Having consulted the weather gods (Rick Shema), and with various mortals, the good ship Iron Lady is bound for Palmyra Island. Mark Fritzer continues his narrative, with interesting fuel burn data at various speeds and RPMs coupled with varying electrical loads.
We left Christmas Island yesterday evening at 1850 hours headed straight for Palmyra. I was treated to a dazzling array of the Milky Way, Southern Cross and a billion other stars while on my first watch of this new leg on our journey. From the beginning, the moon has risen in its full glory and blocked out most of the visible stars, so last night was a real treat.
Our current position is 3°45.6N by 159°36.4W. The sea conditions are extremely benign with waves heights at or below .5 M and the wind out of the SE at 7 knots. It would appear we finally found the dreaded “doldrums”, although they don’t seem so bad from my perspective, sitting in a lounge chair on top of the entryway doghouse, on the flybridge, under shade, sipping from a bottle of water, but I could be wrong. I’m really glad I’m not sitting here trimming sails as I watch the SOG drop down under 3 knots.
The sea temperature slowly started climbing this morning topping out at 86° F which matched the air temp, so captain Steve and I had to stop the boat and go for a quick swim. How many times do you get the chance to swim in 4500 Meters of 86° water?
I’d like to say it was refreshing, but instead it was actually kind of like swimming in salty soup, but still very much worth it.
Around 17:00, Mr. Shabby went bonkers. The reel got so hot from stripping line that you could hardly touch it. I really thought it was going to spool us. For almost 40 minutes we fought the beast on the other end, not catching a glimpse until the very end. Wouldn’t you know it was a beautiful 120pound Yellowfin tuna. The boys are going to eat well tonight!
Since we have averaged just over 11 knots since leaving Christmas, we need to slow down a bit to arrive in Palmyra around 9 am and just after high tide. This gives me the chance to see what different RPMs and loading do to the fuel burn numbers. It is very educational to watch the fuel consumption information available on the Maretron system. It is also quite telling.
By reducing the boat’s electrical loads, we can reduce fuel consumption by .2 litre/NM for a total of 19.1 litres/hour, while continuing to cruise at 1650 RPM. The engine has been running consistently between 184° and 187° F with sea temps running between 82.5° and 84°F. The loading on the engine stays pretty consistent at 50% with very little variation when the alternators are loaded up.
Dropping the RPMs down to 1450 only slowed the boat down to 9 knots. It dropped the overall loading of the engine down 5% to 45%. The fuel burn also dropped to 15.6 litres/hour. This is with the alternators putting out about 220 amps and the inverters providing 15 amps of 230VAC. The seas are mostly calm and the wind is light and variable up to 7.5 knots. If we turn off one of the alternator fields and let the other one come up to 150 amps of output, the fuel burn drops to 14.6 litres an hour and the loading on the engine comes down to 42%. When I turn the alternators off completely, while continuing to have the inverters crank out 15 amps of 230VAC, according to the Victron BMV, I have about 3.5 hours until the batteries are in need of a good charge, which makes sense when you consider the other 24VDC loads we’re running as well. However, the fuel burn drops to 13.3 litres/hour and the engine loading comes down to 40%. You can see that by watching your power consumption, you can increase the range significantly. However, it is pretty nice to be in the middle of the ocean in air-conditioned comfort.
Enough computer tapping for today. I have some fresh sashimi calling my name and I don’t intend to let the guys get a leg up on me.