Hi Micdrow,
>Below is a link to japanese torpedo's in english.
Direct hit!

Right in the summary:
"There were no remarkable features about Japanese torpedoes in operational use during the war, with the exception of the anti-roll stabilizers. The Japanese considered this innovation of great importance in improving torpedo performance."
Apparently, a torpedo not roll-stabilized would tend to hit the water rolled off the upright position, and since the torpedo body would be nose-down, the water elevator would already be in "nose up" deflection and induce a sharp "hook" as soon as the torpedo hit the water.
While running submerged, roll control was also important since it eliminated the requirement to keep the torpedo laterally stable statically, which could only be done by leaving an air bubble in its upper half, restricting space available for equipment and warhead. (Apparently, this layout was used in the early model torpedos, and introduction of roll stabilization allowed the use of larger warheads within the same outer dimensions later.)
From the emphasis in the summary, it sounds a bit as if US torpedoes did not use anti-roll stabilization ... it would have hardly been considered a "remarkable feature" if it would have been in common use in US torpedoes, too.
Regards,
Henning (HoHun)