THE SUBMARINE COMMANDER'S HANDBOOK 1943 Edition

[3catcircus]

Originally Posted by Kendras

Nice ! Very interesting !

What means "double" ????? :

250.) e) Run out and double at a good distance, and then make off on a straight course, in order to get well away from the pursuing enemy forces. Do not double frequently, or continually zigzag, because this results in loss of distance.

254.) d) Run out to a good distance, and double - no frequent zigzagging - and then make off on a straight course, in order to gain on the hunting vessels.

270.) After submerging during an attack, always go down at Once to depth A, and double.

My guess is it means to double back. Meaning - go away from the area a good distance, double back and go off in a direction perpendicular to your heading after completing the 180 degree turn back. This will accomplush the effect of having the boat with its stern away from pursuers, cutting down on noise, immediately prior to departing the area.