Feedback on heating arrangement

[Pizzazz]

I have written about unusual heating arrangements before but wanted to get your feedback on my latest thoughts. This is a 31 foot sailboat with a relatively open arrangement, i.e. the quaterberth is open to the saloon. Southern California climate, very warm during the day, chilly in the evenings.

At dock, it is usually electric heat with multiple heaters and thermostats. I have considered the following heating arrangements while under way or at the islands:

1) A venting arrangement on top of my Origo stove. A picture is attached. It works well but every now and then the flame will go sideways. I guess depending on the wind. My current flue length is 24" and I should probably extend it on the outside of the boat. Two concerns with this option, is it safe enough and it is pretty localized heat. On the safety, I have run it for hours on end and the CO alarm (right next to it) would stay below 30 (closed up boat) if it flares down for a few minutes it could go above 30 at times.

2) Dickinson bulkhead propane heater. It will solve my safety concern but I have the following issues with it: still pretty localized heat, not much difference in cost (cost of 1lb propane bottle vs. 1 qt of ethanol, pretty much equal BTUs, cost and volume; I will be keeping by propane bottles in the anchor locker as larger propane bottles are difficult on my size boat), takes space for a non-essential function (i.e. heat in Socal), harder to adjust vs. the ease of adjustment on the Origo stove. Still, if properly installed it may give me a peace of mind, even with the 1lb bottles.

3) I looked at and decided not to pursue diesel heat at this point. My diesel tank is pretty small and I need it for propulsion and electricity generation. Bulkhead diesel is difficult to ignite and may be too much heat for my needs while forced diesel heat is noisy which is big issue for me.

4) Modified hydronic heat. Basically, my water tank is right below the quarter berth and well insulated from the hull. Assume my tank is half full (~20 gallons). I time my engine run in the evening, to charge my batteries. While the engine is running, I loop back my cockpit shower hot water output to the fresh water tank. I am hoping to get a 50F temp raise on 25 gallons of water incl. the water heater tank). This should store about 50x8x25= 10,000 BTUs. Not much but equivalent to four hours of electric heat at 800 watts which is more than what I use at dock for the quarter berth area. The heat will release overnight. Do you think this is workable?

Another related question is the efficiency of various heating devices. For example, the Origo stove burners are rated at max 10,000 BTUs on ethanol and this is what I get (1 qt will last for two hours on max flame which the energy content of one 1 qt of ethanol). How much of this though goes up the flue? The Dickinson propane heater is spec-ed as if it is 100% efficient, i.e. the fuel consumption x the rated BTUs equal the energy content which is definitely not true since some heat goes up the flue. I understand that the cross flow arrangement of intake and exhaust air of the Dickinson heater is ideal in terms of efficiency but how much is it? 80% perhaps?

Thank you for your thoughts on this rather academical exercise.

SV Pizzazz

[FutureStories]

Has anyone retrofit a rocket stove type setup on board?