Reasonable expected burn time in my Baby Bear?

[turn_n_burn]

I've had a Baby Bear set up in my shop for several years, but I never used it much until very recently for any kind of serious heating. It's a late 70's model (I think), and it has a top exit flue (which is odd) with no baffle plate, and is properly firebricked. The propane I've been using costs more than I want to pay, and I have access to a near constant supply of free mill end 2x8"s, 2x10's, and 2x12's which I usually split in half) all between 10" and 18" long, mostly Doug/Grand Fir/White Pine/Ponderosa. I live in SW Idaho, so hardwood is very rare, except for black locust which can be easily sourced, (people around here hate the stuff, and I only have it once in a while myself).

In short, 1: how long of a burn could I expect with the softwoods and locust by themselves and /or combined?
2: what would be the ideal arrangement of the wood, especially the lumber stuff, to maximize burn time, as well as the ideal draft cap/damper positions?
3:can I stuff the firebox full?
And what is it that causes it to chuff fire out of the draft cap once your kindling really takes off? I can't decide if the sound reminds me of a steam locomotive or a Huey helicopter.

Any insights would be appreciated.

 

[coaly]

The chimney determines flue damper setting if needed, as well as intake opening. The flue damper is a chimney control, that affects the stove. The make and model of stove is not what you set the variable resistance for that the damper causes.

Chuffing could be the very volatile fuel your using out-gasses too fast (the flame from wood burning is gas released from the fuel as it heats) burns the available oxygen, starves, ignites......... (filling with too much cardboard does the same thing) OR the lack of the smooth rising of gasses in the chimney, which causes a low pressure area in pipe and stove allowing atmospheric air pressure to enter firebox with oxygen. As it cools near the top, flow slows or stops allowing cold air to drop into flue. Exhaust gasses rise, then fall causing air pockets to drop....... when they reach the stove outlet, it ignites pushing back towards intake. We would need to know the chimney type (prefab stainless flue or masonry) and pipe configuration. Screen at top?

A faster chuff is more like a flutter. It doesn't sound like you are explaining that scenario.

Depending on chimney draft, a baffle plate helps the most for all operating, control and efficiency issues.

No one can tell you where to set an intake or flue damper control since chimney, pipe configuration, elevation, temperature, required heat, and weather (atmospheric air pressure) determine settings.

You can fill to top with proper fuel and proper vent / operation.

 

[Todd67]

Coaly gave you great advice.

All I will add is what I've experienced with flames jumping out of my draft cap holes.

I sometimes get those flames jumping out of the draft cap holes when the wood is loaded too close to the door and the draft caps are open all the way. Your stove takes a max log length of 18", so loading your stove with 18" wood might be causing the flames to jump out of the draft cap hole.

My stove takes up to a 24" log, so if I load it full of 24" logs I sometimes get those flames out of my draft caps. It rarely happens if I use 20" logs or shorter.

Try using 14" logs or wood and see if that helps minimize the flames jumping out of the draft cap hole. Just a thought...

 

[turn_n_burn]

Mine is a standard six inch single wall pipe, straight up through my shop ceiling. Total height is about 17' from the stovetop to the cap, and the soot accumulation on my screen was light, maybe a 5 percent reduction in draft from totally clean, with little creosote buildup (there was a good amount of carbon black, maybe a sixteenth of an inch, but it all came down when I tapped on the pipe). I generally run the stove pretty hot for 30 or 40 minutes starting from cold, and this is when it happens. Given your advice, Coaly (which I always take as gospel), I think the pitchy wood I'm burning is the main cause, as it seems to be a direct function of the total surface area per unit of mass (aka too much kindling). And I will also look into getting a proper baffle.