Advice on a RMH build in Hokkaido Japan

Give it two three weeks to dry.

To give you an example, of something else. My mass, that i have started heating around mid october, and has been fired daily for three weeks, starts to evenise. I don't have huge swings of temperature in the mass. Looses 2C° an hour approximately. While when it is not properly hot yet. The temps seem to fall faster.

Have you checked out the Finishes forum? Some good stuff and advice in there...
Also, search for natural plaster recipes online. Tonnes of stuff with pictures and videos.
Cement colorant is about the best I've found for getting nice long lasting tones unless you can find clay in the color you like. I just have boring grey clay here so color is really a nice addition.
Always make a little extra and dry into small balls and keep in the closet as when it comes time to patch, you have some that will match.
Yes, I've found the wheat paste to work real good. Doesn't dust off every time you clean the wood chips and bark either.
More info to share, but not sure where your going with your finish so just ask when you get 'there'.

BTW. Is that a picture of the famous Marilyn Mon-Mimi?

Gerry Parent wrote:Have you checked out the Finishes forum? Some good stuff and advice in there...
Also, search for natural plaster recipes online. Tonnes of stuff with pictures and videos.
Cement colorant is about the best I've found for getting nice long lasting tones unless you can find clay in the color you like. I just have boring grey clay here so color is really a nice addition.
Always make a little extra and dry into small balls and keep in the closet as when it comes time to patch, you have some that will match.
Yes, I've found the wheat paste to work real good. Doesn't dust off every time you clean the wood chips and bark either.
More info to share, but not sure where your going with your finish so just ask when you get 'there'.

BTW. Is that a picture of the famous Marilyn Mon-Mimi?

Thanks for the color and finishing tips.

Might try this seashell lime plaster I have later. For now I just want to put something over the rough rocky surface that will fill in, help level and won’t be incredible dusty.

Unfortunately the lovely lady in the faded vintage sticker is not the world famous Miss Mimi. I asked her agent for the rights to use some of her images and he hung up on me. Might have to send a permies persuasive care package 📦

Peter

Can anyone tell me what this drippy stuff on the flue pipe is? I would image it is tar, but not sure. Only a few streaks on the back side of the 15cm flue pipe, just behind the burn barrel as it comes out of the cob mass.

Something I should be alarmed at?
Something I should keep an eye on?
Normal for heavy 12 hour a day burning as the mass dries?
Are we going to die?

Peter, the famous lady and Chimichanga

✌️🔥✌️

Was just researching fire ash as an additive to natural plasters. Found this thesis paper.

Link: http://repository.upenn.edu/cgi/viewcontent.cgi?article=1320&context=hp_theses

Study on the effects of wood ash on natural lime plasters.

Added all the sifted ashes from my stove so far to
to a layer of clay and lime based plaster the other day. We used it to cover the perlite/clay layer around the perimeter of the room and also as an additional layer on the outside of the feed tube.

Only read a bit so far but pretty informative it seems.

If anyone is interested.

Cheers, Peter

Hi Peter;
No worry's about that drip. In fact its a good sign.  This is your moisture leaving the mass!!!  HOO RAY !
It will stop after a while. This is one reason we tape pipe connections to limit how much drips out.

The brown streaks are another one of those details I was mentioning earlier. Its the byproducts of combustion that condense on the chimney pipe and find their way out in any crack they can find. This is particularily true with RMHs because of the much lower exhaust temperatures. If the outside chimney is not insulated, you could potentially have streams of water coming out the pipe - have had this experience myself. With standard piping (one side crimped, the other side smooth) it is recommended to put the crimped side down so that this 'tea' does not leak out but stay inside the pipe and eventually evaporate off or drip down to a collection chamber. No matter how dry your wood is, it will still do this, just more so if your wood is wet. Nothing to worry about as a danger, but something that may continue. Mine did this for a while and then stopped though.  I was not familiar with the spiral chimney that you have so it never occurred to me to mention this tidbit of info. Sorry about that.

Thanks for the link to the wood ash. Will read it when I get a moment.

That drippy stuff is creasote.  https://en.wikipedia.org/wiki/Creosote

I wish I had commented on your chimney some weeks ago.  Good to see you're being careful about burn-temperatures and all that.  The wood gasses should be real hot and fully combusted in the burn chamber/s so smoke isn't full of particulates to condense on that long run of chimney you have.  I don't know about creasote with RMH's, but with low-temperature airtight stoves, creasote builds up dangerously in chimnies, especially at bends.  Usually you would control build-up by placing cleanouts at the bottom of each bend.  That is, inserting a 'T' pipe instead of a 90 degree bend pipe.  Creasote chunks can then fall out of the smoke flow into the catchment , and can be removed without dismantling.  Optimally your stove will burn hot enough in big blasts, to ignite most all of the particulates in the smoke before they coagulate on the sides of the cold chimney pipe up above.  

To check for creasote build-up, tap on the pipe every few months, when you hear stuff falling down off the inside, time to clean it.  In a stone or brick chimney, people burn paper occasionally, for a controlled chimney fire, burning off the gunk.  If too much accumulates, chimney fires get hot enough to burn rafters, or sparks fires on the roof. Slanted pipe won't let creasote fall, so eventually you'll want to insert cleanouts at the bends.  Be ready to take it apart for cleaning.  Schedule it so it isn't a big nasty surprise.  

Traditional ondol chimneys exit at the back or side of the building at floor level, with a stone chimney stack a meter or so from the outside walls.  https://en.wikipedia.org/wiki/Ondol

thomas rubino wrote:Hi Peter;
No worry's about that drip. In fact its a good sign.  This is your moisture leaving the mass!!!  HOO RAY !
It will stop after a while. This is one reason we tape pipe connections to limit how much drips out.

Thanks for that info Thomas!  I was hoping there was experience around RMH and creasote, as they differ from the air-tight cast-iron stoves I've burned.  Of course there is moisture in the cob burning off, that adds to the water vapor, and can explain why the dripping stops after a while.  My little Jotul602 never stopped dripping, because we burned it hot, just long enough to get good coals, then closed down the air so it burned cool, long and slow all night.  I had more than one chimney flue fire with that stove.  One almost took down the building, real flames licking up the walls.  Sobering.

Peter,  Which way is the pipe spiral heading, in terms of dripping from inside? Possible it would drip less upside down?

Antigone, theoretically creosote only occurs at startup in a rocket.

At normal rocket burning temperature, it burns.

Hey guys,

So at present we should be good?
Only have a small amount of this stuff showing up on the bottom piece of vertical flue pipe as it comes out of the cob, behind the burn barrel. About 70cm to the first taped joint. Looks like that piece and the piece above it both have the crimp on the spiral facing up.

Burning pretty hot if I fill her up. Over 400C on the top of the barrel after 5 minutes of burning, but would have to keep the feed tube filled constantly to maintain that kind of temperature. If it just has a few sticks in it and is burning we end up having a small amount of smoke. (See attached photos for reference)

Been experimenting with different wood. Super dry soft wood, hard wood, and nail covered off cuts. Got the high temps earlier with just some off cuts.  

Mass is drying and stabilizing pretty well.
Still not “hot” in the morning, but mass  heats up much faster than before. We are around -3C to -5C outside, but inside is pretty good if we consolidate our living space to the rocket room and the adjacent east facing room. Losing heat through the massive window in the east room, but make up a bit when the sun’s out in passive solar.

All the locals are amazed at how warm it is in the house. They’re use to living in cold houses. I’m used to growing up with central heating in the 80’s. Bit of a difference there.

Starting to think about how to use the heat that collects near the ceiling of the rocket room. Too hot and a bit of a waste. Want to experiment with some fans and a bit of cheap expandable tubing to suck the hot air into other spaces.

Still far from done, but coming along.

Will keep you posted.

Here’s a few photos of our daily activities

Peter and crew...🏔🌞🏔

Peter Sedgwick wrote:So at present we should be good?

I would say so. Worse case scenario (and only if you really feel is necessary) would be to reverse the piping from where it comes out the bench to the roof. Not something that you probably want to do with all that perlite in there but doable. The H chimney cap would also have to be modified to fit the wrong end of the pipe but a little ingenuity with a DIY crimper (aka needle nose pliers) can do wonders.

Burning pretty hot if I fill her up. Over 400C on the top of the barrel after 5 minutes of burning, but would have to keep the feed tube filled constantly to maintain that kind of temperature. If it just has a few sticks in it and is burning we end up having a small amount of smoke. (See attached photos for reference)

I could never get that kind of temperature in that short of time with my RMH with a hard firebrick burn tunnel and perlite riser. Thats the beauty of the CFB. Fast out of the starting gates getting up to clean burning temps in no time! Also, I've found that mine smokes a bit too when only a few pieces of wood are burning. Generally they burn best when full of wood, otherwise the air:fuel ratio is off and there's not enough heat being generated to keep things clean burning.

Mass is drying and stabilizing pretty well. Still not “hot” in the morning, but mass  heats up much faster than before.

That's so good to hear. Don't think it will ever be "hot" in the morning. Its more of a gentle warmth that your most likely to experience that will stabilize the wild fluctuations without the mass.

Starting to think about how to use the heat that collects near the ceiling of the rocket room. Too hot and a bit of a waste. Want to experiment with some fans and a bit of cheap expandable tubing to suck the hot air into other spaces.

I remember you saying something earlier about how your RMH is like an extension of your house. In a sense it is. The room it is in is like a large bell. In this case though, the stratification is not working in your favor so perhaps mixing it up a bit with a ceiling fan would help. One of those Eco fans may help out a bit too.

Peter, didn't you have a chimney thermometer? I would be keen to know what is your temps in the chimney at chest to nose height.

Hey Gerry,

Yeah thanks for the tips. Think we are actually talking about two different types of pipes. The stuff we’re using is actually high temperature air duct piping. There is no male or female side of the pipe. The crimping I was referring to is on the spiral. There’s a separate joint piece that connects two pieces together. (Images attached)

Bought in 2m lengths as that was the longest size we could transport and also logistically install in the house. This stuff is $12 for 2m. The flimsy stainless option is $80 for 2m. Slightly concerned about spalling and heat corrosion, but the brand website states that it pipe is stable at high temperature. Didn’t specify exact temperature. But lots of local use the same spiral duct for traditional wood burning stoves so figure it should be ok.

Gonna try some stuff with fans and ducting to get the hot air, sitting near the ceiling of the rocket room, to move around a bit more.

This whole thing is still super experimental in my mind. Everything is a big laboratory. Inside, outside. Eventually it will all come together and sing. For the time being if there is a bucket of rocks in the room that turns into a temporary dining table no problem. No longer in a race against time.

No time schedule and no one to answer too, except us. That’s the beauty of it.

Gonna try some test top coat earthen plaster tomorrow. Will report on our findings...


Cheers, Peter and the crew

🍄⚡️👩🏻‍🚀👨🏻‍🚀⚡️🍄
      🐕🐕

Satamax Antone wrote:Peter, didn't you have a chimney thermometer? I would be keen to know what is your temps in the chimney at chest to nose height.

Hey Satamax

Yeah! The bi metal thermometer we have is garbage. Planning to get a new one, but been busy handling stuff outside before the snow flies again.

I’m interested too.

BTW, if we are not running the heater at rocket temperature all the time, is that a bad thing? Sometimes we just need a bit of heat. Not hyper stove on steroids.

Peter

I run mine with limited air in a sort of gasification mode, I have a lid that goes over the fire box and just run the secondary air.
I also sometimes run it with a large log that just keeps it ticking over (all shown in my videos) but I think my high mass fire box helps, I don’t know if this would work so well with a CF core?

Fox James wrote:I run mine with limited air in a sort of gasification mode, I have a lid that goes over the fire box and just run the secondary air.
I also sometimes run it with a large log that just keeps it ticking over (all shown in my videos) but I think my high mass fire box helps, I don’t know if this would work so well with a CF core?

Understood, thanks James

Peter, the best way to run it, is full tilt all the time. And cover the barrel according to your  heat needs.

Like Thomas's studio one.




Mind you, don't do this before mass is dry.

You can also play with the circulation of hot air.  TO cool the rocket room and warm the rest.

Well, the snow had all gone on my plot of land, and it's snowing again now! Mind you, i work for a chairlift company in the winter! So we need the stuff!

Satamax Antone wrote: So we need the stuff!

I need it too...🏔🤟🌞🤟🏔

Out of absolute mad sheer luck. Would you know a mate of mine. Francky Moranval?

Your jacket just makes me think of "band of boarders" uniform.

Peter Sedgwick wrote:Think we are actually talking about two different types of pipes. The stuff we’re using is actually high temperature air duct piping. There is no male or female side of the pipe. The crimping I was referring to is on the spiral. There’s a separate joint piece that connects two pieces together. (Images attached)......Slightly concerned about spalling and heat corrosion,

Never seen that stuff before, Thanks for the education on it. I use a galvenized steel piping exiting from my bell to the outdoors. I've used it for at least 6 years now with only a light surface rust showing up on the inside from the condensation that forms but no spalling. I'm confident that it will last many more years.
Look forward to your plaster findings.

Satamax Antone wrote:

Out of absolute mad sheer luck. Would you know a mate of mine. Francky Moranval?

Your jacket just makes me think of "band of boarders" uniform.

Out of sheer luck I don’t personally. But it looks like he’s friends with Rasmus from Vista. Small world getting smaller.

BTW Nice rocket and nice planer...

🏔🏔🏔
🏔👨🏻‍🚀🏔
🏔🏔🏔

Gerry Parent wrote:
Never seen that stuff before, Thanks for the education on it. I use a galvenized steel piping exiting from my bell to the outdoors. I've used it for at least 6 years now with only a light surface rust showing up on the inside from the condensation that forms but no spalling. I'm confident that it will last many more years.
Look forward to your plaster findings.

Thanks for that Gerry,

Good to know. Back to snow and a bit of cold. Will see how we go.

Cheers Peter and the team

Peter Sedgwick wrote:Was just researching fire ash as an additive to natural plasters. Found this thesis paper.
Link: http://repository.upenn.edu/cgi/viewcontent.cgi?article=1320&context=hp_theses
Study on the effects of wood ash on natural lime plasters.
Added all the sifted ashes from my stove so far to
to a layer of clay and lime based plaster the other day. We used it to cover the perlite/clay layer around the perimeter of the room and also as an additional layer on the outside of the feed tube.
Only read a bit so far but pretty informative it seems.
If anyone is interested.
Cheers, Peter

OK, so I finally ploughed through most of this paper. About as dry as a milk bone and had to take it in small chunks but ended up fast forwarding to conclusions in chapter 6 on page 283.
Sounds like it certainly would be worth adding it to any kind of plaster. The charcoal in particular with its micro pore structure holds onto the water minimizing shrinkage, cracking and increasing work time.
"The test results indicate that wood ash does improve the performance of lime plaster for base coat application. All of the properties judged critical for this context including, workability, adhesion, stiffening rate, permeability, and crack resistance were improved with 10-20% of the additive."

Gerry Parent wrote:
OK, so I finally ploughed through most of this paper. About as dry as a milk bone and had to take it in small chunks but ended up fast forwarding to conclusions in chapter 6 on page 283.
Sounds like it certainly would be worth adding it to any kind of plaster. The charcoal in particular with its micro pore structure holds onto the water minimizing shrinkage, cracking and increasing work time.
"The test results indicate that wood ash does improve the performance of lime plaster for base coat application. All of the properties judged critical for this context including, workability, adhesion, stiffening rate, permeability, and crack resistance were improved with 10-20% of the additive."

Yeah,
I have it book marked and reading in small doses. Otherwise my brain gets fried. But interesting to take in just a little bit before I go to sleep.

Just goes to show that all of these materials just fit together, naturally. No need to synthesize them, out of plastic, in a laboratory and mark them up to ridiculously expensive prices. Then brain wash you, with useless advertising, to convince you that you “need” them to make your house warm, dry and safe...

✌️👨🏻‍🚀✌️

This came on the playlist while we were mixing plaster today.
Made me laugh, made me smile.

🐉Peter🐉

P.S. gotta wait for it, it’s towards the end...✌️

The truth finally comes out of who the true pioneers of the RMH's really were. They just didn't have the internet and Permies back then so they just sang about it.

Here's a quick look at how we are burning.

Link:  

Working away on plastering and still drying, but beginning to stabilize.

Will update with more info and photos soon.

Cheers, Peter

Sounds healthy upclose.

Here’s an update on our cobbing in the cold. Definitely not something I would recommend, but it can be done.

Working with mostly frozen wet clay I figured the only thing to do was to get it into plastic buckets and get it inside. From there I added hot water. Just enough the thaw out the clay lumps. Then I sat and worked all the lumps into the water until it was the consistency of thick chocolate pudding. From there I took out as many rocks as I possibly could with my hands, each time squeezing the handfuls of rocks over the bucket to extract as much clay as we could get. Then I mixed the clay bucket with a cheap homemade mixing stick ( will follow up with info on that later) From there ran all the clay mix through hardware mesh into a separate, clean bucket.

That became the clay portion of or base material for our next layer of loose cob/earthen plaster.

Keeping that as one bucket of clay, in a new bucket we added 4 sauce pans of the clay slurry. To that we mixed rice straw roughly cut to 3cm in length and broken up by hand. Tried to brake the straw “tubes” apart as much as I could to reduce the insulation value, but still maintain a bit of fibrous value of the strands.

Didn’t measure the amount of rice straw. Just did it by eye. Adding to the clay bucket as I mixed with the power drill mixing paddle. To that we added sifted fire ash collected from the bottom of the burn chamber each morning. Again not measured, but probably around a coffee cup full.

After that we added roughly 15-25%, by volume of white flour based wheat paste. Started with 25% on the first batch and then decreased each consecutive batch. Seems like 15% by volume is pretty good for this mix.

Once all of the above materials were well blended. We added a equally amount of sand to the mix. One sauce pan full at a time, blending continuously.

This gave us a relatively spreadable earthen plaster mix that we have used to cover most of the areas of the room that have been dusting. We did this 2 days ago and everything is finally starting to dry, although you could walk on it without to much notice after about 5 hours. This is not a final finish layer. Just something to use as a working finish. The plaster was applied to the RMH bench as we were firing so the layer has cracked because of drying too fast, but not really concerned. No more dusting for now. Wheat paste plaster mix smells like a bran muffin while it’s cooking/drying so that kind of cool. Chimichanga think it’s a massive doggy treat and just keep licking the bench, but the surface is hard enough that they can’t really use their nails and dig into it. A problem we were having earlier for sure.

Here are some images of the work flow. By no means master eco builders, but this system seems to be working in our situation.

Will continue to update on the plastering aspect of the project as it develops further.

Cheers, Peter and crew

🏔🏔🏔🏔
🏔👩🏻‍🚀👨🏻‍🚀🏔
🏔🐕🐕🏔
🏔🏔🏔🏔

Here a quick look at how I made a mixing paddle for our cob/earthen plaster. Couldn’t find anything decent at the store so I figured I’d give it a shot.

Bought the longest thin eye tab bolt I could find. Mines 25cm long with an 8mm diameter. Two small mounting holes on the flat section of the rod. Cost $1.75

For the paddle portion of it I just cut a piece of steel from the scrap portion of one of my drum can cut off tops. Made a quick pattern on paper and folded in half then cut to get a mirror of both sides. Just picked a random shape and size I thought would work. Mines a half moon about 19cm wide by 8.5cm tall. Laid the cut paper stencil on the rusty metal and traced the shape, marking the center line as well. Want to get the placement for drilling holes as close to center as possible so that the paddle rotation is relatively centered on axis. Doesn’t need to be mathematically perfect, just close.

From there I rough cut the shape with a cutoff wheel on an angle grinder and then cleaned up the shape with a sanding stone wheel attachment. Drilled mounting holes and bolted with some spare screws and washes I had. Took about 40 minutes to make.

Left the paddle blade flat and didn’t give any propeller twist too it. Figured I’d try as is first before doing anything else.

Works perfect on a battery power hand drill for most thicknesses of cob mud plaster. Just make sure you ease into the trigger or it spits mud everywhere.

20 liter bucket and a hand drill mixing paddle probably won’t cut it for large projects, for small batches and working out plasters for RMHs it seems to do the trick. Paddle definitely beats hand mixing you get a more consistent mix for sure.

Cheers Peter

So we're having some issues with the refectory castable bricks I poured.
This is day 19 of heavy burning, averaging 14-18 hours a day.

The bottom floor brick is totally spalling out. Like an expanded baked cookie.
Bottom half of the floor brick is still intact, but top has crumbled into bits.
Back facing wall brick has snapped in half. Can still use. Just cleaned out and covered the floor of the feed tube/burn tunnel with sifted ash.
Back brick just sitting on the top of the other broken half. Top front brick and left/right wall bricks still in one piece.

Ideas/recipes to getting a more durable refectory castable brick set up that can withstand the heat in the burn tunnel?

Any advice would be much appreciated.

Cheers, Peter

Wow that is a blow and such a shame!

I guess your original product was not up for the job or perhaps you mixed it a bit wet and then heated it to soon?

The standard refractory casting cement I use for my pizza ovens will last for many years of heavy use.
The one I use has added stainless steel needles and burn out fibres, it is rated to 1400c. I also add a further 5% needles and fibres as recommended for high abrasions areas.

There is a quoted amount of water per bag and that is important to stick to, I think it is 4lt per 25kg but I basically mix it as dry as possible.
The dry mix looks impossible to work with but it will vibrate out flat with excess water showing on top even with such a dry mix.

Can you remember the temperature rating of your product?

Fox James wrote:Wow that is a blow and such a shame!

I guess your original product was not up for the job or perhaps you mixed it a bit wet and then heated it to soon?

The standard refractory casting cement I use for my pizza ovens will last for many years of heavy use.
The one I use has added stainless steel needles and burn out fibres, it is rated to 1400c. I also add a further 5% needles and fibres as recommended for high abrasions areas.

There is a quoted amount of water per bag and that is important to stick to, I think it is 4lt per 25kg but I basically mix it as dry as possible.
The dry mix looks impossible to work with but it will vibrate out flat with excess water showing on top even with such a dry mix.

Can you remember the temperature rating of your product?

Hey James

Mine says it’s good to 1100C. Obviously not enough and likely right that I mixed it a bit too wet. Just added water randomly, no measurement. Think I should start with a different product. Should I be getting something with high silica or aluminum or?
When you say needles you are referring to stainless steel sewing needles?

Would the ceramic fiber dust I collected from my board cuttings be of any use?

Peter

If you can expand my picture you can see the needles ...
I think the technical name for the needles is something like  “high extraction burnishing “ but the needles are just an additional product available from my foundry supplier.
The basic refractory mix already has both burn out fibres and needles added but you can add more depends on the proposed use.
The burn out fibres are just tiny almost microscopic strands of nylon, when they get hot they melt away and leave channels for any moister  to escape rather than turning into steam and cracking the cement.
The stainless steel needles are added for abrasions resistance and added strength.
I only add the additional fibres and needles because it is an affordable safe guard on top of an already good product.
Basically refactory casting mix is high alumina cement and crushed fire brick plus’s the manufacturers additives like fibres.
Some are just cement and fire brick dust, some are cement crushed brick .. others have so called secret ingredients... the one I use is not expensive about £15 a 25 kg bag but I build 300kg 60mm thick ovens with it and it seems to work extremely well.
I have a close up of the dry mix, you can just just see te fibres and needles.

Peter, don't worry too much.

You have gravel, mud and ceramic board under that bottom brick.



Just stick the back one with mud, and  fill the bottom cracks with mud, every time you find it's needed when you clean it. And you'll see next spring what you can do to address this. And may be rebuild it as a batch!

May be you could buy a bag of fireclay.

Satamax Antone wrote:Peter, don't worry too much.

You have gravel, mud and ceramic board under that bottom brick.



Just stick the back one with mud, and  fill the bottom cracks with mud, every time you find it's needed when you clean it. And you'll see next spring what you can do to address this. And may be rebuild it as a batch!

May be you could buy a bag of fireclay.

Thanks for that advice. Yeah Matt said the brick is just there to protect the CFB. Board is really doing all the work here.

Open to rebuilding maybe. But maybe just build something different in a new small studio eco shack. Definitely a discussion for a future time.

Looks like I’m gonna be on snow earlier than expected and the rocket project might have to go on the back burner for a bit.

More than anything this whole endeavor has peaked our interest and we are super keen to keep experimenting with as much natural and repurposed materials as possible. One man’s trash is another man’s treasure. Think globally act naturally...

Keep you posted.

Peter and crew

P.S. lights just went out, Rocket still going...🤟👨🏻‍🚀🤟

James,

Will look into the foundery supplies as well. The more I learn the more I want to learn.

Peter