Hunter Heatly of Laguna Beach, CA asks:
Is there a problem with growth accumulationg around the keel coolers? Would the coolers continue work if they did accumulate growth? Have the air conditioning water intakes ever become clogged? What is the largest object that the boat has hit so far (logs, kelp, reef)?
Joe Meglen responds:
Four good questions. When sizing the tubing for keel coolers, the engineers build in a "fouling factor" knowing that some amount of growth will be accumulating over time. Quantifying this exactly is difficult but from our experience with 150+ Nordhavns equipped with keel coolers we have found that the tubing can be completely covered with growth, even shell, without a noticeable loss of heat exchanging capability. Obviously, the colder the water the more growth that can be tolerated. During "Nordhavn's" circumnavigation there has been little growth accumulation and therefore no need for cleaning. There are two things at work inhibiting growth: 1) The keel cooler is 70% copper, 30% nickel and copper inhibits growth, 2) The heat in the tubing kills growth and a boat running almost continually, like "Nordhavn" is therefore less likely to accumulate growth.
Since the crew didn't have air conditioning installed during the first leg from Dana Point to Singapore, clearing clogged AC cooling intakes would have been an issue they would all have enjoyed coping with, especially through the Central Pacific. Clogged intakes are normally not a problem while passage making. It is when you arrive at a busy, congested commercial port that you will start picking up debris, such as plastic bags, that can plug up a sea strainer. So why not use a keel cooler for air conditioning? To get the temperature differential that air conditioning likes, the keel cooler needs to be too large to be practical on a small boat.
So far "Nordhavn" has had a number of close encounters with "dead heads", trees and posts floating we have only hit one piece of timber. This was probably dunnage from a freighter. Of course you want to avoid hitting anything out there but the reality of cruising is that you do occasionally hit something. The robust solid FRP laminated hull of a Nordhavn provides good piece of mind.
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