Oven floor under construction.
Plans for the double chamber from Ernie Wisner were used to build the oven at Alex’s workshop. The basic oven here was modified dimensionally, and a RMH added as well as some experimental air inflow added. So it is a combination of a few authors as well as some trial work here. There’s plenty of stuff on the net too…. Watch this space.. lol.
The oven as well as base is heavily based on Kiko Denzer’s book. (see resources) I read it three times then STUDIED it. It’s a gem full of great building priciples. Cob work as well. Hannah’s baking section was used to make Starter as well as bread.
So the base directly under the oven is made from the same “conductive” mix as the first oven layer. Soil, sand and Clay. Kiko refers to the insulation being like a chocolate covered M&M. (same as a smartie you you mob in far away places…lol). Same principle here.
It’s a layer as “Thick as a Brick” and will be continued all around the oven encapsulating it. The insulating layers will follow suite.
We are heading towards putting a sprinkle of sand on top of the base so that it the fire bricks can be set level.
Next a sand mold of the oven can be made. Jigs for the catenary may be made as the width is about 36″ and the length of the oven is 28″. I’ll make a video of this lot one day. lol.
The sand gets covered with wet newspaper and it was a challenge to keep it from collapsing all the time, especially the burn chamber.
Note that the oven is perpendicular for a few inches before corbelling. (Feature of the dome home copied here… )
Viewed from the side to show both doors and jigs for each catenary. if you like. So what if it’s not symmetrical?
Then it would be called an Asymetrical oven? LOL.
The cobbing under the arch of the base needs some work. I put some chukaloo wire to try hold the cob from fighting gravity. I think it needs stitching to the bag then cobbing?
Taking the sand out of the oven was fairly straight forward. Need longer arms? Used a hoe eventually.
Some lessons learned include:
1. The fire door could do with a wider collar on the oven to snug up to. I built it up a little.
The photo shows the recess built up. The next oven will have a jig made to do this.
It was fired with the Rocket to start drying. It’s actually quite wet inside.
Note the paper hanging down! I managed to skweeeeez in a little to get most of it out.
This is only a 3 inch (75 mm – for Alex, who is learning the metric system.. LOL) single layer.
Good move as I may put an 8″ (how many mm is that Ducky?) Rocket on it? Relocate this one to the front of the oven for tea, steaming sausages, making syrup etc…
It will be relatively easy to fit an 8″ Rocket as one (who is “one”?) can just carve the holes from 6″ to 8″ in the single layer. Good thinking hey. This comes when yawl are sleeping I tell you.
2. Single 3″ first cob layer is self supporting.
The next layers are self supporting as Kiko says.
3. Try cob all in one session. Abit difficult to do alone. The inside came out pretty smooth I must say.
4. Build a larger (longer) base next time. Allow for a longer oven.
5. Some of the cob was a little thin on the firing chamber. Use some 3″ sticks embedded into the sand as depth guages for cobbing.
Some cracks, where the cob was thin mainly. Also, try to do the whole layer the same day if possible. Big job for me working alone.
Only one layer and the sand was removed. It stands alone without any fear of collapsing. The inner cob is a lot wetter than the outer. So removing the sand will quicken the drying out process. Also allows us (who’s “us”?) to check out some rates of heat loss as the other two layers are added. Really hey .. blah blah fish paste.. (an expression compliments of brother Al…) There’s a sales special running for a laser temperature gun that reads up to 900 F, so I might get one if you send me the money? Nope – I got it…
Cobbing the base: