Forums

Gerald German of Houston, TX asks:

Being from Texas where it is always hot, Ii am very curious as to why the air conditioning was not installed to start with. Was this done as a potential fuel savings measure? Or did you honestly expect not to encounter any hot or humid weather on the voyage around the world? When you did install the AC, how much was installed and where was it installed (what areas does it cool and where are the units)? Now that it is installed, how much do you actually use it and does it work off the generator or the main engine alternator? How much do you run the generator?

Jim Leishman responds:

When we built this NORDHAVN 40, we only intended to use the vessel in South East Alaska. It was not specially built for the ATW. Upon return from Alaska in late September, we had a lot of work to do to prepare the vessel and we felt that the AC was something that we could do without. Even if we had it aboard, on certain legs of the voyage we knew we could not use it continuously due to the fuel demands. Bob Beebe's "Passagemaker", Jim Sink's "Salvation ll", and Ghanim Al Othmans's "Othmani" (the latter two - circumnavigating N46s) did not use or have air-conditioning.

During the first leg to Hawaii the temperature was climbing up to about 80 degrees in the day and dropping down to about 75 at night and in these conditions the sleeping cabins were acceptable. There was always wind flow across the boat and we were able to leave windows and door open. It was on the latter legs between Majuro and Pohnpei that things became intolerable with higher temperatures and lots of rain (doors and windows closed). In retrospect, this was due to the two typhoons which were encountered. Since installing the AC system in Yap, it's not been used much as the weather is cooler and dryer (about like the above mentioned Hawaii leg).

We installed a single 16,000 btu Marine Air system - which is controlled within the owner's cabin and ducted into the owners and guest cabin. This is the identical system which we install in the factory and is very effective. Reports from the boat indicate that with the stateroom doors open the saloon is even cooling from the single unit.

Normally two additional units are installed - one 12,000 btu unit for the wheelhouse and an additional 16,000 btu unit installed in the saloon.

The single unit we've installed forward will only run off of the generator. We considered trying to run a unit off of the inverter however the draw is just too much. The average output from the main alternator while running is about 75 amps and the added AC system would be too much for the 130 amp alternator. Additionally the alternators are so inefficient that we probably will burn less fuel to actually run the generator. An alternator producing 100 amps will require 5 to 6 horsepower - when efficiency (about 40%) and belt loss are calculated.

During the next leg across the Indian Ocean, I'll be doing some careful comparisons of fuel consumption with and without the generator running. We believe that while running the main engine at 1,400 rpm (our long range speed of about 6.2 knots) we are consuming about 2 gph and producing about 40 HP. With the stabilizers operating and the alternator producing 100 amps, approximately 10 HP is being consumed before we even spin the propeller shaft. Nearly twenty-five percent of our fuel burned goes to maintaining a constant 1,200 psi of hydraulic pressure (even if the fins are not moving much) and to produce approximately 1,400 watts of electrical power. If the fins are not needed, we can shut off the system and eliminate this draw of approximately 4 horsepower.

 

Close This Window