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Discussion Topic: Bridge Height Gauges
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kfurbank |
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Mardles sometimes
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It is rumoured that the bridge height gauges are not entirely accurate, but set with a margin of error. Is that the case? and if so by what margin are they out? and is that margin the same at all bridges? I realise that gauges do get knocked and there might be a tendency to err on the side of caution when setting the gauges, but as I know the exact height of my boat, it would be useful to know at any time, the accurate clearance under any given bridge. Personally I feel it would be much better to have 100% accurate height gauges rather than having to factor in that they are normally out by anything up to 6 inches.
Happy to support the honest and reliable pubs and businesses of The Norfolk Broads.
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webntweb |
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The gauge on the upstream side of Beccles Old Road bridge seems spot on.
Our bridge guide on the pulpit is set at 6'10" and we waited until the 7ft mark was just showing and passed under with definitely no more than 2" to spare.
Roy
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Captain-Joshie |
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Hi JP
We had to pass under Ludham Bridge yesterday and we need 7' 8", on checking the board up stream of the moorings it said 8 feet so we are going to make it, on getting to the bridge the board said 7 feet 6 inches  so hard astern and into the moorings!
On checking the other side of the bridge the board was somewhere between the too. I took the advise of the boatyard that I'd be OK and we did make it OK.
The boards do need to be acurate exactly otherwise they are useless.
John.
Kind regards, John(Captain
Joshie), Jo & Toby.
'Braveheart' L68 Broom
30/Skipper *
Listening out on PMR Ch4 when
on board*
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kfurbank |
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Mardles sometimes
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Out of interest John, how much clearance do you estimate you actually had under the bridge?
The problem with inaccurate or cautiously set gauges, is that its a bit like the habit of putting the clock forward by 10mins to make sure your not late. Within a short while you automatically take the 10 mins into account and it defeats the purpose. I would rather know the precise height under the bridge and the precise height needed for my boat.
Happy to support the honest and reliable pubs and businesses of The Norfolk Broads.
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Captain-Joshie |
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Here-here Keith exact height to the 1/8th inch or better!
I had my eyes closed  , but Jo reckoned about 2 inches.
John.
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kfurbank |
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Mardles sometimes
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So assuming the actual clearance was 7ft10, if you need 7ft8 and you think there was another 2in spare, then the gauge by the bridge was 4in out, but worryingly the gauge upstream was 2in out the wrong way. I guess it would also help to know where the reference point is set on arched bridges such as Potter, but more specifically Wroxham which is the more frequently used bridge by larger craft.
Happy to support the honest and reliable pubs and businesses of The Norfolk Broads.
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JP |
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Dear Kfurbank,
We continually monitor each gauge board to ensure it is showing the correct clearance for the bridge. The level at which each gauge board is set to take into account the effect of the tide and river flow both pushing the water against and away from the boards which can cause small variations in readings depending on the direction and strength of the tide and flow. To achieve this, detailed measurements are taken at all states of the tide to ensure accuracy. The height given on the gauge boards should be taken as an accurate measure of the height available under the bridges.
Regards
John
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Perfectlady9 |
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It's ok saying the gauges should be taken as accurate but since the one on the Barton side of Ludhan has been replaced its seems way out, at least make both the gauges read the same it would save a lot of people doing a quick reverse when they get to the bridge.
This is the first bridge people come to when leaving Richardsons it does not give them much of a fighting chance.
Doug.
Now I know what Trigger meant
about his Broom !
The Moore the merrier.
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JanetAnne |
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The gauges either side of Potter dont agree with each other or the third gauge in the pilots office.We reckon between the three there is 4in difference! And that was today, not in the past etc
If I am a "woody" how come there are no "fibreglassy's" "plasticy's" or "steelies"?
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Islander |
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Good evening John.
Apart from the accuracy of the gauge boards would it not be possible to make them readable at lower tide levels for those of us with greater airdrafts I.e.8ft. This is a major problem on the southern broads with the greater tidal range where the bottom third of the board is unreadable when entering Norwich, Thorpe old river or Reedham with following tides. The gauges are readable at the lower levels for only a short period after being cleaned by the rangers. Plus gauges further either side of brides to give people time to turn safely and , maybe, moor up to wait for suitable clearance or lower canvas and windscreens.
Colin 
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Apr-28-2016 @ 9:46 AM
