How do locks raise boats?

[magpie patrick]

 

Really? I think the lock will fill to the same height with or without a boat in it. But if my boat is in the lock displacing 16 tons then there must be 16 tons less water in the lock. If you filled the lock and then craned the boat out the level would drop to fill the gap left by the boat.

So the lock is filled by the energy required to lift your boat in?

 

More seriously, the lock also has 16 tonnes less water in when at the lower level. However you do it, an amount of water equivalent in volume to the volume of the chamber between the lower and upper water levels must be admitted.

 

In the case of the Shropshire Union the energy required to provide this water was equivalent to the energy required to prouduce and consume the requisite amount of beer and then process the resulting effluent at the sewage works: this isn't nuclear fusion as far as I'm aware, although perhaps Black Country Sewage Treatment uses different technology.

[Machpoint005]

So the lock is filled by the energy required to lift your boat in?

 

More seriously, the lock also has 16 tonnes less water in when at the lower level. However you do it, an amount of water equivalent in volume to the volume of the chamber between the lower and upper water levels must be admitted.

 

In the case of the Shropshire Union the energy required to provide this water was equivalent to the energy required to prouduce and consume the requisite amount of beer and then process the resulting effluent at the sewage works: this isn't nuclear fusion as far as I'm aware, although perhaps Black Country Sewage Treatment uses different technology.

There isn't any energy required to lift your boat in -- on one possible view, it's a net reduction in the amount of energy expended when the lockful of water flows downhill. Of course, it does depend on how you define the boundaries of your system under study. The boat just happens to be in the right place at the right time.

[jenevers]

 

I seem to remember reading somewhere that this is wrong, so there is nothing to explain.

 

 

MtB

Hmm. Maybe it was something to do with emptying a lock with no boat in the chamber, uses more water than if there is a boat in the chamber. Because a 10 ton boat squeezes 10 tons of water back into the upper pound as it enters the lock, so there less water in the chamber once the gates are closed.

[carlt]

Hmm. Maybe it was something to do with emptying a lock with no boat in the chamber, uses more water than if there is a boat in the chamber. Because a 10 ton boat squeezes 10 tons of water back into the upper pound as it enters the lock, so there less water in the chamber once the gates are closed.

But that 10 tons of boat or water plays no part in the operation of the lock, otherwise the boat wouldn't get over the cill when the lock is empty.

[PaulG]

But that 10 tons of boat or water plays no part in the operation of the lock, otherwise the boat wouldn't get over the cill when the lock is empty.

I think that a lock will use less water going downhill than it would if it was just emptied with no boat in it.

When the boat enters the full lock, it displaces water back into the upper pound. The lock now has less water in it than it did before.

The water is then drained to the level of the lower pound, and the gates are opened.

As the boat emerges from the lock, a volume of water equivalent to its displacement enters the lock, but from the lower pound, not the top one.

So you've saved a volume of water that is equal to the displacement of the boat.

[tillergirl]

 

Surely they are proof that non compliant continuous cruisers are very unselfish, because if they don't move, they don't use any water in locks, and the pumps would not be required.

 

Proof surely that non complaint CC-ers should pay less, and ones that move a lot should pay more?

 

But surely the ones that move actually save CRT money by dredging the middle of canals and keeping the paddle gear operating? So if they save CRT money surely their licence fee should be less or worked out on the proportion of how far they move. The further they move the more discount they get.

 

As for locks? Well I know its the hundreds of lock fairies that inhabit our country that make boats rise in locks...........I've seen them.

Edited June 21, 2013 by tillergirl

[nicknorman]

Amazing innit, you can start a thread on any subject, in this case sub-atomic physics, and it always degenerates into a CCer vs shiny marina boat argument!

[Yellowback]

 

 

 

As for locks? Well I know its the hundreds of lock fairies that inhabit our country that make boats rise in locks...........I've seen them.

 

 

Yes, I've seen fairies by the locks a few times as well!

[Doorman]

So if the sun went out we would all have to go into marinas.

The sun always goes out when you go in a marina.

[Doorman]

nothing to do with boats but a colleague of mine convinced another colleague that Welsh hill sheep have shorter LEFT legs as they stand on a hill side (obviously only facing one way); This was the same colleague who thought that Sven Goran Eriksson was 2 people- Sven Gor and Erikss

My Irish mum always believed that Seb Coe was knighted, even during his pre-eminent days.

 

She thought that he was called Sir Bastian Coe. Brilliant my mum!

[jenevers]

But that 10 tons of boat or water plays no part in the operation of the lock, otherwise the boat wouldn't get over the cill when the lock is empty.

???? I've always thought the cill was at the upper end of the lock so how would you get over the cill when the lock was empty anyway???? You'd be exiting into the lower pound.

 

I think that a lock will use less water going downhill than it would if it was just emptied with no boat in it.

When the boat enters the full lock, it displaces water back into the upper pound. The lock now has less water in it than it did before.

The water is then drained to the level of the lower pound, and the gates are opened.

As the boat emerges from the lock, a volume of water equivalent to its displacement enters the lock, but from the lower pound, not the top one.

So you've saved a volume of water that is equal to the displacement of the boat.

Yes, that's what I thought.

So going down uses a lockful MINUS the weight of the boat but going up uses a full lockful.

So if there were 10 boats going down one after the other, more water would be used than 10 boats going up one after the other.

Edited June 22, 2013 by jenevers

[Doorman]

???? I've always thought the cill was at the upper end of the lock so how would you get over the cill when the lock was empty anyway???? You'd be exiting into the lower pound.

 

 

There are cills at the bottom end of a lock too. These are what the gates abut up to when you close them prior to the two mitres coming together. The level of the lower pound dictates that the boat will float above the level of the lower cill.

 

We once navigated down the Rufford arm of the Leeds & Liverpool canal and some clot had left the paddles open on the next lock, allowing the pound to drain down to a very low level. Upon trying to exit the lock Mrs Doorman at the helm suddenly found that the boat was stuck firm upon the lower cill. As the boat's draught increases closer to the stern, it rested firmly at midships and the boat rocked like a seesaw.

 

It was only after I walked some distance to the next lock to correct the problem, then on return opened the upper paddles of our lock to refil the pound, could we continue our journey.

Edited June 23, 2013 by Doorman

[Pluto]

I think that a lock will use less water going downhill than it would if it was just emptied with no boat in it.

When the boat enters the full lock, it displaces water back into the upper pound. The lock now has less water in it than it did before.

The water is then drained to the level of the lower pound, and the gates are opened.

As the boat emerges from the lock, a volume of water equivalent to its displacement enters the lock, but from the lower pound, not the top one.

So you've saved a volume of water that is equal to the displacement of the boat.

But the displacement of the boat will have raised the lower pound by an equivalent amount, the actual variation being affected by the length of the lower pound, and whether water is running to waste. So due to displacement, there will be a different fall depending upon whether a boat is in the lock or not, and of course there needs to be a similar calculation for the level of the upper pound.