Aloha -
If a ship's penetration value is higher than the target's armor, does penetration happen on anything greater than rolling a one (1) on a die roll?

Are any minuses applied if penetration value  is higher than armored value? 

For example, the HMS Iron Duke has a armor penetration of 7 at medium range w/ her 13.5" guns.  It hits an unarmored ship (AC=6) at medium - does the Duke get a -1 to its penetration roll?

Thanks!