Power Flex

A Nord­havn own­ers’s re­mote cruis­ing habits in­spire a gen­er­a­tor over­haul.

Passage Maker - - Electronics - BY JAMES HAMIL­TON

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.


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.


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.

Swap­ping out Dirona’s

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