Trying to build a Rocket Oven! Help!

I bought the plans and have been cutting into my steel drums and it is tremendously helpful to have step-by-step help, even with how to operate a grinder. It is Idiot proof.

But there are 4 MAJOR deficiencies that are NOT idiot proof and I'm stumped with how to solve the problem.

1. I don't have a clue about how to build the J-Tube. There is go guide with the DVD I bought and not even dimensions with the companion guide. On the site there are some details about building a J-tube, but it requires welding! I'm lucky enough to be able to operate a metal grinder. A welder is wayyyy outside my skillset. What do I do? Just stack up bricks or something? what dimensions?

2. The DVD and the companion guide tell me to use Duraboard. I have no idea where to source it. One place sells 1 sq. ft. pieces of something like it, for $30. Can I just use firebricks?

3. I barely know what cob is let alone how to make it. Is there some sort of high-temp concrete that I can buy from Homedepot or something?

4. How do I mount the oven on the J-tube? Do I build some sort of stand? How high?

I thought if I bought the DVD I'd be able to build a functional rocket oven. I can only build the oven, the J-tube is a mystery. Can anyone help please.

Hmmm...Until someone with experience pitches in it looks to me like a stand is necessary to suspend the barrel containing the oven over the J tube.

Burl Smith wrote:

Hmmm...Until someone with experience pitches in it looks to me like a stand is necessary to suspend the barrel containing the oven over the J tube.

I figured I could just build something out of wood... But how do I clean out the ash? I feel like Im trying to reinvent the wheel overhere.

Yes, I'm not familiar with the design but my preference is concrete block for the stand, maybe 100 blocks at $1/block with a plaster finish. The ash cleanout door used in block chimneys might work. I'll see if I can find it online.

Ash cleanout door

Again I'm unfamiliar with the design or the requirements but if a chimney tile were laid on it's side



with an ash door attached then all you'd need to fabricate is the elbow out of fire brick upon which to stand another chimney tile wch protrudes into the barrel if I'm not mistaken.

Ok the interior dimensions of that tile exceed specifications but might be reduced.

Please check out my thread about our rocket oven:


We are using a wooden frame for the oven.  The J-tube is duraboard supported by bricks - you can definitely build your J-tube from firebrick if you plan on a permanent installation.  (The duraboard version helps if you want your rocket oven to be mobile, like the one Paul has up at the Lab.)

Do NOT look for a hi temperature cement to use in place of cob.  Cob is not hard.  You need SHARP sand (not sandbox sand) and clay and chopped straw, there are recipes all over the place.  

OK, check out my thread here: https://permies.com/t/90413/rocket-ovens/quest-beautiful-rocket-oven  You don't need to decorate your oven stand with mosaic, like I'm doing, but just check out the early photos.

I clean out the ash by scraping it forward with something flat and small enough to fit in the burn tunnel, like a cedar shingle.  Then I lift the ash out where the wood goes in.  I don't have an ash door - this is a very simple design.  It's working great.

Julia Winter wrote:Please check out my thread about our rocket oven:

Julia, This is wonderful. I'm inspired to make some cob after a cursory look about how to make it. Here in central Texas we have a clay rich soil.

Question. (or two)

Around your firebricks duraboard I notice you have some sort of masonry? Are those just concrete blocks? Also, what are you using to cement them together? I do see some sort of bonding material between the blocks.

I like how you later-on covered the entire J tube in Cobb. I hope to reproduce that since we have access to hundreds of thousands of pounds of clay rich dirt and sand.

Thank you for helping answer my questions!

The bricks are held together with a clay slurry.  It's bright white because when building the oven we used a bag of purchased clay, like for making pottery.  I'm thinking it's porcelain clay or pure kaolin, given the color.

Yes, I think the blocks surrounding the duraboard are just concrete.  They are protected from the heat by the duraboard.