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Height of bridges


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The air draft for vessels is usually quoted in the brokers details. But where do I find out the detailed heights of each bridge to make sure the boat will not get stuck under a low bridge. I am thinking of a boat just under 8 foot high to travel on the Leeds and Liverpool canal.

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Truth is, you can't, because the water level of canals can vary; and in any case, rarely are bridges horizontal, they are normally arched, so its to do with the profile of the bridge vs the profile of the boat; and an allowance for maneuvring or inaccuracy in lining it up etc. Also the air draft will change due to (mainly but also other stuff) water tank contents, diesel tank contents, any other tanks, how many on board etc. And of course squat (but you'd never rely on squat to get through a low bridge unless you were bonkers, of course!). Also if there's a hidden obstruction underneath a bridge (in the water on the bottom, or on the edge possibly) it could throw the boat's direction, or raise it, or one side, etc so you'd need a bit of wiggle room.

8 foot sounds on the high side to me, I'd personally just avoid an 8ft high narrowboat rather than be constantly worrying about bridges. But others may vary.

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27 minutes ago, Paul C said:

Truth is, you can't, because the water level of canals can vary; and in any case, rarely are bridges horizontal, they are normally arched, so its to do with the profile of the bridge vs the profile of the boat; and an allowance for maneuvring or inaccuracy in lining it up etc. Also the air draft will change due to (mainly but also other stuff) water tank contents, diesel tank contents, any other tanks, how many on board etc. And of course squat (but you'd never rely on squat to get through a low bridge unless you were bonkers, of course!). Also if there's a hidden obstruction underneath a bridge (in the water on the bottom, or on the edge possibly) it could throw the boat's direction, or raise it, or one side, etc so you'd need a bit of wiggle room.

8 foot sounds on the high side to me, I'd personally just avoid an 8ft high narrowboat rather than be constantly worrying about bridges. But others may vary.

Ahh " Squat " a rather embarrassing moment for the QE2 amongst others. When I took my boatmasters for the Notts Princess I was actualy questioned re the phenominen and luckily I new about it.

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1 hour ago, Justinstop said:

The air draft for vessels is usually quoted in the brokers details. But where do I find out the detailed heights of each bridge to make sure the boat will not get stuck under a low bridge. I am thinking of a boat just under 8 foot high to travel on the Leeds and Liverpool canal.

Is eight feet the height above the waterline?

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I don't think there is such a guide available, all you will get is the height restrictions for each canal and on the L/L it is about 8', that being the height of Foulridge, and possibly Gannow, tunnel.  You are right on the limit.  A few years ago we met a guy with an old Thames cruiser that had 7'9" and I believe he got through Foulridge. 

 

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1 hour ago, mrsmelly said:

Ahh " Squat " a rather embarrassing moment for the QE2 amongst others. When I took my boatmasters for the Notts Princess I was actualy questioned re the phenominen and luckily I new about it.

The same reason aircraft wings fly!

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  • 1 month later...

Height is not just for boaters, towpath users also encounter varying degrees of height particularly with the traditional bridges are lowest at the side of the waterway. There is also a problem in certain areas where subsidence has affected height above the waterway. Those who look after the waterway have a responsibility to maintain the height so that craft can pass under them. From a heritage issue original bridges were made to the specifications laid out by the canal company and engineer. Since that time there has been a host of different types ranging from railway to modern road types. They all appear to maintain a safe height over the navigation and it would be of use where boaters indicate where this is not the case. The worst cases of height is where a navigation is blocked by a new bridge such as happened on the BCN at Swan Village where the Black Country Route cut off navigation onto the Ridgeacre and denied boaters of a useful mooring beside the Pub!

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The Imray book Canals & Rivers of Great Britain & Ireland used to have the max dimensions to be able to pass & lowest bridge heights on that waterway But it was printed a good time ago so I have no idea if it has been updated to include the new/replacement bridges The amount of tumble home on the cabin is also a limiting or other wise factor

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10 hours ago, X Alan W said:

The Imray book Canals & Rivers of Great Britain & Ireland used to have the max dimensions to be able to pass & lowest bridge heights on that waterway But it was printed a good time ago so I have no idea if it has been updated to include the new/replacement bridges The amount of tumble home on the cabin is also a limiting or other wise factor

When we tried to take Fulbourne up Reach Lode some years ago I found that the Imray map gave the width depth and headroom available, but failed to note that Upware Lock is only about 65ft long!

When the bow was here:

Ouse16.JPG

the stern was here:

Ouse15.JPG

 

 

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2 minutes ago, David Mack said:

When we tried to take Fulbourne up Reach Lode some years ago I found that the Imray map gave the width depth and headroom available, but failed to note that Upware Lock is only about 65ft long!

When the bow was here:

Ouse16.JPG

the stern was here:

Ouse15.JPG

 

 

I remember measuring that for someone who was planning to go that way

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11 hours ago, David Mack said:

When we tried to take Fulbourne up Reach Lode some years ago I found that the Imray map gave the width depth and headroom available, but failed to note that Upware Lock is only about 65ft long!

When the bow was here:

Ouse16.JPG

the stern was here:

Ouse15.JPG

 

 

I did say in my post that it was originally printed a long time ago & did not know it had been updated

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