Weighing a dinghy on bathroom scales

The trouble with weighbridges is the lack of accuracy. They are normally to the nearest 20-40kg. Depends how accurate you want to be.
I think that I would make sure that the boat is on a level surface, get three bathroom scales and do it that way. Weigh, then move the scales around so as to eliminate any variation between the scales' accuracy.
 
Note to self: don't ask a slightly humorous question if hoping for a serious reply.

Whilst ignoring the unusual quantity and variety of nonsense contributed after the useful first few posts, I should clarify that I don't have a trailer, my club doesn't have a lifting hoist or weighing equipment, I only have one set of bathroom scales, and I don't desperately need to know the boat's weight...

...so I reckon the bathroom scales will suffice, especially when the surface beneath the other wheel is made level with the top of the scales. But I don't understand why three sets of scales (for the three points of ground contact) would measure the pressure on each point, more accurately than one set of scales moved between the three adjusted points in turn.
 
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dancrane said:
Note to self: don't ask a slightly humorous question if hoping for a serious reply.

Whilst ignoring the unusual quantity and variety of nonsense contributed after the useful first few posts, I should clarify that I don't have a trailer, my club doesn't have a lifting hoist, I only have one set of bathroom scales, and I don't desperately need to know the boat's weight...

...so I reckon the bathroom scales will suffice, especially when the surface beneath the other wheel is made level with the top of the scales. But I don't understand why three sets of scales (for the three points of ground contact) would measure the pressure on each point, more accurately than one set of scales moved between the three adjusted points in turn.
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Because the weight distribution shifts. For instance, if you kist the jockey wheel, the trailer wheels carry more of the weight.

No matter how the weight is distributed, if you put a scale beneath the jockey wheel and each of the trailer wheels, then add the three weights, that'll be the total weight.

If you want a rough idea, one set of scales will be close enough, especially if you put something close to the thickness of the scales under the two points not being weighed.
 
dancrane said:
Note to self: don't ask a slightly humorous question if hoping for a serious reply.

Whilst ignoring the unusual quantity and variety of nonsense contributed after the useful first few posts, I should clarify that I don't have a trailer, my club doesn't have a lifting hoist or weighing equipment, I only have one set of bathroom scales, and I don't desperately need to know the boat's weight...

...so I reckon the bathroom scales will suffice, especially when the surface beneath the other wheel is made level with the top of the scales. But I don't understand why three sets of scales (for the three points of ground contact) would measure the pressure on each point, more accurately than one set of scales moved between the three adjusted points in turn.
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Because of the levelling problem.
 
Sure, I see that the distribution shifts with angles - but given that my scales are barely one inch in height, and if, with a couple of pieces of one-inch ply, I can equalise the height as I weigh all three points, isn't the result unlikely to differ more than a tiny amount, from the result of weighing all three 'corners' simultaneously?
 
I was going to suggest a long beam with fulcrum. Boat on short end, dancrane tiptoeing along the other end until the boat lifts. Tape measure and maths to find the solution. :-)
 
dancrane said:
...so I reckon the bathroom scales will suffice, especially when the surface beneath the other wheel is made level with the top of the scales. But I don't understand why three sets of scales (for the three points of ground contact) would measure the pressure on each point, more accurately than one set of scales moved between the three adjusted points in turn.
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It won't be more accurate provided the wood stacks are the same thickness as the scales, it just eliminates the potential error of getting the thickness wrong.
 
dancrane said:
Sure, I see that the distribution shifts with angles - but given that my scales are barely one inch in height, and if, with a couple of pieces of one-inch ply, I can equalise the height as I weigh all three points, isn't the result unlikely to differ more than a tiny amount, from the result of weighing all three 'corners' simultaneously?
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It will work but who knows how accurate it would be.
 
Buck Turgidson said:
I was going to suggest a long beam with fulcrum. Boat on short end, dancrane tiptoeing along the other end until the boat lifts. Tape measure and maths to find the solution. :)
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Already been suggested. Plus Dan still needs the scales to find out how much he weighs :rolleyes:
Unless one hangs Dan off a fulcrum with a weight & moves that along to work out dan's weight
Then put the weight on a fulcrum with another weight to work out the weight of that weight. then another fulcrum to work out......... :unsure: :confused:
 
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The long beam and fulcrum is a nice idea, makes me think of an old-fashioned schoolmaster trying to instill an interest in physics in the unruly boys. Possibly Will Hay, somehow seated on the outer end, and the whole set-up spinning round and round to loud cheers that drown his protests. ;)
 
dancrane said:
The long beam and fulcrum is a nice idea, makes me think of an old-fashioned schoolmaster trying to instill an interest in physics in the unruly boys. Possibly Will Hay, somehow seated on the outer end, and the whole set-up spinning round and round to loud cheers that drown his protests. ;)
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If we did it with Dan he might be burned at the stake for being a witch, if he weighs same as a duck.
python witch sketch
 
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