Power Flex
A Nordhavn owners’s remote cruising habits inspire a generator overhaul.
Alittle over a year ago, we worked our way south from Fanning Island, Kiribati, towards Nuku Hiva in the Marquesas Islands. We were on a long, fuel-constrained run where we would cover 2,600 nautical miles without refueling. For most of the trip, we were heading up-current and into 30-knots of winds on the bow. The waves were fairly well-developed and spray filled the air day after day. The outside temperature was well over 80°, and the master stateroom was 88°, which made sleeping difficult. With the doors open for ventilation, a thin layer of airborne salt soon covered the interior. We were not crazy about closing the boat up and running the air conditioning, because that consumes more fuel and it was going to be a couple of weeks of generator run time at very low load.
As we neared Nuku Hiva, we concluded that we had far more fuel than we were going to use, so we might as well be comfortable and run the air conditioning. Typically I won’t run the generator at under 20 percent load for long periods, but it’d live with it, and it was so wonderful and relaxing to finish the last few days of the crossing sleeping well, in air conditioned comfort. This trip convinced us we needed to find a way to air condition the boat underway without running the generator.
POWER NEEDS
In the Tuamotus, we were diving daily and loving it. It’s remarkable to look up from 140 feet below and be able to clearly make out our dinghy floating above us, and then look the other way and see 150 feet down to the ocean floor and be surrounded by beautiful fish, sharks swimming by, and a sea turtle making a pass through the area. It was incredibly beautiful, but we found ourselves wondering what would happen if our generator failed. Without the generator, we can’t fill SCUBA tanks, can’t make water, and can’t use the washer, dryer, or oven. The inability to make water when that far “out there” is not at all appealing. Our goal is to never have a trip end early, or be redirected by a fault, and it would be very difficult to get generator parts flown into some of the obscure, uninhabited islands we visited on this trip. We needed a backup to the generator, but really have no space for another generator aboard Dirona.
As we continued across the South Pacific we spent the vast majority of the time on anchor. But when we did go to a marina, the shorepower was rarely better than 15A. Some of those 15A connections could only reliably deliver 12A without triggering the breaker, and in some places the shorepower capacity was over-taxed by the visiting boats and consequently was sagging badly. Also, they were often 50-cycle connections and Dirona is a 60Hz boat, so we couldn’t run most 240v appliances without running the generator.
We really felt we needed some way to draw what the shorepower had to offer, but to not trigger a breaker and not have to manage the boat to a consumption of less than 15A. Both Atlas and ASEA offer shorepower frequency converters that would handle the cycle difference, but they are expensive—friends have spent as much as $50,000 on shorepower conversions— and they still don’t allow running the boat well at over 25A while drawing under 15A on the shorepower connection. The frequency converters didn’t look like a good solution for the entire problem.
SHORT CIRCUIT
After many nights of thinking through options on passage, and planning and drawing up different solutions during the day, we came up with a solution that appears to solve all the problems outlined above. We installed the new design when we arrived in Whangarei, New Zealand, and, having used it for the last year, it really does seem to nail every requirement we hoped for, plus a few more.