Did you try the 3:15 sec rule for the speed? That is working for me and not hard to master. The notepad method is not a reliable method to use for range and speed and I am not using it much.
I determine the course and range by this method.
http://www.subsim.com/phpBB/viewtopic.php?t=49376
And then use the 3.15 sec rule for speed. You also can determine the speed after identifying the target with the Hydrophone, but don't know the link for that. I will look for it though if you want me too.
http://www.communitymanuals.com/shii...ee_Minute_Rule
Also make sure that you open the torpedo door before firing (Q) and that your AOB is set correctly. Ideal line up is 90Port when target is traveling from right to left, and 90Starboard when traveling from left to right.
Good luck!