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Testing in a lock makes sense I suppose as the lock by its design is probably at least twice as deep as the canal above and below it and you can vary the water level IN the lock, lowering it  if the sub were to get in trouble 

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6 hours ago, Mattc6911 said:

Testing in a lock makes sense I suppose as the lock by its design is probably at least twice as deep as the canal above and below it and you can vary the water level IN the lock, lowering it  if the sub were to get in trouble 

 

1 hour ago, Nearholmer said:

On a pedantic technicality, the water in a lock when full will be equal in depth to the depth of the lower part of the canal, plus the difference in height, which can sum to less than twice the canal depth. 

Quite.

There is a canal lock at Hawkesbury where the drop is usually not more than 6-9"

It is where the Coventry Canal and the Oxford Canal, (which were built to slightly different levels) join.

Originally they didn't join but ran side by side into Coventry:

https://maps.nls.uk/view/115633858

Edited by melmerby
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12 hours ago, 25901 said:

One under test in the canal 

9D275328-03AE-4513-80AB-5F66717B3B52.jpeg


 

Quote

 

Broadbent (Huddersfield)

Thomas Broadbent and Sons Ltd helped with designing and actually built the X20 Midget Submarine. The X20 was a very well safeguarded secret and had been developed from its predecessors over the last couple of years.

Following its completion, it was disguised as a large Motor Boat, with tarpaulin and framework put all around the Midget Submarine. It was then transported under armed escort to Hillside Railway Sidings, and taken north to the River Clyde where she was laid down.

http://rnsubs.co.uk/boats/yards/broadbent.html

 

A "very well safeguarded" secret? Quite possibly correct, despite all the neighbours watching. It's the stuff of urban legend.

 

But see those two lads on the left watching it happen? It might have been a different story when they grew up.

Eee, when I were a lad, there were submarines in the canal.

Yeah, right, pull the other one.

 

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2 hours ago, melmerby said:

 

Quite.

There is a canal lock at Hawkesbury where the drop is usually not more than 6-9"

It is where the Coventry Canal and the Oxford Canal, (which were built to slightly different levels) join.

Originally they didn't join but ran side by side into Coventry:

https://maps.nls.uk/view/115633858

 

 

But I've also been through a lock  that was much much deeper than the combined depth of of the top and bottom of the canal, so my observation remains perfectly valid :rolleyes:

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35 minutes ago, Mattc6911 said:

 

 

But I've also been through a lock  that was much much deeper than the combined depth of of the top and bottom of the canal, so my observation remains perfectly valid :rolleyes:

The questions would be:

"How do you know the lock is deeper than the canal?"

"Why build a lock that is deeper than the canal?"

Totally unnecessary and wasteful of cost and materials.

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22 minutes ago, Mattc6911 said:

It is where the Coventry Canal and the Oxford Canal, (which were built to slightly different levels) join.

Originally they didn't join but ran side by side into Coventry:

 

Very shallow locks between two canals operated by separate companies are called Stop Locks and were designed to prevent one canal from "stealing" the water supply of another canal.  Another example of such a lock is the one at Autherly Junction between the older Staffs&Worcs canal and the Shropshire Union canal, with a drop of 6 inches from the Staffs&Worcs.

 

Despite the existence of the stop lock, such junctions were often a bone of contention between companies and due to onerous tolls imposed for the passage of boats by the Staffs&Worcs for the short section between Autherly Junction and Aldersley Junction (BCN), a bypass canal was proposed, which brought the tolls down without having to be built.*

 

The deepest single lock on the UK canal system is Tuel Lane lock**, which has a fall of over nineteen and a half feet, but is a modern concatenation of two locks on the restored Rochdale Canal.   Previously, the deepest lock was Etruria Top lock on the Trent&Mersey canal, with a drop of about fourteen feet.

 

4 minutes ago, melmerby said:

The questions would be:

"How do you know the lock is deeper than the canal?"

"Why build a lock that is deeper than the canal?"

Totally unnecessary and wasteful of cost and materials.

 

The depth of locks depends on how steep the hill you're going up or down is.  You can avoid locks if you build along a contour line, but that makes for a longer journey and costs money to build.  Or you can cut through hills with cuttings and tunnels , or avoid changes of level and take a shortcut  by using an aqueduct to cross a valley, but all those are expensive too.

 

Sometimes a deep lock, or a staircase of shallower locks is the cheapest way to get where you want to go! *** 

 

*     https://en.wikipedia.org/wiki/Autherley_Junction

**   https://en.wikipedia.org/wiki/Tuel_Lane_Lock

*** https://en.wikipedia.org/wiki/Lock_(water_navigation)#Staircase_lock  ( plus more info on locks than a reasonable person would want to know...)

 

 

 

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19 minutes ago, melmerby said:

"Why build a lock that is deeper than the canal?"

Totally unnecessary and wasteful of cost and materials.

 

Granted you might have "normal" inland canals in mind. However, if we include canals or waterways with entrances to the sea, the most extreme example I can think of is the Cumberland Basin lock gates in Bristol, with a maximum tidal range of 47 feet. Plus the depth of the inner harbour. So 50 feet (at least) under a boat in the lock at highest tide.

 

https://wiki2.org/en/Cumberland_Basin_(Bristol)+Newton

 

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1 hour ago, Hroth said:

 

The depth of locks depends on how steep the hill you're going up or down is. 

The bottom of the lock never needs to be lower than the canal bed of the lower end water level.

 

So the depth of the lock never needs to be more  than from the water level on the upper side to the canal bed on the lower side.

 

In fact some locks have a sill at the upper end so that the gates aren't full depth, boaters have to make sure their vessel is at the lower end of the lock if going down to save getting grounded.

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I knew my pedantry would cause trouble!

 

The case I had in mind was Fenny Stratford on the Grand Union, which is an ordinary lock, in an ordinary canal, with a rise of c12”, allegedly to compensate for accumulated surveying errors, although I’ve never quite believed that.

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1 hour ago, KeithMacdonald said:

 

Granted you might have "normal" inland canals in mind. However, if we include canals or waterways with entrances to the sea, the most extreme example I can think of is the Cumberland Basin lock gates in Bristol, with a maximum tidal range of 47 feet. Plus the depth of the inner harbour. So 50 feet (at least) under a boat in the lock at highest tide.

 

https://wiki2.org/en/Cumberland_Basin_(Bristol)+Newton

 

But that's a ship lock into a dock complex., I should imagine that ship canals (not going to look them up) have similar dimension locks.  You could test a full size submarine  in one of those! 

 

20 minutes ago, Nearholmer said:

The case I had in mind was Fenny Stratford on the Grand Union, which is an ordinary lock, in an ordinary canal, with a rise of c12”, allegedly to compensate for accumulated surveying errors, although I’ve never quite believed that.

It wouldn't  surprise me!

 

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According to an online boating gazetteer:

 

“This is a lock with a rise of 0′1″

 

Which, if true, and I don’t think it is, would be immeasurable, due to the leakage through the gates causing it to have no rise at all. 
 

But, whatever the figure truly is, it’s small.

 

And, a more plausible explanation says that it was installed as a temporary measure in 1802, while water levels were lowered to allow bank repairs, and, just like my temporary DIY jobs, has been left in place ever since.

Edited by Nearholmer
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39 minutes ago, melmerby said:

The bottom of the lock never needs to be lower than the canal bed of the lower end water level.

 

So the depth of the lock never needs to be more  than from the water level on the upper side to the canal bed on the lower side.

 

In fact some locks have a sill at the upper end so that the gates aren't full depth, boaters have to make sure their vessel is at the lower end of the lock if going down to save getting grounded.

The depth of a lock is what you  see when you're  in a boat coming in at the bottom and look up.  The water depth in a lock chamber when "empty" is about 4' which would have been the original working depth of an English narrow canal. This is easily seen  by  looking  at the top gate when the lock is empty, the distance between the waterline on the gate and the top cill will be about 4'

 

Top gates are about 6' deep overall, bottom gates will be as deep as the fall of the lock.

 

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10 minutes ago, Nearholmer said:

According to an online boating gazetteer:

 

“This is a lock with a rise of 0′1″

 

Which, if true, and I don’t think it is, would be immeasurable, due to the leakage through the gates causing it to have no rise at all. 
 

But, whatever the figure truly is, it’s small.

I've  been through MK on the GU a couple of times but I don't  remember  Fenny Stratford  lock! Even if it's  a bit more than an inch fall it's  miserably unmemorable...

Edited by Hroth
Doing this on a tablet, fighting the auto correct...
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It’s got a swing bridge across the middle of it, a railway bridge over one end, and there is a good builders’ merchant around the corner who has a planing-machine and will cut hardwood strips to precise sizes for a few pence.

 

Does that help?

Edited by Nearholmer
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3 hours ago, melmerby said:

The questions would be:

"How do you know the lock is deeper than the canal?"

"Why build a lock that is deeper than the canal?"

Totally unnecessary and wasteful of cost and materials.

 

https://en.m.wikipedia.org/wiki/Tuel_Lane_Lock

 

 

Been down a simular one and its a blurry long way down !

 

Edited by Mattc6911
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Re - "a good builders’ merchant around the corner who has a planing-machine and will cut hardwood strips to precise sizes for a few pence".

 

Where? - I need to know soon.

 

Travis Perkins have moved from Fenny Lock to Denbigh - and lost their wood machining in the process.

 

Regards

Chris H

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3 hours ago, Hroth said:

 

Very shallow locks between two canals operated by separate companies are called Stop Locks and were designed to prevent one canal from "stealing" the water supply of another canal.  Another example of such a lock is the one at Autherly Junction between the older Staffs&Worcs canal and the Shropshire Union canal, with a drop of 6 inches from the Staffs&Worcs.

 

Despite the existence of the stop lock, such junctions were often a bone of contention between companies and due to onerous tolls imposed for the passage of boats by the Staffs&Worcs for the short section between Autherly Junction and Aldersley Junction (BCN), a bypass canal was proposed, which brought the tolls down without having to be built.*

 

The deepest single lock on the UK canal system is Tuel Lane lock**, which has a fall of over nineteen and a half feet, but is a modern concatenation of two locks on the restored Rochdale Canal.   Previously, the deepest lock was Etruria Top lock on the Trent&Mersey canal, with a drop of about fourteen feet.

 

 

The depth of locks depends on how steep the hill you're going up or down is.  You can avoid locks if you build along a contour line, but that makes for a longer journey and costs money to build.  Or you can cut through hills with cuttings and tunnels , or avoid changes of level and take a shortcut  by using an aqueduct to cross a valley, but all those are expensive too.

 

Sometimes a deep lock, or a staircase of shallower locks is the cheapest way to get where you want to go! *** 

 

*     https://en.wikipedia.org/wiki/Autherley_Junction

**   https://en.wikipedia.org/wiki/Tuel_Lane_Lock

*** https://en.wikipedia.org/wiki/Lock_(water_navigation)#Staircase_lock ( plus more info on locks than a reasonable person would want to know...)

 

 

 

 

 

Just to say you somehow crossed melmersbys quote with my name. . . Thought i didnt remember saying anything about coventry ! :laugh_mini:  but I DID quote him  

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