Nice dry chunks. I just use regular splits for a woodstove or fireplace, and cut them to lengths of about 6" on my bandsaw(it's the safest way I've found).

We'll use a quite a bit if it's cold out(say late October) but then again, we like to use it. Ours is very hot and puts out a lot of heat. I bring a sailbag or reusable shopping bag full of chunks and kindling for say a weekend and put it in the bottom of a hanging locker.

The little woodstove I posted would be more efficient on firewood I would guess being more of an airtight woodstove.

Our fireplace heater uses more. For heaters, solid fuel stoves work with a lot of radiation as well as convection. In our boat, once the stove gets hot(the cast iron and tile front), it begins to warm anything that is hit by the radiation(including us). Then the whole boat begins to warm up. There's a lot of btu output from these.

They won't work for most boats of course and I wouldn't think of it as full time heat. But it works well for the spring and fall in Maine. It's very simple too, all you need is wood.