Quote:
Originally Posted by Reverie
After a push to the surface with more than Slow Speed, regardless of boat/crew condition, rain or shine, Spring-Summer-or Fall (Forget Winter: there's Still No Snow), this Type II may rise to the challenge (pun). Marching at a fuel conserving One Third Ahead, the speed may cruise to 7kt, push to 8kt, or even claw to, perhaps scavenge 9kt; all with no consistency.
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One Third Ahead is not the most fuel efficient speed, though it is the most efficient of the engine telegraph positions. If you use set according to knots, you want to aim for 8, which is about 10% more fuel efficient than the engine telegraph setting.
If you want to be really accurate, you can adjust speed until you make 215 RPMs (in a VIIB), which is the most fuel-efficient RPM setting. (A mod exists that will make the telegraph setting the most efficient; perhaps some kind soul will remind me what it is).
However, if you do set speed to "8 knots," you are merely ordering your Engineering Officer to "make turns (rpms) for 8 knots." Your boat will achieve those 8 knots in calm winds and smooth seas, and if no engine power is being used to compress air or recharge batts. But in rough seas, you can easily find "making turns for 8 knots" giving you only 5 or 6 knots of actual speed.