C&RT License Survey

[magnetman]

4 minutes ago, MartynG said:

This balance is achieved only when the cycle is completed and the boat leaves the lock . 

This is not correct. 

 

 

[agg221]

9 minutes ago, beerbeerbeerbeerbeer said:

right, if we conclude that saving water is not dependent on boat size in locks:

waiting to share locks to conserve water is a waste of time?

 

 

No, because that is about lock cycles rather than about water per cycle. If two boats go through together in one lock cycle it takes half as much water as two boats going through in two separate cycles.

 

Alec

[beerbeerbeerbeerbeer]

3 minutes ago, magnetman said:

Obviously if there is more than one Boat in the lock then each individual Boat is using less water so sharing locks if possible is ideal. 

 

…definitely confused now

 

I thought it was decided: a fat boat in a lock will use no more water than a thin boat (using same lock),

so how is one thin boat waiting to share with another thin boat going to use less water?

[magnetman]

 

Boat entering lock pushes water out. Boat exiting lock does not do this. It moves water but if there was a hole to be filled then the lock would not have achieved a level and the gates would not open. 

 

As the Boat moves out of the lock it is displacing water but this simply a function of it moving in a channel. 

 

Totally different thing happening. 

1 minute ago, beerbeerbeerbeerbeer said:

 

…definitely confused now

 

I thought it was decided: a fat boat in a lock will use no more water than a thin boat (using same lock),

so how is one thin boat waiting to share with another thin boat going to use less water?

 

Surely the idea overall, taking into account number of Boats, is to use less water. Its obvious that if two Boats go through a lock -each Boat- uses half of the water because it is a fixed amount which is shared. If it was one Boat they would use all of the water. 

 

So per Boat narrow beam vessels if they share locks individually use less water than a wide bean which is unable to share the lock. 

 

 

[beerbeerbeerbeerbeer]

13 minutes ago, agg221 said:

No, because that is about lock cycles rather than about water per cycle. If two boats go through together in one lock cycle it takes half as much water as two boats going through in two separate cycles.

 

 

 

 

Edited December 17, 2023 by beerbeerbeerbeerbeer
Forget what I just said 😃

[magnetman]

Just now, beerbeerbeerbeerbeer said:

? therefore it can be said a fat boat uses the same water as two thin boats

OR a fat boat uses twice the amount as a thin boat?

 

 

Yes but you are assuming that narrow boats always share wide locks. In reality this doesn't happen. 

 

 

 

One could equally say that a canoe uses a tenth of the water if there are ten canoes in the lock. 

 

But there aren't. So they don't. A single canoe will use the same amount of water as a spider in a walnut shell rowing boat or a 71ft narrow boat with a load of coal in it if it is the only object in the lock. 

[agg221]

9 minutes ago, beerbeerbeerbeerbeer said:

? therefore it can be said a fat boat uses the same water as two thin boats

OR a fat boat uses twice the amount as a thin boat?

 

 

Correct - when the narrowboats share the lock.

 

Alec

[Momac]

27 minutes ago, magnetman said:

This is not correct. 

 

 

Yes it is

[magnetman]

No it isn't. 

 

Its a completely different process when a Boat is exiting a lock to when it is entering a lock. 

Edited December 17, 2023 by magnetman

[beerbeerbeerbeerbeer]

5 minutes ago, magnetman said:

Yes but you are assuming that narrow boats always share wide locks. In reality this doesn't happen. 

 

 

 

One could equally say that a canoe uses a tenth of the water if there are ten canoes in the lock. 

 

But there aren't. So they don't. A single canoe will use the same amount of water as a spider in a walnut shell rowing boat or a 71ft narrow boat with a load of coal in it if it is the only object in the lock. 

What happens in reality is really unimportant,

this is simply theory we’re talking ain’t it?

 

because in reality or in practice we know fat boats use less water going through locks because they only have half the system to navigate where as thin boats have the whole system to navigate and rarely share wide locks. 
and canoes should never be using locks,

dunno about spiders in walnut shells

[Momac]

1 minute ago, magnetman said:

 

Its a completely different process when a Boat is exiting a lock to when it is entering a lock. 

Only in your head 

[magnetman]

When it goes in it pushes water out of what is about to become a fixed container.  When it goes out all it is doing is moving through a restricted channel with the associated water movement. 

 

The water displaced by the Boat (going down) has already been expelled from the lock otherwise the gates would not open.

 

When the Boat moves out of the lock obviously water has to replace it but that is nothing to do with the fact it is a lock it is simply a Boat moving through a restricted channel.

An open lock is part of a channel. A closed lock is a container. 

 

Yes the channel itself is a container just a much bigger one and usually there are things like bywashes and leakage which would make the channel itself an irrelevant part of the calculations. 

[beerbeerbeerbeerbeer]

5 minutes ago, agg221 said:

Correct - when the narrowboats share the lock.

 

Alec

Right, I’m definitely quitting now because I thought the common point of view was now; it didn’t matter what size of boat you had it used the same water as any other boat 

[magnetman]

5 minutes ago, beerbeerbeerbeerbeer said:

Right, I’m definitely quitting now because I thought the common point of view was now; it didn’t matter what size of boat you had it used the same water as any other boat 

IF THERE IS ONE BOAT IN THE LOCK 

 

 

 

 

It seems too simple but the Boat actually IS a block of water. It occupies the space previously occupied by block of water. For this reason when in a closed container it is impossible for it to do anything other than what a block of water would do. 

 

So a lock full of water is actually the same thing as a lock with a Boat in it. 

 

Just because it is a Boat does not mean it can defy the laws of physics. 

Edited December 17, 2023 by magnetman

[magpie patrick]

30 minutes ago, magnetman said:

Yes but you are assuming that narrow boats always share wide locks. In reality this doesn't happen. 

 

 It does much of the time on the K&A, especially in summer - Juno has been the third boat in a lock on a number of occasions

[magnetman]

2 minutes ago, magpie patrick said:

 It does much of the time on the K&A, especially in summer - Juno has been the third boat in a lock on a number of occasions

Yes thats why I put 'always' in

 

Its cool when multiple Boats can share locks. 

[beerbeerbeerbeerbeer]

13 minutes ago, magnetman said:

Yes thats why I put 'always' in

 

Its cool when multiple Boats can share locks. 

yes, because it obviously saves using a lock full of water for each boat in the lock. 

[magnetman]

It is a very clever approach. Unfortunately some people want big Boats. 

 

Small Boats are generally better. 

Edited December 17, 2023 by magnetman
ttpo

[cowpie]

Are we looking at weight, density or mass here.

A 16 ton narrowboat floating on the surface 18 m x 2m x 0.5 m below the water line = 18 cubic metres of displaced water,

or a 16 ton block of solid steel which would be fully immersed (unknown volume but at a guess only 5 or 6 cubic metres)

Which would displace the most water ?

Or is this a red herring?

[Iain_S]

20 hours ago, ditchcrawler said:

What about the Falkirk wheel with boats just coming down ?

Initially, that will "pump" a quantity of water equal to the boat's displacement up to the upper pound, with the water displaced from the top caisson and flowing into the bottom one, then getting transferred to the top as the next boat comes down. However, with the extra water in the upper pound, the effect would diminish with successive boats, as the extra water in the upper pound would result in the top caisson filling to a higher level than the lower one.

 

This effect, however, would be negligible compared to the water added to the upper pound by the necessary operation of the staircase locks to bring the boats to the top of the wheel, and the pumps and sluices would operate to keep the levels correct. 

[1st ade]

19 minutes ago, cowpie said:

or a 16 ton block of solid steel which would be fully immersed (unknown volume but at a guess only 5 or 6 cubic metres)

Steel is roughly 8 Ton a cubic metre (eight times denser than water) so 16 Ton = 2 cubic metres

Edited December 17, 2023 by 1st ade
Get the units right!

[magnetman]

14 minutes ago, cowpie said:

Are we looking at weight, density or mass here.

A 16 ton narrowboat floating on the surface 18 m x 2m x 0.5 m below the water line = 18 cubic metres of displaced water,

or a 16 ton block of solid steel which would be fully immersed (unknown volume but at a guess only 5 or 6 cubic metres)

Which would displace the most water ?

Or is this a red herring?

The block of steel is a red herring because it doesn't float. 

 

If you take the requirement to be floating out then everything changes. 

 

 

Just now, 1st ade said:

Steel is roughly 8 Kg a cubic metre (eight times denser than water) so 16 Ton = 2 cubic metres

Is this the newly patented xtralite steel ? 

 

 

 

Thousand 

[1st ade]

2 minutes ago, magnetman said:

Is this the newly patented xtralite steel ?

Spotted that about 30 mS after pressing "post" - and will now be merged...

[David Mack]

2 hours ago, magnetman said:

Surely the idea overall, taking into account number of Boats, is to use less water. Its obvious that if two Boats go through a lock -each Boat- uses half of the water because it is a fixed amount which is shared. If it was one Boat they would use all of the water. 

 

So per Boat narrow beam vessels if they share locks individually use less water than a wide bean which is unable to share the lock. 

The amount of water used when cycling a particular lock is dependent on the dimensions of the lock, but not on the size of the craft using (or not using) it. So a 14 ft wide lock uses (approximately) twice the amount of water per cycle as a 7ft narrow lock of the same fall. So if two narrow boats share a wide lock, the the amount of water used is the same as if the two boats had used two cycles of an equivalent narrow lock (assuming they weren't short enough to share the narrow lock).

So when the GUCCCo widened the locks between Napton and Birmingham, and adopted carrying by pairs of boats, the water consumption was unchanged - in fact it would have increased at Knowle where the 6 narrow locks were replaced with 5 wide locks, each a little deeper than the predecessors. What the widening did offer was the opportunity to use wider craft or more efficient operation of narrow craft, which would result in operational cost savings.

[Arthur Marshall]

The error is surely in thinking that where a boat is, is a particular, specific cube made up of boat and water. It isn't, because water is a fluid, and the boat affects the entire pound in which it sits. It doesn't displace separate chunks of water as it goes along, it all equalises out. So going into an open lock affects nothing. Craning it into a closed one would, but that rarely happens. Because a boat in a lock is at exactly the same level it was before it went into it, there is no difference to anything from when it was outside the damn thing.  You're floating at the same height because the same amount of water is there as there has been since you entered the pound, as there was before you entered the lock. And, as canals are generally managed by weirs etc to stay at a constant level, size or mass of boat makes no odds.