I've built two, both used automotive fans.
On one I used a heater blower and motor salvaged from and old car, used the housing that came with it, and used a PWM speed controller, they control speed by pulsing the power, (turning it on/off rapidly) instead of with resistors etc. The motors and blower are designed to be quiet and move a lot of air.
At first this was built into a drop board for the companionway, but later I remounted it into a dorade type box that would drop into the forward hatch. Very nice on hot but rainy days!
Second was an electric cooling fan (front/back of radiator), also controlled with a PWM controller, this was mounted in a drop board for the hatch. These are bit louder than the heater blowers, so, unless you're like my wife and like the sound of a fan to sleep, I only use it during the day. But with the PWM at lower speeds will be pretty quiet.
At low speeds neither draw a lot of juice, and both can be made to look good.
Advantage with the fan motor is that it is designed to handle 60+mph wind and rain, so it's good for a wet environment
On one I used a heater blower and motor salvaged from and old car, used the housing that came with it, and used a PWM speed controller, they control speed by pulsing the power, (turning it on/off rapidly) instead of with resistors etc. The motors and blower are designed to be quiet and move a lot of air.
At first this was built into a drop board for the companionway, but later I remounted it into a dorade type box that would drop into the forward hatch. Very nice on hot but rainy days!
Second was an electric cooling fan (front/back of radiator), also controlled with a PWM controller, this was mounted in a drop board for the hatch. These are bit louder than the heater blowers, so, unless you're like my wife and like the sound of a fan to sleep, I only use it during the day. But with the PWM at lower speeds will be pretty quiet.
At low speeds neither draw a lot of juice, and both can be made to look good.
Advantage with the fan motor is that it is designed to handle 60+mph wind and rain, so it's good for a wet environment