Select to expand quoteImax1 said..decrepit said..forceten said..
Sinking the board seems simple enough. How then to measure the water displaced ?
You could overflow the tank, wait for it to finish dribbling, then catch and measure all the water displaced by he board. Or have marks on the side of the tank.
Or instead of catching the water , take the board out and measure how many liters to fill it again.
I like this 3 large beers , several scotch , and 2 tequila and all.
The idea of sinking the board in a tank and measuring the volume of water has merit. But who has a tank that would take a board? I guess you could use a long skinny tank and sink the board sideways to the centreline.
Measuring the volume of cuboids is easy enough to do and all you need is some straight edges and squares and a ruler. Normally you would do one width and thickness measurement at each point along the centreline. There's no reason why you can't take lots of measurements at lots of points. It's not hard to do.
^ Local farmer may have stock watering trough large enough. As long as its not an RB to be tested.
Or make a 4x2 frame n a tarp to make a trough large enough. Relatively cheap. Had a fish pond built this way n it lasted years before it leaked.
Imax1, Whatchu got in that beer mate? So you want to hold the barbell n stand on the board until it just sinks?? Id like to see that!!! 
I imagine it like a Benny Hill moment.....
Dude, just lay the weights all over the deck til it just sinks.
Select to expand quoteforceten said..
Sinking the board seems simple enough. How then to measure the water displaced ?
You don't. You measure the weight required to sink it.
1 litre = 1 kg
The way to do it (IMO) is to put it in a swimming pool upside down. Put a big green plastic bin on it. Fill the bin from the garden hose until the board sinks. Mark the level on the bin. Tip the water out. Put bin on scales. Refill up to the mark. You might have to suspend it from a hanging scale in which case you need to take care not to distort the shape of the bin. Add the weight of the board to the scale reading. Call kg litres.
Select to expand quoteolskool said..
Imax1, Whatchu got in that beer mate? So you want to hold the barbell n stand on the board until it just sinks?? Id like to see that!!! I imagine it like a Benny Hill moment.....
Dude, just lay the weights all over the deck til it just sinks.
Just saying , it be fun to watch
Select to expand quoteNotWal said..forceten said..
Sinking the board seems simple enough. How then to measure the water displaced ?
You don't. You measure the weight required to sink it.
1 litre = 1 kg
The way to do it (IMO) is to put it in a swimming pool upside down. Put a big green plastic bin on it. Fill the bin from the garden hose until the board sinks. Mark the level on the bin. Tip the water out. Put bin on scales. Refill up to the mark. You might have to suspend it from a hanging scale in which case you need to take care not to distort the shape of the bin. Add the weight of the board to the scale reading. Call kg litres.
Provided it is pure distilled water at sea level and 20 deg.
But I'd rather watch olskool balancing on his upsidown free ride , naked , with a bucket of water
Or....
you could climb onto your board , ( minus the fin ) , in six inches of water holding a big bucket of water . Slowly tip the water out. When the board starts to float and go sideways note how much water you have poured out before falling and snapping the wrist that you just fell on.
Or if ou have a tank of water, probably an old oil drum would do, just stick it in nose first to the half way point measure water level then stick it in tail first to half way and measure the water level, add the to up and done. Easier than sinking the whole board at once and uses a small tank
Select to expand quotetryharder said..
Or if ou have a tank of water, probably an old oil drum would do, just stick it in nose first to the half way point measure water level then stick it in tail first to half way and measure the water level, add the to up and done. Easier than sinking the whole board at once and uses a small tank
I think , NOT taking the piss, that this does make sense to you. I appreciate the suggestion, but it makes little to me.How are you measuring the water.
EDIT: I was thinking you have the barrel sideways, ahhh its right side up , so the measure is easy on the inside of the drum, submerging the board I think will be fun, and then to measure the displaced water.
umm
Select to expand quoteforceten said..tryharder said..
Or if ou have a tank of water, probably an old oil drum would do, just stick it in nose first to the half way point measure water level then stick it in tail first to half way and measure the water level, add the to up and done. Easier than sinking the whole board at once and uses a small tank
I think , NOT taking the piss, that this does make sense to you. I appreciate the suggestion, but it makes little to me.How are you measuring the water.
EDIT: I was thinking you have the barrel sideways, ahhh its right side up , so the measure is easy on the inside of the drum, submerging the board I think will be fun, and then to measure the displaced water.
umm
Yes right side up, submerging the board wouldn't be do hard as your only doing half at a time so problably only need 50-60kg or put it in when empty, tie it down then fill with water, take board out and see how much the water level drops.
Select to expand quoteNotWal said..forceten said..
Sinking the board seems simple enough. How then to measure the water displaced ?
You don't. You measure the weight required to sink it.
1 litre = 1 kg
The way to do it (IMO) is to put it in a swimming pool upside down. Put a big green plastic bin on it. Fill the bin from the garden hose until the board sinks. Mark the level on the bin. Tip the water out. Put bin on scales. Refill up to the mark. You might have to suspend it from a hanging scale in which case you need to take care not to distort the shape of the bin. Add the weight of the board to the scale reading. Call kg litres.
How about using the weights off the weight bench that never get used for anything else, place them on the hull of the board until it sinks. This may have to wait till summer when you can brace it while standing next to it so the weights don't fall and hit the pool edges or bottom. 1kg = 1 litre, Still can't understand how you get the swimming pool upside down
Geez people, so many methods.
You are missing the easiest one for sure.
Open the vent screw, and use a funnel to slowly - very slowly - pour in petrol and see how much it takes.
Select to expand quotejoe windsurf said..
don't forget to light it ... 
Is there a way to measure burnt toxic fumes to find out volume ?
I usually freeze the board in a large rectangular ice cube. Measure the ice cube then chip off the ice in chunks. Because the ice is in chunks it is easy to measure on a normal scale. Take the original length x height x width of the ice cube and then deduct the weight of the ice. Because water expands when frozen you need to divide your end result by 1.09.
Get a discarded board box in a reasonable state from your local windsurfing shop that's big enough for your board. Put the board in it and fill the rest with sand. Measure the sand's volume or weigh it and devide it by the weight of 1 litre of sand. Calculate the volume of the box as lengthxwidthxdepth. Volume of board = vol. of box - vol. sand.
Try not to distort the shape of the box when filling with sand and pack the sand as tight as you can.
Haven't tried the above, so it is just a theoretical solution
^^^ I like that but sand does not completely fill it.
I reckon look at the manufacturer's measurement for boot space in your car- or even better a friend's car.
Put your board in, cut into sections if need be, then use a measured amount of epoxy to fill the rest. The math should be easy.
Select to expand quoteSparky said..
Read the farkin number on the side of the board!
2 boards , one I modified from its original , cut nose, added a different shorter nose /shape ,rails changed, tail reworked. The starting volume was known. The guess is to use the removed amounts, seat of the pants educated guess. Board 2, is a Maui custom that has no volume shown, for customs this is typical, bought used from 2nd owner.
Once better established I will crayon the volume on the side .
Run the board through a wood chipper a few times then measure the volume of the powder with your mum's measuring jug.
Don't do it on a windy day.
Select to expand quotejoe windsurf said..
when i got my first board - BIC Dufour
i tried to calculate the volume based on measurement
joewindsurfer.blogspot.com/2008/10/sailboards.html
here is an exerpt
-------------------------
Nowadays that should NOT be necessary. Information is posted directly on the board.
Older boards or custom boards did not have data on the board.
Since my BIC Dufour was received before much internet and after it's popularity - so, NO info in the mags, i did a calculation of the volume at that time ...
It may be fairly obvious that volume is area and not weight, butt i wish to stress the obvious just the same...
Let me see if i can dig up my calculations :-)
First I broke the board down into sections and used the theory that a circle would reflect the shape of the board - this yielded a volume of 462 liters = obviously way OFF.
Next looked up the area of an oval which is length times width times 0.8
Again broke the board up into sections and came up with a figure of 157 liters. This is a little more reasonable, butt obviously low. It looks much bigger than my 160 liter short-board !!!
The closest approximation was using the simplest method. The board is 378 cm long, 68 cm wide and 11.5 cm thick. These values are all at the longest, widest and thickest points. If we assume the board was a block then 378 * 68 * 11.5 = 295.6 liters. Now we know it is not a block and if we assume it is more like an oval shape from the top, then 295.6 * 0.8 = 236.5 liters. We are already approaching more realistic numbers. We know that the board is also shaped. Since the board is NOT a lean mean machine, then perhaps we can apply the oval logic i.e. use a 0.8 factor. So 236.5 * 0.8 =189.2 liters. This number is only 5 % off the figures literature has given me - namely 200 liters.
So, i would simply use this method to estimate volume of a board in the future.
Length in cm * width in cm * thickness/height in cm * 0.8 (for oval) * 0.8 (for shaping) / 1000 (to give liters)
Will try this approach with the modern 160 short-board to test validity.
Length = 268 cm
Width = 79 cm
Height = 10 cm
So, 268 * 79 * 10 * 0.8 * 0.8 / 1000 = 135.5 for a 160 liter board
This is a larger margin of error 25/160 * 100 = 15.6 % error.
The problem here is there is a significant difference between a 135 and a 160 liter board.
How can we adjust for that and where is the error coming from ?
My original estimate for thickness was 13 cm and adjusted to 12. When i looked from the side, i put 10 cm.
If i put 12 cm as the thickness check out the results !!!
268 * 79 * 12 * 0.8 * 0.8 / 1000 = 162.6 liters
WOW - cannot get much closer than that...
2.6/160*100 = 1.6 % error ONLY
This shows that the thickness MUST be evaluated CAREFULLY...
I had time today to study this JOE. Using your formula . On a known 105L boards from the factory( yes we are aware that the factory quotes are not 100% accurate )
This came out to 101
The thickness varies from 10.5 to 6.4, using 5 measures with a digital caliper , the average was 9.142.
A 3.8 % less than quoted.
I have to say this is/was by far the easiest to do, any I'm extremely happy with the results .
Greatly appreciated.
To expand on water solutions: I'm going to engage a Huey Chopper from the nearby base, to drop a board from 500AGL, and be positioned in such position to measure displacement . This could serve a secondary purpose , checking the effectiveness of my helmet, further the promptness of my life insurance to pay my bride.
Carry on, and the door may not hit you in the arse.LOL...several smiley faces 
I'd simply suggest comparing float with other boards of similar size. Ideally find a slightly bigger one and a smaller one.
Select to expand quoteManuel7 said..
I'd simply suggest comparing float with other boards of similar size. Ideally find a slightly bigger one and a smaller one.
Simple was to measure the test board and compare similar length and width to others, then compare several of the same dimensions and volume.
using this method above the Nelson Custom board was 82L, using Joes its 81L .
Select to expand quotebhc said..
Get a discarded board box in a reasonable state from your local windsurfing shop that's big enough for your board. Put the board in it and fill the rest with sand. Measure the sand's volume or weigh it and devide it by the weight of 1 litre of sand. Calculate the volume of the box as lengthxwidthxdepth. Volume of board = vol. of box - vol. sand.
Try not to distort the shape of the box when filling with sand and pack the sand as tight as you can.
Haven't tried the above, so it is just a theoretical solution
Doesn't matter if the box distorts it won't affect its volume.
Select to expand quotetryharder said..bhc said..
Get a discarded board box in a reasonable state from your local windsurfing shop that's big enough for your board. Put the board in it and fill the rest with sand. Measure the sand's volume or weigh it and devide it by the weight of 1 litre of sand. Calculate the volume of the box as lengthxwidthxdepth. Volume of board = vol. of box - vol. sand.
Try not to distort the shape of the box when filling with sand and pack the sand as tight as you can.
Haven't tried the above, so it is just a theoretical solution
Doesn't matter if the box distorts it won't affect its volume.
Have you done this ?
Displacement method, from magicseaweed.com/news/the-guild-factor-will-help-you-find-that-magic/10280/
