hoop said..
For the method of sinking the board and weighing the amount of water used to sink it, yes you need to take the weight of the board into account.
Volume is still just volume though. The weight of the object has nothing to do with volume.

That's true, but the cheapest way we have of measuring the volume is to apply the simple correlation between weight and volume of something, and as it happens, we know quite accurately what the density of water is. It's one gram per cc, or 1kg per litre.
So since we can't measure the volume of the board easily due to it's complex shape, we can simply find how much weight it takes to only just sink the board.

The bucket doesn't have to be filled with water. It can be filled with anything, housebricks, beach sand, and Joe windsniffer can even use buckets of carp. It doesn't matter so long as we can weigh it afterwards

However, if he uses carp, he will have to lift the whole lot out of the pool and lift it onto the scales, because the rest of the family will chuck a wobbly if he dumps it in the pool., specially as his is frozen and it will sit there all winter for the neighbours to see.

Also,.. he has already said he can't lift 160 kg. Neither can I.
So the good thing about using water is, just measure the level and then tip it out.
If you used house bricks, you could load them up and then unload them and count them, then put the same number back in when the bucket is on the scales.

One problem which hasn't been mentioned is, when the board is close to fully loaded, it will be really hard to keep the whole lot upright. Loading boats of any description to the maximum usually has the tendency for the boat to turn upside down and tip the load into the water.
You will need about three people to do the test to fill the bucket and make sure it all stays upright

hoop said..
It seems some people are getting confused between volume and flotation. Forget boards for a little while. You have 2 cubes 1metre x 1metre x 1metre.
They don't have to do anything they're just cubes. 1 is made of polystyrene and 1 is made of lead.
The volume of both is 1000 litres.

yes

succinctly stated.

hoop said..
Volume is volume. It has nothing to do with weight.

Weight is important because the board is already displacing its own weight in the water. A 100L board that weighs 5kg will only support 95kg (in fresh water) before submerging.

Lol logs,boards,flotation
Finally gives meaning to the old saying, "This board sails like a piece of sh**"

No. Not tried yet.
We're all waiting on you reporting back on the flotation properties of canadian carp.
We don't want to start the test off with any wrong input data.

hoop said..
Volume and displacement are two completely different things!

I was hoping someone would ask, but none have, so,.. what is the difference?
I would have thought a 100 liter board volume had a displacement of 100 liters.

I dont know anymore ,,,,,,,,,

,if you got chick leg wobbles and an arched hump back and fall off all the time you need more volume and and width

if your doing the walk of shame back to the car park, from down wind, when the wind drops 10 knots you need more volume and width

I carnt do this anymore

Whats the weight of 1 litre them ...........of salt / fresh and toilet water

^^^ if I were u, I'd say that I referred to displacement of an unweighted board in a pool

hoop said..
God damnit! I've talked myself into a corner now.

Just say it's because of the troposphere. Nobody will question that because they don't want to sound dumb.

Of course, it all changes when you are on a plane. The displacement is almost negligible.

Not if you have the privilege of a really fat person being seated next to you on a plane - their displacement definitely isn't negligible

The only two practical ways you can accurately measure the volume of a physical board(as opposed to a design file) are to;

A) measure the displacement by submersion into a vessel of vertical sides then calculate the surface area of the water and multiply by the height of the displacement. You may have to do this in two halves of the board either in length or width to avoid struggling with the board or having to find a huge vessel to contain the water.

B) survey the board with a laser, plot and calculate.

Measuring the flotation requires you to measure the weight of the board and subtract that from the measured volume. This is the sum of the weight the board will support in fresh water before sinking.

Fresh Water is considered to have a density of 1000 kg/m³ and sea water 1025 kg/m³. Therefore objects of equal volume and weight will be more buoyant(you do the math) in Seawater - its about 1 quarter of 1%(edit) 2.5% more buoyant - or a squids fanny hair laymans terms.

Buoyancy in water is also variable in different water temperatures - below are the categories of water temperatures used by Lloyds Register of British & Foreign Shipping(again I'll leave you to calculate in accordance with your local region) Warmer water is less buoyant hence on a ship the TF watermark will be highest and the WNA will be lowest(lowest displacement = highest flotation)


TF – Tropical Fresh Water
F – Fresh Water
T – Tropical Seawater
S – Summer Temperate Seawater
W – Winter Temperate Seawater
WNA – Winter North Atlantic

Simples

Man0verBoard said..
The only two practical ways you can accurately measure the volume of a physical board(as opposed to a design file) are to;

A) measure the displacement by submersion into a vessel of vertical sides then calculate the surface area of the water and multiply by the height of the displacement. You may have to do this in two halves of the board either in length or width to avoid struggling with the board or having to find a huge vessel to contain the water.

B) survey the board with a laser, plot and calculate.

Measuring the flotation requires you to measure the weight of the board and subtract that from the measured volume. This is the sum of the weight the board will support in fresh water before sinking.

Fresh Water is considered to have a density of 1000 kg/m? and sea water 1025 kg/m?. Therefore objects of equal volume and weight will be more buoyant(you do the math) in Seawater - its about 1 quarter of 1% more buoyant - or a squids fanny hair laymans terms.

Buoyancy in water is also variable in different water temperatures - below are the categories of water temperatures used by Lloyds Register of British & Foreign Shipping(again I'll leave you to calculate in accordance with your local region) Warmer water is less buoyant hence on a ship the TF watermark will be highest and the WNA will be lowest(lowest displacement = highest flotation)


TF ? Tropical Fresh Water
F ? Fresh Water
T ? Tropical Seawater
S ? Summer Temperate Seawater
W ? Winter Temperate Seawater
WNA ? Winter North Atlantic

Simples

I agree with all that,.. except, the size of the squid needs mentioning.
From the density of sea water which you quote, and which appears correct, that makes the ratio (1025/ 1000 X 100) -100 = 2.5% higher flotation in sea water.
That would require a very large squid and not one we are familiar with. Perhaps in canada?

That would also be consistent with the difference I have noticed when swimming in salt water vs fresh water. Fresh water is noticeably less buoyant than salt water, more consistent with 2.5% rather than 0.25%.


Also, the categories you list above omit the newest addition 'WWC' , which is 'Water with Carp'.
It's a recent canadian initiative.

I agree the most rational person in a case like this is Barn (Mark second by a nose), where are you son ????
Sea Breeze needs you !

I'm still sticking by my point that volume is just volume. It's not displacement and it's not weight.
I've used a few different techniques to determine the volume of boards . 1st one is a volume tank. Similar to Man Over Boards idea. It's a rectangular tank with measurements on the side and a power assisted winch to pull the board under the water. Very simple and effective.
The second one is to take offsets and or templates and punch the numbers into a programme like Akushaper or Shape 3d and it will give you the volume.
The third one is to hold the board up, shut one eye and stick your tongue out and say I reckon that's about 83 litres. Probably not as accurate as the first 2 but you get reasonably good at it after a bit of practice.

shoodbegood said..
I agree the most rational person in a case like this is Barn (Mark second by a nose), where are you son ????
Sea Breeze needs you !

Barney has been doing a lot of slalom sailing lately.




Today I heard that he joined the GPSTC and bagged a swag of PBs.
He shouldn't be long now,he's still walking his board upwind.