I wote this on the Searunner
Forum. Thought I might throw it in here.
The number one thing (you probably already know this) is warm air absorbs moisture, and cold air cannot.
This is why clouds condense as the air rises and cools. It is why the wettest side of a mtn. range is on the windward side. The warm moisture laden air comes in warm and low and is forced up the side of the mtn, and cools and squeezes all the rain out, and the leeward side of the mtn. or Island is dry.
I will tell you a short story about something very similar to your boat. (I know I lived aboard 25 years ago on a 37' in the winter with a wife and 2 year old)
On my boat in Alaska
boat) we have two "shelterdecks" They are rooms that are about 40' Long and 8' wide or so. Made of steel
. They were added to the boat on the port and Stbd. side to increase ultimate stability. The idea is if the boat heels over to where the Shelter deck is in the water, the added buoyancy will act like a big buoy fender
, and hold the boat up.. They are water tight if the door stays closed. They were also air tight until I got involved.
The crew "customized" the rooms to be the hang out place out of the weather
. They are in there soaking wet with their rain gear
on all the time. The installed a couple heaters also. The floor is bare plywood
. With the heater cranked up, the place became warm enough, but was soaking wet all the time, walls wet, floor never got dry etc. It was like a sauna.....I knew what was wrong. All they were doing was warming up the air inside, which would come in contact with the cold floor and wall and ceiling, and the warm wet air would condense as it cooled, So all the cold surfaces were wet. Any frame or anything that was in contact with the outside cold air, was like a heat sink, and would be cold in this room.... Lots of wet.
The crew thought I was nutz.
I took a 4" PVC pipe and marine
tex'd (epoxy) in place to the outside and piped to to the back of the heater. I covered the back of the heater with foil so the only air it could suck was from outside.
I put an exhaust pipe at the other end of the room. I swear within 24 hours this place was bone dry. All the rain gear
they hung up was dry, their boot got dry, sweatshirts....on and on. The floor was dry enough after while they could paint
All well and good. But as I get new crew (or one stubborn Portuguese guy) or if it gets real cold and dry out. They will remove the pipe and open the heater up. Sure enough I can spot it right off when the floor is wet.
If I was heating a Searunner
. I would pipe some air in from outside. Should be easy to do, from an underwing. And move it through the heat source. You do not need an exhaust as that boat has plenty of ventilation I bet. If you are bringing in cold dry air, you arfe creating a postive pressure inside the boat, and the warm wet air will escape.....
But the concept
. The rule
is. Cold air is dry. You need to warm up dry air and move through the boat and it will absorb water as it finds its way out.
If all you are doing is warming up the same air that is inside the boat, it will not excape, and only become stale without movement, and condense on your cold spots.