Weighing things on board

[TheWilk]

I have a Saturday night conundrum for you.

 

I'm on a diet and so I could do with both kitchen scales and bathroom scales. But now my mind is broken trying to figure out if these will work on board a boat. Bear in mind I'm moored in a deep coastal dock so I move around a fair old bit.

 

Obviously the old style balance scales wouldn't work because I'm never level. I'd like some high tech electrickery scales but I have no idea on what principle they work. The only scales I think will be foolproof are those fisherman's ones that you hang stuff from, which might be ok for weighing food but I think I'd have a problem suspending myself from one...!

 

So can anyone with a better mind than me advise? Or failing that, if you have bathroom scales on board and a spare person, could one of you weigh yourself and the other one go outside and rock the boat, in the name of science?

[Barry]

Get some posh scales, keep them on the boat, use them on the dock side

 

Job done and all your neighbours entertained - sorted

[Paul's Nulife4-2]

Hi ya,

Very simple solution,I think you've over thought the problem.

Forget the diet, get rid of any on board mirrors,Donuts are good for you. The Strawberry jam ones surely count as one of your 5 day,& use the hanging fishermen type scales for weighing the food,if you must.

Good luck.

 

By the way,,where are you currently moored, just being noisy.

Edited March 15, 2014 by Paul's Nulife4-2

[Guest]

You weigh what you weigh.....

 

You don't weigh any less if you weigh yourself on a boat...

[TheWilk]

Get some posh scales, keep them on the boat, use them on the dock side

 

Job done and all your neighbours entertained - sorted

 

I'm in a marina on floating pontoons... it'd be a bit of a walk every time I wanted to weigh out some pasta!

[bottle]

I'm on a diet

 

Is this the one week, one month, one year or the rest of your life diet.

 

Now to get serious, I would think that any 'bathroom' scales would work, if you stand still, the difference, if you get thrown about by gale force winds etc, would be easily noticed whilst standing on them, just take an average or wait until it's not choppy.

 

All scales need to stand on a hard, solid surface not carpet.

 

As for weighing food I use the good old fashioned balance beam scales, I am on the canals though but someone walking around and rocking the boat is not a problem.

[Theo]

thing tovto get to grips with is what you are really trying to measure. You want to work out how much stuff you are eating. This means you are trying to measure mass, not weight. Weight is the force of gravity on a mass and is proportional to mass so if the gravitational field strength is constant and it pretty well is as long as you remain in conditions of zero acceleration on Earth, you can use a force measuring machine to measure mass. Pretty well all normal weighing scales do this.

 

OK so far?

 

Now to keep to conditions of zero acceleration you need constant velocity. Can you achieve this? Most of the time it will be pretty easy because your constant velocity can be zero. As long as you are not bouncing up and down there will be nothing to accelerate the scales.

 

The NE consideration is that of angle to the gravitational field. The error due to heel or trim will increase with angle.

 

Displad mass = actual mass x sine of the angle of heel or trim.

 

 

 

 

 

 

 

ctual mass = actual mass x sine of the angle.

[dmr]

You could get a tape measure and measure how much the boat goes down in the water when you get on.

Actually this sounds rather rude, perhaps a vernier might be better?????

 

If you can get a fishermans type scale that reads high enough then you can indeed weigh yourself by hanging from it. This is useful because its good exercise which is a good way to loose weight. Trouble is you might end up with arms like popeye.

We had a balance like this where I used to work (for weighing engines) and we regularly weighed ourselves with it.

Seriously, the little electronic balances are great for weighing food and lots of other boaty things too. Do you know how much a lump of coal or log for the fire weighs????

 

..........Davei

thing to get to grips with is what you are really trying to measure. You want to work out how much stuff you are eating. This means you are trying to measure mass, not weight. Weight is the force of gravity on a mass and is proportional to mass so if the gravitational field strength is constant and it pretty well is as long as you remain in conditions of zero acceleration on Earth, you can use a force measuring machine to measure mass. Pretty well all normal weighing scales do this.

OK so far?

Now to keep to conditions of zero acceleration you need constant velocity. Can you achieve this? Most of the time it will be pretty easy because your constant velocity can be zero. As long as you are not bouncing up and down there will be nothing to accelerate the scales.

The NE consideration is that of angle to the gravitational field. The error due to heel or trim will increase with angle.

Displayed mass = actual mass x cosine of the angle of heel or trim.

 

Corrected cos it's cos not sin.

 

Are you sure its not the Cos ?????

Edited March 15, 2014 by Theo
Cos not sin

[Theo]

Aaargh

 

Blooming tablet! It confuses me and now I have edited the wrong post. Moderating powers have gone to my head.

 

N

To conclude the stuff what I was writing...

 

The angle is important so keep the boat level but don't worry too much. An angle of 10 degrees will still give readings 98.4% accurate, and 10 degrees is a huge angle of list.

 

Bizzard would tell you to use oil damped scales to overcome the problems of bouncing up and down. That discussion can come later.

 

N

[Bettie Boo]

I have a cheap and cheerful set of electronic kitchen scales for cooking which seem to work just fine.

 

As for bathroom scales I haven't had a set in years, but when trying to loose weight; if the jeans are getting loose, I know I'm succeeding, if they are getting snug I need to consume less caramel iced Doughnuts

[Wanted]

Get a large jar and on dry land weigh out all of the standard things like rice, pasta etc. mark a line on the jar with a sharpie and lable it. Job done.

 

Forget weighing yourself and start to measure your waist instead, I gauge my self on trouser size and ability to do up top button!

 

Good luck with it all

[john6767]

We have both bathroom and kitchen scales on the boat, they are just old ones from home and a both are electronic ones. I can't see why there would be an issue in using either on a boat, although they will not be perfectly level, so that will introduce a small inaccuracy. As the electronic ones use strain gauges and not springs I would have thought they would be more tolerant if that is what you are concerned about.

[Paul's Nulife4-2]

I have a cheap and cheerful set of electronic kitchen scales for cooking which seem to work just fine.

 

As for bathroom scales I haven't had a set in years, but when trying to loose weight; if the jeans are getting loose, I know I'm succeeding, if they are getting snug I need to consume less caramel iced Doughnuts

Oi,,

Leave them alone,,,

[Bettie Boo]

Oi,,

Leave them alone,,,

hehehhehehe

 

and you were suspicious of your dog

[Paul's Nulife4-2]

hehehhehehe

 

and you were suspicious of your dog

Actually,I thought I saw your dog on my boat this time yesterday !,,& Ive just noticed a suspicious white patch on your dogs nose, YES,,You can run,,PUPPY!.

[nicknorman]

You will never get an accurate weight on a boat because depending on how heavy you are, the boat will sink a little more or less when you step on board. This moves you nearer or further from the centre of the earth and thus affects the local gravity. So in order to work out how much the boat moves down when you step on board, you need to know your weight, and in order to know your weight you need to know how far the boat moves down when you step aboard. It is Heisenberg's uncertainty principle for fatties!

[cereal tiller]

You will never get an accurate weight on a boat because depending on how heavy you are, the boat will sink a little more or less when you step on board. This moves you nearer or further from the centre of the earth and thus affects the local gravity. So in order to work out how much the boat moves down when you step on board, you need to know your weight, and in order to know your weight you need to know how far the boat moves down when you step aboard. It is Heisenberg's uncertainty principle for fatties!

Sounds more like Kronenburgs theory Nick,dates right back to 1664?

[Paul's Nulife4-2]

So,,do light beers,weigh less,,& therefore even lesserer on a boat on the coast,& lessererer on a boat on the canal !

[ditchcrawler]

Should I have a Plimsoll Line on my Narrowboat?

 

[RLWP]

We have both bathroom and kitchen scales on the boat, they are just old ones from home and a both are electronic ones. I can't see why there would be an issue in using either on a boat, although they will not be perfectly level, so that will introduce a small inaccuracy.

 

Multiply by the cosine of the angle of tilt, I think

 

Cosine 1 degree is 0.9998, or an inaccuracy of 0.02%

 

to get a 1% inaccuracy, you need the boat to be 8 degrees off. If you've got a tilt of 8 degrees you'll be worried about much more than your weight

 

Richard

[Paul's Nulife4-2]

I think she only needs to weigh her pasta & cerial portions out !.

 

But I use the above method to tell me when my Cider seller (Bilge) needs re stocking.

[mark99]

Yes Nick - funny enough if you stand in a bucket on board and pull the bucket handle real hard you can levitate.

[Paul C]

Its a pretty simple conundrum. Simply weigh yourself during the rough seas etc, and at the same time weight a reference mass of known weight eg a 10kg weight. When you make an instantaneous reading which you suspect is influenced by the boat's movement, also make an instantaneous reading of the reference weight and use it to calculate the relevant correction factor. You'd need to weigh both you and the reference object near to one another, to get the same (relative) accelerations on each.

[TheWilk]

Well I went out and bought some scales today. It's pretty blowy and I'm bouncing around quite a bit. This is what happened...

 

 

If finally seemed to come to rest at 61g. Then I went all the way up to the marina building and weighed it again (ignoring funny looks) and it came out as 59g.

 

Not bad for what I need I suppose, I'm not a very good cook anyway, it always comes out burnt. I just better not start dealing crystal meth.

[davey b]

I just better not start dealing crystal meth.

 

Were you planning to? Boating can be expensive but....