How to make airship?

I'm thinking of the one in Tale Spin, a battlecruiser sized aircraft that can sustain flight.  Some helium tanks may be needed        inside the craft, protected enough not to suddenly burst or catch flame.  And propellers might help.     

know whats lighter than a helium tank?
a vacuum tank.

clearly we just need to find a super light and super durable material than maintains shape under an atmosphere of pressure.