Austin Shackles

Did a 3-batch burn*.  Without the bench (as last year) that would've been the limit of efficiency, beyond that it started to waste heat up the chimney.

1) Starting: Didn't seem to be an issue, with the bypass open I did have to deploy the flue primer but then I also had to do that on the first start last year.  With full bypass, the stove behaved the same as without the bench.

2) 1st batch: Got the bypass shut in what felt like more or less normal time span judging by last year's running.  Bypass closing is determined by the temperature in the lower "oven" space, as shown on the handy-dandy thermometer I fitted to the door - when that gets to around 100°F it's time to shut the bypass.  With the bench the stove slowed down somewhat but didn't actually stall, probably it went a bit inefficient burn for maybe 15 minutes.  

3) 2nd/3rd batches:  The stove warmed up slower than before.  During the 3rd batch, some warmth (but not much) apparent in the bench, and the oven temp dial got higher but not as high as without the bench.

4) after burn complete:  Once the 3rd batch had burned down to low embers, I opened the oven door a tad: as discovered last year this stalls the flue and prevents heat wastage up the chimney which otherwise continues to draw heat from the now-hot stove.  This tactic is equivalent to putting a bung in a J-tube.

The flue base temperature where it goes out of the stove to head outside was noticeably lower than last year during the 3rd batch, showing that the heat had remained inside and wasn't going up the spout.

Further testing will follow:  I want to try a 4th batch, and see how warm the bench gets; I also have in mind tweaking the gas flow to persuade more hot gases to run through the bench and less through the oven.  Likely this will mean inserting a brick in the oven space to deflect some of the gases.

* I'm on a mission here to standardise the terms:  a "batch" is a single load of fuel in the firebox, filled as full as is convenient.  A "burn" is a period during which 1 or more additional batches are added when the previous batch has burned to just the right point to shove the embers down the far end of the firebox where they light the next batch.   Oh and "doing a Paul" is when you forget to go check it and come back to find half a dozen small embers glowing folornly in the firebox and have to deploy additional kindling or the gas blowlamp to re-ignite it

I don't think cutting into the bottom is going to help it.

I assume this is a commercially-made stove from the look of it.  What is the small flap on the lower side of the wood feed for?  Is that some additional air intake? I would probably consider things like wind direction or poor fuel as a reason why it might not start.  I would expect if you once got it burning that it would continue to burn given good dry fuel.  

Experience has taught many people that steel is not a good material for an insulated riser in a mass heater such as the J tube type which Paul advocates for.  If you get it to burn hot enough to be really efficient it will start to destroy the steel.

Burra drew my attention to this thread and we had a quick thinky (as I do most of the cooking when we're both here) - I could easy enough knock up a nice quick pasta dish with basil from the garden, onions, mushroom, peppers and so on which we ordinarily have al the time.  The tomato sauce in bottles from Lidl turns out to be vegan when I check although I don't think it's labelled as such but there aren't any animal products on the list.  Or I mostly have fresh tomato in the fridge anyway.  Or I could do a veggie curry if I cooked the rice specifically: we often have cooked rice read but that isn't vegan as Burra puts "skinny bits" in it for collagen to help are increasingly aging joints.  But there's plenty of uncooked rice and it doesn't take that long to cook.  We also mostly have frozen cooked beans or chickpeas in the freezer.

On mine I was building pretty much exact to Matt's plans with the focus on making the internal spaces the right size; since the bricks I can get here are not quite the same size as the US ones the outside dimensions differ a bit.  As I have no reason to suppose I need to take it apart completely, I used some bought-in refractory mortar which is, I believe, used to make brick ovens and barbeques to build the body of the stove.  The last couple of layers are done with sand-clay mix so I can get the top off for maintenance should it be needed.  I've also got a tube of some fire cement stuff which I think is intended for sealing metal flue pipes and the like.  That's proved handy for replacing some of the top-edge bricks which didn't want to stay put with the clay-sand mix.  To be fair, I made snazzy 45° angles on the front corners which means small triangular brick cuts which don't have much area to bond to

I'll be interested in your results with clay and sharp sand.  On my build, because I didn't have any sharp sand to hand the parts that are done with clay mortar (mostly the internals of the core firebox and the top layers of the stove casing, the latter so it can be got apart if needed)... Those parts are clay mortar made with what is locally called yellow sand which is what you would normally use for rendering, not bricklaying.  It proved not all that good and it tends to come apart too easily.

The most part of the stove casing is done with some bought-in refractory mortar which I think they sell for building brick ovens.  That means I can't dismantle it easily but then I have no intention of doing that, I'm more concerned with longevity. I can access the core by lifting the top off the stove, if I need to.  In fact I did end up needing to as a couple of the firebricks cracked and had to be repaired.  I don't know if they are inferior quality or if that was just bad luck.

before I put the lid on it, here's a picture of the adaptation at the back of the stove to connect to the as-yet-virtual bench.  Space considerations meant that this space is a bit tight.  On the right is the inlet* for hot air from the stove, and on the left the outlet to the base of the flue.  The outlet part looks constricted but actually it's not, the ports in the stove body are about 8x6" (20x15 cm approx) and that outlet at the narrowest part is about 16x3" so in fact it's the same size.  Since the chimney is 6" / 15cm inside diameter anyway, none of this restricts it excessively.  



Yet to decide if I divide the bench lengthwise until part way along so that the warm/hot gases from the stove are constrained to go along the bench further before they can go off down the exit.  Probably not needed, but also, not a great deal of work to achieve, I just need to extend that central divider some.  The bench will be a strat chamber not a mass, at least to begin with.

* if you're the bench, it's the inlet...

Just to add I'm trying to create a distinction between "batch" and "burn".  The way I see it, when you fill up the firebox with fuel and light it that is a batch, and that's what distinguishes a batch-rocket (stove) from something like a J-tube where you feed it little and often.

A "burn" is composed of 1 or more batches and is the time during which the stove is alight until you decide not to feed it any more.  This, I think, conforms to the idea of a "burn" in a J-tube.  And if it doesn't, I'd like it to.  So for example you could do a 1½-hr burn in a batch stove which used 3 or 4 batches, and after that the stove and bench would all be nice and hot for the rest of the day/night.

You're doing way more experimental dry-stack than I did!  I basically just built it, making sure the internal spaces in the core and within the body came out right using the bricks I could source.  However, you're planning things like water heating which I didn't do.

As for storing heat, you store heat in the hot water and I assume your hot water tank is inside the house. If you find you want more heat in the stove body/bench then you can just burn another batch of wood.  Without the bench on mine I found that more than 3 consecutive batches (i.e. one fire-box stacked with wood) started to overheat the chimney, so was wasting fuel.  I expect/hope that with the strat-chamber bench which I'm adding this year, I will be able to to do an extra batch or two without losing too much heat.

At the base of my chimney is a single-skinned 45° bend before it switches to double-skin going through the wall.  During the first and second batches on each burn that bend is merely warm to the touch, showing that the flue temperature is nice and low and the heat is remaining mostly in the stove.  At the end of the third batch it starts to get hotter although you can still touch it without burning yourself.  At that point I usually let the fire go out, since burning any more would send too much heat up the chimney.

It's very like my situation living in Portugal.  I don't speak the language especially well as I've only been here about 8 years.  

If I want to write a post for a Portuguese-speaking forum it's much easier for me to write it in English.

What I do is to write in English and then use google translate or other online translator to translate it, but then I read through it in Portuguese and see if I think it looks like it makes sense.  If I'm in doubt over the translation, then I translate it back to English to see if it looks right.  I wouldn't use "AI" to edit something as it's too prone to add stuff I don't want.

Here's an anecdote about translation.  I used to play a multi-player online game where you spent about 6 weeks building up to a final phase.  In the final phase, in order to succeed, your team had to work very well as a team and follow instructions exactly.  We constantly had a problem where one player failed to do this.  Well, it turned out that he was from Egypt and spoke almost no English, his native tongue was Arabic.  After a quite a bit of playing with google translate back and forth form English to Arabic I managed to explain the issue and give him some basic help with how the "endgame" worked.  The trick of copying what the translator put out (I, obviously, can't read Arabic) and re-translating that to see if it made any sense was definitely useful!

Here's the thread for our build in case you haven't yet found it.

Matt Walker tiny stove build

There's a fair bit in there and quite a lot of Q and A.   It's a pretty standard build without any water heating or such, the only slight difference is it's mirrored compared to the plans.

If you don't have the size bricks that are in the plans, you need to start by getting the internal sizes of the core correct (my core is also built with firebricks), then make the stove body contain the core including insulation space around it, and then also make sure the internal passages in the stove are right.

The bench inlet/outlet are at the bottom of the stove.  Bench inlet (form the stove) is at the back of the descending flue (on the left in my build), bench outlet is at the base of the chimney.  On the plans, these are marked as optional if you don't plan to add a bench.
I'm reliably informed that it works as-is, but it's also possible to place a brick over the outlet from the bottom "oven" space into the flue so as to push more heat into the bench.  I'll be (finally) building the bench for ours soon, so no doubt there will be a few more posts added about that.