Thursday, 9 February 2012

On Manoeuvres (8)

This is one of an occasional series of tips about manoeuvring a narrow-boat on the canals and rivers. There may be other ways to achieve the same result. However, the method has been devised or adapted by me using trial and error. (Trial and Error are two of my regular boating companions) Our boat is 50 feet long and has a keel depth of twenty five inches and weighs in at a tad over eighteen tons. The techniques described are intended to help new comers to boating.

Today, its taking a boat through a lock.

It would be good practice to go and gongoozle (boating term for people who like to watch boats) a few boats passing through a lock. Talk to whoever is operating the lock and ask them to demonstrate the process. Passing through a lock with a boat is a daunting prospect for the first time. However the process is a fairly straight forward one. The lock is a container with a set of large gates at each end. The gates can be opened to allow a boat to enter or exit the lock.
Tip 1: Generally speaking, the large lock gates are never open at both ends of a lock at the same time. There is one exception at what are called Flood Locks, when the lock gates are only used when a river is in flood conditions and the water level needs to be controlled at different levels at each side of the lock.
Inside the lock are smaller gates under the water level called paddles. The paddles can be opened to allow water into or to escape out of the lock. The paddles are variable and can be opened bit by bit to limit the flow of water in or out of the lock. When a lock is empty, and a paddle is opened the water passing through the paddle into the lock is under considerable pressure. As the level of water in the lock raises, the pressure of water passing through the paddle is reduced, as the water level equalises.

Tip 2: Rule of thumb, on a lock the opening the opening of the paddle should match the water level in the lock. Open the paddle a small amount until the lock is a quarter full then open the paddle to the quarter open point. When the lock is half full open the paddle to half open. It is the same at the three quarter filled point and three quarter open on the paddle. When the lock is past the three quarter mark you can open the paddle further towards fully open. After you have done a few locks you will gain experience and will soon be able to judge how much to open a paddle.

Tip 3: Under normal operating conditions, the paddles should never be open at opposite ends of the lock at the same time. If a lock fails to fill or drain check that the paddles are not open at both ends.

How you tackle the lock will to a certain extent depend upon which way you are going. The purpose of the lock mechanism allows a boat to either go up a level or down a level. This is achieved by draining water from the lock and lowering the boat down a level. Adding water into the lock and raising the boat up a level. The lock acts like a lift for boats going between two floors.

Setting up the lock.

You “set the lock” so that your boat can enter through the large lock gates. Because other boaters use the lock, on arrival you must never assume the condition the lock has been left in. Always check that everything is set in a safe condition before you operate any paddles.

In our example we are going to be going uphill. When we arrive we can see that the lock gates are closed at both ends. The lock chamber is full of water and there are no other boats in the lock.

Tip :4 It is good practice to check that there are no boats approaching the lock from the uphill side. If boats are approaching the lock, wait until the boat arrives and let it enter the lock. This will help to conserve water in the canal.

Our first task is to check the lock paddles at the other end of the lock are fully closed in the down position. We use a crank handle called a windlass to operate the lock paddles. Once we know that the paddles are closed and that no more water can enter the lock from the uphill side. It is time to open the paddles on the downhill side to let the water escape from the lock. Using the windlass, we open the paddle to allow the water to escape. If we look over the gates we can see the water surface swirling and bubbling around. The swirling and bubbling will continue until the water level is the same on both sides of the gate.
Tip :5 It is physically impossible to open a lock gate if the water levels are not the same on both sides of the gate. If there is a tiny difference in water level the gates will not open.

Lean on the lock gate, whist waiting for the lock to empty or fill. When the water level are close to equal on both sides of the gates. You will feel the lock gates “ease” as the weight of water is removed. It is now time to prepare to open the lock gate. The gates are mounted on large hinges like a door. However, the gate will also have a large balance beam attached. We push the gate open using the balance beam. The gate will only move very slowly as it opens.

To open the gate, stand at the end of the balance beam. Put your back to the beam and push with your legs. Leaving the gate paddle open will help to reduce the amount of effort that is needed.
Tip :6 Never pull a lock gate open, if you slip or lose your grip you will fall backwards, possibly into the canal or into a muddy puddle.
Once our boat has entered the lock we should return the lock to the standard position. All gates and paddles closed. Now go to the other gates and operate the paddles to bring the water level up. Remember to use a gradual opening of the paddles to stop the inrush of water causing the boat to bang into the lock sides. Take your time for the first few locks until you have gained some experience.

Going downhill it is the same process, of operating the paddles only this time to release water from the lock. There is one important difference. The top gates do not reach all the way to the bottom of the lock. There is a lock cill that protrudes a small distance into the lock. There will be a white cill marker on the lock side. You must ensure that the boat is clear of the cill marker. If the boat is not clear of the cill, the rudder can catch on the cill as the water level falls. As the water level falls the boat will begin to tip upwards. If your boat gets hung up on the cill. Close all paddles to stop water from exiting the lock. Now gently open a top paddle to let water slowly fill the lock. Once the boat is floating free, move clear of the cill and then empty the lock in the normal way. Remember to check the tiller is fully working and not damaged in any way.

Tip :7 If there is any kind of problem when operating a lock – you must close all paddles as quickly as possible. Stopping the flow of water in or out of the lock. This will give you time to think about what you need to do to resolve the problem. If someone has fallen into the lock closing the paddles will stop water turbulence and make it easier for them to be rescued.

Tip :8 If a lock seems to be taking a long time to fill or or drain. Check that you have not left a paddle open on the other lock gate. This is the most common mistake made by new and occasionally by experienced boaters. For the new boater its because they are short of experience. For the experienced boater because they fail to check the gate paddles.

The last three items you will need are the anti-vandal or handcuff key, a BW or watermate key and a lock spike. These items may be needed to operate locks depending on the area. Because of vandalism some locks have to be secured to stop the vandals from draining pounds. As you arrive at a lock, using the appropriate key you work the boat through the lock and then secure the gates and paddles again after use.
Tip :9 In some areas where vandalism is more prevalent whole sections of canals have to be locked over night. You may be required to “Book Passage” with area lock keepers through such areas.

Some lock gates are very heavy to open and close. I find that even the heaviest of gates will move albeit very slowly. Don't be afraid to ask anyone to give you a hand with opening and closing of the lock gates. Generally people are quite happy to help. On wide locks a narrowboat will thread through with only one gate open. If one gate is extra heavy then test the other gate and see if it is easier to open.

There is usually a reason why a lock gate is difficult to open. Check for floating debris that is getting trapped between the lock gate and the lock wall. You can use the boat pole to push logs and other items clear. However, in exceptional circumstances if there is no one around to assist. Then you can use the bow line of the boat to pull a gate open. Do this by securing the line to the lock gate at the top of the mitre. Then put the boat into reverse and gently ease the gate open. You can also use the nose of the boat if you are inside the lock to gently push a gate open.

You can in circumstances where a lock gate is proving difficult to close after entering a lock, flush water from the propeller in behind the lock gate to assist the gate to close. This will help to reduce the physical effort needed to close the gate. However, always agree with the person operating the lock what you are going to do to assist first.

If a lock gate will not fully close, check to see if there is any debris like a log trapped in between the gates. Opening and closing a gate will usually dislodge the debris. However, some gates that are worn will not close and will have a small gap. When you start to run water into the lock the water pressure will force the gate shut.

Last but not least, you will sometimes have difficulty with what are called a "Ghost Gate". This is a gate that will not stay in the closed position. As if being opened by a hidden hand, the gate will sometimes open past the halfway point in just a few seconds. In these circumstances, crack open the paddle a small amount on the gate at the other end of the lock to send a small amount of water into or out of the lock. Holding the gate closed for just a few seconds will let the water level build or fall enough to hold the gate shut.


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