dmun's 36" geodesic oven part II

[dmun]

Here's the view of the oven enclosure at the current height, almost at the top of the brick section:



You will note that there is an aluminum brick vent installed on the top right. This is a nice little unit the size of a brick that is made for this specific purpose. Here is a blurry view of the inside of same:



An overall view, with maker:

[dmun]

The final brick layer is in the form of what I was calling dentils, until I did a bit of research. Dentils are on the angled part of a gable, and in classical architecture were intended to refer to the protruding lath that roofing was nailed to in rustic structures. Horizontal bumps mimic the ends of joists, and are called corbels:



Here's what the dry assembled bricks look like, without their decorative angle cuts:



I can't mortar them in yet, because I need access to the inside to build the chimney supports, and insulate the oven.

[dmun]

Last weekend I built four tapered cast concrete supports in the exterior part of the oven enclosure, with rebar crossing between them. These will support a re-inforced concrete slab at the top of the masonry section, at the level of the corbeling, that supports the exterior masonry of the story-and-a-half high masonry chimney enclosure.

The reason for this is so that the considerable weight of the chimney will not bear directly down on the dome, but be supported by the slab under the oven, and the foundation underneath.

Here's a picture of the wood forms for the rear supports:



You can see the completed supports with their rebar connector in front.

This is a view of the form from the inside, showing the bent rebar loop going down into the leg:



This is a top view, showing the mis-placed rebar touching the flue tile:

[dmun]

The smoke chamber for the rumford fireplace is bigger than the one for the oven, both at the top and the bottom. It is made of two pieces of 8 by 12 inch flue tile:



The cut pieces line up like this (notice they tilt back):



Here are the two sections heat-stop mortared together:



Notice the two slots cut in the bottom. These are for the hinge bearings of the fireplace damper. Here's the damper blank in position:



My design for this damper didn't take into account the fact that the smoke chamber tapers upward. I had to laboriously cut angles in the damper with the angle grinder, after the welding was done. Note the wrench in the photo, the shaft is squared on the end, and will have a decorative external damper handle, rather than those nasty arrangements where you have to reach up a sooty fireplace throat to close the damper.

[dmun]

The oven smoke funnel was mortared in place on it's prepared tilted stand:



Now the internal opening around the dome was crudely enclosed with scrap wood:



This was in preparation for the insulating of the oven. Here's the wool blanket shoved around the oven:



Warning to oven builders. This stuff is seriously nasty. Worse than fiberglass. Wear gloves, long sleeves, and a face mask. I'm still itching.

In this picture you get a glimpse of the tops of the chimney supports and rebar. I had to cut the rebar in the front, because it ended up in a place that conflicted with the chimney path.

I then filled all the cavities with perlite concrete, up to the level of the cut arch in the concrete block wall. This should give me about four inches of addtional insulation above my blanket:

[Hendo]

David,

Looking good ....

I've followed your project in detail, but may have missed something along the way. What is the purpose of the deep well under the hearth slab? Won't this make wood retrieval difficult, and/or create a potential water entry point through to your internal fireplace?

Paul.

[dmun]

Hi, Paul,

That recess below the wood storage area is a sump for a sump pump. My workshop floor is built on an old garage floor slab, and is under grade. In bad rain conditions I have had need of a lower place to drain water to, and pump it out. Since I had to go three feet below grade for my footings, I figured I might as well use the space.

It will have a pressure treated floor for the bottom of the wood storage.

[dmun]

Today, I'm preparing to pour the re-inforced concrete slab that supports the chimney. Since the space below will have no access, I have to use a piece of concrete board to support the slab. Since the stuff is brittle, I've stacked up some scrap insblok19 on top of my vermiculite concrete to support it in the center:



I've filled the empty space with scrap fiberglass insulation with the paper backing stripped off. Hey, why throw it out? You can see the top of the support stack sticking up in the center. Those rebar pieces in front had to be temporarily bent out of the way to get the cement board in place.



Here is the enclosure ready for the slab pour: The external brick course, that holds it, is mortared in. The cement board pieces are in place, the cross pieces of rebar are wired in place, and i've wrapped a half thickness of insulation blanket around the flue, not so much for insulation as to supply an expansion space for the hot flue.

[dmun]

Today: pouring the slab. I made scrap wood plugs go go between the corbels, and started dumping concrete into the space:



Starting to smooth it out: notice the anchor bolts in the slab to secure the upper part of the tower.



No matter how stiff the concrete is when I pour it into the forms, it always seems to have too much water on it when I float it smooth. I didn't help that it was starting to rain when I was finishing the slab. I think getting mason quality finish on poured concrete is more of a skill than I am going to accquire in the course of one oven project.



After I got the slab as smooth as it was going to get, I covered it with a tarp, but that's far from watertight because a bunch of water can come off the studio roof directly onto the wet slab. It's now pouring rain, and I'm a bit worried that my portland is going to be washed out onto the lawn by morning.

[james]

David,
You have done such fantastic work. Have you thought of trying to get your oven featured in a newspaper or magazine?

Of course we can't wait to see you fire it. :-) I've been working on the pizza e-book and I have pizza on the brain.
James