adding ship components to tech tree

Hi I've got a quick question, I've created a custom tech tree I'm trying to figure out how to add a ship component to the tech for example medium hull tech unlocks medium ship hull.  I'm currently using the tech editor tool that came with ToA, and i don't see and option there I looked a the regular games tech tree and put the correct model (lrgbuilding0.bik) its the only thing I can think of, but nothing shows up in game.