What is the length of a true wire?

[OKO]

10/10 sounds strange to me :
torpedoes will run always must faster than subs, usually 3 to 4 times !
so when the torp will reach 10 NM, the subs will be certainly at less than 3 miles from the original launch point.
I should have found 5 miles (for subs) / 15 miles (for torp) a best setting.
But maybe there is no way to put 15 miles of wire in the torp ....