Hello.I would like to ask you what kind materials you are using to build a passager vessel about 80cm for exaple.Thank you.

Nikos,
A lot will depend on what you are comfortable working with, also is it a Static model or going to be RC'd !, if RC then you have to think of weight issues, if it's static then there is no problems with weight.
Most ship models of that dimension will be made with ply bulkheads and planked with balsa and then covered with glass fibre. The superstructure will often be ply or balsa (I personally prefer plastic sheet) and the various ships fittings being from brass, alloy, plastic, resin, wood etc etc.
HTH.