Don't bother. They are all underpowered, and aren't useful at all, except perhaps in the very early game. Design your own. You can do much better yourself, besides which, it can be a heck of a lot of fun. Check out the stickied post about ship designs to get some idea of what you can do. Good gaming.

There is a program called Galactopedia that is an offline technology tree of sorts. It also gives you the techs and what they will enable you to do.

Not sure if we are allowed to post the link here but will give it a shot

http://www.kynosarges.de/Galactopedia.html

Its sometimes nice to know what advances you will need to research in order to get to a certain level of ship hull but other then the start up ships you get with a new senario always build your own as others have said before me.

About the only thing the core ships do is give you a very basic template on which to build better designs (which I believe was the intent of having them in the first place)