My first Rocket heater - questions about my core

Hi all, first post to your forum. I have been trolling it for the past few days absorbing as much info as i possibly can. I think i am ready to make my first rocket heater. But there is some information on the path i am taking that i am unable to find. I am hoping the nice folks at permies could give me a hand .

My main question is in reference to my heater core i am going to be casting tomorrow. My first build will be a temporary set up until i can get the resources to do a good build. But i would like the core to be as solid as possible if i can, with what i have. First mention i would like to make is that nowhere in my area could i find fire clay, so making my own refractory was out of the question. And unfortunately the only product i could find in any bulk was a 25lb tub of dry mix refractory cement (for almost $70 CAD). And i am unsure on a few specifics. I also have a 110 L bag of perlite to add to it as well as insulate the box. First i am curious to know if anyone could guide me as to how much perlite i should be adding to this stuff (or if i should scoop some vermiculite out of my poorly insulated -asbestos filled- attic, with extreme caution of course) something is telling my i will get a better product with the vermiculite, and if i should follow the mix ratios that are labelled on the bucket. Second is i live in an area where -20c is a all to common reality and if i should go with a 6" or a 8" core to heat up my just under 800 sq' living space ( again my walls have an insulation R-value of less than 10, if any at all). Third is how thick should the walls of my j tube be, i am going to design it based on the dragon core that keeps popping up on my searches. Cast it in halves to allow expansion and joint it with a gasket. I also have seen a few different dimension specs for the feed, burn, riser. Anywhere from 1,2,3 to 1,2,4. But the plans i have gotten for signing up for your news letter are 15, 21, 47. There is also a part where it says the feed tube is 5 x 5.5 is this an error?

Will thank anyone in advance, and most likely afterwards. You have a nice forum here, and i am happy to now be a part of it!

Sharing only what I've read here and there, a 6" system should be good for 800 square feet. There is a lot of information on the casting cores & risers. I haven't paid as much attention (yet) as I'm currently using stacked fire brick.

Have you seen Mat Walker's site: http://www.permsteading.com/viewtopic.php?f=6&t=289&sid=dc3370be6ef9405db7fa9bbf8f8a1af9 ?

Keep in mind this begins over two years ago but is still a very current topic.

Good luck!

Hi Kaj; Welcome to permies! Well where to start... I guess first off I should steer you towards ianto evans book rocket mass heaters , readily available online. This book will answer a lot of your questions. Also you need to go to you-tube and watch the videos from (broaudio) of matt walkers cast core and the cast riser video! attempting a two piece cast with only a 25# tub of refractory could be tough. Keep looking for clay, try a pottery supplier , call every building supply for miles around, call a mason and see if they can help. If you have your mind set on a two piece cast then you will want to locate 50# sacks of +2200 degree insulated refractory , i'm sorry but your 25 lb tub will not go very far. Now on to vermiculite.. don't use it . perlite when available is the better product. If your 800' home was well insulated a 6" rocket would work for you but in your case I would opt to build the bigger 8". You have very much to learn about building a rmh correctly don't rush in , winter is already half over. Get the rocket stove book and read/read/read, spend hours reading old posts here at permies its amazing how many of your question are already answered . You mentioned you are in Canada, Add a location in your profile and their may be a rocket builder nearby that could help you. Taking the time now will help you have a successful first build ... if you rush in you may spend hard earned $ and time only to be disappointed with the outcome.

how much perlite i should be adding to this stuff

0

Third is how thick should the walls of my j tube be

2.5-5 cm

I also have seen a few different dimension specs for the feed, burn, riser. Anywhere from 1,2,3 to 1,2,4

it's ratios. not dimension

Kaj Lind : Welcome to Permies.com and our sister site Richsoil.com, and the Rocket, Wood stove and Cob Forum Threads !

Size does matter, but you are kinda in a range where The 8'' system will be too big 90+% of the time (or unneeded) , a 6'' system is most likely all
that you will ever need, but days and days of -20 C or -4ºF would tax your system, though certainly a little tightening up and insulation should help you a lot.

Remember the cheapest / Green~est unit of energy ever is the one you don't use ! Please give us a little more information on your climate / location (?!)

Matt Walker has indeed done most of the heavy lifting for you, that is why you got so many recommendations from fellow members ! Just, Please! Be Care-
füll and use Due diligence ! There is a huge Boatload of Stinking,steaming crap on U-tube, and a lot of flaming units of death !

The worst part is knowing that these "Look what I have done ' videos will have zero follow-up to report on that units failure, and within 90 days there will be a
new crop of Franken-clones and other dangerous copy-cats !

For the Good of the CraFt ! Big AL

Personally, I think you should do more reading and research. To say "I'm casting tomorrow" and then ask the kinds of questions you asked tells me you are not ready for that step. Relax, take a breath, and slow down.

I suggest getting some fire brick, like 50 to 100 of them, and start by building a basic J-style rocket stove outside. Then add a barrel, and seal it and get it to draft properly. Then you will be able to take some temperature readings and start thinking about fitting this beast to your site. Of you may decide you prefer to have a batch box style. Again, build it outside, mocked up in fire brick. Get the basics down first. Then think about how these need to be modified for your home site.

Bummer, I know. No one wants to hear, slow down and relax, heheh.

Books: I think you need to study the basic book everyone talks about. It won't tell you everything you need to know, but it will get you off to a well grounded start.

Videos: Watch all the ones you can find on YouTube which feature the Wisners (Ernie and Erica). Good stuff. Again, not all you need to know, but useful info.

DVDs: This is optional, but you may find the Woodstove 2.0 or whatever it is called useful. Four DVDs. Good info.

What else?

Go to Donkey's forum too. Lotsa to read there: http://donkey32.proboards.com/#category-1

Keep reading here too.

What else? You might want to buy one of the plans the Wisner's sell. I have a couple of them, and no, I do not think they tell you everything you need to know. Nothing does! But it *will* show you what they did in a real live build, and one that has been used for at least one year, successfully. This is very, very good info.

Then after absorbing all this, you'll start getting it set in your head. Then you can start sketching your layout and your plans, and folks here will be happy to poke holes in it All for safety's sake, of course.

Oh by the way, I'm not picking on you. I suggest these recommendations because it is the basic path I have followed.
If you can take in the info easily -everyone is different in that speed- you'll get it together in a matter of weeks, and maybe a few months.
Then you build. And then you find out the stuff you can only find out by getting your hands in the cob!
Feeling the various cob mixtures, is exactly that in my opinion - feeling. Read all you can, watch all the videos you can, for sure, for sure. But there is nothing like getting that mix going in your own tub, with your own hot little hands getting into the clay, perlite, and whatever else you end up using. I really, really feel that part can only be learned by doing. But that could just be my own limitation. *I* could only learn it that way.