Saturday, November 1, 2014

Dorade Alignment (Tuggers Vol. 61)

By Craig Kurath, Annie #38


I had an interesting occurrence last month while on a fairly short and rough voyage from the lovely artist community of Langley, WA.  I traveled from Annie's home port of Port Townsend, WA to spend the evening in Langley and then the next day went on to Kingston, WA, where the Port Townsend Yacht Club was going to have our "Oktoberfest Brats & Beer in Kingston."  As we came around the south end of Whidbey Island, I commented that either there were a lot of small white fishing boats out or the wind was really blowing in the Puget Sound.  There were no small white fishing boats out there.  As we approached the shipping traffic lanes, the swells were three to four feet tall and were on our port bow.  The good news was I could point directly into the swells and our true course over the ground, compliments of wind, swells and tide was going to take us directly to Kingston.  What luck! There was a little green water coming over the rail and really strong spray made using the windshield wipers mandatory.  Annie and the crew were up to the ride, although the autopilot was not and I got to steer for the entire distance, a rare event for me.

Upon arrival, I was shocked to find that it was so rough, water had sloshed out of the toilet bowl! That was a first time for me.  Then I decided I had not dogged the port well enough. Then a little light went off: There was so much solid spray during the crossing, the dorade could not handle it and had dumped fresh air and salt water into the head!  In Kingston, I was telling a friend who is a retired supertanker captain about the event and he gave me an interesting lecture.  The bottom line is dorades work better facing backwards, drawing air out of the interior of the boat and aren't facing large seas.  I have seen many discussions about having a dorade facing each direction for better airflow and am sure this works very well.  I think I am going to leave both facing aft for the time being, allowing the starboard dorade to draw the hot air out of the engine room.

More discussions about dorades are found in The Best of Sail Cruising, by Anne Madden, and The Warm Dry Boat,  by Roger McAfee.  They agree that dorades should be facing aft, drawing air out of the boat.  They state that the natural airflow in powerboats underway (or pointed into the wind) is from the aft, venting into the forward part of the boat.  They further suggest that hatches should be hinged forward so they will draw warm, moist air out of the boat while preventing spray or worse from entering the boat when they are open.  Maybe when I replace or repair Annie's hatches I will reverse them.



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