6" to 8" Conversion at the seacow

[ByronC]

For rock my area is almost exclusively limestone. Mostly large wheelbarrow size and up. But it's really hard stuff to tool by hand, and super labor intensive to work with.

The day job limits my spare time, otherwise I'd enjoy hand sculpting a cob rocket. Solid clay based building bricks have lots of advantages for my situation. Since I'll be working singlehandedly, the big advantage of bricks is that they will make for quickly "framing up" the RMH and building thermal mass to boot, cutting way down on the amount of cob work.

On down the road if I get tired of looking at all the brick, there is the option of "skinning" the heater in stone, or adobe, or whatnot.

[mannytheseacow]

I can definitely identify with your reasons for using bricks. Those were exactly the reasons that I chose them, too. One thing I have noticed over the last couple years with the brick, though, is that they never get warm. There are several places in my bench where I subbed in a piece of limestone for a brick, just for aesthetics. Those limestone pieces get really warm to the touch but the bricks never do; no matter how long or hard I push the burn. For that reason, I wouldn't use brick again. I'll bet even a concrete block or paver would even be better than red bricks, and still give you an easy surface to put a skin on. Matt's method of using cement board for a frame/surface is probably the fastest method out there, and gives so many options for finishing.

[matt walker]

Hey Manny, when you get a chance would you mind sharing how your experience with the bypass has been? I am planning to put one in my home heater when I do summer cleaning and such. What have you learned?

[mannytheseacow]

Wow, that's a topic beckoning many tangent discussions. Yeah, I like the bypass. I would hate to have people read this and think that a bypass will fix all their issues, though. You know, if you don't have that temperature differential between the inside and outside, a stove with a bypass won't work much better than a stove without a bypass.

I don't use it much for burning. From time to time if I have a draw issue at startup I'll open the bypass briefly for a little extra suction.

I use it more at shutdown time on those really cold days. I'll open the bypass and close the feed off with some bricks, and then shut the main damper. If any cold air leakage is occurring then it is drawing straight from the house and firebox (hopefully) without drawing from the mass. All in all, I'm really glad you recommended it when I was doing the rebuild. I wouldn't go tearing up a stove to put one in, especially in a warmer climate. But yeah, overall a good thing.

It's a good place for water heating, too. There is a lot of energy build up right there whether the bypass is open or not, and taking heat off the bypass to heat water doesn't take much away from mass heating when the bypass is shut.

Can I just say again how much I love my stove? People have to realize that it takes some work. There's a lifestyle change involved and some finagling. I was about ready to throw the towel in on the 6 incher, but once the system size was balanced, mass was balanced, and I got into the swing of forecasting heating needs 12 hours ahead of time, it's a dream. So unfortunately, there's no easy dimensions available for building a stove you'll love if you don't spend the time getting dirty and mad at it first a few times. Now with my system tuned I can just about touch the exhaust when the barrel is running at 800*. I don't have a thermometer but comparing to a pot of boiling water, I can keep my hand on the exhaust much longer, so I'm guessing maybe 160-ish. It's still hot enough to get the cement chimney column warm to radiate warm air into my upstairs through the wall like my old potbelly did but my 6" ran out of juice by that time.

[matt walker]

Awesome update Manny, thank you so much. I'm looking forward to the bypass mainly for the reason you state, to isolate the mass from cooling air running through it when the stove is out. I also could use a little oomph at start up to warm things up at the back end since my stove runs right at the ragged edge. Thanks man, I'll keep you posted when I tear into mine.

[mannytheseacow]

Well folks, another winter has come and gone on the old RMH and I thought I would post a little update on it. First of all, I used less wood this winter than I ever have before. I don't know if it's the quality of the wood, climate change, or just continuing to learn the ropes... or maybe a combination of all three, but burning season is just about over and my wood shed is still totally stuffed.

About four times this year I had a serious smokeback issue which was caused from the stovepipe used on the interior of the riser as a form burning away and dropping down into the back of the burn tunnel, effectively blocking all air flow. An easy enough diagnosis, but the hard part is that it doesn't just come out... the disintegrated bottom of the pipe could be broken away to return air flow, but the part above it was always still solid enough that I would have to leave the top in place and wait for it to happen again. Give it some time, and sure enough, it happens again. It happened again yesterday, and finally has disintegrated enough that I could chip the whole thing apart and remove it. So, it should be good to go now, but it can be kind of scary when you're burning and all of a sudden it drops and fire is rocking straight out the feed tube! Especially if you're not home and it's the wife or kid that it happens to!

The bypass idea is still working great, especially in the off season. One thing I have learned though is that if it's kinda warm inside, and it's kinda warm outside (like 50* outside and 60* inside) and the bench still has some heat in it, the stove starts up better with the bypass closed rather than open. Makes sense once you think about it, but I get in the habit of just starting up what I think is a cold stove in the off season with the bypass open, when there is still more residual heat left in the bench than one might think.

Last part of the update, the core has cancer. That's the thing with these stoves... they need to be continuously patched... and that's ok. It's not a big deal. I've got an old itchy dog that is constantly scratching her face on the outside of the stove and wearing the surface off, but more importantly I've got some major wear on the inside of the burn chamber. Looking at the beginning of this thread it seems that this is my third winter on this core and it is pretty worn out. I've done some significant patches on it this winter and just did another patch today. Getting into the back of the burn tunnel where the air changes direction and goes up the riser there is a spherical wear patter that has worn almost entirely through the whole core. The top of the burn tunnel is like coarse lava, and the feed (of course) is pretty abused (yes Matt, sometimes people jam wood in like cavemen... it's not me, I swear! ). I think it's time for a rebuild this summer. I might go with my first batch-box. We'll see. I like the idea of slowing the stream down and minimizing particulate matter, but I don't like the idea of not being able to cram any length of wood I like in there... I think the time to do it might be soon. What I have noticed is that when I built this core I was burning in it almost immediately. Alternatively, my little cook stove got some significant time to cure, and the core is like concrete. Granted, it doesn't get used as often as the house heater, but I'm thinking that maybe I need to do this rebuild soon and let it cure all summer before burning it next season. I'll keep y'all posted....

[matt walker]

Thanks for the update Manny, it's a good one.