Rocket stove recomendations for a Newbie?

Hey Everyone,

I have been lurking about for quite some time with great interest. I have been looking forward to warm weather so that I can start tinkering with my first RMH just for fun.

Well, that was the plan until I opened my electric bill the other day. This is our first winter in our new (to us) 340sq ft home and I knew our heating cost would be something to contend with but I did not expect almost $400 for a month!!

Now I am motivated to come up with a practical method of burning wood as efficiently as possible. The RMH concept looks great on the efficiency side but I am not certain how I can implement it practically.

Space is VERY limited and the layout is not flexible. I have an available "cubby" that is 42"w x 24" d x 44" t and is built of wood. I don't think that I can place the rocket stove in that space and I have some reservations about having the firebox of my first attempt at a homebuit wood stove inside my living space.

Q: Is it practical to place the burn chamber etc outside and duct the heat inside? How about heating water with the stove and using some sort of hydronic solution inside?

Q: Are lumber (2x4) scraps a reasonable fuel? Any issues? I have easy access to a quantity of this.

Q: Has anyone come up with any sort of feed system that would keep the heater fueled for several hours?

Q: I see that metal is not the ideal material to line the firebox/chimney. How about using a cardboard (sonotube) liner as a form for fire clay? It would be sacrificial and burn out during my first burns.

I am sure that I will come up with a few more

Thanks for your assistance.

Steve

i saw your post and recognize desires that you may want, seem like the desires i built into my system.

1 my system is portable and is on wheels and have a small footprint. my rocket stove unit is roughly 3ft and holds a remarkable amount of stored heat in the RMH base unit alone with out my mass bench and i have instructions on how to build it with video documentation and pictures and many updates.

2 i cook on the top of my RMH, bake with it, and heat my water and my house.

3 my system can be as efficient burning or long burning as you want with 8 hour burning lengths.

4 i have 30 second cold start ups and reaches full load in minutes with no babysitting.

5 extra large feed chamber allows easy starting access.

6 large loading can handle 10.5'' x 18'' logs

7 large feed chamber and access port allow easy cleaning and maintenance.


i can move my system out on the porch in the summer to cook on so it doesnt heat the house in the summer.
First Rocket stove heats water with pics

Steve Smyth :Welcome to Permies.com, our sister site Richsoil.com, and the Rocket and wood stoves Forum Threads ! I think it would be helpful to follow along at this

on going forum thread and then ask questions here -at least to start ! ///Seelink below :


https://permies.com/t/52684/rocket-stoves/chimney-sealed-RMH


Have you been to Rocketstoves.com to Download your PDF Copies* of the New 3rd Edition of Rocket Mass Heaters? This is ''The Book" and will Save time, effort,

Money/materials and frustration as you learn the basics of Sizing your Rocket to include The need for Constant Cross-sectional areas C.C,-S.A.s and length ratios

of the 3 parts of the combustion core, their sizes, shapes, and orientations to themselves and the whole . All the math is 4th grade stuff .

It is strongly recommended that you build your Rocket out doors a then move inside when you have proved you have a working model .

The Rocket Mass Heater RMH, like all other Wood stoves is a space heater, and like a wood stove it should be placed in the core of your

house and where it can be easily watched. As you are adapting your RMH to your house some compromises are to be expected.Lets see.


Q1a) See above , There is never a sufficient reason to put a RMH outside, Your Rocket can only serve you as well as you serve it, if it is in

a remote location- tending it will Always be an interruption of your life, and a Drudges task that you will invent excuses not to avoid .

THis is a difficult project for a 1st time builder, and requires modifications to the homes structure !

Q1b) Any water system using solid fuel stars off with a handicap -you can't just turn off a RMH /Wood stove. To be safe this system

must be an un-pressurized system that circulates water by syphoning action. Without a sufficient volume of circulating water you will be in

danger of the over heated water flashing to steam an explosive ''Boom Squish'' event ! Think Boston Marathon Bombing only with more

Full body, Full thickness burns - If some one is in your house when this happens they will probably be family !


Q2) Split into 2X2s they will make excellent fuel, your wood should be small, very dry, and fine split


Q3) Yes! however a traditional D.I.Y. 6'' J-Bend RMH, easily capable of being built by a 1st time builder will provide you 12-24 hours of heat

radiating from your Thermal Mass Bench for every hr of attention. Worse case should be 2 hour long burns a day. The batch box style RMH

is an advanced build requiring the skills you learn building your 1st Rocket and a few special components, plus space Vertical and Horizontal

and some special tools !


Q4) Sonotubes™ can be used as a sacrificial form to allow you to create a Heat Riser out of Fire clay and Perlite, Fire brick is still needed for

the Feed Tube and Burn Tunnel there they deal daily with not only heat but the increased amount of Wear that will rapidly Crumble ordinary

Fire clay and Cob mixtures !

It will help us help you if we have your general location ( elevation is often important ) and climate, and later a sketch of your proposed layout.

For the good of the Crafts ! Big AL


* One to use, one to lose, and one to loan to a close friend

Figure I'll pop in and try to help a little since it's RMH season and it's forefront in my mind anyway

First, I'll second what Allen said about putting it outside. I built our beautiful, super efficient and hard working RMH out in our "sunroom" (a cheapo diy, plastic "half hoop house" attached to the south side of the camper we stay in while working toward our cabin) and the thing is such a pain in the side to deal with now. We don't really have a choice in the matter, but if you do, just don't Cooler intake air will cool your combustion some (with air below freezing doing so pretty significantly). That's just the start of it, though. Because it wont be "handy", you're likely to have more issues with the wood getting stuck as it feeds itself into the burn and causing you to lose your efficiency...these guys do definitely require LOTS of fiddling to keep things burning efficiently. I wouldn't mind one bit fiddling with something that's right there, but with the feed tube out of sight (and earshot), it's easy to not realize when that throaty, rockety goodness is less than ideal ... before you know it, either the thing is smoking back because wood fell in to the burn tunnel, blocking flow, or you're hanging over the thing like you're praying to the ol' porcelain goddess, dizzying yourself as you blow on what coals are left in an attempt to suss some life back into that incredible burn you had just moments before. Needless and super annoying to say the least

We HAD to put our entire system "outside" in that sunroom (a camper trailer doesn't work well with a RMH no matter how creative you get). That means we miss out on tons of the RMH benefits. We also have to run the thing 5x more than we would otherwise need to, keeping it going for sometimes 12-14 hours on those really frigid, subzero nights here in central Maine. That also means we burn tons of wood compared, a waste of resources, and have to stay up all night when it's really cold in order to feed and tend the beast. I absolutely love the RMH, but absolutely hate that it's "out there".

Put that baby inside, *in its entirety*, if you can possibly find the space ... it will save you a million and one headaches down the road and allow you to love that beast the way I wish I could.

As for attempting a hydronic system, the RMH is definitely not ideal for such application. Best to stick to the original, proven techniques with these guys, especially on your first build. One little miscalculation, clog or sharp bend causing an air lock and you'll have the potential for a steam explosion. If you want something for hydronic heating, look into methane digestion and those small "on-demand" propane water heaters for ideas. A RMH is a beast designed to work a specific way - deviating from this often results in total failure...when there's water in the mix, that failure could turn catastrophic

Any wood will burn in the RMH, even green/wet/rotted stuff. Ideal, though, is going to be dry hardwoods. Size of wood is going to be dependent on the size of your system as well. In our 8" beast, we burn wood ranging from 1" diameter round/unsplit pieces of poplar, alder and willow up to 6" split chunks of beech, birch and maple. In our new 4" RMH system, however, we're lucky to keep a 2" split piece of super dry fir lit long enough to burn down on its own...most of the wood that goes in there needs to be 1/4" to 1/2" diameter. (that brings up another tip - go bigger if you can...easier to work with, more heat and less headaches with the larger systems)

The biggest issues with dimensional lumber will be 1) the "chimney effect" you get with straight/vertical pieces of wood sitting side by side that create an interruption of flow, throwing smoke upward rather than sideways, and 2) pieces of wood creating a sort of "dam" that blocks flow of gasses into the burn tunnel. Burning dimensional lumber, even split down into smaller pieces, will require more fiddling to ensure things don't block up and cause smoking back. Of course, most of your dimensional lumber is going to be softwood as well (fir, pine, etc) and so wont deliver as much heat as, say, oak or beech or black locust. If you have a little bit of space, I'd recommend growing fuel - black locust grows like a weed and coppices beautifully, allowing you to get a lot of hot/long burning fuel in short rotation cycles from a very small area.

As for longer run times, your best bet is larger diameter and harder fuel woods like osage orange and black locust. You can push it a little on length of fuel wood (we routinely get away with pieces as long as 3 feet) but expect more and more issues with pieces hanging up, falling over sideways, etc as you go longer. Thicker pieces in a larger system will last a good long while. This morning bottomed out at about -1*F and I fed our 8" a chunk of beech about 6" wide, 4" deep, 2 feet long around 5am. I happened to look out there at 7am and about 1/4 of that chunk was still burning happily.

As for heat risers, I tried a few different techniques over the past few years:
1) 8" inner metal stove pipe with clay/perlite mix and 12" surrounding metal stove pipe...this failed with the inner metal degrading and collapsing in, causing the system to block up
2) 8" inner metal stove pipe with clay/perlite/peat moss and 12" surrounding metal stove pipe...this failed as the peat moss burned out and the air pockets in the clay were too large/clay too crumbly and the system stopped being as rockety
3) 8" inner metal stove pipe with 2" ceramic fiber blanket wrap and 12" surrounding metal stove pipe...this failed as the inner metal collapsed in again like #1
4) 8" inner metal stove pipe with 1" ceramic fiber blanket wrap, soaked in clay slip to give it a little thermal mass, and another 1" ceramic fiber wrapped around that, in 12" metal surround ... works awesomely for a year now

The ceramic fiber blanket was a little pricey, but so worth it in the end. Also, I built my core using the old standard of regular clay bricks (not fire bricks) and perlite. I used the plan from the old Ianto Evans book. Including purchase of all new materials, total cost for my 8" system's core came to around $300 - that includes the fiber blanket, bricks, perlite, course sand and 8"/12" round metal heating duct (incredible how expensive those elbows and tees are!).

Figured with my personal experience living with one of these for the last few years as our primary heat source, I might be able to help at least a little. You'll love your RMH if you build one, regardless of where you put it, but be prepared to end up in a love/hate relationship if you put that feed outdoors or in any other harder to access place.

Steve Smyth wrote:Hey Everyone,

I have been lurking about for quite some time with great interest. I have been looking forward to warm weather so that I can start tinkering with my first RMH just for fun.

Well, that was the plan until I opened my electric bill the other day. This is our first winter in our new (to us) 340sq ft home and I knew our heating cost would be something to contend with but I did not expect almost $400 for a month!!

Now I am motivated to come up with a practical method of burning wood as efficiently as possible. The RMH concept looks great on the efficiency side but I am not certain how I can implement it practically.

Space is VERY limited and the layout is not flexible. I have an available "cubby" that is 42"w x 24" d x 44" t and is built of wood. I don't think that I can place the rocket stove in that space and I have some reservations about having the firebox of my first attempt at a homebuit wood stove inside my living space.

Q: Is it practical to place the burn chamber etc outside and duct the heat inside? How about heating water with the stove and using some sort of hydronic solution inside?

Q: Are lumber (2x4) scraps a reasonable fuel? Any issues? I have easy access to a quantity of this.

Q: Has anyone come up with any sort of feed system that would keep the heater fueled for several hours?

Q: I see that metal is not the ideal material to line the firebox/chimney. How about using a cardboard (sonotube) liner as a form for fire clay? It would be sacrificial and burn out during my first burns.

I am sure that I will come up with a few more

Thanks for your assistance.

Steve

One more tip from my personal experience - use "bells". You get more heat from the gasses in a shorter length of bench if the chamber is larger than the diameter of your system. They really help suck that heat out of the exhaust and will save you quite a bit of money on ducting/pipe. For example, our 4" system has a run of about 15 feet - the entire bench is a chamber about 1 foot tall, 2 feet wide, composed of rocks, clay and sticks/logs. This is working beautifully and extracts just about every bit of heat from the exhaust The 8" system has a combination of ducted bench (about 20 feet) and 2 large bells (a 6" tall, 10 foot wide circular bell the dog adores and a 10 foot, 1 foot tall, 2 foot wide chamber through the duck house). The exhaust temp coming out of this baby is often cooler than the air temp going in the intake ... again, those bells are made of rock, clay and wood...very strong once they set up nicely and nicer to the wallet if you're looking at buying ducting new.

Thanks Everyone for the input.

It looks like I need to keep searching for a solution unless I want to build an addition to make space to put the stove inside.

I still want to build an RMH but it will have to wait for summer and will serve my outdoor entertainment area.

Thanks again.

Steve

why not build a mobile rocket stove on wheels.

Steve Smyth wrote:Thanks Everyone for the input.

It looks like I need to keep searching for a solution unless I want to build an addition to make space to put the stove inside.

I still want to build an RMH but it will have to wait for summer and will serve my outdoor entertainment area.

Thanks again.

Steve

Disappointing but understandable...but then again, the problem *is* the solution, right? Do you have a couch in your living room begging for a warm in the winter, cool in the summer replacement? How about a shoddy kitchen table you could replace with an earthen masonry slab replete with slate/granite/marble or natural wood top? I find it hard sometimes to remember that cob can be shaped and molded to nearly anything you want...I mean, you can literally build an entire home out of the stuff. Of course, do keep in mind that the cob will take time to dry, too, during which time the mass isn't going to help with heating as much, so winter is probably not the best time to be building the beast anyway. Depending on your house/home design, there's quite a few options available for installing one of these babies, though. My mind goes to the old barn where they tore up the flooring to install the ducting under-floor:



Another option is using vertical mass since the footprint needs to be small but the height is often not as much a factor. This would be basically a series of large cylinder or box shaped bell chambers, constructed of brick masonry, metal drums with drystacked mass, or even just some cob and rock. See the illustration on this page for an example of what I mean: http://www.dragonheaters.com/castle-build-masonry-heaters/ (I'm not affiliated with the dragon heaters people myself but know one of the permies is - she might pop in to give you some tips on space-saving designs if she's around)

More than one way to skin a cat ... er, layout the mass for a rocket

Tristan Vitali wrote:Another option is using vertical mass since the footprint needs to be small but the height is often not as much a factor.

http://heatkit.com/research/2009/lopez-rocket.htm