As it happens, I have just been working on a future thread, of which this is a part of.
To calculate the density of an unknown sample of wood:
Chop off a sample piece. Size or shape is not important. However, the larger the sample, the more accurate the data.
Attach pure lead to achieve neutral buoyancy (just below the surface).
1. Accurately weigh the sample+lead, in grams.
2. Accurately weigh the lead only, in grams.
One gram of water occupies a volume of one centimeter cubed. Therefore, the volume of the sample can be calculated, knowing that the density of pure lead is 11.389gm/cm³.
3. Calculate the volume of the lead by dividing the weight of the lead only by 11.389
4. Calculate the volume of the sample by subtracting the volume of the lead from the weight of the sample+lead weight.
5. Calculate the weight of the sample by subtracting the weight of the lead only from the weight of the sample plus lead.
6. Calculate the density of the sample by dividing the weight of the sample by the volume of the sample.
Now I've got a headache, as I suspect anyone else reading this has.
But from the information you have given above, I calculate a density of 0.55gm/cm³.
To calculate this, convert all your figures to metric (grams and centimeter cubes). Divide the weight by the volume.
This figure is very high for balsa, which is normaly about 0.12gm/cm³.