How long did it take to reload the tubes after firing?

Sources vary but generally state that it was between five and ten minutes per tube. Some of the variation in the estimates might depend on how much of the work was done ahead of time, between the firing of the previous torpedo and the start of the reload.

Reloading was usually done while submerged so that the boat would be steadier. First, the outer door had to be closed and the tube drained. Then the inner door on the tube would be opened. The skid with the reload torpedo had to aligned with the tube. Ropes and pulleys were then used to haul the torpedo into the tube. Remember that the torpedo weighed as much as a small car does now. The skid had rollers to help move the torpedo along and the wooden blocks that cradled the torpedo were greased to reduce friction. Three men were probably enough to pull the torpedo into the tube, but there may have been additional men available to help.

The engine starting switch had to be up against the stop block so the engine would start as soon as the torpedo was fired. A spindle also had to be inserted from the tube into the torpedo so the gyro could be set from the TDC.