Chris Adlam

Karl, thanks for your suggestions. I think the junction between the barrel and the flue might be a little tight; 4" between the insulation and beginning of the flue, although there is more space below and on the sides. Changing that now would be the hardest part.

The burn barrel was removed; it was too tall and killed the draw.

The barrel gets nice and hot (400F), the heat just disappears after that! So I'm still going to wait for it to dry before doing anything drastic, in case everything magically resolves itself.

Cindy Mathieu:

Could you please explain what you mean by those dimension? I tried to make a bell-shaped cavity, as described in the Ianto Evans book, at the junction of the barrel and the flue. That was the hardest part to figure out, but since it draws OK, I thought I did it well enough.

I don't have any great photos, but here is the one that shows the junction best. It is now covered with (a lot of) cob.


Paul Carter:

The Evans book mentions 250 degrees as a standard exit temp, so that is what I was expecting. Plus, I was expecting the bench to heat up at least a little, even when wet. Have you actually experienced it not working at all until fully dry?

Thank you,

Chris

Hi permies,

I just put together a rocket mass heater (8" system, 55 gallon drum). I fired it up and it draws OK, which I thought at first meant it was a success. But now I can't decide whether or not it's working properly. My main problem is that the temperature of the gasses in the exit flue remains low (not above 100 degrees after a mere 10' cob bench). I have tons of condensation pouring out the inspection holes, including the one right after the barrel, which I gather shouldn't happen when the smoke is hot enough. The wet bench (6" of cob over the flue as recommended in the book) doesn't heat up even after 10+ hours of running the stove continuously. I would very much appreciate some help from folks who have experience with these stoves. My BIG question is: will these problems go away as the cob dries, or is there a structural problem I need to address (I would really like not to have to dismantle the cobbed-in barrel!)?

So my questions are:
-Is a brand new, still wet stove supposed to work right away (gasses exiting the building over 200 degrees, etc.), or is this a temporary situation, and the issues are going to fix themselves when it dries?
-Could the problem be: weak draw due to obstruction in the barrel, poor construction of the barrel-exit flue connection, inadequate heat riser insulation, etc. (which would require starting over)?
-Could it be that too much heat is being lost through the exposed part of the barrel (top third), and that I could fix it by cobbing it all over?

For more details I should say that the stove draws OK when hot, though it occasionally backs up. The top of the barrel reaches 400 degrees with the best fires. I was planning to have a cob bed after the bench, but since it's not heating the bench I'm postponing that. I don't think the length of the flue or number of bends is an issue because I have experimented with firing up the stove with the inspection hole at 10' open, hence simulating a short flue (the draw increases a little but nothing to write home about). My heat riser and burn tube are kick-ass, made with firebrick.

I'd really like to know if I can relax and wait for the stove to dry, or if I need to take it apart while it's still wet to fix it! Why isn't it making more heat?! Winter is coming and I'm freaking out.

Thanks for your help,

Chris Adlam
Willamette Valley, OR

paul wheaton wrote:

Conifers are allelopathic - they sorta poison the competition.

Actually, it is incorrect to say that conifers are allelopathic. Repeat: conifers are NOT allelopathic. Allelopathy describes the secretion of chemical substances that prevent or stunt the growth of other plants (e.g. black walnut secretes juglone). Conifers do not secrete any "poisons".

The reasons some plants grow less well or not at all under conifers is not because of chemical warfare on the part of the tree. It is, to the best of my knowledge, because they are very heavy feeders that monopolize nutrients to grow fast (the video shows how fast they grow compared to oaks), suck up most of the water and create drought conditions in the upper layers of soil (in the summer months at least), and because their dense, superficial root system prevents other plants from establishing themselves.

There are those who say that conifers acidify the soil. I have yet to see scientific evidence of this. I used to believe this because everyone seemed to say it was so, but then when I tried to find out more about it, I was confronted with a total absence of evidence. If anyone can find reliable scientific literature demonstrating an acidification of the soil under conifers, either because of the needles or some root secretion, I'd be glad to know! Until then I'll stay skeptical of the whole conifer=acid thing.