Wednesday supplementary

Sarah has asked in a comment "Why is J always steering?"

There are two answers -

Rob is often taking the photographs, and

Stan is still learning but is catching on very fast

But so that the truth may be told - here is Stan, relaxed, happy and in charge.

This brings me to two big lessons that we have learned on this trip.

For you to understand these lessons, I must first tell you of the workings of a lock.

I think you all understand that a lock is a tank which enables a narrowboatman to raise, or lower, his boat from one level to either a higher or lower level.

When raising the boat through a lock, the crew must first ensure that the lock is empty. To do this they open the paddles on the sluices on the bottom gates and allow the water to flow out. When the water level on the inside of the lock is the same as that on the outside, the lock doors can be opened allowing the helmsman to drive the boat into the lock. The paddles are closed, the doors are closed, and the paddles on the top gate are opened allowing the water to flow into the lock, raising the water level and thus the boat.

When the level on the top side of the lock is the same as that on the inside of the lock the top gate can be opened and the boat driven out. In this manner a boat can the raised a substantial height (the deepest lock on the system is 12.5 feet).

Similarly, when lowering the boat, the boat enters at the top, the top gate is closed, the bottom gate paddles are opened, allowing the water to flow out, and when the levels on the inside and outside are the same, the bottom gates can be opened and the boat driven out.

For the practical among you; the top gate is a single gate which, when closed, sits on a wooden and concrete cill (frame) and is held closed by the weight of the water in the canal.

This picture is taken from inside the lock as the water is emptying out the bottom gates and shows the top gate firmly in position with some water leaking round it. You can also see the cill (sill) with the water pouring over it. It sticks out into the lock like a step. More about the cill later.

The lower gates are a pair which fit together in a wedge shape pointing into the lock. They are forced together by the weight of the water in the lock. There are always leaks and lots of water splashing about the place.

These gates are closed, with the lock full.

The same gates open, with the lock empty and the boat ready to emerge.

This lock is empty, with the top gate closed

A lock is said to be "set" if, when one arrives at a lock it is ready for the boat to be driven straight in with out all the hassle of filling or emptying it.

Now, to the lessons learned. And, as of this afternoon it is no longer two, but three.

1. When entering a lock to "lock down" one the crew has to wait until the top gate is closed before the bottom paddles are opened. The top gate was still half-closed when one of the bottom paddles was opened so the water in the lock surged towards the bottom gate. The top gate was snatched away from the crew member closing it and slammed shut with a mighty thump. The slamming gate sent a wave down the lock lifting the boat and dropping it again, The wave hit thje bottom gates and came this time sending the boat crashing back into the top gate. Not a happy experience for the helmsman.

2. When approaching the bottom gates of a full  lock when "locking up" - slow down. The helmsman on duty later admitted to a "mis-judgement". He seemed to hit the gate at speed. The two gates were forced open a fraction of an inch and slammed shut again. The jet of water that came out of that small slit was very impressive and flooded the front of the boat. Fortunately the doors were shut!

3. When the book says in big letters "When in a lock always keep well clear of the top concrete cill behind the boat" they mean it!!!!

The boat was in the lock, the top gate was closed, and the two crew members opened the bottom gate paddles. Suddenly the helmsman (correctly) shouted "STOP" "STOP". I have to say the reaction time of the two crew members was amazing as they realised what had happened - the back of the boat was caught on the cill. In fact the boat was already nose down in the lock. The two crew members ran back to the top gate and opened the top paddles, lifting the boat and restoring it to the correct alignment. We all needed time to pause and reflect before we went back to the beginning of the routine and successfully negotiated the lock. It happens so quickly and can cause huge damage to the propeller and the rudder.

Here endeth the lesson, which I hope meant something to someone!