This wood, I think: hardwood Is a wood so hard that you wear out drill bits trying to drill through it. It also is heavy and would sit lower in the water increasing stability. I don't know if it was possible that Noah had access to wood like this.
Think about this for one second would you... If it is so tough to work with today's modern wood working technology Noah would have had no chance.
That and for a craft the size of the ark the wood would have to be easy to work and in plentiful supply. Ebony is expensive because it isnâ€™t that common.