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Boat length measurements


Mick in Bangkok

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17 hours ago, Murflynn said:

which is why traditional methods work best.

when I started on site as a setting-out engineer all that was required for each building was four 90degree corner frames, each set at a fixed datum level and with a nail to hold the string line in each of the 2 directions; brickwork was always straight and true, 'cos the brickies understood the system.  Surveying has become a dark electronic art and for simple structures is just a load of bollix.

Well, it rather depends on what you're doing.  Your system of setting out may result in the brickwork being straight and even the four corners being correct, relative to each other.  But my side of things the more common problem lies in the structure being somewhere other than where it should be.  Sometimes, quite differently.  And even when I started in an allied side of the profession, my colleagues were having to allow for the curvature of the earth using not much more than a pencil and paper.

But for measuring the length, a straight piece of hard bank and a plank either end of the boat, square to it main axis would be pretty good.

For width, find a reasonably straight and parallel lock chamber (check with a laser?) and measure the gap.  Perhaps push a length of timber in the gap to find out what's remaining.

 

 

 

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3 hours ago, Tacet said:

For width, find a reasonably straight and parallel lock chamber (check with a laser?) and measure the gap.  Perhaps push a length of timber in the gap to find out what's remaining.

 

err .......   MtB was trying to get it right to the nearest millimetre.

as I said, string lines are the foolproof and accurate answer. 

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4 minutes ago, Murflynn said:

err .......   MtB was trying to get it right to the nearest millimetre.

as I said, string lines are the foolproof and accurate answer. 

Two strings would be pretty good.  But it wouldn't confirm that the the maximum departure from a vertical plane is not at differing heights on each side.  And there would be an appreciable sag over the length of a boat, which would rather confuse measuring a boat with other than vertical sides over the depth of the sag. 

If you want it to a mm (which will be challenging) you would need to some form of 3D modelling.

 

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