Since buying the boat we've had a serious problem with the windows fogging up while underway in cold weather and the diesel heat on. This is not specific to this boat, it was a problem on our last boat as well. The solution has always been to place an oscilating fan on top of the helm and plug it into the cigarette lighter. It worked ok on the last boat (31' Camano), but the broad front windos of the 36' Express Trawler proved to challenging. Plus, the fact that the digital compass was critical for the radar GPS overlay to work properly, made it a serious problem that the electric motor would cause it swing wildly as it went through it's oscilations. Not to mention that whenever the chop kicked up, the fan would move around or fall over. A better solution had to be found.
I researched what I thought would be the best type of fan to install and how to do it. What I came up with was to use four cross flow fans, one above each window, blowing down. Cross flow fans are a sort of hybrid between a centrifugal (squirrel cage) and an axial fan (traditional). They are generally used to cool electronics in semi- confined spaces. They provide a wide and thin blast of air at higher pressure than an axial fan, but higher volume than a centrifugal fan. Although they are not widely used as computer cooling fans, they are ideal for that application. I got to thinking that this was about perfect for trying to move a thin layer of air over a wide window with minimal current draw and without subjecting the passengers to a blast of cold air in their face. The ideal fan turned out to be one made by a car audio company called "Stinger" that was intended to used to keep audio amplifiers cool in compact professional competition installations. It is roughly the size of a pack of golf balls: 1.75" x 1.75" x 8.5". It produces a column of air about 8" wide. I had to fabricate some L-brackets to get them situated properly so that they blew air towads the reverse raked windows while hanging from the headliner, but they work beautifully. I wired them all to one switch at the helm, so if the windows fog up, the pilot need only flip a switch and be greeted by the four party harmony of the fans clearing the view ahead. Since they operate at a relatively high RPM, they take a couple seconds to get up to speed, so they sound like four tiny little jet engines warming up. It's kind of fun to flip them on and off.
Anyway, I mounted them behind (forward of) the header board that runs around the perimiter of the headliner, so they're obscured from view and the wiring is routed through the cavity above the headliner, so you never know they're there until you turn them on. I will take pictures the next time I'm on the boat.
