Re: Aft hatch wind scoop
We/ve never had luck on natural ventilation in the aft stateroom. The exception is when you are at a dock and the hatch is open and pointed at the wind. One of the problems is that the cockpit dodger and any bimini also blocks air flow to that area.
There is a theory that air from the forward hatches can push through the boat and the passageway and exhaust through the rear hatch but in practice this really doesn't work. Even with the companionway door closed the airflow is not enough and the passageway (with the pilot berth) usually heats up more than other areas of the boat and warms that air. This has been true of both our Santorin and our SM.
Some owners have installed 2 computer sized fans in the porthole from the cockpit. In our Santorin we simply placed a 12V Endless Breeze fan outside the hatch.
In our aft cabin of our SM we have had very good performance from a Caframo Sirocco fan. It has 3 speeds and at 24V its draw is: 0.06 amps for 90cfm, 0.11 amps for 114 cfm and 0.17 Amps for 140 cfm. It is easy to run a wire under the wood trim from the 24V supply to the rear cabin lights. The fan is fully gimbaled so it can be flipped if you want to use it to exhaust air or angled to direct air to a specific area in the rear stateroom. It is very quiet and almost undetectable at its lowest speed.. What is most unique is that if mounted correctly (see link to photos) it can be flipped up (held by sturdy detents, not friction) to operating positions or flipped down flush with the bulkhead and completely out of the way. The fit is perfect for the SM and it is possible that you could even fit 2 although 1 has been adequate for us in the tropics where even at the dock we have not needed AC. The fan is fairly large and can move a great deal of air but we almost always use it on the low setting. It also has a timer so you can set it for 2,4,6 hours or continuous. We don't know what we would do without it. It also clears security bars if you have them--ours are usually removed for safety reasons. We also have 2 Hella fans on the rear bulkhead but do not use them very much. Fan: http://www.caframolifestylesolutions.com/product/marine/sirocco-ii-draft/ Photos of it installed are here and show how it is stowed under the hatch-- https://photos.app.goo.gl/DMXzPz9SzpwEXZW19
Bob and Suzanne KAIMI SM429