Quote Originally Posted by qwertyxsora View Post
but not all of the wood displaces water.
What do you mean?

Just dunk one hundred percent of it under water. Measure the displaced volume of water. Then divide the mass of the wood by that volume. Its really not that hard.

(The water absorbed by wood should be negligible - If you want, you can cover it with something and work out the volume displaced by the cover and then minus that from the total displaced volume. But thats only if you have to be very accurate)