Tuesday, 24 September 2013

A tale of three locks.

We left Thrupp in an early morning mist and after watering and saying Hi to Maffi we set off to Shipton Weir Lock.

There are several explanations as to why the lock chamber here is an odd shape, personally I think they had the plans the wrong way round so instead of being seven feet wide and twelve feet deep it is twelve feet wide and seven feet deep. Either that or, by the time they got here, they were bored with building all the same shape so had a shot at something different. Boringly it seems that it is just a water control device as this is where the River Cherwell leaves the canal.

About a mile further on, just below Baker's Lock, is where the river joins the canal from under this side bridge. So for a mile we were boating on the Cherwell, a river we had last seen at Oxford, where it flows into the Thames.
When we arrived at Northbrook Lock we were warned by a descending boat that the bottom gate wouldn't open fully so we might need to give it a nudge.

Result? We jammed solid, could move neither forward nor back. We eventually shifted her backwards by lifting the top paddles and flushing her out. By now other boats had arrived so, in the finest traditions of the canals, we set too with a will.

First a meeting of minds to discuss the problem.

Then judicious exploratory operations. We detected a build up of silt in the gate recess.

Some vigorous stirring with the boat shaft then working the gate too and fro and the gate finally surrendered and swung fully into the recess.
Success! We went on our way rejoicing.

Upper Heyford, a perfect juxtaposition of Church, Manor House and barn, all built in the local stone.
We were aiming to stop just above Somerton Deep Lock.

This is why it's called deep lock. At twelve feet it's one the deepest narrow locks on the system.

This is the view looking back once the lock is full.

This was the view looking forward, islands of floating reeds everywhere. Note the piled up weed on the lock side. We eventually cleared a path through and made it to our chosen spot.
Fishing tomorrow?

Watch this space.............


Maffi said...

Sorry I dint get to come over for a chat. See you somewhere on the system. We must stop and have a beer or two.

Maffi said...

Shipton Weir Lock was so designed to maintain the appropriate water level in the Thrupp pound. When it was built most boats were 70/72 foot long and you could only get one boat in the lock at a time. Thus had the lock been only of normal narrow lock dimensions (width) then each time a boat came through the lock only one foot of water would have been fed into the pound. Subsequently as the boat left the pound it would use 6 foot of water going through Roundham Lock. This would have been a net loss of 5 feet in the pound. The same goes for boats travelling the other way. By making the lock so wide as much water goes into the pound as goes out for each 70/72 ft boat.

In this modern boating world you can get up to 4 boats in the lock passing only one foot of water into the pound. When they exit the pound they will use 24 feet of water a net loss of 23 feet.

Even though the gates leak and do to some extent redress the balance the Thrupp pound has been down most of the summer. Today its about 5 inches. In a shallow canal that is a lot.

Hope this explains the odd shape.

Graham and Jill Findlay said...

It would be good to meet up for a beer, paths will cross one day!