sauna rocket stove progress

there was a request for photographs of the rocket stove I'm building to replace the failing electric heater in the sauna my great-great-uncle built.  rather than do one big post after it's all done, I thought I would serialize it and show the progress as it happens.  hopefully this way I can get feedback before it's too late if it looks like I'm doing something really stupid.

before we go further, how about a little sauna vocabulary?

sauna: in Finnish, it sounds like "sowna".

löyly: I won't try to teach the pronunciation, but it's sort of the steaminess and smell and general pleasantness of the sauna.  if you want more löyly, throw more water on the rocks.

saunatonttu: sort of a spirit or gnome that lives in a sauna and protects it.  generally helpful unless you don't respect the sauna.

vihta: branches tied together to whack yourself with.  traditionally made out of birch and tied with a root.

kiuas: the stove.  what we're really interested in here.

this won't be anything really revolutionary.  I'm using the burn unit geometry described in the RMH book, but without any of the mass.  the sauna won't be used continuously so heating up fast is more important than long term temperature regulation.

for bricks, I'm using some refractory bricks I got from a friend locally.  he bought pallets and pallets of various sizes and shapes from an aluminum smelter when it shut down.  this is what I got:



according to the inscription on every sixth or so brick, they're 9"x4.5"x2.5".  planning to make mortar out of screened clay and sand as described in the book.

for the heat riser, I'm using a four-foot piece of eight-inch diameter steel pipe.  a family member works with natural gas pipelines, and this was part of a much longer pipe that had been hanging around for many years.  the working plan is to insulate the riser with a couple of inches of perlite and clay slip held in by some hardware cloth.  here's the pipe and bricks mortared together with some clay for a rough partial mock-up:



the heat exchanger will be a sixteen-inch diameter steel pipe that has not arrived yet.  I believe both pipes are .255 inches thick.  where the models in the RMH book have a tea kettle heating up, this stove will have a metal pail of water preheating so it vaporizes more readily when tossed on the rocks: better löyly.  haven't worked out exactly how the rocks will be arranged on the heat exchanger just yet, but I'm imagining a cage of some sort made out of hardware cloth.  that doesn't sound very nice to look at, though, so other ideas would be appreciated.

rather than seal the heat exchanger/stove base junction with cob, I bought a stove door gasket.  it's a fluffy piece of woven fiberglass that I'll cement to the bottom of the heat exchanger.  the pipe is heavy enough that it won't go anywhere unless there's a pretty serious earthquake or somebody tries to tip it over.  this way, I can have a look at the guts without any serious demolition.

right now, I'm planning to make the exhaust out of galvanized flashing.  it will be square or rectangular coming out of the stove, just because that seems easier with rectangular bricks.  I'll make a 90 degree turn up at which point I'll spread it out substantially to a much longer rectangle to maximize surface area and heat exchange with the air since I won't have 30 feet of mass to strip heat out.  then out the wall using a piece of nice class-A chimney to protect the wood.  picked that up from a freecycler a few years ago.

I'm planning to paint the wall side of the stove and exhaust with high temperature paint with an insulating ceramic additive mixed in.  the wall is protected from the existing electric heater by a couple of panels that I suspect are asbestos.  I think I'll leave those in place and also paint them with some of the insulating ceramic for further protection, as the stove will only be about six inches from the wall.  if anyone thinks I'm going to burn the place down with that tight placement, please let me know.

I haven't decided whether to insulate the stove from the concrete slab it will be sitting on.  heating the slab up won't do me much good, but it will be more work to insulate.  if I do insulate, I'll probably use more of the perlite/clay slip.  thoughts?

that's about as far as I've gotten so far.  tearing out the old heater tomorrow, and hopefully starting to build shortly after that.  feedback or advice will be greatly appreciated.

I've never had a sauna, so i am kinda wondering what you use a sauna for?

Also is the sauna attached to the house and would there be a way to use the heat from the sauna to do double duty - like cook or heat the house?

sauna is an all-purpose remedy for finns.  my wife's family is all finnish.  they have a sauna at their place in the upper peninsula. 

sauna is great for sinus and respiratory problems.  it's wonderful for stress relief.  it's a great way to take a shower and stay clean.  it's great for skin issues and for detoxification.  i also understand that the sauna was the place where many women gave birth because it was cleaner and a high temperature inhibited bacteria and other nastiness.

the reality is that it's just a shower until the sauna gets to 120 degrees.

to the OP: what a great idea!!!  i'm interested in how fast the rocket heater heats up the sauna.  my father in law's wood stove takes about 90 minutes to really get up to temperature.  this may be by design, though, since it gives a chance to bath younger kids before it gets too hot for them.  when the kids are done, it's my turn to enjoy a beer and a steam!

ronie wrote:
I've never had a sauna, so i am kinda wondering what you use a sauna for?

Also is the sauna attached to the house and would there be a way to use the heat from the sauna to do double duty - like cook or heat the house?

I use a sauna to get really hot and sweat a lot.

this sauna isn't attached to a living space, but there's a chance I could build a greenhouse attached to it.  I do use it to dry laundry, sometimes, and to incubate miso and tempeh.

we typically shoot for about 180 Fahrenheit, which takes over three hours with the current electric heater.  I figure this new heater ought to be able to beat 200 Fahrenheit pretty quickly and easily, which is nice.  up to 240 Fahrenheit is pleasant if humidity is low.  I don't really know how long it will take, but I'm guessing maybe 30 minutes to get warm and 45 to get real good and hot.

ronie wrote:
I've never had a sauna, so i am kinda wondering what you use a sauna for?

In Russia the sauna is used to detox after a night of drinking.  You sit in the sauna and let the sweat carry out all the toxins.  A good way to wake up is to spend some time in the sauna, then run outside and jump into a hole you've cut into the ice on the lake.  (Jumping into a cold shower also works.)  Then, after you've finished shrieking with pain and your heart has decided to start beating again (just this once, you hear? and don't get no funny ideas, now) you do it all over again.  Sauna, sweat, soak.  Repeat.

it's sort of surprising to me how long I'm comfortable soaking in really cold water after I've gotten really hot in a sauna.  I'm not sure how that sort of behavior treats our cardiovascular organs, but the practice exists in plenty of cultures, so I expect it isn't that terrible.

on to my progress today:

dragged the old heater out.



when I opened up the service panel, it looked to me like it would be pretty easy to fix this thing.  it still worked last week, it was just taking way too long to heat up because only one of the two elements is connected.  if anybody local is interested in it, speak now (before my packrat nature kicks in) and you can have it.  pulling that out left this space for the new kiuas:



I'll probably have to remove the plumbing you can see.  it was nice to have that there, so I might just try to rearrange it to work with the new setup.  my grandpa put that in to spray water on the rocks of the old heater.  it's got one of the flush valves you see in public bathrooms attached to a shower head.  sprayed water for a few seconds, then shut off.  I would probably set it up to fill up a pail instead of spraying on the rocks.

you can also see the two white-ish panels protecting the cedar walls.  I don't really know what asbestos looks like, but I've found other asbestos around the property, so it wouldn't surprise me if that's what these are.  took a closer, though unfotunately not very clear, photo:

any guesses?  click on that picture for a much larger jpeg.

spent a couple hours cleaning mortar off used clay bricks for use where the fire bricks would be overkill.  anybody know of a better method than tapping them with a ball peen hammer?  because I'm kind of tired of that.

ronie wrote:
I've never had a sauna, so i am kinda wondering what you use a sauna for?

Also is the sauna attached to the house and would there be a way to use the heat from the sauna to do double duty - like cook or heat the house?

In days of old.... The sauna was the first building erected on a homestead. It was where women gave birth, the old went there to die, the young came of age and later got married. it was where grain was dried, meat smoked and malt dried to make beer. They also bathed there as today. It was the place that was warm in the winter. It was also a place that discouraged lice, nits and cockroaches in the less sanitary conditions of the past. While the word sauna comes from Finland, there have been huts or buildings of the same function in all northern climates as far back as 4000 years. Both in North America and Northern Europe.... right through to eastern Russia.

Info from "The Book of Masonry Stoves" by David Lyle

It seems in those days many buildings where built on a homestead instead of trying to fit it all in one building. Fire was a real problem with softwood trees for fuel, putting it in a separate building just made a lot of sense. Different styles of buildings worked better in summer then in winter. A summer kitchen of just a roof over the stove was cooler to work in and didn't over heat the house.  Even today in Mongolia, the average family will use two Ger (yurts) in the summer but only one in the winter.... using the extra insulation from the second to keep the winter Ger warmer.

Not so sure where I read the rest

not a whole lot of progress today.

used an old perforated baking sheet to screen some clay for mortar.



the sand I mixed in was pretty wet, so the mortar ended up a little sloppy.  I'm hoping that won't cause problems.

I put down one course of bricks to hold an insulating bed of perlite and clay slip.



I discovered that if there is such a thing as a natural talent for bricklaying, I am not afflicted with it.  got very slightly more proficient at it by the end, but I only had sixteen bricks to practice on, so I'm still very much toward the incompetent end of the learning curve.

perlite isn't arriving until Friday, so I can't do much more construction yet.  I'll lay out the first course of fire bricks for the burn unit for visualization purposes.  I'll put a couple of bricks down directly on the slab where the bottom of the feed tube will be and I'll put a few more under the heat riser to support the weight.  and I'll clean cement mortar off more used bricks.  bought a cheap masonry chisel today, which I'm hoping will make that chore a bit easier.

Why are you not using cement mortar?

ronie wrote:
Why are you not using cement mortar?

a few reasons.  chief among those is that the clay and sand takes a lot longer to set, and that it's a lot easier to break apart if I screw it up.  I would also like to be able to tear this whole thing out without too much trouble.

didn't do anything too exciting today.  spent a while cleaning bricks and laying out the brick parts of the burn unit.  after seeing the bricks in the actual space, I think I'm decided to spin the whole thing around 180° from my original plan.

looks good Tel.

you might think about a SS mixing bowl for the heated rocks. the spray head for water on the rocks is a good idea if you can keep it. Also remember to insulate the heck out of the heat riser.  (one of the typical things that folks forget when using well case) Nari can fill you in on what happens when the stove temps equalize.

Ernie Wisner wrote:
looks good Tel.

you might think about a SS mixing bowl for the heated rocks. the spray head for water on the rocks is a good idea if you can keep it. Also remember to insulate the heck out of the heat riser.  (one of the typical things that folks forget when using well case) Nari can fill you in on what happens when the stove temps equalize.

thanks, Ernie.

my plan was to insulate the pipe with just shy of 3" of perlite and a little clay slip all around.  with a 16" pipe as my heat exchanger, that's as much as I've got room for.  does that sound like enough to do the job?

yep just make sure you put as little clay as possible in the perlite mix. you want as much air in it as you can get.

Remember we are dealing with heats that are in excess if 2000 deg F so its a fun balancing act to get the mix with just enough clay to vitrify with little enough to not mess up the insulation properties. Wish i had better info but each clay is different.
I really want to see this build when its done.

course i like a good sauna any ways; I suspect its in the blood

Ernie Wisner wrote:
yep just make sure you put as little clay as possible in the perlite mix. you want as much air in it as you can get.

Remember we are dealing with heats that are in excess if 2000 deg F so its a fun balancing act to get the mix with just enough clay to vitrify with little enough to not mess up the insulation properties. Wish i had better info but each clay is different.
I really want to see this build when its done.

course i like a good sauna any ways; I suspect its in the blood

light on the clay: check roger.  Ernie, I would be pleased to have you come see it when it's done.  I'm not too far from you.  heck, anybody in the area is welcome to stop by for a stove tour and sweat.

progress today: put in a bed of perlite and clay to provide a bit of insulation from the slab.  went a little heavy on the clay to provide a little support.



the two bricks on the left will be the bottom of the feed tube.  the two on the right will support the weight of the two heavy steel pipes.

put a heater and fan on it, but I'm guessing I'll have at least a day before this sets up enough to proceed.

I sure do appreciate the blow by blow. It's great to see your progress.

Silver wrote:
I sure do appreciate the blow by blow. It's great to see your progress.

good.  I'm hoping folks will point out mistakes if they see them.  my slow progress should make it easier for me to undo something if I screw up.

put another layer of clay bricks around the outside, placed the bottom bricks of the burn unit, and filled in with perlite and clay.



then the next level of the burn unit and more insulation.



biggest problem so far is that I didn't screen the sand for the mortar very well, so I had to pull some little stones out today.  learned that lesson, though, so future batches will be more carefully prepared.

ran out of cleaned clay bricks, so there's some time with a hammer and masonry chisel in my future.  heat exchanger arrives Wednesday, and I'm hoping to be ready for it by then.

forgot the camera, so no new pictures today.  put in the next course of fire bricks and placed the 8" pipe.  something that I've been worried about is fitting the 16" pipe over the top since the ceiling is fairly low.  I'm holding off sealing the 8" pipe for now, because I think I may need to tip it to get enough clearance.  that's going to be a bit touchy.  it'll take at least three strong-ish people in a rather small space moving rather heavy things very carefully.

been putting off cleaning more clay bricks, and I need them before I go any further.  I also need to install some sort of shield for the wall closest to the heat exchanger.  I had planned to move one of the two asbestos sheets, but after trying to pull out the nails I'm pretty sure that's not going to work.  so I'll leave those where they are and rig something else up to protect the wall.

may not update for the next couple of days, as I've been putting off some other work that is becoming more urgent as temperatures drop.  back soon, though.

yeah, with asbestos tiles, you might be better off leaving them where they are and painting them with a paint capable of handling the high temperatures.  seal and forget, rather than remove and breath.

I'm not entirely sure they're asbestos, but it seems safer to assume that they are.  I don't think there's much risk of them crumbling into something airborne, fortunately, so I think the health risks are minimal.

the one I briefly tried to move felt a little bit like wet particle board that has lost it's integrity, and I really doubt it would have survived a move intact.  it's still providing some protection where it's at, as the exhaust will pass close to it, so I'll just leave it be.

I've got a respirator handy in case I change my mind.

Awesome project.
And thanks for all the cultural anecdotes about sauna history, everybody.

I'm going to chime in a sprinkle of "two cents" on some of your questions, even though I may be coming in too late:

- Distance from wall: If that's a wood wall, I hope the 'barrel' equivalent is in the asbestos-insulated corner.  I'm afraid from re-reading your notes that you are putting the 'barrel' against the un-insulated wall, with the fuel feed in the corner. 
You'll likely need a heat shield.   
(Heat shield: Get a thermally resistant panel - even just some scrap metal will help, though something like refractory, ceramic tile, or cement-board is better - some bolts, and some 1" spacers cut from some type of pipe.  Bolt the panel onto the wall using the spacers to maintain a 1" gap for air flow between the panel and wall, all the way around, but especially at top and bottom.)

- Distance from ceiling: a concern.  I can see your point about tilting and many big people in a small space.  Might even be worth setting up a block and tackle, so you can hang the barrel component in place while you fix the seal on the heat riser.  Or pre-stack them inside each other, then move into the finished space, and have 2 guys hold them both up, then release the inside one onto your fresh mortar seal, then release the outside one onto its seating. 
I hope the finish height does allow plenty of room to the ceiling: Masonry heaters allow at least 18", and wood stoves something more than that.  Might need a ceiling heat shield too. 

- I'm glad you decided to insulate under the firebox.

- How to hold the rocks:
-  I'd be tempted to put the rocks directly on top of the metal barrel itself.  This is the hottest part of the system, and a place where cooling is useful to the draft of the system.  And in saunas I've visited, you want the rocks hot enough to go "hssss" and put out steam when you wet them.  The exhaust is very warm, but I've never heard anything go "fsss" at my exhaust cleanouts, even when we expose them while the system is actively burning.
- You might be able to add a decorative cut-metal rim from the same type of pipe, or use heavy iron wire to make an attractive cage.  I like spirals and Celtic knots, myself, if you have the time.  Or use your newly-developed masonry skills to lay a dry, no-mortar course of brick to hold the rocks in place.

- Cleaning bricks:
Cement mortar is a pain in the butt.  It's easy to break the brick instead of the mortar.  If it was lime or clay mortar, you would not be bothered by it, as you can simply dust the bricks together like erasers, catch the edges of the mortar, and flake it off.   
We sometimes use the bricks themselves to knock the mortar off, and just keep the pieces for infill.  Better still is a brick set (like a wide, cold chisel) that you can tap with a mallet.  Easier on the hands than a ball peen hammer, anyway.  Set the bricks on something firm, but not brittle, like asphalt or a little chunk of plywood, to get a good whack with less chance of shattering the brick.
Grinding off the last few bits can be more effective than chipping, and you can do it with any reasonably hard, flat thing ... like a brick for instance.

- Bricklaying is tricky.
I'm still learning, and it's hard to share verbally.  Best to watch an experienced bricklayer work for about 30 minutes, then try it for two hours, then watch him again.
Things I can convey verbally:
- With clay mortar, make sure the bricks are wet or damp so the mortar sticks.  Looks like you are doing fine on this, or your mortar is wet enough that it is sticking just fine anyway.
- Don't try to put an even layer of mortar in place like you are finding on the old bricks.  Instead, make a nice ridge of mortar, then press the bricks together, so the mortar squishes in between and you don't get air bubbles.  You can spread the ridge of mortar down where you are going to place the brick, or "butter" each brick as you place it.  Then tap your brick down until it's flush and level.  You can do the same thing, simultaneously, with the sideways joints by buttering the side of a brick with a little sideways wedge, then tapping it in before you tap it down. 
- Don't tap it too far; lay the whole course with some wiggle room, and then level the whole course. 
- Also, notice how the corner joints in your burn tunnel course make kind of a spiral, like a sunwheel or swastika?
That's a good trick to use, so you can make inside corners without running joints, by varying that spiral clockwise or counterclockwise.  When you have a straight line along one side of the box like on the bottom layer of red bricks, then you will need to cut half-length bricks or be very lucky to get even dimensions in the next course.  You don't want running joins (places where two bricks edges line up vertically) because they tend to fall apart easier, just like with Legos.

- For the heat riser, we usually put a ring -shaped ridge of mortar on the bricks, then lower the heat riser onto it, level, and set it down firmly in place.
- Make sure the gap between the heat riser and the flat surface of the barrel is right (about 2-2.5 inches) even with the differences in mortar and brick heights of their supporting courses.  Use thicker mortar or broken brick if needed to make up a partial difference in heights.

thanks a lot, Erica.  you're not too late at all.

that is a wood wall.  pretty old cedar or redwood.  I was initially planning to put the barrel (pipe, in my case) in the corner with the asbestos, but changed my mind as I started laying things out.  your suggestions for a heat shield were roughly the direction I was headed.  I've also got some high temperature paint and some ceramic additive that's supposed to insulate against radiant heat.  I'm not counting on that to do everything, but I'm going to paint the wall side of the barrel and whatever I use to shield the wall with this stuff.  I'm hoping it will give me a little more wiggle room, at least.

from the ceiling: there will be at least 24", possibly a little more.  I'll pay close attention to the temperature right above it.  if it's getting too high, that will get a shield as well.

I don't think a block and tackle will work, as the ceiling in this sauna isn't fixed to any really strong structural wood.  we may be able to block it up with some extra bricks or boards while setting the heat riser, though.  putting them up together could work, too.

on the topic of setting the heat riser: what is the best way to make that joint?  you mentioned a ring of mortar, but I'm transitioning from a square to a circle.  right now, the riser is setting on three bricks with gaps at the corners.  should I break a couple of bricks to set under the riser in those corners?  cover the gaps with brick chips and mortar?  something else entirely?

rocks: I was figuring I would put a pail of water on the very top to heat up and dip from there to toss on the rocks.  I envisioned some sort of doughnut-shaped metal basket that would fit over the top to hold the rocks near the top, but still allow room for a bucket there.  certainly haven't worked it out entirely just yet, and your ideas sound good.  really hot rocks is very important, though.  creates good negative ions that make the whole experience a lot more pleasant.  that's one of the big motivations to go with a wood stove in there instead of fixing the old electric heater.

brick set: looked at one at the hardware store.  bought a masonry chisel instead.  it's much easier than the hammer alone for cleaning bricks.

bricklaying: I was slowly muddling through toward some of your suggestions on my own, but your tips will help me a lot for the remaining courses.  for the clay bricks, I did have to use one split brick for each side of the rectangle on the second course, but my new masonry chisel made that pretty easy.

thanks again, Erica.  I think you saved me a fair amount of head-scratching.

tel jetson wrote:
thanks a lot, Erica.  you're not too late at all.

that is a wood wall.  pretty old cedar or redwood.  I was initially planning to put the barrel (pipe, in my case) in the corner with the asbestos, but changed my mind as I started laying things out.  your suggestions for a heat shield were roughly the direction I was headed.  I've also got some high temperature paint and some ceramic additive that's supposed to insulate against radiant heat.  I'm not counting on that to do everything, but I'm going to paint the wall side of the barrel and whatever I use to shield the wall with this stuff.  I'm hoping it will give me a little more wiggle room, at least.

I'm glad.

You can also offset the barrel a little more toward the room if you need to - this generally moves most of the heat toward the room, though it can create a small hot spot on the narrow side.  Would give you a few more inches for a heat shield, anyway.

I haven't used spray-on ceramic heat protection, though we did just find a pamphlet for it at our clay shop.  Please let us know how it works out. 

we may be able to block it up with some extra bricks or boards while setting the heat riser, though. 

Sounds practical.

on the topic of setting the heat riser: what is the best way to make that joint?  you mentioned a ring of mortar, but I'm transitioning from a square to a circle.  right now, the riser is setting on three bricks with gaps at the corners.  should I break a couple of bricks to set under the riser in those corners?  cover the gaps with brick chips and mortar?  something else entirely?

We find that if the burn tunnel is sized right, the heat riser will rest on the bricks on all 4 sides but not on the corners.  We usually encase the heat riser in insulation before installing it, so that the insulation container also helps stabilize the riser against the brick. 
We build our round ridge of mortar right on the edges of the square brick hole, and use thick earthen mortar (we call it "thermal cob" in other places) to make a good seal in the corners.  Reaching in through the fuel feed, you can smooth the inside and remove any mortar that squishes through and falls in.

Your method, supporting it on 3 bricks and then filling the gaps, could work well.  My only concern would be to avoid narrowing the opening too much; it could be easy to squish mortar in, or shove wedges in, farther than necessary for support.

p.s. A pet peeve:

ronie wrote:
Why are you not using cement mortar?

Tel's reasons are good ones.

tel jetson wrote:
a few reasons.  chief among those is that the clay and sand takes a lot longer to set, and that it's a lot easier to break apart if I screw it up.  I would also like to be able to tear this whole thing out without too much trouble.

didn't do anything too exciting today.  spent a while cleaning bricks and laying out the brick parts.

I'd like to add:

Cement mortars don't handle high heats well (the lime cooks out and erodes).  In woodstoves and fireplaces, either dry masonry, or fireclay mortars, are preferable.  If cement is used, it must be refractory cement rated for the relevant temperatures.

My pet peeve is the over-use of cement in applications where it is destructive.

  Cement does not suffer from damp, and in fact will set underwater.  But it does transmit damp to other building members.  Transported moisture from cement mortar slowly destroys soft clay brick and some types of stone.  Cement stuccos cause catastrophic failure of earthen (adobe or cob) walls, in several cases walls that had previously withstood centuries of weather with minimal maintenance.
  Cement in effect transmits the problem of damp closer to the user, where hopefully it can be dealt with more conveniently.  When mis-used, it creates damp interfaces that compromise other materials' integrity and residents' health.

And its durability and adhesion, that make cement so popular, also makes it a pain in the butt to remove.  (I've spent a lot of time chipping old mortar off bricks, and lime mortar actually protects the brick, while cement mortar adheres and chips the brick with its removal.) 
In effect, cement and concrete are usually a permanent solution to a temporary problem.

Ernie Wisner wrote:
Also remember to insulate the heck out of the heat riser.  (one of the typical things that folks forget when using well case) Nari can fill you in on what happens when the stove temps equalize.

I sure can.  Here's the link to the workshop report (with pictures).

http://norishouse.com/archives/436

Nori

Erica Wisner wrote:
You can also offset the barrel a little more toward the room if you need to - this generally moves most of the heat toward the room, though it can create a small hot spot on the narrow side.  Would give you a few more inches for a heat shield, anyway.

any range you would give for the temperature of that hot spot?  an off-center barrel was also part of my plan.  the high temp paint I've got is good to 1000 Fahrenheit.  is it likely to be hotter than that on the outside of the narrow side?

thanks for the link, Nori.  insulation it is.

not that we have seen Tel about 800F if you push the system with oil normally around 400 to 500F for a good clean burn. a small magnetic burn indicator can be had from a local hardware store for about $10.00 and it will help you see the barrel temps.

Ernie Wisner wrote:
not that we have seen Tel about 800F if you push the system with oil normally around 400 to 500F for a good clean burn. a small magnetic burn indicator can be had from a local hardware store for about $10.00 and it will help you see the barrel temps.

good to hear.  makes things simpler for me.

bought some sort of cement panel today to cut up into shields for the wall and ceiling.  got some screws and spacers and washers, too.  I'm hoping that will be the end of my purchases for this project.

asked about making the duct work in another thread, that I'm bringing over here now.

Chris K e n d a l l wrote:
If you want the heat to radiate from the exhaust pipe, as long as you are following the dimensions for the heater, i figure you don't need any kind of round on the pipe. Rectangular should be fine. Your system isn't gonna be horizontal, embedded in anything, so the heat will rise like other fireplaces. If you want the heat to radiate from the pipe and not up the flue, you might want more resistance. Maybe?

It is easier to cut a square into a round pipe. Much.

Do you wanna continue this thread at the thread for your sauna?

Chris

without a properly appointed shop, how would you recommend bending the galvanized sheet?  I've got some tools, but nothing specifically for this sort of thing, apart from maybe some tin snips.

the other question I have concerns the junction at the round stove pipe.  how should I do that?  I'm imagining cutting a hole the same shape as the rectangle duct, then cutting at the corners of the rectangle maybe an inch down to make tabs to bend over inside the round pipe.  then secure it with screws and some caulk.  that sound at all reasonable?

I have a 3' long brake in my garage but if i need to bend something longer...

I bought some used stuff at a habitat store this past fall and bent it up on a picnic table. I used a piece of angle iron longer than the duct, so longer than 60", sat it on the long side of the picnic table; the table is 8'. The angle iron is gonna have to be sat opening down: imagine your left hand making the L shape, like kids do when they're signing "loser". Rotate it clockwise 90 degrees; that's how the angle's sat on the table. Then I laid the metal on top of the angle, inside of the duct down, so it's kind of counterintuitive but you'd have to mark the duct on the other side from the one you're bending, unlike using a shop brake. then I put a long 2x4 on top of the duct, flush with the angle iron, and used locking C vise grips to hold the wood on top of the angle so's it wouldn't wiggle. Then I pushed the metal down, gradually, pushing it at the edge it's clamped at the table. Takes a couple of pushes to get the metal to sit close to 90, then I took my tinner hammer, a riveting hammer with a nice flat hammering surface, and hammered the corner tight. If you're trying to make a piece of duct from one piece of steel, you do this three times, assuming the snaplock connection makes the fourth bend.

This will give you an idea of how it might look: http://www.ch601.org/tools/bendbrake/brakeplans.pdf

I used this guy's brake as a mental model of how to hold the metal down; the first piece of angle iron serves as backing for a tight bend; the second angle iron in his pix serve to secure the metal, I used a piece of wood; the third piece of angle he used to actually move the metal, I used my hands since it was just 26 gauge, what's usually sold in the stores for residential.

If you don't want to go buy angle iron, I have found it on craigslist for free in the disguise of bed frames. The stuff they make hollywood frames out of is almost always six foot.

Cutting metal is dicey but you wanna make sure you have reds and greens aviation snips, not the skinny ones from Wiss but a decent pair like Midwest, they sell them at Sears as a set and they have fatter blades than your regular snips. You have it fairly right and I'm assuming your duct is connecting to the round at a ninety degree angle, but first you wanna cut the shape of the round duct into the rectangle, make sure it fits up dry, mark out the new shape of the rectangle onto the round, cut out your hole in the round duct, fit it up again, scribe back about three quarters of an inch on the rectangle and make tabs. It's more secure on the pipe if you dovetail it, fold out every other tab so half the tabs are inside the round and half are flat on the round, then you can screw the ones on the outside and flatten the ones on the inside and it'll be secure.

I would suggest some expensive high heat caulking; I recently used Hilti's FS-1 to seal some holes on a regular fireplace flue and after three weeks I'm still smelling it cooking when I have a few too many pieces of wood in it.

Good luck and feel free to ask away. I'll be back and forth tomorrow, gotta go buy some cheap screws from a Restore.

Chris

Erica Wisner wrote:


Tel's reasons are good ones.
I'd like to add:

Cement mortars don't handle high heats well (the lime cooks out and erodes).  In woodstoves and fireplaces, either dry masonry, or fireclay mortars, are preferable.  If cement is used, it must be refractory cement rated for the relevant temperatures.

My pet peeve is the over-use of cement in applications where it is destructive.

   Cement does not suffer from damp, and in fact will set underwater.  But it does transmit damp to other building members.  Transported moisture from cement mortar slowly destroys soft clay brick and some types of stone.  Cement stuccos cause catastrophic failure of earthen (adobe or cob) walls, in several cases walls that had previously withstood centuries of weather with minimal maintenance.
  Cement in effect transmits the problem of damp closer to the user, where hopefully it can be dealt with more conveniently.  When mis-used, it creates damp interfaces that compromise other materials' integrity and residents' health.

And its durability and adhesion, that make cement so popular, also makes it a pain in the butt to remove.  (I've spent a lot of time chipping old mortar off bricks, and lime mortar actually protects the brick, while cement mortar adheres and chips the brick with its removal.) 
In effect, cement and concrete are usually a permanent solution to a temporary problem.

It looked to me that the clay bricks were not going to get much heat as they look insulated from the rest of the stove.

I was thinking of ordinary mortar mix as time saving in this app. The screening of the clay looked labor intensive, but you are right Tel's reasons are good ones as are yours.

ronie wrote:
It looked to me that the clay bricks were not going to get much heat as they look insulated from the rest of the stove.

I was thinking of ordinary mortar mix as time saving in this app. The screening of the clay looked labor intensive, but you are right Tel's reasons are good ones as are yours.

Screening the home-sourced clay is a quality control choice, works like a cheese grater to make it mix more evenly, as well as eliminating any gravel or roots.  I don't usually use anything smaller than 1/4 inch mesh.  Then we make a smooth slurry/slip with a paint mixer.  But his small screen might actually save time on the mixing, he's essentially making an instant clay 'powder' in wet form. 
Lime mortar or bagged, powdered fireclay would not need to be screened.  Not sure how the bulk prices compare to 'ordinary' mortar mix, fireclay is about $20 the 50lb bag here, and lime was cheaper than that if I remember right.

You're right that temperature is not the issue on the red-brick surround.  My concern is the trapped moisture.  It's gonna be a damp place, this one: steam/condensation, sweat, steam from any wet wood, damp inherent in the building process, and also potential spills from the sauna.  I hope he's allowed for decent drainage and drying.

Cement traps this moisture, keeping it from escaping over time.  Moisture levels over 15% would de-stabilize any earthen masonry within the box.  Dry-stacked masonry, or vapor-permeable materials that allow water to escape again, will help keep the system drier between uses.

The other option if you are into cement mortar for the casings, is to go with cement-compatible materials all the way through the install.  That means something like refractory cement to stabilize the perlite insulation; and probably dry-stacking the firebrick with refractory insulation around it, an expansion joint, then the cement-mortared masonry casing.  Soft clay brick would not be compatible here, you'd need the harder-fired modern brick.

Then trapped moisture would not affect the stability of the hot elements, though it could lead to steam-cracking in various places as the system heats up.  Hopefully, they'd come up with a warmup and cool-down protocol that would keep the system relatively dry for firing.

The technicalities of making high-temp devices compatible with cement mortar might explain some of the high cost of code-compliant masonry heaters.

when I saw 1 of those pictures, I thought to myself: OH! asbestos in a sauna! that is terrible! I am only judging by the looks of it, but I strongly recommend to REMOVE IT QUICKLY. instead of your sauna solving respiration problems, you can get into some very serious problems (lung cancer) with that stuff in there.

xul wrote:
when I saw 1 of those pictures, I thought to myself: OH! asbestos in a sauna! that is terrible! I am only judging by the looks of it, but I strongly recommend to REMOVE IT QUICKLY. instead of your sauna solving respiration problems, you can get into some very serious problems (lung cancer) with that stuff in there.

fortunately, it isn't at all friable, so it won't be getting into anyone's lungs.  asbestos can be nasty stuff, for sure, but in this form it isn't a danger to anyone unless there's some sandpaper or grinding involved.

So did my post help? Didja bend that metal?

Chris

Chris K e n d a l l wrote:
So did my post help? Didja bend that metal?

Chris

haven't done it yet, but I think you're post will end up being helpful.  I've still got some more building of the stove to do before I know the ideal dimensions of the duct.  just wanted to figure some of it out ahead of time rather than scramble when the time comes.  I'll certainly post about it when I get there.

Erica Wisner wrote:
Similar to cutting a hole for a window or dryer vent.  You cut through the siding and TG (or remove it in pieces if that seems easier), frame in a box in the wall itself to fit around the hole, and make sure you have enough thermal protection to keep hot pipe from setting dry wood on fire.  You can get triple-wall connections for ducting or stovepipe, or boxes designed to accept round stovepipe, to keep the pipe centered in the hole.  Or you can build your own with high-temp insulation and heat-resistant supports.  When we plumb these through cob walls, we sometimes stuff some perlite-cob around them.  We've used commercial triple-wall, or created simple flashing collars from scrap metal, for off-the-grid exhaust ports on RMHs.

I'm suggesting high-temp for your stove because  it's a big one with a short exhaust, so you may still be at stovepipe temperatures exiting the wall rather than the low temps that most RMH's achieve.

I've got a piece of stainless steel Class A chimney that I was planning to use for the piece through the wall.  I believe that's the same as triple-wall, but it wouldn't surprise me to find out that I am mistaken.  figured I would just leave a half-inch all around and collar it on both sides.  if that doesn't sound adequate, I'll definitely reconsider other options.

tel jetson wrote:
I've got a piece of stainless steel Class A chimney that I was planning to use for the piece through the wall.  I believe that's the same as triple-wall, but it wouldn't surprise me to find out that I am mistaken.  figured I would just leave a half-inch all around and collar it on both sides.  if that doesn't sound adequate, I'll definitely reconsider other options.

Sounds like the right stuff.  Sometimes it's triple-wall with air gaps, sometimes a smaller, insulated double- or triple-wall section.

New, it usually comes with instructions that tell you the acceptable clearances. 
I think ours had a 2" minimum clearance for thru-roof; we gave it about 4" as the box and flashing made that easy to do.

I found some pix at:
http://www.efireplacestore.com/class-a-chimney-pipe.html
and
http://hearth.com/econtent/index.php/articles/installing_a_woodstove

in case that helps anybody.

-Erica Wisner

haven't made any real progress, but I wanted to post a few more photos.



the three bricks on top there aren't permanent.  the heat riser isn't either, yet.  just set it up for visualization purposes.

here you can see how much space there will be above the heater:



here's the heat exchanger:



that had a protective coating of bitumen on it that I ground off.  any suggestions for maintaining that nice shiny metal look?  I'll probably just end up painting it with black stove paint, but it would be great to be able to see the metal.

my piece of class A chimney:



it's got some handy brackets to bolt it to the wall.  looks like it was real nice at one time.  now it's just functional.

tel jetson wrote:
the heat exchanger:

that had a protective coating of bitumen on it that I ground off.  any suggestions for maintaining that nice shiny metal look?  I'll probably just end up painting it with black stove paint, but it would be great to be able to see the metal.

You can oil the metal like you would cast iron, with walnut or vegetable oil.  It does darken up a bit, but you get some of the metal sheen on the highlights, and it keeps it from rusting.

Erica Wisner wrote:
You can oil the metal like you would cast iron, with walnut or vegetable oil.  It does darken up a bit, but you get some of the metal sheen on the highlights, and it keeps it from rusting.

nice.  I'm definitely going to try that.  any recommendations for the best oil?  I saw some expired walnut oil and grape seed oil and flax oil all for real cheap.

tel jetson wrote:
nice.  I'm definitely going to try that.  any recommendations for the best oil?  I saw some expired walnut oil and grape seed oil and flax oil all for real cheap.

I'd grab both the walnut and the flax.  I don't know much about grape seed oil.
But the walnut oil is Ernie's preferred choice for the metal treatment. 
Flax oil = linseed oil without all the nasty additives, good for paints and woodworking as well as the Omega-3's.