you are carrying.

[RLWP]

Using the anchor correctly is also another point to think about. Just dumping it overboard isnt going to help you no matter how much chain or rope you are carrying.

 

And here we run into another reality of narrowboat life compared to tidal boating. Most narrowboaters are going to use their anchor in exactly that way. The engine has failed, you are being swept towards a weir, throw the anchor overboard and hope.

 

Richard

[luctor et emergo]

I know it is obvious, but perhaps this is a good time to point out that, before one 'throws the anchor overboard and hopes for the best', one should ensure that said anchor is tied to a solid part of the boat... unlike a mooring line were you take up the slack before you tie off...

 

 

 

[Naughty Cal]

And here we run into another reality of narrowboat life compared to tidal boating. Most narrowboaters are going to use their anchor in exactly that way. The engine has failed, you are being swept towards a weir, throw the anchor overboard and hope.

 

Richard

 

In that case you may as well just head for the wier and hope. The anchor wont hold the bottom if just thrown overboard.

 

I know it is obvious, but perhaps this is a good time to point out that, before one 'throws the anchor overboard and hopes for the best', one should ensure that said anchor is tied to a solid part of the boat... unlike a mooring line were you take up the slack before you tie off...

 

 

Good point. And the emphasis should be on a SOLID part of the boat. The forces exerted, should the anchor take hold, will be quite large, and could easily rip a t-stud from the front of a narrowboat.