Pulling Negative Gs

Marathon, FL
No LL

This is education week for me. Along with other amenities, Marathon offers some free seminars on topics relevant to cruisers. So far this week, I've been to a seminar on power management and batteries, one on refrigeration systems, and a third seminar on solar and wind power for boats. Tomorrow I'm going to a seminar on how to fish for your diner in the Bahamas -- highly relevant.

No matter how much I know, I always learn new things in such environments. One interesting thing I never thought about before was design of marine equipment to withstand negative Gs.

Pulling negative Gs usually refers to flying. It is anything that makes you rise up out of your seat unless your seat belt is tight. On a sail boat it occurs when you are tossed around by the waves. Of course we've learned to tether ourselves and to use things like seat belts on the stove. Our friend Don Campbell even tethers himself down in his bunk. Sitll, I never thought about the design of boating equipment. Here's a couple of examples:

1. lead acid batteries: All batteries have a space in the bottom for particles of lead to collect. During use, lead flakes off the plates. The flakes pile up in the bottom. When the top of the pile touches the bottom of the plates, it shorts them out and the battery becomes useless. Marine batteries must consider how the piles of flakes are stirred up and moved around by the negative G forces.
   
   
2. Refrigerators: A two quart container full of liquid or a jar of pickles and stored inside the refrigerator can become a missile when subjected to negative Gs. Specifically, it can fly up in the air then crash back down under positive Gs >1. The crashes have been known to smash the walls of the refrigerator.

I'm sure that there must be lots of other examples I still haven't heard of. It reminds me of an old question I had that I never heard and answer to, nor will I ever hear it no doubt. Nuclear propulsion system on submarines boil water in to steam, then pass the steam through a turbine. What happens when the submarine turns on its side or turns upside down? I have lots of friends from the submarine service, and lots more who designed naval reactors. When I ask them that question, they all give me the only answer possible -- that's classified.