72' by 6'10 etc etc

[twbm]

I'm currently being trained to be a trainer, and as part of the course work have to do a twenty minute presentation to what will be a very picky audience of fellow students. I'm going to talk about the canals and my interest in them including a potted history of the systems development. A question I'm bound to get asked is 'Why that size'? I've never actually heard any logical reason for the traditional narrow canals - and given that the Bridgewater was built for 72' by 14' wide boats the subsequent development of a system at 6'10" wide, or 62 feet long, depending on which way you go is even more odd. I understand that a narrow cutting or tunnel is less work than a broad one, but why not 8, 9 or 10 feet?

 

Anybody know?

[muddywaters]

Sure someone will correct me if I'm wrong.

But would assume it was the most cost effective way to build them at that time

[NB Lola]

Sure someone will correct me if I'm wrong.

But would assume it was the most cost effective way to build them at that time

 

 

http://en.wikipedia....sh_canal_system

 

from that linky

 

Standard locksFor reasons of economy and the constraints of 18th century engineering technology, the early canals were built to a narrow width. The standard for the dimensions of narrow canal locks was set by Brindley with his first canal locks, those on the Trent and Mersey Canal in 1776. These locks were 72 feet 7 inches (22.1 m) long by 7 feet 6 inches (2.3 m) wide.^[11] The narrow width was perhaps set by the fact that he was only able to build Harecastle Tunnel to accommodate 7 feet (2.1 m) wide boats.^[11]

 

His next locks were wider. He built locks 72 feet 7 inches (22.1 m) long by 15 feet (4.6 m) wide when he extended the Bridgewater canal to Runcorn, where the canal's only locks lowered boats to the River Mersey.

 

The narrow locks on the Trent and Mersey limited the size of the boats (which came to be called narrowboats), and thus limited the quantity of the cargo they could carry to around thirty tonnes. This decision would in later years make the canal network economically uncompetitive for freight transport, and by the mid 20th century it was no longer possible to work a thirty tonne load economically.

 

 

Edited January 23, 2011 by NB Lola

[boatmoving]

7ft is half of 14ft, so you can get two narrow boats in a wide lock. slightly wider boats are very wasteful of water.

 

Why 6ft10in? Maybe because boats tend to spread a bit, so the boats are built just slightly narrower than the locks?

[Chertsey]

A student once asked me, 'I can't find anything on the internet, do you think I should try the library?'

A book might be your best bet here, Hadfield's British Canals, perhaps, or Hugh McKnight's Shell Book of the Inland Waterways? Whatever you do, don't mention 6'10"! There is a lock on the Chesterfield that was restored to that width but the historic standard was 7' and your pair presumably built to a width of 7 foot and half an inch? And a length of 71'6" (joshers are shorter at around 70' I think?) but shorter for the Erewash... I thought this dimension originated with the Bridgewater Canal 'starvationers' which iirc were actually even narrower.

 

7ft is half of 14ft, so you can get two narrow boats in a wide lock. slightly wider boats are very wasteful of water.

 

Why 6ft10in? Maybe because boats tend to spread a bit, so the boats are built just slightly narrower than the locks?

Only modern boats are built to this dimension, to play safe as many locks have narrowed somewhat over the years. The standard for working boats was 7' or even a bit more.

Edited January 23, 2011 by Chertsey

[Gibbo]

slightly wider boats are very wasteful of water.

 

<Gets popcorn ready>

[carlt]

Only modern boats are built to this dimension, to play safe as many locks have narrowed somewhat over the years. The standard for working boats was 7' or even a bit more.

Save some for me, Gibbo.

[Guest User]

"Why 72' x 6'10" ?" .... why not ?

[magpie patrick]

There isn't actually a standard seven feet beam, nor 72 foot length. 72 feet won't fit in some narrow locks. What is now the Llangollen had a ruling width of 6 foot 9 in 1904, while some narrow canals had over seven feet. Boats didn't travel the length and breadth of the system then. A GUCCC boat could be built to 7 foot 1 inch because it was not intended it would leave the GU system.

 

A boat at more than half the beam of a lock is wasteful because you can't get two in the lock, The Thames and Severn suffered badly for this as their locks were 12 feet 6 wide, or thereabouts.

 

I think the smallest official narrow boats were for the Somerset Coal Canal, at 6 feet 10 by 69 feet, this is because they were half a K and A barge, which is 13 feet 8 by 69 feet. You can't get two 72 feet boats side by side in K and A lock, and when I helped Luctor down Caen Hill with his boat, we could't share because he's a little over the 7 feet. I've also had a notional six foot ten beam jam with only one gate open on the K and A

[carlt]

"Why 72' x 6'10" ?" .... why not ?

The Huddersfield Narrow had a max beam of 6'11" and length 70', the Stratford on Avon Canal; 7'1" x 74' 6", Llangollen; 72'6" x 6'10", the Shrewsbury Branch of the Shroppie; 74' x 6'4", etc.

[zenataomm]

I understand it's all to do with the width of the thruster rockets the Romans attached to their horse drawn ponies or something ..........

[Chertsey]

Save some for me, Gibbo.

I think the point I was making was that there wasn't a single standard, but that the boats the OP is involved with are outwith the dimensions he mentioned. I just mentioned some other standards - admittedly not all of them. Didn't know that about the Hud though even though I lived almost on it for a while. Perhaps the OP can impress his audience by listing the dimensions of every waterway in the country.

 

Would it be wrong, however, to state that 7' is the most common standard?

 

I understand it's all to do with the width of the thruster rockets the Romans attached to their horse drawn ponies or something ..........

Now you mention it I do recall seeing an explanation based on that... something to do with cart wheels and the width of two horses. Can't recall where though, and don't know how much credence to give it.

[RLWP]

<snip>

 

Now you mention it I do recall seeing an explanation based on that... something to do with cart wheels and the width of two horses. Can't recall where though, and don't know how much credence to give it.

 

I think you are getting mixed up with some spurious nonsense about the railway gauge used by Stephenson

 

Richard

[Pete of Ebor]

I'm currently being trained to be a trainer, and as part of the course work have to do a twenty minute presentation to what will be a very picky audience of fellow students. I'm going to talk about the canals and my interest in them including a potted history of the systems development. A question I'm bound to get asked is 'Why that size'? I've never actually heard any logical reason for the traditional narrow canals - and given that the Bridgewater was built for 72' by 14' wide boats the subsequent development of a system at 6'10" wide, or 62 feet long, depending on which way you go is even more odd. I understand that a narrow cutting or tunnel is less work than a broad one, but why not 8, 9 or 10 feet?

 

Anybody know?

 

One theory goes back to Brindley and his building of the T&M canal - specifically of Harecastle Tunnel. Having worked out how to build it he realised that if you double the size of the bore of a tunnel, you quadruple the amount of earth which has to be excavated, but more importantly to him, that if you halve it, you quadruple your saving. Imagine a circular tunnel bore of radius 1 metre. For every metre you bore, you must remove 3.14 m³ of spoil, but double the bore to 2m radius and you must remove 4 times as much i.e. 12.56 m³. Having grasped this, he realised that he could save a lot of money by building Harecastle Tunnel narrower, so he decided upon 7' rather than 14' which was already in general use on many rivers. Once Harecastle Tunnel was built at 7', it bacame the standard for the midlands canals.

[Guest]

I'm going to really show my ignorance here of issues around canal building but ism't it just down to what the individual 'standard' for a particular company was - which then varied by which ever company came in (including those owned by the railways) - lead engineers on the project than had to juggle the various company requirements which then changed as companies changed hands...... :unsure:

[Guest User]

The Huddersfield Narrow had a max beam of 6'11" and length 70', the Stratford on Avon Canal; 7'1" x 74' 6", Llangollen; 72'6" x 6'10", the Shrewsbury Branch of the Shroppie; 74' x 6'4", etc.

... yeah but... the OP is asking why was that specific dimension chosen as a standard .... these other figures are all in the same ball park, give or take, soooo, why were these specs adopted in each case ? I understand the limitations of construction and the savings gained on tunnelling a narrower bore .... but why were these particular sizes chosen ?

 

Edited to add: I'm rather taken with the thought of an engineer somewhat arbitrarily saying, "let's make it it big enough for boats 72 ft long by 6'10" feet wide" for no better reason than it sounded about right.

Edited January 23, 2011 by Graham!

[the grinch]

just to add to the dimensions dilema ours on the Wey and Arun are 68ft x 12ft !!

[magpie patrick]

... yeah but... the OP is asking why was that specific dimension chosen as a standard .... these other figures are all in the same ball park, give or take, soooo, why were these specs adopted in each case ? I understand the limitations of construction and the savings gained on tunnelling a narrower bore .... but why were these particular sizes chosen ?

 

Edited to add: I'm rather taken with the thought of an engineer somewhat arbitrarily saying, "let's make it it big enough for boats 72 ft long by 6'10" feet wide" for no better reason than it sounded about right.

 

Well on the Chesterfield that's not far off the truth. Hugh Henshall was the engineer, having taken over from James Brindley when he died (HH was Brindley's brother in law). There was no way that a narrow boat, horse drawn, was going to get from the T&M to the Chesterfield, but it was a gauge that worked...

 

I think narrow gauge railways follow the same principle, all the two foot, two foot six, three foot six gauges aren't connected, except for the last one in Queensland only

 

If the K and A had been 60 feet by 18, the coal canal would have been 60 feet by 9...

[RLWP]

<snip>

 

I think narrow gauge railways follow the same principle, all the two foot, two foot six, three foot six gauges aren't connected, except for the last one in Queensland only

 

<snip>

 

You'll get outed again at this rate Patrick.

 

Spooner influenced railways, independent railways, light railway act railways, government controlled railways, WWI surplus railways?

 

Lots of reasons for different narrow gauges.

 

Richard

 

<Richard waits for some smart-alec GWR fan to turn up to argue that anything less than 7' 1/4" is narrow-gauge>

Edited January 23, 2011 by RLWP

[Bimbly1]

Lots of reasons for different narrow gauges.

 

Nothing changes, today we have incompatible chargers for different models of cell phones instead of one for all.

[Timleech]

Well on the Chesterfield that's not far off the truth. Hugh Henshall was the engineer, having taken over from James Brindley when he died (HH was Brindley's brother in law). There was no way that a narrow boat, horse drawn, was going to get from the T&M to the Chesterfield, but it was a gauge that worked...

 

I think narrow gauge railways follow the same principle, all the two foot, two foot six, three foot six gauges aren't connected, except for the last one in Queensland only

 

What about the pics of pairs of narrow boats on the Trent with a square sail?

 

3' 6" is the standard gauge in Southern Africa

 

Tim

[PhilR]

 

3' 6" is the standard gauge in Southern Africa

 

Tim

 

And they had Starvationers there too?

[carlt]

... yeah but... the OP is asking why was that specific dimension chosen as a standard ....

 

It isn't a standard, therefore it wasn't chosen as one.

 

If there was a "standard" then it would be 7', or more, rather than 6'10", but try telling BW that.

[Guest User]

It isn't a standard, therefore it wasn't chosen as one.

 

If there was a "standard" then it would be 7', or more, rather than 6'10", but try telling BW that.

 

Ok, irrespective of whether or not it was a standard; why was any specific dimension originally arrived at over any others (on any of the waterways) ?

[carlt]

Ok, irrespective of whether or not it was a standard; why was any specific dimension originally arrived at over any others (on any of the waterways) ?

Economy, geology, copying other canal dimensions (but cocking it up), many reasons...possibly even building a lock narrower than planned and then saying "I meant to do that!"