A Befuddlement over Water

February  2, 2019

Day 121

Noon Position: 45 43S  141 17E
Course(t)/Speed(kts): ESE 6
Wind(t/tws): NWxN 10 – 12 (for the day, 10 – 20)
Sea(t/ft): W5
Sky: Stratus (for the day, often clear)
10ths Cloud Cover: 10
Bar(mb): 1015, falling
Cabin Temp(f): 64
Water Temp(f): 54
Relative Humidity(%): 60

Sail: Twins poled out full

Noon-to-Noon Miles Made Good (nm): 147
Miles since departure: 16,860
Avg. Miles/Day: 139

Days since Cape Horn: 64
Miles since Cape Horn: 9,221
Avg. Miles/Day: 144

Longitude Degrees Made Good (degrees minutes): 3 15
Total Longitude Made Good Since Cape Horn (degrees minutes): 208
Avg. Long./Day: 3.26

Another steady night of wind aft but without stars. I woke often to make sure it continued to blow from the WNW, as the forecast called for a northerly shift which would have required deck work, but none came. I got a solid eight hours sleep. Second night of that. 

I’m edging S a bit in an attempt to get below a high (a blob of calm) that will settle in here in two days, and from that point on, it appears we’ll get variable and light winds all the way to New Zealand. The Snares are now 1,034 miles E and S. If I can figure a way to keep our miles up at around that magic number, 143 a day, then we should be at South Island within a week.

—

Yesterday’s project was to repair the fresh water tank gauges, dead a month and more now, so that I could get a water level reading. 

The gauges aren’t anything special, just metal rods that project down into the tanks with a floating sensor attached–much like what is in a car. 

This means they are pretty much useless on a boat in anything but flat water. But that’s what we had yesterday, or, if not exactly flat, at least we had the wind right aft. 

I spent two hours attempting to trace what I thought would be a disconnected wire, but it turned out the units simply needed to be re-networked. 

Then the real fun began. 

There are two water tanks; they are in-line (Forward and Aft) in the keel and each holds 100 gallons for a total payload of 200 gallons of water. Both were full upon departure from San Francisco 120 days ago. 

I used the Aft tank for the first 30 days after departure. I’ve used the Forward tank for the remaining 90 days of the voyage to date. I’ve caught 20 gallons of water, and all of that has gone into the Forward tank.

I budget to use one gallon of fresh water a day at normal ration. So, that means the Aft tank should have 70 gallons remaining (70% full) and the Forward, 30 (30% full).

The tank gauge readings were–Aft Tank: 81% full; Forward Tank: 74% full.  

Yes, there was some boat motion, so I took twelve readings, threw out the high and low and averaged the rest.  

But, golly, how could I have MORE water on hand than I calculated? That kind of thing never happens.

I noodled this all afternoon. 

Maybe I caught more than 20 gallons. I rechecked the transfer container. No, it is, in fact, a two gallon jug. 

Are the tanks bigger than I recollect? I went back to photos of filling the tanks with a hose gauge. No, they are 100 gallons each. 

Could it be I’m using less than I thought? This seems unlikely as I counted ounces used by activity, and my activities don’t vary that much. True, I’m not drinking my allotted two liters of water a day down here. I’m just not that thirsty in this cool weather, but could that be driving such a wide variance? 

Is there a connection between the variances? Though quite different, I found they imply something similar. Amount remaining divided by the number of days used per tank is about .6 gallons per day … in both cases. 

Well, that’s interesting. The gauges suggest I’m using about 2/3rds of a gallon a day, not the one gallon in the budget. And, wait, that’s HUGE; that means I have plenty of water for the remainder of the trip!

I was at the point of celebrating when the real truth dawned on me. 

The tanks are irregularly shaped; like the keel, they are wider at the top than on the bottom, and the gauges don’t know this. They are simply reporting the water level in the tank. 

So, back to square one. By calculation, I have 30 gallons in the Forward tanks and 70, aft; or, 100 days of water remaining, and I’d guess first stop is still 120 or more days away.