Who can tell me some popular websites about ship stability or ship mechanics or ship building?

This Wikipedia article should get you started. If you have access to Google where you are or another search engine, you can search “ship building” and several pertinent sites will come up.

Welcome to Fluther.

Or this. I wish I could forward the question to Art Vandelay, but alas, he is no longer with us. He may not have been a naval architect, but hey, an architect is an architect, right?

A quick google search turned up this article: link