Ship Model Sizes

Would someone out there give me a go-by on basic ship classes and model
sizes?

I have been reading Star Wars RPG.  In 1/2400 scale, an Imperial Star
Cruiser would be about 67 cm long!?  About the only model I have in that
genre is a Corellian Corvette at about 6.3 cm from Micro Machines (Rebel
Blockade Runner??).

I would appreciate any help on this subject.

Bobby Mock