Now that I've read thru this thread, I'm still not sure which kind of board this discussion would be referring to, if any, but this is the WS side of the site.
Should volume include weight in some sort of way? Seems to be the main question. Well that depends.
In windsurfing it sure does, you can have two identical boards, made by the same company, one carbon, and one epoxy sandwich or something similar, with identical volume, but the carbon board weighs measurably less.
The carbon board will sail much faster, less friction, it's the way it is, so the volume is only part of the story.
So just how bad do you really need to know only the volume? As compared to what?

That's all I know, I will now return the control over to the rest of the pack.

joe windsurf said..
asked on the Fanatic and StarBoard forums to see if we get any more "interesting" comments
non, not about ice n carp

Thierry on the SB forum agreed with my original idea

Farlo on Fanatic forum had one that i had not hear of yet:
"Take a spring dynamometer, attach it to the board and sink it totally. You must have some sort of anchor or ring in a place deep enough, preferably a pool. As the board wants to float, it will pull with a force equal to its volume (in liters) less its weight (in Kgs). This may require a few meters of rope. Don't forget to close the vent screw..."

You will still have to take into account the weight of the board for the same reason as I said earlier.
If the board weighs 110 kg and has a volume of 111 liters, then it will take a force of 1 kg to hold it down, and clearly, the board does not have a volume of 1 liter.

If you include the weight of the board, then it will give the right answer. (Neglecting salt and/or carp content)

{edit} oops,.. I just read it more carefully and you have already included that in your reply.
"less its weight (in Kgs)" So now I agree entirely,..because it's what I said right back on page 1 , except that it make no allowance for carp.

TheSailingMoose said..
Take a suitable person (Mark?), someone who is full of hot air for natural buoyancy but also sufficiently full of s*** to weigh the board down.

Sorry for whatever I must have done to insult you, and good luck with the rest of puberty