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Permies likes rocket stoves and the farmer likes rocket stoves:  J-tube vs. L-tube permies
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rocket stoves: J-tube vs. L-tube

paul wheaton
steward

Joined: Apr 01, 2005
Posts: 15039
Location: missoula, montana (zone 4)
    ∞
After having seen both in action, I used to think the J-tube was craziness looking for disaster and now I think J-tube is really the only way to fly. 

Why would folks wanna use L-tube?


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Kathleen Sanderson


Joined: Feb 28, 2009
Posts: 969
Location: Near Klamath Falls, Oregon
    
    1
On the subject of rocket stoves, I have a question for you.  I've been working on house plans for future use, most likely when I move back to Alaska sometime in the next five years or so, and have been frustrated with trying to position a heated bench inside a small cabin where the heat needs to stay in the center of the house.  I end up with an awkward arrangement of rooms or an excessive amount of hallway.  Would it be possible to have the flue run under the floor instead of inside a raised bench?  That would make my design process much simpler!

Kathleen
paul wheaton
steward

Joined: Apr 01, 2005
Posts: 15039
Location: missoula, montana (zone 4)
    ∞
Yes.

Of course, there could be some issues depending on what your floor is made of.
Kathleen Sanderson


Joined: Feb 28, 2009
Posts: 969
Location: Near Klamath Falls, Oregon
    
    1
The floor would be earth, sealed.  How would you manage the cleanouts?  That seems to be the thing I'm having the most trouble figuring out.  I re-read Ianto's rocket-stove book over the weekend (between scything the yard and starting to empty out my bedroom so I can replace the carpet with wood -- plywood -- flooring).

Kathleen
paul wheaton
steward

Joined: Apr 01, 2005
Posts: 15039
Location: missoula, montana (zone 4)
    ∞
The cleanouts would be the same for either L-tube or J-tube, wouldn't they?  Although I suppose that with an L-tube you could drag the ash out instead of grabing handfuls.
Kathleen Sanderson


Joined: Feb 28, 2009
Posts: 969
Location: Near Klamath Falls, Oregon
    
    1
I guess what I'm having a hard time with is that if the flue runs through a raised bench, you can have horizontal cleanouts, but if the flue is in the floor (especially with a house built underground or at least earth-bermed) can you get adequate cleaning with vertical cleanouts, reaching down from holes in the floor?  Are cleaning rods flexible enough to do that (maybe use Y's instead of T's?)?

Kathleen
paul wheaton
steward

Joined: Apr 01, 2005
Posts: 15039
Location: missoula, montana (zone 4)
    ∞
My understanding is that the tubes beyond the combustion chamber rarely need any cleanout.  And when they do, it is right next to the combustion chamber.

Kathleen Sanderson


Joined: Feb 28, 2009
Posts: 969
Location: Near Klamath Falls, Oregon
    
    1
Thanks, Paul.  Another question:  Ianto says in the book not to burn spruce in these stoves -- do you know why he said that?  If we end up back in the Interior of Alaska, spruce is about all we'll have to burn (at least at Tok, where my brothers live).  I know it creosotes stovepipe up pretty bad, but am thinking that the combustion chamber on a rocket stove should aleviate that problem.

Kathleen
paul wheaton
steward

Joined: Apr 01, 2005
Posts: 15039
Location: missoula, montana (zone 4)
    ∞
No idea.  I asked Erica to pop in and help answer some of these questions.  Maybe she knows.

Erica Wisner
volunteer

Joined: Feb 10, 2009
Posts: 734
Location: Okanogan Highlands, Washington
    
  87
Freeholder wrote:
Thanks, Paul.  Another question:  Ianto says in the book not to burn spruce in these stoves -- do you know why he said that?  If we end up back in the Interior of Alaska, spruce is about all we'll have to burn (at least at Tok, where my brothers live).  I know it creosotes stovepipe up pretty bad, but am thinking that the combustion chamber on a rocket stove should aleviate that problem.

Kathleen


So Paul asked me, and I thought about it, and then I asked Ernie .... and here come the results:
1) Spruce is pitchy. 
It's not the creosote, so much as the characteristics of the burn itself.  (You're right, once it gets past the burn chamber, there's not much creosote or smoke left, and with the pipes encased in earthen masonry, there's little chance of it catching fire or doing much damage if it does.)

But within the burn chamber:
  Softwoods often burn pitch-first, and then stand on their little foamy charcoal ends.    So for a J-tube feed, the effect is that the fire moves up the wood, chasing the pitch, and the charcoal on the ends doesn't burn down fast enough to keep the fire in the right spot.  Smokes back.  Burns too quick, and too slow, at the same time.
  (I've been thinking about fire lately as a super-speed fungus: it resembles 'brown rot' fungi, which eat lignin first, leaving checkered brown cellulose.  Fire, too, feeds on the complex wood oils and proteins first, and leaves the carbon for last.  Softwoods have proportionally more cellulose, and less lignin, with their spread-out pale growth rings.)

  If softwoods is your main fuel, I'd definitely recommend creating an ash pit below the fuel feed, like on Ianto's drawings.  That gives the fire a little more room to handle those charcoal ends. 
  Your AK spruce is generally denser (tighter-grained) than our softwoods, which is good.  We get really big-grained spongy "spruce" and "fir," force-grown on tree farms, that are really basically papier-mache masquerading as sticks.  They are like cellulose foam.  Weird stuff, takes forever to finish burning, but gives little heat.  Fruitwood twigs & trimmings work a lot better for us here.
  With your dense spruce, it may not be a big problem, if you design your stove to draft well in the first place.  Tall heat riser, compact feed tube, maybe a little extra height on your burn tunnel, and cut your wood to fit the feed tube, not stick up above. 

If you're going to burn pitchy wood (or any wood, for that matter), season it well.
Like most wood for rocket stoves, it may do better in straight rounds with the bark still on, rather than square splits.  1" to 6" around, you can split some for kindling but the main fire will be made of circles and a few wedges, not squares.  You can mix it with tamarack or well-cured willow, and find a blend that burns well for you.

I would definitely recommened either
1) stick with the dimensions in the book as closely as possible, including 8" diameter pipe,
or if you are able,
2) experiment on your AK property when you get up there, and see if you can adjust the dimensions for optimum function using your fuels and weather patterns.
    If you have to build the first season you get there for shelter, then collect as much local info as you can ahead of time.  Get your brothers up there to monitor weather, storm wind direction, etc. (Or send them the book, and see if they'll play around with it.)  Or have a back-up plan for shelter e.g. a woodstove, fireplace, or friend's house.

2) You were talking about Cleanouts:
Yes, you can build them sticking up.  Most folks clean them out with a Shop-Vac, except Ianto, who uses his hands.  You can also use a rag on a wire cable (thread it through then pull the rag through after), or a chimney brush on a flexible snake.
  Like Paul said, the critical area for ash build-up is near the manifold / barrel area, and of course the burn chamber itself. 
  Ernie's friend Shannon Dealy build a 10" diameter system into a floor, and he put his cleanouts poining up. (a T-shaped joint with the main pipe, or a 3-way joint sticking up from a corner). He covered them with tile  When it's time to clean, he pulls the tile off, pulls the cap on the T-joint, inserts a shop-vac or brush, and then reassembles the whole thing.  You don't have to do this often, but it can be very handy in case you get a rat's nest or wad of newspaper stuck somewhere.
  The other note from Shannon's experience: Beeswax is not an ideal finish for a heated earthen floor - tends to get sticky when warm.  Linseed oil or another curing oil might work better; or just sprinkle water to keep the dust down.

Also, Ernie says, you'll want substantial insulation UNDER the floor. 
Mineral insulation like perlite, pumice, or something that can hold your floor stable, would be good.  (Synthetic foams can work, but they also break down in certain conditions, and could de-stabilize an earthen floor.  You could pour a concrete slab, and use suitable insulation.  But be sure everything's laid right the first time, and expect it to crack - many slabs do.)  It also helps if the insulation can drain, and is stable when wet, in case anything leaks.

2 reasons for insulation:
1) Permafrost is cold. 
And
2) it's what holds the tundra up. 
In tundra country, putting a lot of heat into the ground destabilizes the ground, and your foundations, without necessarily warming your house. 
  If you're planning to get down below the permafrost for your bermed house... and Ernie says in places it's 20 feet deep, depends where you are ... then you just have to worry about the heat loss.  And seasonal flooding...


  Thinking about this project, I'm reminded that permaculture is about appropriate design for your place: bioregion, site, personal space.  Designing a house on paper, to be built "somewhere" in future, is an iffy proposition.  Features that work well in one region, don't necessarily work in others.  You might need several designs, to handle things as basic as sun angles, let alone humidity or permafrost contingencies.

  It would be worth looking into northern European and Arctic cultures, to see what they tend to do about building in that circumstance.  I personally don't know anyone living in cob / with an earthen floor in those regions.  Flemming Abrahamsson does rocket and masonry stoves in Denmark, and he's an architect who could consult on your design if you're interested.

Also, if you're digging down more than a couple of feet, air-exchange is an issue. 
Our building code in the lower 48 likes fresh air to enter the building lower than the stove's air intake. I think on the grounds that hot air rises, and you don't want smoke filling your house or running backwards up the fresh air intake.

Igloos are built with an air-trap in the entry, like a sink's U-trap, so warmed air stays inside the highly insulative snow block dome.  They are heated with minimal fire, traditionally mostly with oil lamps as I understand it.  And of course body heat.

Ernie suggests an air intake, possibly sunk into the floor itself for a little pre-warming, that opens near the stove mouth and can be closed when not in use.

Ernie thinks it's fine to build with cob up North, and he's lived in Alaska so he'd know better than I would.  But he says to take appropriate precautions.  I asked him to go into detail:

1) Insulation.  Lots of it.
2) Air supply: bring in a pipe from outside at floor level.  You can plumb this through the bench / floor to pre-warm the air if you want.
3) Sink the stove into the floor and make sure your heat riser is plenty tall.  You DON'T want smokeback in a sunken, enclosed space.
4) Earth berming is good, gets the house out of the wind, but DRAINAGE is an issue. 
5) You want surface drainage to be away from your house, in 3 levels:
a) below-ground drainage of the foundations that drains to daylight in a frost-safe way.  Foundations and floor pad should be at least 2 feet below floor level.  And allow enough floor thickness to encase your pipes in cob above and below.
b) drainage away from the house around the berms
c) a third ring of drainage, for surface water, beyond the berms.  Water flows across the top of permafrost in the spring (or any thaw), and will try to "float" a house that's not protected.  Most houses don't float so good, they just crack. 

I hope this is useful.  Ernie knows a fair amount about the Artic as well as rocket stoves, so I figured I'd put it all down.

My own personal note: 
  If you have never built a house before, you may be surprised at what's involved.  I'd encourage you to practice now, wherever you are - create a well-drained patio, build a cob bench or tipi-pad on it, put in a pizza oven.  Build a rocket stove mock-up, even just the brick firebox, and use it for canning season so you get the hang of feeding it.  (It also takes some time to get it going once it's cold - if your Alaska dream home is a vacation retreat, you may want a more conventional fireplace that's easier to start when cold.)

You may find that there are designs from northern Europe for houses that work beautifully with a central chimney, masonry-stove, or set of fireplaces.  Rooms can radiate off this feature, with a sculpted "fireplace" or mural on the cob surface that faces into each room.  Check out the Masonry Heaters Association for some inspiration; they have conventional, modern, and funky stoves all built along traditional European lines (vertical masonry mass). 
  If building your stove into the floor makes too many drainage and insulation problems, here's another design consideration:  Your heat doesn't need to be in the exact center of your house.  A curved, heated mass will radiate heat toward the inside of the curve - you can create a bench along a curved wall, that will warm things in the center of the room beautifully.  Or place the radiant heat barrel near the center, and build the stove into one wall - a "hot wall" that can be shared by a living space and bedroom or bathroom, for example. 

  I also like the phrase "Build your barn first" - get some practice, and don't sweat the details.  Build a single-room workspace that will ultimately be the toolshed, or potting shed, but will keep you warm and dry while you observe local conditions and get ready to build your "real" house.  Modern equivalent is living in the garage while building the main house.

Good luck, and have fun. 
Ernie and I would love to get up to Alaska together one of these days.  If you want to keep in touch, email us: questions@ErnieAndErica.info

Yours,
Erica Wisner


Play with nature, make nifty stuff:
www.ErnieAndErica.info
Kathleen Sanderson


Joined: Feb 28, 2009
Posts: 969
Location: Near Klamath Falls, Oregon
    
    1
Erica, thank you so much for that long response!  It answered several questions.  I printed it off (as I'm at work, and don't have a computer at home -- that works, anyway). 

That makes sense about the pitch in the spruce.  There is also aspen in the area, but not nearly as much, and aspen really doesn't burn well (but does it burn better in a rocket stove?  Anyone know?).  I'll be mainly burning 'squaw wood' because I'll be getting the firewood myself (middle-aged female with a bad back), so it probably will mostly be round with the bark on.  You mentioned willow -- we probably won't have any on our land (settled land in the Tok area is mostly dry land), but if I was able to get some I would.  The nearest tamarack that I know of is near Fairbanks, so nearly 200 miles away.  May be some closer, but I don't know where.

I'll see if one of my brothers can do a little experimenting.  Doug is presently building a new house -- they've been renting -- but I don't know if his wife would go for something 'funky' like a rocket stove.  Plus she's got poor health and might not be able to tend it, though they have been heating their rental with a regular wood stove.  My other brother is disabled and home most of the time so maybe he'd be willing to play with it.  There isn't any clay in that area that I know of for the cob bench -- Mark may know of a clay source nearby, though.  I was thinking of building a ferrocement bench and filling it with gravel, compacted -- lots of that available.  Has anyone done anything similar to that? 

I won't have electricity at my place so shop-vacs are out of the question.  I'll have to be able to clean out the flues by hand somehow.

Yes, definitely the floor will be insulated.  I won't have to deal with permafrost, as the Tok area is very well drained, but it does freeze quite deeply (four to six feet)every winter.  I've been studying the houses that the natives built for a long time -- they dug into the ground a couple of feet, and earth-bermed over the top of the structure.  That's basically what I plan to do, using Mike Oehler's PSP construction method.  It will be a big advantage to have modern water-proofing materials --- lack of water-proofing is why the Indians lived in tents in the summer, rather than using their earth houses year-round.  We've lived in Tok for several years already, and even in a framed cabin, it helped a lot to berm up around the outside.  Without waterproofing, though, the lower parts of the walls were slowly starting to rot out. 

Cob is out of the question in that climate and location, as even if I could find a seam of clay (there is one up the Taylor Highway, I think, but am not sure of the exact location, and it would be fifty miles or more) the building season is so short that wood will work much better.  I think the PSP method is fast, and I'll get someone with a backhoe to put the dirt back over the house!  (If my brothers don't have one, they'll know someone with one!)  I'll have to build a barn (same method) while I build the house, so time will be of the essence. 

An air-intake is definitely in the plans.  When we lived up there before, we didn't have one, and had a smoky chimney, and I always had a bad headache when I was indoors.  So ventilation is high on the priority list. 

One of these days, I'll bring my plans to work and scan them into this computer, so I can post them here.  I have helped build a couple of houses, and have built a small barn by myself, so I do have some experience, but not with the PSP method.  I'm working on figuring out how to manage the large posts and beams required with a minimum of help -- might have an able-bodied nephew or two around to help, but they might be working elsewhere by the time we get back up there.

I'd like to stay in touch with you and when you make your trip, if I'm up there, maybe we can get together!

Kathleen
Erica Wisner
volunteer

Joined: Feb 10, 2009
Posts: 734
Location: Okanogan Highlands, Washington
    
  87
Freeholder wrote:
...
There is also aspen in the area, but not nearly as much, and aspen really doesn't burn well (but does it burn better in a rocket stove?  Anyone know?).  I'll be mainly burning 'squaw wood' because I'll be getting the firewood myself (middle-aged female with a bad back), so it probably will mostly be round with the bark on. 
...

I don't know if his wife would go for something 'funky' like a rocket stove.  Plus she's got poor health and might not be able to tend it, though they have been heating their rental with a regular wood stove. 
...
I was thinking of building a ferrocement bench and filling it with gravel, compacted -- lots of that available.  Has anyone done anything similar to that? 
...
I won't have electricity at my place so shop-vacs are out of the question.  I'll have to be able to clean out the flues by hand somehow.
...
Yes, definitely the floor will be insulated.  ... It will be a big advantage to have modern water-proofing materials --- lack of water-proofing is why the Indians lived in tents in the summer, rather than using their earth houses year-round.  We've lived in Tok for several years already, and even in a framed cabin, it helped a lot to berm up around the outside.  Without waterproofing, though, the lower parts of the walls were slowly starting to rot out. 
...
Cob is out of the question in that climate and location, as even if I could find a seam of clay ...
An air-intake is definitely in the plans.  When we lived up there before, we didn't have one, and had a smoky chimney, and I always had a bad headache when I was indoors.  So ventilation is high on the priority list. 
...
I'd like to stay in touch with you and when you make your trip, if I'm up there, maybe we can get together!

Kathleen


Aspen, squaw wood - Round wood with the bark on it works great in our stove, better than split wood in most cases.  (Cherry bark's pitch pockets can be a problem.) The main thing is that it's straight, so you can avoid jamming and little "chimneys."
...
Rocket stoves are slightly trickier to run than a "regular" wood stove, but in a way, they're also easier.  Less time spent burning it, and less time wiggling the wood around once it's burning. 
I wouldn't try to convince any sister-in-laws to let a cement one in the living room sight unseen, but maybe put one in a wood shop and see if they enjoy it.
...
Ferrocement with gravel - closest I've heard of is a masonry bench with sand.  You lose some of the thermal conductivity, and storage, but it seems to work well enough for their research project.  Consider multi-sized gravel & sand at the least, or maybe something like lime cement if you can get it, to get better packing & contact around the pipes. 
Here's the members-only forum where I saw that project: http://donkey32.proboards.com/index.cgi?
...
Ianto cleans his stoves by hand (there are something like 7 of them in his little "cobville" at this point) unless there is a dire necessity.  He has to get a special generator or miles of extension cords to run power tools up there.  A chimney-sweep's tools should also work if you have strategically placed cleanouts to allow reasonable access.

Cleanouts in a floor can be placed pointing up, with a tile covering the capped duct.  They'll get hot, but probably not much hotter than the rest of the floor.  If you need to you can insulate the tile.  (Or use it to warm your feet.)
...
Nothing like the combination of evolved wisdom and personal experience.  How did the natives heat their bermed homes?
...
Headaches are bad.  Carbon monoxide is cumulative, and it takes a long time to recover. 
Start playing with prototypes now, don't try to get fancy with the design but see how much (or little) smoke you can make when firing one.  We have the luxury of letting 55-degree breezes through our house if we get too lazy with the fire, but it sounds like you'll need to keep the smoke from happening from the get-go.

Hope that helps, and keep in touch.

-Erica
http://www.ErnieAndErica.info
Kathleen Sanderson


Joined: Feb 28, 2009
Posts: 969
Location: Near Klamath Falls, Oregon
    
    1
Erika, you asked how the natives heated their homes -- they used small open fires in the middle of the floor, with a small closeable hole in the roof for the smoke to go out.  Similar homes in northern Scotland were known as 'black houses' and the lungs of the inhabitants probably were black!  Of course, the open fires also gave light for the windowless structures, and if we had no choice, I could live with that, but would prefer something that vents the smoke outdoors!

The Eskimo peoples used similar houses but usually heated them with oil lamps -- these wouldn't smoke as bad as an open fire, but since they were burning either seal oil or fish oil or whale blubber, they probably didn't smell too great.  I guess we are spoiled.

Kathleen
Laura Sweany


Joined: Aug 08, 2009
Posts: 218
Location: Seattle, WA
A brief addendum to the previous conversation; not only did people in early cultures develop breathing problems from indoor open wood fires, but blindness was a common old-age malady due to smoke damage to the eyes.  Yuk.

I have a 23-food 1975 Winnebago camper that we use as a detached bedroom, and last year we paid thru the nose to heat the space with an electric open-coil space heater.  All this talk of rocket stoves and hobo stoves has got me thinking about taking out the propane stove and converting it's corner into a spot for a small pocket rocket surrounded with bricks or some such thermal mass.  The space is about 2.5' wide, 2.75' deep and 4' tall.  I'm sure I'd need to add some kind of heat-resistant barrier against the walls and floor; how big a space would I need to dedicate to a small pocket rocket in order for it to be safe?  And is this whole idea just crazy to begin with?  Any help you can offer will be much appreciated.


"It is, of course, one of the miracles of science that the germs that used to be in our food have been replaced by poisons." - Wendell Berry
allen lumley
pollinator

Joined: Mar 16, 2012
Posts: 2380
Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''
    
  39
Kathleen and Laura : approximately 40% of the world still uses a three rock fire with the burden failing on those at home all the time, women ,the old and children, these are still mostly inside fires with all the maladies you mentioned and LOTS of lung problems !

There is a type of in floor heater using all types of fossil fuels that being suspended between the joists starts heating the living space right at the floor , this could be duplicated by digging a root cellar like pit in the center of your house putting down a cement pad which would need to be insulated from the thermal mass of the RSMH with an exhaust under your floor to an exterior chimney !

I am thinking that you would want an extra tall stack of 1 1/2 55 gal drums (or higher) just to have a place for direct radiation of heating, or not, it's your house.

Building any where its a good idea to centralize your water useage/plumbing as much as possible, i would think interior walls would be best, outside of that, I'm outside my expertise ! g'LUCK . - PYRO - maticly yours allen L.


Success has a Thousand Fathers , Failure is an Orphan

LOOK AT THE " SIMILAR THREADS " BELOW !
M Ploni


Joined: Apr 22, 2012
Posts: 9
Can someone direct me to an explanation and graphic describing the differences between the L-tube and J-tube?

Thanks.
Andy Cook


Joined: Apr 04, 2011
Posts: 40
Location: Bangalore, India and Southeast Alaska
    
    1
M Ploni wrote:Can someone direct me to an explanation and graphic describing the differences between the L-tube and J-tube?

Thanks.


The horizontal leg of the L is the burn tunnel, the upward leg is the heat riser. Add a little upward leg to right side of the horizontal leg of the L and that is the short feed tube, which forms the J design.
Satamax Antone
volunteer

Joined: Sep 24, 2011
Posts: 934
Location: Southern alps, on the French side of the french /italian border 5000ft high Southern alpine climate.
    
  13
paul wheaton wrote:After having seen both in action, I used to think the J-tube was craziness looking for disaster and now I think J-tube is really the only way to fly. 

Why would folks wanna use L-tube?



Paul, only way to fly when you need longer burn times and more heat, horizontal batch rocket. Which is a L tube


God of procrastination (Pratchett's style) )
 
 
subject: rocket stoves: J-tube vs. L-tube
 
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