I’m sure I’m being stupid but…..

[MumHunOnTheCanal]

We went through Crofton yesterday which is on restricted hours owing to the very viable low water level at the summit. That all makes sense. 
 

BUT. 
 

surely. 
 

and this is where my naivety makes me question my logical thinking. 

“PLEASE LEAVE THIS LOCK EMPTY”

 

Does this not defeat the object of trying to reduce the water loss? People emptying the locks after they’ve gone up because the signage says so? Thus moving the water down and out?
 

I’m sure I’m being stupid and there’s a counter argument somewhere….. please give it me  

[BWM]

1 minute ago, MumHunOnTheCanal said:

We went through Crofton yesterday which is on restricted hours owing to the very viable low water level at the summit. That all makes sense. 
 

BUT. 
 

surely. 
 

and this is where my naivety makes me question my logical thinking. 

“PLEASE LEAVE THIS LOCK EMPTY”

 

Does this not defeat the object of trying to reduce the water loss? People emptying the locks after they’ve gone up because the signage says so? Thus moving the water down and out?
 

I’m sure I’m being stupid and there’s a counter argument somewhere….. please give it me  

This is normally done when there is a serious leak in the lock walls, especially when there is a property next to the lock.

[David Mack]

On wide canals the bottom gates usually leak at the mitre due to narrow boats entering and leaving the lock through a single gate and rubbing against the closed gate. If a lock is left full with the top gates ajar, then a lot of water can be lost. Whereas emptying the lock forces the top gates closed and much reduces any further loss.

[dmr]

The K&A is unusual in that many locks do not have a bywash (water channel round the side of lock), so the water flow goes through the lock. There are openings "letter boxes" at the top paddles to let the water in and the bottom paddles are left open to let the water out.

Some locks have been modified to have a bywash but I don't think the Crofton ones have.

If the paddles are not left up then heavy rain can cause quite a flood.

 

Ideally you should maybe only empty the lock if you are the last boat of the day and rain is due.....but that would be too difficult to apply.

[robtheplod]

30 minutes ago, David Mack said:

On wide canals the bottom gates usually leak at the mitre due to narrow boats entering and leaving the lock through a single gate and rubbing against the closed gate. 

Crikey i do this all the time (just open the one lock gate).... is this considered bad practice?

[ditchcrawler]

3 minutes ago, robtheplod said:

Crikey i do this all the time (just open the one lock gate).... is this considered bad practice?

Its the buggers that do it in narrow locks that get me, they leak in exactly the same place 

[cuthound]

Just now, ditchcrawler said:

Its the buggers that do it in narrow locks that get me, they leak in exactly the same place 

 

Bloody inconsiderate canoeists....

 

[beerbeerbeerbeerbeer]

9 minutes ago, robtheplod said:

Crikey i do this all the time (just open the one lock gate).... is this considered bad practice?

Not if you can steer and don’t hit the gates 😃

[Francis Herne]

2 minutes ago, ditchcrawler said:

Its the buggers that do it in narrow locks that get me, they leak in exactly the same place 

Presumably due to people opening zero gates and just pushing them open with the boat.

[system 4-50]

18 minutes ago, Francis Herne said:

Presumably due to people opening zero gates and just pushing them open with the boat.

I was happy to push narrow gates open when I could see the lock was empty.  It was a slow process as it required drifting up to the gates oh-so-slowly until contact made with ample bow fenders before revving up a little to open them.  My main concern was being able to see that the moving gate arms wouldn't knock over any onlookers.

Edited August 3, 2023 by system 4-50

[Mad Harold]

1 hour ago, BWM said:

This is normally done when there is a serious leak in the lock walls, especially when there is a property next to the lock.

This is the case with lock 1E on the HNC.

The lock leaks into an adjacent garage's celler.

[IanD]

6 minutes ago, system 4-50 said:

I was happy to push narrow gates open when I could see the lock was empty.  It was a slow process as it required drifting up to the gates oh-so-slowly until contact made with ample bow fenders before revving up a little to open them.  My main concern was being able to see that the moving gate arms wouldn't knock over any onlookers.

The problem is that the "<" edge of the hull at the bows below the gunwale tends to rub against the edge of the bottom gate as the boat goes in, which wears away the wood a tiny bit. Since this edge is in a similar place in most boats, the bottom gates end up with a worn-away section 1-2 feet above the waterline which then leaks when the lock is full. You can see this on *many* bottom gates... 😞

Edited August 3, 2023 by IanD

[Pluto]

49 minutes ago, dmr said:

The K&A is unusual in that many locks do not have a bywash (water channel round the side of lock), so the water flow goes through the lock. There are openings "letter boxes" at the top paddles to let the water in and the bottom paddles are left open to let the water out.

Some locks have been modified to have a bywash but I don't think the Crofton ones have.

If the paddles are not left up then heavy rain can cause quite a flood.

 

Ideally you should maybe only empty the lock if you are the last boat of the day and rain is due.....but that would be too difficult to apply.

They are often found on Rennie canals, such as the Rochdale, Lancaster and K&A. The 'byewash' is a slot by the upper ground paddle, usually called an 'airhole', which connects with the ground paddle tunnel. Excess water can then pass down and into the lock chamber, which it fills before overflowing over the bottom gates. The level of the top of the bottom gates has to be and inch or so above that of the upper gates so that they can be opened when the chamber is full. If the level is below, the upper gates become very difficult to open. I suspect the reason for the system was to keep the bottom gates wet, and thus watertight. Their problem is that it is very easy for the airhole to become filled with rubbish. Today, there can be leakage into adjacent property if the chamber is left full, but this was unlikely to happen when new.

 

A couple of examples of mitre wear on Barrowford Locks.

 

[dmr]

11 minutes ago, Pluto said:

They are often found on Rennie canals, such as the Rochdale, Lancaster and K&A. The 'byewash' is a slot by the upper ground paddle, usually called an 'airhole', which connects with the ground paddle tunnel. Excess water can then pass down and into the lock chamber, which it fills before overflowing over the bottom gates. The level of the top of the bottom gates has to be and inch or so above that of the upper gates so that they can be opened when the chamber is full. If the level is below, the upper gates become very difficult to open. I suspect the reason for the system was to keep the bottom gates wet, and thus watertight. Their problem is that it is very easy for the airhole to become filled with rubbish. Today, there can be leakage into adjacent property if the chamber is left full, but this was unlikely to happen when new.

 

A couple of examples of mitre wear on Barrowford Locks.

 

 

 

Your "airhole" is a "letterbox" on the K&A but I never knew if this was a common term or unique to a few CRT workers on the K&A. I had always assumed this scheme was done to save costs rather than to wet the bottom gates, but you could be correct as you usually are.

The K&A Froxfield locks got bywashes a few years ago, something to do with the enviroment agency and Kennet water quality I believe, but prior to that they did cause serious towpath flooding if not left empty.

I note that some Rochdale locks have the airhole and a bywash so maybe the bywashes were added later, possibly during restoration?

 

The real classic mitre wear is a fairly tight groove at the bottom gate just where the rubbing strake of a typical boats sits.

[Hudds Lad]

16 minutes ago, Pluto said:

They are often found on Rennie canals, such as the Rochdale, Lancaster and K&A. The 'byewash' is a slot by the upper ground paddle, usually called an 'airhole', which connects with the ground paddle tunnel. Excess water can then pass down and into the lock chamber, which it fills before overflowing over the bottom gates. The level of the top of the bottom gates has to be and inch or so above that of the upper gates so that they can be opened when the chamber is full. If the level is below, the upper gates become very difficult to open. I suspect the reason for the system was to keep the bottom gates wet, and thus watertight. Their problem is that it is very easy for the airhole to become filled with rubbish. Today, there can be leakage into adjacent property if the chamber is left full, but this was unlikely to happen when new.

 

A couple of examples of mitre wear on Barrowford Locks.

 

I've often wondered why they don't have some sort of bolt-on sacrificial strips on the mitre, that when worn can be easily replaced thus leaving the rest of the gate intact. Some sort of composite board made of recycled material for example.

Or are they stuck with what they can do/use due to heritage status etc.??

[dmr]

Just now, Hudds Lad said:

I've often wondered why they don't have some sort of bolt-on sacrificial strips on the mitre, that when worn can be easily replaced thus leaving the rest of the gate intact. Some sort of composite board made of recycled material for example.

Or are they stuck with what they can do/use due to heritage status etc.??

 

On some locks they do and I think its in softwood, but whatever is used will have to take the full load of the water pushing the mitre together so a soft rubber strip or whatever might be a disaster.

[GUMPY]

Another reason for emptying the lock and leaving a paddle up is that  BW* rebuilt a bunch of bottom gates 4 inches higher than the design.

This defeats the design of the bywash so that with the bottom gates closed the level in the pound above is 4" higher which in places ( lock 59 in the GU for one) leads to it overtopping the bank in wet weather.

 

* BW denied this was the case and that the gates were the same but having lived in immediately above the lock for 8 years it was obvious. I believe the reason they did it was to raise the level so they didn't have to dredge but nobody thought it through 🤔

10 minutes ago, Hudds Lad said:

I've often wondered why they don't have some sort of bolt-on sacrificial strips on the mitre, that when worn can be easily replaced thus leaving the rest of the gate intact.

They do in wood on many of them but it never gets done.

Edited August 3, 2023 by GUMPY

[BoatinglifeupNorth]

1 hour ago, robtheplod said:

Crikey i do this all the time (just open the one lock gate).... is this considered bad practice?

CaRT published something on it last year or around that time, telling boaters to open both lock gates and not to use only one because of this problem.

[Hudds Lad]

13 minutes ago, GUMPY said:

They do in wood on many of them but it never gets done.

Yeah, i guess that's the other problem having a serviceable part. Nobody services it  

[Pluto]

24 minutes ago, Hudds Lad said:

I've often wondered why they don't have some sort of bolt-on sacrificial strips on the mitre, that when worn can be easily replaced thus leaving the rest of the gate intact. Some sort of composite board made of recycled material for example.

Or are they stuck with what they can do/use due to heritage status etc.??

The problem they would have is making the strip firm enough so that it withstands boats hitting and rubbing against it.I suspect the damage done by the fixings holding the strip to the mitre post would only allow replacement to be done once. I was told that BW had tried rubber strips, but that they were often caught by a boat rubbing against them and pulled away from the mitre. They do use rubber on the continent, but it is much easier to fix and replace them with steel gates.

 

In the days before health & safety, on worn gates it was usual to run a saw down the mitre from a ladder, taking out any imperfections. When fitting gates, they would get the mitre to fit at the sill, and then have half an inch or so clearance at the top of the gate. As the chamber filled, the load on the gates increased and they would flex very slightly to ensure a good seal right up to the top. It is one reason wooden gates were preferred to steel.

[Mike Todd]

2 hours ago, BoatinglifeupNorth said:

CaRT published something on it last year or around that time, telling boaters to open both lock gates and not to use only one because of this problem.

Yes but they forgot that most K and A locks have no top gate footboard and to do this you have to leap up onto the balance beam to cross over on the gates. I used to be able to do this but alas it is now a challenge too far! Short sightedly, they seem to removing some bottom gate footboards if there is a nearby bridge, usually very humped.

[BoatinglifeupNorth]

I’m seeing more bottom gate footboards damaged due to being rammed by boats, often taped off.

Edited August 3, 2023 by BoatinglifeupNorth

[Alway Swilby]

We got told off by a lock keeper for only opening one gate at one of the Upper Thames locks above Oxford. After that I did notice that there was minimal mitre leakage at all the Upper Thames locks.

[Midnight]

9 hours ago, Goliath said:

Not if you can steer and don’t hit the gates 😃

Everyone thinks they can. The number of worn and leaking gate mitres suggests they can't. There are people on this forum who have complained when I've opened the second gate for them 🙄 

[blackrose]

Narrowboats should pay an extra license fee for the all damage they cause to lock gates. I'm going to start a campaign and submit a petition to CRT. 😋