Tuesday, March 28, 2017

Locking time calibration

Trying to find an average time taken to  through a canal lock is a daft thing to do, so of course I had a go at it last week. It’s akin to asking how long is a piece of string.  Nevertheless, on our trip down to Banbury and back, we did have a go at it and I don’t think I would have predicted the results.  On Canalplan (genuflect genuflect), Nick suggests a default time of 12 minutes to pass through an individual lock.  I had been thinking that that might have been a trifle optimistic, taking into account that half the time the locks will not be set in your favour when you arrive.  Well it turns out that the Herbie crew,( i.e. Kath and myself, a well oiled machine, often well oiled by closing time too but that’s another story) can do a bit better than Nick suggests, given a lock with no other boats to wait for.

We measured the time from when the crew steps off the boat to work the lock until the time when he or she gets back on board and we continue cruising.    Bear in mind a couple of things.  a) These were narrow Oxford canal locks with double bottom gates and b) the steerer assists by working the offside paddles when the boat is at the top of the lock and c)we try not to walk right round the lock to open both bottom gates but shove one of them open by standing on one and giving the other a hefty back heel, it works.  Often I’m happy to step across the gap between and open and a closed gate, but Kath understandably doesn’t try it. So, in summary we’re reasonably slick at it.  Anyhow here’s how it went.

Downhill, lock in our favour on arrival               6 minutes

Uphill, lock in our favour                                  6 minutes

Downhill, lock set against us                          10 minutes

Uphill, lock set against us                                8 minutes

Downhill, one boat in front +I waiting below,   15 minutes

Not exactly a scientific study, the sample was way too small, but over all it actually was a lot quicker than I would have guessed.  I imagine if we tried it in the school holidays on this popular canal, we’d be happy to average 15 minutes.   So the answer is, it all depends.  It might be six minutes, it might be an hour.  I think that outside peak times I might go for an average of ten minutes.  Let’s suppose then that we do ten locks in a day (they don’t come thick and fast down the Oxford), the difference between Nick’s 12 mins and our 10 mins would only make a difference of 20 mins all day, and we might easily waste that chatting or messing about before we start.  Proof if proof were needed that boating is not an exact science.  Does that make Canalplan or my CanalOmeters redundant?  No, not really.  Having some idea of how far you can expect to get in a day, or a week is really useful, especially when in unfamiliar territory.

One other thing. We also worked out our average cruising speed.  I would have estimated 2.5 mph or less, given that in places there were long lines of moored boats to crawl past.  In fact it turned out to be 2.8mph.  I think that’s a figure we’ll stick to on this canal.

3 comments:

Giles Williams said...

*nods sagely while sipping a pint*

eeyore said...

I am surprised at the 2.8mph figure. Knowing that you do crawl past moored boats and knowing how shallow the Oxford Canal can be, I would have thought 2mph would be nearer the mark. Have you measured the times for Somerton Deep? The locks are only 6'10" fall above Banbury, most are between 8'6" and 12' below Banbury so take up to twice as long to fill and empty. And yes, a August Summer Saturday could be spent at Cropredy lock waiting for the Marina folk and Fairport crowds to dissipate!

Neil Corbett said...

By Jove you're right Eeyore. I hadn't thought of that. Is that why it changes from double bottom gates to single ones down that end?