If you spent 5 minutes looking you would find the answer yourself. I gave you the answer and you don't believe me. So maybe check for yourself.
Plus I said .2 belt and the rest BULGE until you lose a knot.

It is because Japanese armour is very weak. You better use the speed advantage to get the best out of the ship. This goes for all nations btw, except UK. 
UK is the only nation that has some ships that are worth AWing.

All other nations are to be armoured as Austin said. 

Hint for playing the Yamato is to keep ships at angle 45 and let those with more range come to you. Yamato does incredible damage at angle 45.