What Does Bridge Height Actually Mean?

[JohnK]

I realise this sounds like a stupid question. Indeed, perhaps it is. But that never stopped me before

 

So if the height boards say six foot under say Potter Heigham bridge what does this actually mean?

It can’t be six foot at the highest point of the bridge can it?

If it did then no six foot air draft boats could get under it could they?

Because they’re going to be six foot high for maybe three or four feet wide aren’t they?

But then it can’t be the lowest point because that touches the water

 

So many questions! Apologies if this has already been discussed.

 

 

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[Vaughan]

This is why you need a pilot for Potter bridge!

Seriously though, you are quite right. Under a bridge such as Vauxhall or Thorpe, then your known airdraft is what counts. Potter and Wroxham being arched bridges, it depends on the beam of your boat at its highest point (usually handrails) as well as its maximum airdraft.

I am not sure at what point on the arch, they give the "height" of Potter bridge - I am sure someone here can tell us.

So to hell with the height shown on the gauge - approach it slowly, have a look and judge for yourself, using the mark one eyeball.

[JohnK]

I’m assuming that as the bridge is made out of stone, the boats made from GRP, wood, canvas and glass .... approach with enough speed the bridge will transform your boat into the size it needs to be to fit through


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[Vaughan]

1 minute ago, JohnK said:

I’m assuming that as the bridge is made out of stone, the boats made from GRP, wood, canvas and glass .... approach with enough speed the bridge will transform your boat into the size it needs to be to fit through

It always has done, for hundreds of years but we all hope that one day, a boat might win!

[CambridgeCabby]

Something to ask Robin to help achieve with his new acquisition (stc of course)

[JohnK]

Well I’ve just spent half an hour on Google and found nothing that tells you what it means.
I can see this leading to me touring the broads with a tape measure and notebook


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[LizG]

Some while back someone on here did post the information - put a search maybe into the forum (I think it was this forum?)

With my boat it isn't so much a height issue at Potter these days but the width of the old canopy when lowered

Liz

[stumpy]

I think I  remember it was Strowager, possibly on the other side, who posted a full survey of the bridges, complete with annotated photographs. ISTR the measurements are taken from a couple of feet off the centre line. 

[Daddy Mouse]

It would be handy if everyone who has taken their boat through Potter posted what type of boat it was and whether it was really tight or a bit of clearance.

[JohnK]

w-album and stumpy. You are both absolutely right.
Found it. Not sure it’s ok to post links here to other forums so I won’t.
What an awesome bit of work.


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[LizG]

Just now, Daddy Mouse said:

It would be handy if everyone who has taken their boat through Potter posted what type of boat it was and whether it was really tight or a bit of clearance.

Picture of my boat! A recent one with the canopy up and an old one from 2012, pre doing up where we later went through Potter - as to how much room, that always depends on the bridge height but I won't take her through (or the Pilot) unless there is 6 ft 3 inches.  The Pilot would probably go for less but they might not like to because of insurance!!!!

[Daddy Mouse]

She looks to big at first glance. It's good for us novices to see what will go through.

[stumpy]

No Worries is a Bounty/Elysian 27AC, with everything down I measured her at 6'4" - if either of the bridges is under 6'6" it's a swift U-turn I'm afraid. 

[LizG]

Just now, Daddy Mouse said:

She looks to big at first glance. It's good for us novices to see what will go through.

She was built by Herbert Woods specifically to go through Potter..........as were all their original wooden boats even the 42 foot ones!

[Guest]

I've always assumed it is the maximum clearance i.e. a height reading of six foot would allow a theoretical boat one inch wide with an air draft of five foot eleven and three quarter inches to pass through with a quarter inch clearance (less the arch radius of one inch).

[BrundallNavy]

Here’s  Nipper going through, I need 6ft 3”.

Edited November 5, 2017 by brundallNavy

[charlesa]

Juliette, Martham, 5ft -10”, only just !

[JennyMorgan]

5 hours ago, brundallNavy said:

Here’s  Nipper going through, I need 6ft 3”.

Clearly built for the Broads!!

[BroadAmbition]

I take 'B.A' through regular if the pilots office gauge states 6ft5" or more.  That gives me a 2" clearance to play with.  The tallest point on 'B.A' is 6ft3" being the mast bracket, so in theory I could take her through with 6ft4" showing on the gauge.  'B.A'  is 40ft x 12ft.  She was constructed in 1966 by Jack Powles.  Like many boats of that era, the boats were designed and constructed for the Broads and Broads bridges, the holiday maker adapted themsens to the boats.  Nowadays sadly this has changed.  The boats are constructed / designed for the holiday maker and the boats have to adapt themsens to the Broads

Hope this helps

Griff

 

[TheQ]

in the green book they have a list of bridges  / pictures and some dimensions

http://www.thegreenbook.org.uk/

Click in the left hand  column,,       green book / Bridge dimensions and type

and a link to Strowgers bridge height measurements

http://the-norfolk-broads.co.uk/viewmessages.cfm?Forum=22&Topic=26694

[KaptinKev]

On 06/11/2017 at 00:19, BroadAmbition said:

I take 'B.A' through regular if the pilots office gauge states 6ft5" or more.  That gives me a 2" clearance to play with.  The tallest point on 'B.A' is 6ft3" being the mast bracket, so in theory I could take her through with 6ft4" showing on the gauge.  'B.A'  is 40ft x 12ft.  She was constructed in 1966 by Jack Powles.  Like many boats of that era, the boats were designed and constructed for the Broads and Broads bridges, the holiday maker adapted themsens to the boats.  Nowadays sadly this has changed.  The boats are constructed / designed for the holiday maker and the boats have to adapt themsens to the Broads

Hope this helps

Griff

 

Hi Griff, I would be interested to know that when they give an air draft of a boat, I assume this is on it's own and when fully laden with people, fuel, water and goods so to speak, how much can this affect the air draft?

[MauriceMynah]

Stumpy, I too run an Elysian Bounty 27AC and the pilots won't take her through if Potter is showing 6' or less, I take her through at 6' 4". I failed to get her through at 6' 2" a couple of years ago. :(

[Victoryv]

On 05/11/2017 at 19:53, charlesa said:

Juliette, Martham, 5ft -10”, only just !

We had a fancy to pop through the bridge for a couple of days, a couple of weeks ago. Left Martham and moored by the fishermen just before the new bridge, no other boats on the mooring as we walked down to the pilots office to check the height, 5ft 7inch, no chance there then! quick wander up to Lathams for teacakes (excellent by the way) and back to the boat. Moored in front of us was Juliette, which ten minutes earlier had been moored on the pilots side, now what sort of magic had occurred here ? one of the Martham boats lads had bought it through, such skill and not a little brave, also perfect timing, end of season and both forward hand rails perfectly sanded and ready for varnish!

Ideally I like 6ft 10inch or more to get through, and even then I am a bit outside my comfort zone. If needs must I have done it at 6ft 1inch, not much room for error. If I can see the stone stanchions at the base of the bridge out of the water I am happy to go, if it looks a bit tight I moor up and check the gauge in the pilots office.I never get complacent about the bridge, still scary aiming all that lovely wood and varnish at a small hole, but the feeling the first time you do it for yourself is right up there.

I like the challenge of the bridge, wouldn't want to lose it.

[JanetAnne]

I took Andy's Judith through at 5'11"

The pilot said "if you don't get through tonight you won't be getting through for the next three weeks"! Tonight meant just before midnight.

We stripped everything off the top as you can imagine. Anxiously watching the pilots gauge  (through the window by torchlight) the time came to go for it. And we did. 

The fwd end went through no problem but the noise from behind was horrendous.  Being nothing short of pitch black I feared the worst not being able to see much so we moored and I inspected the damage. Not a scratch!

We eventually worked out that the wind had lifted the corners of the canvas canopy as we went through and that was the noise amplified by the darkness and bridge chamber effect. There was a slight rub on the corner of the material.

When I told Andy he said "don't know what you were fretting about. She'll do 5'9" with the speed under her"

Not with me at the helm I thought! 

Gotta love that bridge. 

[charlesa]

When we took Juliette through at 5ft 10" I had folded the whole canopy down into the cockpit, and I'm glad we did !!