If you take the shield off of it there is 6 small holes that go into the shoe brick through the bottom of the stove as well as two large holes that go into the refractory. If you smell smoke or hear a whoosh, that is where it comes from.
I have found you have to let the first stage of secondary burn do its thing and only back off the air to a low setting after everything is in the last 3rd of the burn or you will be having whoosh sounds and mini explosions.
I have never had any smoke problems, only occasional whooshing, and only in the first third of the burn. I have a taller stack, so I think a better draft than you. I wonder if you had a taller stack, and then used a damper halfway into the burn to cut the draft? I guess I can find that out if I add a damper to my pipe.
First year, I stuffed some foil into the side openings where secondary air flows in - that maybe cut it back some, but it still pulls in from the seam of the shield. I have not really played around with the secondary air supply in any methodical way, but I think I will try.
Installing a pipe damper did little to help slow this stove down when the secondary cranks, if anything it actually can increase your fire dome temps, due to slowing of the gasses passing through and upsets the blance.
Sounds like the secondary air is what needs reducing here, rather than the draft. Do you see these spikes whether primary air is open or closed? If you wanted to extract more heat from the firedome, that damper might be a good thing, but sounds like it is already burning too hot. A lot like all the stories from VC Everburn-ers.
Interesting enough, that secondary combustion package draws air in when the damper is open, not allowing you to operate the stove as a classic type when in bypass.
I used the dampner in the pipe to slow down the opened bypass fires when it is warm out.
This is the most annoying thing, and why I intend to put a damper in sometime (and why I originally tried the foil). My current solution (yesterday!) was to add bricks to make the firebox smaller - too early to tell how that will work, but seemed good last night.
If anyone looks at their oakwood anything less than 2 1/2 notches is chocked out primary air, just left with the 3/8 pre drilled safety hole.
The other thing about cutting primary all the way back is that the logs in the front don't burn well, and the glass soots up. Almost always need it open a little to keep clean glass and good burning at front of the firebox.
My verdict, is the flaw is in the lack of secondary air regulation to slow this baby down.
I'd be interested to hear if anyone really has gotten a good 12 hour burn out of this, maybe on a slower drafting chimney???
I seem to get my longest burns when I have not emptied the ashes or let the coal bed burn down, so the bottom of the firebox is packed with days worth of 24/7 burning remnants. Maybe not 12 hour burns, but 8-10 no problem. Burn times seem shorter with no ashes in the pan and only a moderately deep coal bed. Not sure if this is really true, or why it would be? But I suppose in having all those coals is filling up every cubic inch of the lower firebox - I'm counting them as part of the current burn, when really they are a part of the previous burn - meaning my fresh load of wood is not truly a separate "fresh" load. Does that make sense?