Select to expand quotehoop 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
Select to expand quotestehsegler said..
Another method is to read the label with the boards specs that the manufacturer printed onto the board.
No. That's just silly. Why would anyone want to do that? 
Select to expand quotehoop 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.
Select to expand quotepweedas said..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
"You will need about three people to do the test to fill the bucket and make sure it all stays upright"
Yes, that makes a lot of sense now. That was what happened when I tried to learn windsurfing. Two of my friends to stop the board from flipping over, and one friend to hold the tail to stop me from taking off. Mind you, it was about 2 knots of wind then. I actually suggested to glue the mast upright, just like a sailboat. They thought I wasn't very bright 
Select to expand quotehoop 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**"
rub a dub dub
three men holding a tub
the butcher, the baker
the carbon-poley maker
then they all sailed out to sea 
so, has anyone tried the three(3) man bucket tip ??
results ??
too much ice n carp here ...
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.
Select to expand quotehoop 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.
In terms of the stated volume on boards is it not related or meant to be related to the floating characteristics ? or are you using special foams or something that will give a 100 litre board floatation of a 120 130 140 polystyrene liters 
or is this related to weight,,, reducing weight to increase floatation ............
Does carbon / fiberglass differ greatly to the floatation for a board..............guessing a large boat / ship it would
Jumping around on a great variety of SUPs stating their volume has lead me to this conclusion
100 litre volume ( polystyrene fiberglassed or skinned with say 4 to 6 oz all over ) = 100kg of weight to be able to just float on, you will be super unbalanced at 29 inch wide and struggle to stay upright, if you then add 20 to 25 litres to your given weight at 30inches you can stand in some sort of comfort ..........more litres and width from there, the easier it is to stand relaxed
Hmmmmmmmmmmm i feeling half human half beast 
Select to expand quotehoop 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'm still concerned about the floating poo.... surely water density plays a role... so what about the dark "Johnson" blue water or even the greenish one if you pee before dumping it ??
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
Select to expand quoteseanhogan said..
I'm still concerned about the floating poo.... surely water density plays a role... so what about the dark "Johnson" blue water or even the greenish one if you pee before dumping it ??
I can't answer that right now.
I'm still waiting on some urgent feedback on all this from our man in canada.
But you can take some comfort now that there is an international effort to get to the bottom of it all.
Select to expand quotehoop 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.
Select to expand quotepweedas said..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.
100 Litres is the actual volume of the board. If you are to "fully" submerge the entire board in a fluid, it will displace 100 Litres of fluid. However, if the board is only partially submerged, or it is a 'floater", the displaced fluid will equal to the volume below the fluid line. Lets say about 60% of the 100 Litres board is below the water line, 60 Litres is the displacement of the board.
Of course, it all changed when you are on a plane. The displacement is almost negligible.
Select to expand quote
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
Select to expand quoteJupiter said..pweedas said..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.
100 Litres is the actual volume of the board. If you are to "fully" submerge the entire board in a fluid, it will displace 100 Litres of fluid. However, if the board is only partially submerged, or it is a 'floater", the displaced fluid will equal to the volume below the fluid line. Lets say about 60% of the 100 Litres board is below the water line, 60 Litres is the displacement of the board.
Of course, it all changed when you are on a plane. The displacement is almost negligible.
Yes, my understanding is that volume and displacement would be exactly the same, if you sink the board completely.
The problem here seems to be one that has been around for years in our industry and that is the difference between volume and "buoyancy" .
The real thing we want to know is how buoyant the board is (can't seem to add the link to the Wikipedia article on buoyancy, but it is good). Some of my really old boards have a buoyancy warning printed on them. I don't know why the convention for windsurfing boards is to talk about volume? Perhaps it was easier to measure than buoyancy and gives a reasonable indication of how 'floaty' a board is?
To measure how much floatation (buoyancy) a board has (or a turd, to keep on topic) all you need to do is rig a scale so you can pull down on it forcing the board down in some water until it sinks. Of course water density counts here so just like when sailing, my board is more buoyant in the sea than a fresh water lake.
(I feel like I haven't paid enough attention to the density of crap in my answer or considered the implication of the body of water being frozen in Canada.)
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
Select to expand quoteJupiter said..pweedas said..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.
100 Litres is the actual volume of the board. If you are to "fully" submerge the entire board in a fluid, it will displace 100 Litres of fluid. However, if the board is only partially submerged, or it is a 'floater", the displaced fluid will equal to the volume below the fluid line. Lets say about 60% of the 100 Litres board is below the water line, 60 Litres is the displacement of the board.
Of course, it all changed when you are on a plane. The displacement is almost negligible.
That sounds logical, and now that I think about it, I have heard of ship capacities being measured as a displacement figure. e.g. "the ship has a maximum displacement of 50,000 tons." meaning combination of ship weight and load displaces 50,000 tons of water, be it fresh, salty, frozen, or full of carp.
I don't think boards are sold that weigh (or way) though. You have to make the rough calculation yourself when you select a board volume of 'your weight plus 20 liters', depending on how you are going to use the board of course.
Select to expand quoteMan0verBoard 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.
Select to expand quotestehsegler said..
Another method is to read the label with the boards specs that the manufacturer printed onto the board.
Reading this thread, I deem
stehsegler's method to be the easiest, but presumably duncanlax's board has no label?
2nd - rwg's theodolite method.
notwal's method has the inherent problem of not being able to read the scale once a large bucket is placed on it...
MOB 's large tank method has potential but finding a large rectanglar tank of suitable dimensions is problematic.
Thinking along similar lines though, this may be more practical.
Soften up a patch of sand on the beach and level it.
Push your board in half way, then in an adjacent patch of sand turn the board over and press it in to the same level. Using a container of known volume fill the depressions with sand until the surface is level again. Add up the volume of sand used.
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 !
When you are thinking of buoyancy, then it is definitely about displacement. Mind you, boards of different designs have different shapes. Some have more volume at the front, some in the middle, and some at the back. It of course will depend much on where you stand on the board.
Lets say you have a "centre of mass" somewhere in the middle, and you place the equivalent amount of weight of yourself, and the rig combined over it, the volume of fluid displaced will be your buoyancy measure.
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.
If you could find a fish tank long enough you could fill it with water to the brim and only sink one side (half) of the board to the middle (stringer line). Times the tank's surface area with depth of water displaced and times by two and voila, you have the volume. That said, Hoop is right as the density of the material is the critical component to its floatation capacity.
Other than a fish tank you could build a watertight plywood box say 40cm high 2400 long and about 25cm wide - it'd do boards up to 80cm wide.
Easier still would be a 44 gallon drum (modified to 1200 high). Dunk one end of the board and times depth displaced by area and then repeat for other end. then add volume of the two ends together
Select to expand quoteshoodbegood 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.
How about cutting up the board into short pieces, and submerge the pieces in a small fish tank? Sure you will need to number each piece so that you can put them back as one. A bit tricky in the last operation 
Worth the try ...
