how did the damage go from 4000 to 8000 lbs damage with the same plane and same payload?
you should study more...
ok ill im only going to explain this once
1 U.S. torp is 2000lb...ok
torps do 2x damage
hence 1 U.S. torp does 4000 damage
2000 x 2 = 4000
ok if your still with me this is going to blow your mind
the PBY can carry 2 U.S. torp
2 U.S. torps can do 8000 damage
that is 4000 damage + 4000 damage = 8000 damage and one cv sunk

u should work on reading comprehension and some simple math...j/k