Back on the boat, every once in a great while your schedule would work out such that you had two or even three watches in a row off, with no drills or training you had to get up for. Since a lot of at-sea submarining involved being able to function effectively with little sleep, it was always nice to take advantage of these times to recharge your body just like a very long charge would do for the ship's battery. Like with the battery charge, we used to call this type of power-nap an "equalizer".
Some people had a gift for being able to do an equalizer right -- 12 or more hours of continuous sleep. I was never able to make it that long in one shot, but I would be able to sometimes get 12 or 13 hours of sleep in a 24 hour period (like I did yesterday, shifting from night shift back to a normal sleep schedule -- 13 hours sleep in a 21 hour period). How about my commenters -- were you a "rack hound", or were you able to resist the "call of the rack"? ("Joel, come sleep in me," my rack used to whisper softly...)