Well, what is fair then?

[chris w]

I am sorry if I confuse the issue, but does it all work out the same using metric units, litres, instead of gallons?

 

Surely Mr Archimedes has a lot to answer for.

 

It only works in gallons because water was invented before the SI system. If you use the decimal system (litres) then you only get 100 pence in each pound.

[Natalie Graham]

It does. 40,000 gallons passes from the upper level to the lower. And it will take 40,000 gallons to refill the lock - with or without a boat. The fact that the boat displaces 5000 gallons (in my example) back into the top pound is irrelevant as is the fact that when it exits the lock at the lower level 5000 gallons of the lower pound restores the residual amount of water in the "empty" lock from 5000 gallons to 10,000 gallons. To pass either up or down this example lock requires the movement of 40,000 gallons from the higher level to the lower. The 5000 gallon boat will reduce the quantity of water in the full lock chamber from 50,000 to 45,000. But it will also reduce the residual empty lock amount by 5000 gallons from 10,000 to 5,000. Therefore 40,000 gallons have been passed from upper to lower. Every time.

 

 

Yes. There has been a lot of overcomplicating the obvious, and hope my above post helps to eliminate the chaff from the grain.

Aaarrggh!

 

Read what you have just written.

 

'40,000 gallons passes from the upper level to the lower.'

 

'the boat displaces 5000 gallons (in my example) back into the top pound'

 

'when it exits the lock at the lower level 5000 gallons of the lower pound restores the residual amount of water in the "empty" lock from 5000 gallons to 10,000 gallons'

 

'it will also reduce the residual empty lock amount by 5000 gallons from 10,000 to 5,000'

 

I will try again.

 

The empty lock has 10,000 gallons in it. The remaining capacity is 40,000 gallons. So filling it puts 40,000 gallons of water in from the top pound. Put the 5,000 gallon boat in as well and (as you say) 5,000 gallons of water is displaced back into the top pound. The lock now contains: the 10,000 gallons that were in there when it was 'empty' a further 35,000 gallons of water from the top pound and a 5,000 gallon displacement boat. Now the gates and paddles are closed. The lock has 35,000 gallons of water in it from the top pound. That is it. The gates are closed. The paddles are closed. Whatever happens from now on, how is it possible that any more than 35,000 gallons of water can be transferred from the top pound?

 

Now the lock is emptied. If the lock contained only water then the 40,000 gallons of water which came from the top pound would be emptied into the bottom pound. However it doesn't contain only water it contains a boat which is equivalent to 5,000 gallons. As the boat will not pass through the sluices, and as 40,000 gallons must be removed to bring the lock level with the lower pound then, in addition to the 35,000 gallons which has been put in from the top pound a further 5,000 gallons of the water which was in there when it was 'empty' must also be removed. As you also agree, this leaves the residual empty lock amount as 5,000 gallons plus the boat. When the boat leaves then, to quote, '5,000 gallons of water from the lower pound restores the 'residual' amount of water in the "empty" lock from 5,000 gallons to 10,000 gallons'

 

If you work the lock without a boat in it then 40.000 gallons of water from the top pound goes in the lock and 40,000 gallons comes out at the bottom. There is no need for the 5,000 gallons from the bottom pound. That bit doesn't happen. The fact that it does happen when the lock is operated with a boat in it should tell you that less water has come down from the top pound.

 

Yes, 40,000 gallons of water is removed from the lock to work the boat through it, but in the case of a 5,000 gallon displacement boat, 35,000 gallons of this amount is transferred from the top pound to the bottom and the remaining 5,000 gallons was in the 'empty' lock when it was at the level of the lower pound, this water is temporarily removed into the bottom pound when the lock is emptied and returns from the bottom pound when the boat leaves the lock. This 5,000 gallons is not transferred from the top pound.

 

The 'empty' lock will only accommodate a further 40,000 gallons. If you put a boat in there as well you don't have room for as much water.

 

Natalie.

Edited December 1, 2008 by Natalie Graham

[Steilsteven]

I agree fully with your analysis too.

 

Chris

 

Me too.

 

Keith.

[Gibbo]

It's not a conundrum, it just depends how you define your starting and finishing points.

 

As I said several eons ago, it is convenient to define the water in the lock as part of the top pound when the lock is full and top gates open, and part of the bottom pound when the lock is 'empty' (ie at its lowest level) and the bottom gates are open. At other times the water in the lock is best treated as a separate quantity. The bit that gets transferred from top to bottom is the bit that goes through the paddles - no more, no less - and it is independent of the size (or presence) of a boat.

 

The argument has apparently dragged on because nobody properly defined the terms of the discussion. I understood this to be the amount of water 'used' by a locking operation (up or down) and we have established that this quantity is always the same for a given lock.

 

However, Gibbo has been trying to point out that in the grand scheme of things a boat-displacement's worth of water moves in the opposite direction. This is correct, but the fact is not germane to the discussion. The water that flows into the lock when the boat leaves is pushed out again by the next boat entering to go up.

 

Which is what we have been saying since Friday.

 

Put in some obfuscation, whether deliberate or accidental, and a bit of pure pig-headedness, presumably deliberate, and we tend to lose the plot. zzzzzzzzzzzzzzzzzzzzzzzzz

 

Backpedalling. Severely.

 

You were wrong.

 

Accept it, deal with it and move on.

 

Gibbo

Edited December 1, 2008 by Gibbo

[chris w]

Aaarrggh!

 

Read what you have just written.

 

'40,000 gallons passes from the upper level to the lower.'

 

'the boat displaces 5000 gallons (in my example) back into the top pound'

 

'when it exits the lock at the lower level 5000 gallons of the lower pound restores the residual amount of water in the "empty" lock from 5000 gallons to 10,000 gallons'

 

'it will also reduce the residual empty lock amount by 5000 gallons from 10,000 to 5,000'

 

I will try again.

 

The empty lock has 10,000 gallons in it. The remaining capacity is 40,000 gallons. So filling it puts 40,000 gallons of water in from the top pound. Put the 5,000 gallon boat in as well and (as you say) 5,000 gallons of water is displaced back into the top pound. The lock now contains: the 10,000 gallons that were in there when it was 'empty' a further 35,000 gallons of water from the top pound and a 5,000 gallon displacement boat. Now the gates and paddles are closed. The lock has 35,000 gallons of water in it from the top pound. That is it. The gates are closed. The paddles are closed. Whatever happens from now on, how is it possible that any more than 35,000 gallons of water can be transferred from the top pound?

 

Now the lock is emptied. If the lock contained only water then the 40,000 gallons of water which came from the top pound would be emptied into the bottom pound. However it doesn't contain only water it contains a boat which is equivalent to 5,000 gallons. As the boat will not pass through the sluices, and as 40,000 gallons must be removed to bring the lock level with the lower pound then, in addition to the 35,000 gallons which has been put in from the top pound a further 5,000 gallons of the water which was in there when it was 'empty' must also be removed. As you also agree, this leaves the residual empty lock amount as 5,000 gallons plus the boat. When the boat leaves then, to quote, '5,000 gallons of water from the lower pound restores the 'residual' amount of water in the "empty" lock from 5,000 gallons to 10,000 gallons'

 

If you work the lock without a boat in it then 40.000 gallons of water from the top pound goes in the lock and 40,000 gallons comes out at the bottom. There is no need for the 5,000 gallons from the bottom pound. That bit doesn't happen. The fact that it does happen when the lock is operated with a boat in it should tell you that less water has come down from the top pound.

 

Yes, 40,000 gallons of water is removed from the lock to work the boat through it, but in the case of a 5,000 gallon displacement boat, 35,000 gallons of this amount is transferred from the top pound to the bottom and the remaining 5,000 gallons was in the 'empty' lock when it was at the level of the lower pound, this water is temporarily removed into the bottom pound when the lock is emptied and returns from the bottom pound when the boat leaves the lock. This 5,000 gallons is not transferred from the top pound.

 

The 'empty' lock will only accommodate a further 40,000 gallons. If you put a boat in there as well you don't have room for as much water.

 

Natalie.

 

Natalie

 

That's correct. But we knew this anyway. The lock is filled normally with 40,000 gallons but it needs only 35,000 gallons once it has a 5,000 gallon boat in it. There is indeed 40,000 gallons passed through the bottom sluices made up, as you rightly say, of 35,000 gallons from the top pound and 5,000 gallons temporarily "borrowed" from the "empty" lock until the boat moves out of the lock.

 

I think it's just bad wording on Dominic's part. He also describes what happens and IMHO understands fully what is happening. 40,000 gallons is not passed FROM the top pound TO the bottom pound, I agree with you. But 40,000 gallons IS passed TO the bottom pound (until the boat comes out of the lock).

 

Chris

[Natalie Graham]

Natalie

 

That's correct. But we knew this anyway. The lock is filled normally with 40,000 gallons but it needs only 35,000 gallons once it has a 5,000 gallon boat in it. There is indeed 40,000 gallons passed through the bottom sluices made up, as you rightly say, of 35,000 gallons from the top pound and 5,000 gallons temporarily "borrowed" from the "empty" lock until the boat moves out of the lock.

 

I think it's just bad wording on Dominic's part. He also describes what happens and IMHO understands fully what is happening. 40,000 gallons is not passed FROM the top pound TO the bottom pound, I agree with you. But 40,000 gallons IS passed TO the bottom pound (until the boat comes out of the lock).

 

Chris

 

Yes, I thought we all knew that too by now. I guess I was misled when Dominic posted, twice, that the same amount of water passes from the upper to lower levels irrespective of the size of the boat and then you and others posted that you agreed with his analysis. I must remember to read what people think and not what they write, eh? Still, I guess Gibbo was right, it looks like you all got there in the end.

 

Natalie.

[chris w]

Yes, I thought we all knew that too by now. I guess I was misled when Dominic posted, twice, that the same amount of water passes from the upper to lower levels irrespective of the size of the boat and then you and others posted that you agreed with his analysis. I must remember to read what people think and not what they write, eh? Still, I guess Gibbo was right, it looks like you all got there in the end.

 

Natalie.

Well, he caught up with us actually as his version was based on magically appearing boats.

 

From the day your boat first "set foot" in the canal system, you incurred a -V3 deficit which you carry around with you everywhere you go. In Gibbo's version that was ignored and in mine it wasn't. But we both know exactly what actually happens and have no difference of opinion on that.

 

Chris

Edited December 1, 2008 by chris w

[Gibbo]

Nope. Here's what I actually wrote..............

 

A big boat going down a lock transfers less water from the upper level to the lower level than a small boat.

 

A big boat going up a lock transfers more from the upper level to the lower level than a small boat.

 

A big boat going down a lock, out into the pound, then back up the same lock uses excatly the same amount of water as a small boat doing the same thing.

 

Now.... as all boats must, roughly, on average, go back where they came from (otherwise all boats would end up in the same place) the total used by each boat is the same regardless of size.

 

Lots of people disagreed with the above. They were wrong.

 

Many people absolutely insisted (one of them still does) that the size of the boat makes no difference and the amount of water transferred from one level to the next* was always the same. It isn't and never has been.

 

They now (well most of them) accept the above as statements of fact.

 

There has been some serious backpedalling in the process though.

 

*Note the words "transferred from one level to the next" - not "moves through the paddles" or something else that some have now tried to pretend is what they were talking about.

 

Gibbo

Edited December 1, 2008 by Gibbo

[Mr B]

If I understand what is now being said (maybe I do not understand a thing)

Way back before I went back to my 'watch with mother physics' I was essentially correct with my post 134

 

 

I think this topic has moved on a bit but here is my comment

Refering to post 95 and post 122

 

Say you were approaching a lock to go down.

If the lock was empty and had to be filled then 10000 galls would be put into it.

Boat of 1000 galls displacement enters lock then 1000 galls leaves by top gate.

 

Only 9000 galls of the 10000 galls used to fill the lock will drain out to let the boat down as the boat leaves the lock the other 1000 galls enters from lower level by the gates

 

It follows that a boat of a smaller displacement will use more water to go down a lock.

 

Barry

 

 

Wrong!! read the expanation above - it describes the situation perfectly then go back to "Watch with Mother - Physics, Lesson 1"

 

You can't see what the Illuminati can see easily

 

Just because you can't hear the music, it doesn't mean the dancer is mad!

 

Chris

 

PS - It does seem as if locks have got bigger over the pages.

Barry

 

Does this mean that smaller boats should be charged more for a greater water usage?

[chris w]

If I understand what is now being said (maybe I do not understand a thing)

Way back before I went back to my 'watch with mother physics' I was essentially correct with my post 134

 

 

 

 

 

 

 

PS - It does seem as if locks have got bigger over the pages.

Barry

 

Does this mean that smaller boats should be charged more for a greater water usage?

The reason you are still wrong in your thoughts is that you believe (as evidenced by your last line) that a smaller boat uses more water overall. It does not; it uses exactly the same amount of water as a larger boat overall.

 

On entering a pound through a lock, a smaller boat takes less water from the pound than a larger boat. On leaving the pound through a lock, a smaller boat takes more water from the pound than a larger boat. The amount that any boat gives or takes to the pound is exactly the same for that boat at opposite ends of the pound and so overall is totally idependent of boat size.

 

Once a boat has passed through a pound, the volume of water in the pound is left unaffected by the size of the boat that just went through.

 

Chris

[Mr B]

The reason you are still wrong in your thoughts is that you believe (as evidenced by your last line) that a smaller boat uses more water overall. It does not; it uses exactly the same amount of water as a larger boat overall.

 

On entering a pound through a lock, a smaller boat takes less water from the pound than a larger boat. On leaving the pound through a lock, a smaller boat takes more water from the pound than a larger boat. The amount that any boat gives or takes to the pound is exactly the same for that boat at opposite ends of the pound and so overall is totally idependent of boat size.

 

Once a boat has passed through a pound, the volume of water in the pound is left unaffected by the size of the boat that just went through.

 

Chris

 

Chris

I totally agree that

Once a boat has passed through a pound, the volume of water in the pound is left unaffected by the size of the boat that just went through.

 

I was thinking about a lock not a pound so using your explanation but reversing it so that

 

 

On leaving the pound through a lock, a smaller boat takes more water from the pound than a larger boat.

 

On entering a pound through a lock, a smaller boat takes less water from the pound than a larger boat.

 

 

I follows that a small boat uses more water.

 

 

I am sure you will come back with another explanation

 

OK I'll go back to 'watch with mother'

 

Barry

[chris w]

It follows that a small boat uses more water.

 

Barry

Just for completeness, in case someone joins this debate now and doesn't read the rest.................Over one individual lock that's correct, as regards the TOP pound. Over 2 locks, there is no difference of course as the inequality cancels out.

 

Chris

Edited December 2, 2008 by chris w

[Gibbo]

Just for completeness, in case someone joins this debate now and doesn't read the rest.................Over one individual lock that's correct, as regards the TOP pound. Over 2 locks, there is no difference of course as the inequality cancels out.

 

Chris

 

That's correct in that there is no difference in the pound between the two locks.

 

But there is a difference between the pound at the top of the 1st lock and the pound at the bottom of the second lock in the case of the small or large boat.

 

 

Gibbo

[Natalie Graham]

To sum up, hopefully;

 

A larger boat uses less water to go down a lock.

 

A larger boat uses more water to go up a lock.

 

Thus the quantity of water used to a pass through a lock does vary according to the size of the boat.

 

However, in practice, as boats will normally go up as many locks as they go down, overall usage of water is not related to the size of the boat.

 

Natalie.

[Gibbo]

To sum up, hopefully;

 

A larger boat uses less water to go down a lock.

 

A larger boat uses more water to go up a lock.

 

Thus the quantity of water used to a pass through a lock does vary according to the size of the boat.

 

However, in practice, as boats will normally go up as many locks as they go down, overall usage of water is not related to the size of the boat.

 

Natalie.

 

Agreed.

 

That looks remarkably similar to post #155 which was an attempted summary of your post #108

 

Gibbo

 

However, in practice, as boats will normally go up as many locks as they go down, overall usage of water is not related to the size of the boat.

 

Natalie.

 

Just to wear my pedant's hat for a moment..........

 

It doesn't matter how many locks they go through. A round trip involving 4 locks down and 3 locks up will use the same water for a big or small boat.

 

Gibbo

[WJM]

"A larger boat uses less water to go down a lock.

A larger boat uses more water to go up a lock.

Thus the quantity of water used to a pass through a lock does vary according to the size of the boat."

 

Absolute total non-sense. Every time a lock is operated a slice of water from the bottom of the lock is moved in or out. That slice is the length and breadth of the lock and the height of the rise/fall. It makes no difference what is floating above that slice, big boat, little boat, no boat. Whatever is floating above the slice NEVER penetrates it because if it did it would be grounded in the lower phase of the operation.

Edited December 2, 2008 by WJM

[Gibbo]

"A larger boat uses less water to go down a lock.

A larger boat uses more water to go up a lock.

Thus the quantity of water used to a pass through a lock does vary according to the size of the boat."

 

Absolute total non-sense. Every time a lock is operated a slice of water from the bottom of the lock is moved in or out. That slice is the length and breadth of the lock and the height of the rise/fall. It makes no difference what is floating above that slice, big boat, little boat, no boat. Whatever is floating above the slice NEVER penetrates it because if it did it would be grounded in the lower phase of the operation.

 

Oh dear.......................

 

Natalie is correct. Read the thread. Honest!

 

Gibbo

[WJM]

The only way for the size of the boat to vary the amount of water used is for the lock to be drained totally and the boat to roll out on wheels - following archimedes principal. Given that it floats throughout, then the water used by the lock is constant.

 

However, when the boat moves out of the lock, it forces its own volume out of the pound and back into the lock behind it. Given that this effect works both ways, it pushes the same volume back into the pound as it leaves, then the only time the water levels are affected (other than the fixed loss when operating a lock) is when a boat is craned in or out of the canal.

 

 

 

 

----------------------------------------

 

 

Water and boats floating in it are the same thing. It is only when you add or take away a boat by crane that there will be a loss or gain.

Edited December 2, 2008 by WJM

[Gibbo]

However, when the boat moves out of the lock, it forces its own volume out of the pound and back into the lock behind it. Given that this effect works both ways, it pushes the same volume back into the pound as it leaves, then the only time the water levels are affected (other than the fixed loss when operating a lock) is when a boat is craned in or out of the canal.

 

Who mentioned "levels"?

 

Read the thread.

 

Natalie is correct.

 

Gibbo

[Natalie Graham]

"A larger boat uses less water to go down a lock.

A larger boat uses more water to go up a lock.

Thus the quantity of water used to a pass through a lock does vary according to the size of the boat."

 

Absolute total non-sense. Every time a lock is operated a slice of water from the bottom of the lock is moved in or out. That slice is the length and breadth of the lock and the height of the rise/fall. It makes no difference what is floating above that slice, big boat, little boat, no boat. Whatever is floating above the slice NEVER penetrates it because if it did it would be grounded in the lower phase of the operation.

 

I think you've missed about 18 pages of the discussion.

 

What I wrote is correct, the proof is in the preceding pages.

 

Natalie.

[Gibbo]

Water and boats floating in it are the same thing. It is only when you add or take away a boat by crane that there will be a loss or gain.

 

This bit has me puzzled!

 

A pound has 10,000 gallons of water in it and a boat.

 

Crane the boat out. How much water is in the pound?

 

Crane the boat back in. How much water is in the pound?

 

Gibbo

[WJM]

If the boat weighs 15 tonnes and you crane it out then the level in the pound falls by 15,000 litres. (I love the elegant simplicity of metric!) You have removed part of the boat/water mix. You will need 15,000 litres to restore the level.

Edited December 2, 2008 by WJM

[Gibbo]

If the boat weighs 15 tonnes and you crane it out then the level in the pound falls by 15,000 litres. (I love the elegant simplicity of metric!) You have removed part of the boat/water mix.

 

I repeat my first question "who mentioned levels"?

 

And the second question..... How much water is in the pound before craning the boat out. How much water is in the pound after craning the boat out?

 

 

Gibbo

[WJM]

By removing a 15,000 litre boat from the water/boat mix in the pound, you remove... 15,000 litres of water/boat.

 

The pound contains 15,000 litres less water/boat mix after you remove the boat. If you dont have another boat to replace it then you will need 15,000 litres of water to maintain the same level.

Edited December 2, 2008 by WJM

[Gibbo]

By removing a 15,000 litre boat from the water/boat mix in the pound, you remove... 15,000 litres of water/boat.

 

1. How much boat do you remove?

 

2. How much water do you remove?

 

Gibbo

Edited December 2, 2008 by Gibbo