Measuring my boat's width

[Scholar Gypsy]

I am interested - following a minor incident getting stuck on the Chesterfield this summer - in measuring the width of my boat fairly accurately. When it was built we were told it is 6'10", but I've never actually checked (and it has been stretched twice since then anyway).

 

Anyway, does anyone have any practical suggestions for how to do this, with the boat in the water?

 

[i've come up with a couple of Heath Robinson approaches so far, involving a timber frame of adjustable width that filts around the boat, or two plumb lines with heavy weights on suspended from a piece of timber that I can move up and down the roof. I don't have any laser surveying equipment, nor narrow locks within easy reach (that's option 3). I should probably do some feeling around under the water to see if there is a loose bit of rubbing strake.]

 

I look forward to Bizzard's contribution ....

[FadeToScarlet]

We measured ours with the surveyor when we bought it, because it's fairly crucial for an old boat. We used plumb bobs and a tape measure. The tricky bit was that the hull is very bashed in between the knees, by more than an inch in some places, so we.measured all the wide bits to find the widest one.

Edited August 26, 2015 by FadeToScarlet

[TheBiscuits]

Tight string lines in a full wide lock?

[bigste]

Lay a length of wood or metal across the top. Hang a plumb bob down each side ( a piece of string with a weight on the end).

Measure across the top with a tape measure. So long as you do it on quiet water with no boats passing it is very accurate, certainly to within 3mm or eighth of an inch.

[David Mack]

Lay a length of wood or metal across the top. Hang a plumb bob down each side ( a piece of string with a weight on the end).

Measure across the top with a tape measure. So long as you do it on quiet water with no boats passing it is very accurate, certainly to within 3mm or eighth of an inch.

 

But that only tells you the width at a particular point, but not if your boat is curved in plan.

 

Its also going to be less reliable for a boat which is 'Birmingham Square' i.e. the hull sides are vertical down to a 7 ft baseplate, rather than tapering in to a 2m wide baseplate, as the widest point may well be below the water line, where it is more difficult to check your plumb line is just touching the widest point.

[BEngo]

You need:

 

A wide lock ideally with a fairly straight coping line.

An absence of boats wanting to use the lock

A tape which will reach across the lock

Some chalk

A chalk line may help.

 

Mark the lock side at regular intervals both sides- say every 3 ft. These are your measurement points. If the lock is curved drop a chalk line on the copings either side and use these as your measurement references.

 

Put the boat in the full lock with the bow or stern at one of the measurement points and tie up tightly to one side. Check that there are no major 'wobbles' in the lockside, or if there are, measure the distance to the boat from the lock side (chalk line)at each measurement point. Record these and where they are.

Measure and record the distance between the other lock side ( chalk line) and the boat at each measurement point

Move the boat out of the lock.

 

Measure the width of the lock (between the chalk lines) at each measurement point and record it next to the lock-side to boat distances at the same point.

 

Apologise to the huge queue which will by now have built up, even if the cut has been deserted for the last week.

 

In turn, subtract the first measurement and the second measurement from the third measurement at each point.

 

The answer is the width of your boat at each point.

 

You can then, if required, draw the whole thing to scale and that will also show if the boat is banana shaped.

 

N

[bizzard]

Take three 8ft long planks and join them end to end with one screw, stiff, but not too stiff but tight enough to adjust them, and U have made a big U shaped caliper. Stand on the roof with it and let each side arm dangle down closing them in to measure the boats widths points as you move along, each time heaving them up to measure between the two arm ends with a tape measure.

Other uses include, head measuring for when buying hats, measuring the length of sleeping big cats in the jungle, including tail, bomb aiming practice and gunsight training ect.

[John V]

You never fail to raise a smile Bizz,

[bigste]

'But that only tells you the width at a particular point, but not if your boat is curved in plan.'

 

The op only asked about measuring the width. If he wanted to know about bananas I'm sure he would've asked.

 

*******************************

Edited August 26, 2015 by DeanS
REMOVED CONTENT - PLEASE RE-READ THE SITE GUIDELINES

[bizzard]

Search for banana shaped locks to make measurements of banana shaped boats. I don't think Fyffes banana boats are banana shaped.

[patty-ann]

There is a most impolite post...quite shocking.....I do hope its not in response to Mr Bizzards wonderful idea which should I need to measure a sleeping cat in the jungle I will most assuredly copy.

[bizzard]

There is a most impolite post...quite shocking.....I do hope its not in response to Mr Bizzards wonderful idea which should I need to measure a sleeping cat in the jungle I will most assuredly copy.

May I suggest that by lengthening the two arms of the caliper by precisely an extra 10ft it can be shuffled along the ground towards the big cat to measure its length quite safely, even when its a wide awake big cat.

Doing this makes it also good for measuring Teradactyles, Albatrosses and giant Midges wingspans.

[magpie patrick]

'But that only tells you the width at a particular point, but not if your boat is curved in plan.'

 

The op only asked about measuring the width. If he wanted to know about bananas I'm sure he would've asked.

If you cannot come up with a better idea I suggest you shut the f--- up'

 

He got stuck in a lock - that is why he is asking. Getting stuck in a lock is not just down to width but down to "bend" in the hull

[Machpoint005]

Take three 8ft long planks and join them end to end with one screw, stiff, but not too stiff but tight enough to adjust them, and U have made a big U shaped caliper. Stand on the roof with it and let each side arm dangle down closing them in to measure the boats widths points as you move along, each time heaving them up to measure between the two arm ends with a tape measure.

Other uses include, head measuring for when buying hats, measuring the length of sleeping big cats in the jungle, including tail, bomb aiming practice and gunsight training ect.

 

Two screws, shirley?

[bizzard]

 

Two screws, shirley?

No! no! I forgot to explain. Two screws to make the gauge plus a screw that must be loose in the head for attempting it.

[magnetman]

 

He got stuck in a lock - that is why he is asking. Getting stuck in a lock is not just down to width but down to "bend" in the hull

Measure the lock width at regular intervals and different heights with a LASER range finder

 

Or for measuring the width of the boat perhaps have a look down the sides, locate any obvious-looking wide spots if possible then arrange to use a LASER range finder to measure this width by finding a point on the cut where both banks are fairly level like a concrete piling, measure width of cut with LASER then put boat there and measure width from outside shell plating of boat. Then do the math

 

LASER is a handy tool for this although a little costly possibly. Ultrasonic is cheaper but rather less accurate. .

Or. Drill tiny hole in lining measure the depth from lining surface through insulation to the steel with the depth gauge on a caliper. Do this both sides then measure distance from lining to lining then add the two depths and 12mm for steel

 

 

I would have thought serious hull deformation would be visibly obvious from paint damage and by looking down the sides of the boat..

Edit fr typoss

No! no! I forgot to explain. Two screws to make the gauge plus a screw that must be loose in the head for attempting it.

Not an 8ft long screw then

Edited August 26, 2015 by magnetman

[Scholar Gypsy]

Thanks to all for their replies - and sorry for the delay in replying - we were hill walking yesterday (photo below).

 

I was glad to see both of my Heath Robinson approaches work in practice. I am pretty confident that the boat is not banana shaped (or wasn't when it was in dry dock - photos here). The base plate is certainly narrower, I think 6' from memory. I still think the problem is the lock not the boat, but I do need to check for eg displaced anodes or a loose rubbing strake.

 

Edited August 27, 2015 by Scholar Gypsy

[MtB]

Lay a length of wood or metal across the top. Hang a plumb bob down each side ( a piece of string with a weight on the end).

Measure across the top with a tape measure. So long as you do it on quiet water with no boats passing it is very accurate, certainly to within 3mm or eighth of an inch.

 

 

This only works in conditions of zero wind or air movement, Beaufort scale 0. Even the slightest breath of air makes the plumb bobs swing around by a few millimetres, wrecking the degree of accuracy needed. I know this having tried it. And simply impossible on a windy day.

 

Same will happen if the boat is afloat too, I suspect. Slight movements of the vessel will make the plumb bobs swing...

[Murflynn]

obtain a 40ft container

cut the roof and ends off and dispose of.

carefully cut one side off at the base.

weld the bottom of the loose side to a 40ft piece of 4x2 channel.

carefully lift the boat and place onto the base of the container, so the boat just touches the intact side in 2 places.

lift the loose side and carefully slide it towards the exposed side of the boat until it just touches in 2 places.

check the sliding side is vertical.

mark the position of the loose side on the base.

remove the loose side.

lift the boat out and dispose of.

replace the loose side in the marked position.

measure the distance between the loose side and the intact side.

 

SIMPLES

[Machpoint005]

 

 

This only works in conditions of zero wind or air movement, Beaufort scale 0. Even the slightest breath of air makes the plumb bobs swing around by a few millimetres, wrecking the degree of accuracy needed. I know this having tried it. And simply impossible on a windy day.

 

Same will happen if the boat is afloat too, I suspect. Slight movements of the vessel will make the plumb bobs swing...

 

A couple of vertical spririt levels would work better - at least they wouldn't be affected by the wind. As for the boat rocking, that would depend on how tender it was.

[Wanderer Vagabond]

Thanks to all for their replies - and sorry for the delay in replying - we were hill walking yesterday (photo below).

 

I was glad to see both of my Heath Robinson approaches work in practice. I am pretty confident that the boat is not banana shaped (or wasn't when it was in dry dock - photos here). The base plate is certainly narrower, I think 6' from memory. I still think the problem is the lock not the boat, but I do need to check for eg displaced anodes or a loose rubbing strake.

 

2015-08-26 15.40.47.jpg

I went through the lock you mentioned today, again without any problem so there is no difference between going up and going down. Having spoken with several people on the Chesterfield they tell me it is actually Lock 48 (not 47 as you stated in an earlier post) that has historically caused the problems, someone with a sense of humour called it Stret (or Straight) Lock . I'll be passing through that one tomorrow.

 

As another Heath Robinson suggestion for measuring boat width I would try tying your gangplank (or other piece of wood) squarely across the stern and then with a cheap laser pointer direct it from the bows along the side of the boat onto the board, first on one side then the other, marking where the laser light beam hits the board (you will need someone to assist!). The distance between the two should be your maximum boat width.

Edited August 27, 2015 by Wanderer Vagabond

[Scholar Gypsy]

I went through the lock you mentioned today, again without any problem so there is no difference between going up and going down. Having spoken with several people on the Chesterfield they tell me it is actually Lock 48 (not 47 as you stated in an earlier post) that has historically caused the problems, someone with a sense of humour called it Stret (or Straight) Lock . I'll be passing through that one tomorrow.

 

As another Heath Robinson suggestion for measuring boat width I would try tying your gangplank (or other piece of wood) squarely across the stern and then with a cheap laser pointer direct it from the bows along the side of the boat onto the board, first on one side then the other, marking where the laser light beam hits the board (you will need someone to assist!). The distance between the two should be your maximum boat width.

 

Thanks very much. In their recent emails CRT tell me that Stret Lock (no 48) was widened a few years ago, and they thought Shireoaks Middle (no 43) was the next narrowest. I got through 48 (Stret) OK, but not 47.(Deep lock).

 

I like the Laser pointer idea, maybe also using some vertical battens to make sure I measure the boat at its widest point (ie not between the rubbing strakes). Then I could also use a couple of boards suspended from a batten running across the bows of the boat, as target.

[MtB]

As another Heath Robinson suggestion for measuring boat width I would try tying your gangplank (or other piece of wood) squarely across the stern and then with a cheap laser pointer direct it from the bows along the side of the boat onto the board, first on one side then the other, marking where the laser light beam hits the board (you will need someone to assist!). The distance between the two should be your maximum boat width.

 

That sounds an imaginative and good idea.

 

I can't imagine it being more accurate than about +/- 1/4" though, and 1/4" can be the difference between slipping through and getting jammed.

[Wanderer Vagabond]

 

Thanks very much. In their recent emails CRT tell me that Stret Lock (no 48) was widened a few years ago, and they thought Shireoaks Middle (no 43) was the next narrowest. I got through 48 (Stret) OK, but not 47.(Deep lock).

 

I like the Laser pointer idea, maybe also using some vertical battens to make sure I measure the boat at its widest point (ie not between the rubbing strakes). Then I could also use a couple of boards suspended from a batten running across the bows of the boat, as target.

I can't say that I noticed Shireoaks Middle being particularly narrow but then we got through Deep Lock OK as well, our main issue has been depth rather than width as I've felt us scrape a few cills getting into/out of locks. Good luck with boat measurement, I hope it works. Since I'm moored outside of The lock Keeper pub I could measure the lock for you, but I don't carry a tape measure

 

Just as an aside, I watched the video of you going into West Stockwith Lock on a different thread, very impressed

 

 

That sounds an imaginative and good idea.

 

I can't imagine it being more accurate than about +/- 1/4" though, and 1/4" can be the difference between slipping through and getting jammed.

I'm not sure exactly how accurate the suggested method would be, if it were +/- 1/4" I think I'd be happy with that since, in hot sunlight, my boat can bend by a lot more than that if the sun is on one side of the boat. The guy who fitted out the boat (Phil Abbot) made allowances for expansion with the internal fittings and I often see a gap of over an inch open up on a hot day (although sometimes the doors on that side of the boat wont close!).

[David Mack]

 

Thanks very much. In their recent emails CRT tell me that Stret Lock (no 48) was widened a few years ago

Stret Lock used to be signed as 6 ft 10.5 ins wide. Fulbourne got stuck there in 2009. We tried going in forwards and backwards but the engineroom front bulkhead got stuck just below the bottom gate both ways round.

 

Shortly afterwards Chertsey failed to get through Morse Lock, so we deduced that Chertsey is wider than Fulbourne, and that Morse Lock is probably rather tight also. But I've not heard of other boats getting stuck there though.

 

Thanks very much. In their recent emails CRT tell me that Stret Lock (no 48) was widened a few years ago

Stret Lock used to be signed as 6 ft 10.5 ins wide. Fulbourne got stuck there in 2009. We tried going in forwards and backwards but the engineroom front bulkhead got stuck just below the bottom gate both ways round.

 

Shortly afterwards Chertsey failed to get through Morse Lock, so we deduced that Chertsey is wider than Fulbourne, and that Morse Lock is probably rather tight also. But I've not heard of other boats getting stuck there though.