Air draft

[The Dreamer]

Our boat is registered as having an air draft of 1.8m (6ft).  I recently checked this, and indeed the highest non-moveable point is the Maxiview aerial, which comes in at spot on 1.8m.  Last week, in planning a journey up the Trent and Mersey, I noted that on the CRT Waterways Dimensions document, it suggests that the whole canal from Preston Brook to Burton-on-Trent has an air draft maximum of 1.75m (5ft9in).  I was not especially worried about this for three reasons.  Firstly we used to own a share in a boat moored at Great Haywood.  I cannot recall the hight of that vessel, but she did not present as being especially high, or low, and I could not think of any situations, rattling up and own the T&M, that caused us anything close to an issue.  Secondly, our boat is ex ABC.  For the last two decades ABC boats have been made, to a fairly standard pattern, at Pinder’s, fitted out at Alvechurch and then distributed to their various yards.  Three of these, including Wrenbury Mill where ours was based, sit on or close to the Four Counties Ring, and therefore the boats will need to be able to travel the T&M without issue.  Lastly, at a pinch, if we got to a bridge and found ourselves to be in a sticky situation, we could pull over and I could dismantle the Maxiview to bring the height down.  So last Monday, off we set from Fazeley.

 

Yesterday we turned on to the Middlewich Branch, at Wardle Junction (or, for the pedants, we turned onto the Wardle Canal), having had no issues with height at all.  In fact, we also have a quick release mast for the 4g aerial, that raises 25cm (10in) over the Maxiview, that stayed up the whole time, and two roof boxes, that raise about 15cm (6in).  These are designed to lift off and stack in the seated stern area of the semi-trad, but we had no cause to even contemplate doing so.  In short we came through a whole area, marked by CRT as being 1.75m,  at height of 2.05m.  The closest we got was Newcastle Road (115), which CanalPlan AC warned us about, but did not offer a height, in the event we had a good 10cm (4in) to spare.

 

To some degree none of the above bothers me, but with a height discrepancy of 25cm, at some point I am going to become complacent and get seriously caught out, so how hard can it be for CRT to get these dimensions more accurate?

Edited February 9, 2020 by The Dreamer

[Jen-in-Wellies]

Part of the problem is that it is a single height number, when many of the low bridges and tunnels are arched. The profile of the boat counts for as much as the highest point. You see this in particular with Standedge Tunnel, where the rules and check gauges you have to pass before the CaRT boys and girls in blue will let you through measure the width across the cabin top as well as the highest point. The wider the cabin roof, the lower the maximum air draft they'll allow. For a particular canal, the low height might have come from a bridge, pipe line, or other obstruction that has since been removed, or rebuilt, yet the CaRT headline number has never been updated. The person compiling the list might be some office bod with no knowledge of that canal. If they wrote down a height that was too high and someone got stuck they would get in to trouble. If the height is too low, then owners of higher boats will either chance it and find it is fine, or not go at all. No bad come back for the CaRT person.

 

Jen

[The Dreamer]

29 minutes ago, Jen-in-Wellies said:

Part of the problem is that it is a single height number, when many of the low bridges and tunnels are arched. The profile of the boat counts for as much as the highest point. You see this in particular with Standedge Tunnel, where the rules and check gauges you have to pass before the CaRT boys and girls in blue will let you through measure the width across the cabin top as well as the highest point. The wider the cabin roof, the lower the maximum air draft they'll allow. For a particular canal, the low height might have come from a bridge, pipe line, or other obstruction that has since been removed, or rebuilt, yet the CaRT headline number has never been updated. The person compiling the list might be some office bod with no knowledge of that canal. If they wrote down a height that was too high and someone got stuck they would get in to trouble. If the height is too low, then owners of higher boats will either chance it and find it is fine, or not go at all. No bad come back for the CaRT person.

 

Jen

Yep, get all of that, so quite literally, one size does not fit all.  Thus making the whole document a speculative guess on behalf of a very risk adverse CRT, and therefore it ain’t worth the paper it’s written on!

[Alan de Enfield]

I cannot remember where it is, but somewhere on the T&M there is a paired lock which has bridges at the tail.

(Could be around Stoke somewhere)

 

Our friends went thru the left hand side (heading North) and we went thru the right hand side, they are a bit under 6 foot and they ripped off their cratch

 

The LH side bridge is several inches lower than the RH side one.

[Col_T]

Quote

Yep, get all of that, so quite literally, one size does not fit all.  Thus making the whole document a speculative guess on behalf of a very risk adverse CRT, and therefore it ain’t worth the paper it’s written on!

Fair comment - but there are many people who are re-assured by documents like this, and who might agitate for the creation of such a thing.

[ditchcrawler]

1 hour ago, Alan de Enfield said:

I cannot remember where it is, but somewhere on the T&M there is a paired lock which has bridges at the tail.

(Could be around Stoke somewhere)

 

Our friends went thru the left hand side (heading North) and we went thru the right hand side, they are a bit under 6 foot and they ripped off their cratch

 

The LH side bridge is several inches lower than the RH side one.

I think that is the first set of locks below where the Macc goes off at Kidsgrove

Edited February 9, 2020 by ditchcrawler

[Alan de Enfield]

Just now, ditchcrawler said:

I think that is the first set of locks below where the Macc goes off at Kidsgrove

That rings a bell.

Is it a railway bridge ? From memory it is all sorts of RSJ's / Girders under the bridge.

 

All my books and charts of packed away no we are no longer on the canals so I cannot have a look-see.

[Ray T]

Air draft? Yes it is a tad windy.

Sorry couldn't resist.   

[Rambling Boater]

This is exactly why talking to someone with experience (and who you can trust) is always better than a machine.

 

Even if it goes wrong, you can become that person!

Edited February 9, 2020 by Rambling Boater