I have to agree that "the best defense is a good offense." I have, after a number of attempts, been able to successfully engage destoyers using the following technique:
1) Navigate so that the destroyer is coming from the rear.
2) Set your torpedo depth between five and ten feet for destoyers (five feet for gun boats.
3) Lock the periscope on the target.
4) Use rudder control rather than compass. Maintain the average enemy route on the 180 degree line. That is, directly aft of the sub. Try not to use large rudder movements. Maintain a speed of at least "standard." Keeping him on the 180 degree line lessens the gyro angle and shortens the run time for the torpedo because the route is shorter.
5) Open the torpedo doors to save time ("Q"). Torps on "fast" and "contact/influence"
6) Use the attack map to verify torpedo's track. Wait until the destroyer get within about 400 yds and fire. I don't even use the periscope, but rather use the attack map. My XO can call out info to me.
I can confidently engage destroyers using this method (and survive). I have tried a "Down the throat" approach, which is more difficult because of the closing rate between the two vessels.
Note: If you fire too late, the torpedo will not arm. If that happens "Crash Dive" and pull down the periscope because he is going to run over you. Immediately order "periscope depth" as he goes over and re-engage as he moves away. Set up again. This time with the forward tubes. Make sure that you get everything ready BEFORE you start the engagement. Good Luck. Let me know how you do.
Old_tex