I had to flip a few faces in 3ds but it's done at last ! I also made an occlusion map for it, it took ages ! then I realized I had not one but 3 clones of my tower stacked on top of each other
if you look closely at the picture you(ll notice some elements are missing, their faces are flipped, the black face showing.
I also made the submarine class image, taken from the section of the sub found at Fisher-thorpe :
