Tanzania/Canada

[SteveS]

Re: Tanzania/Canada

Thanks Dave!

[cobblerdave]

Re: Tanzania/Canada

Dear SteveS
Now your starting on the dome proper a couple of things. First course consider standing the bricks on there end to start... why it gives you more usable room as the first 11 INCH( thats you brick lenght?) is vertical wall not an angled one you can get dishes etc closer.
Do a mock up on a flat piece of ply (or whatever) of the shape of the oven dome. Draw some curves with the correct height of the oven sit some bricks in place this will give you the angle of the spaces between the bricks. cut some wedges on these will be your guide as you go up. Check the photo i sent and you see them.
. The brick face in the oven are not mortered, each course of brick sit on its bottom edge with the one underneath only the backs are seperated by the cement the angle being set by the wedges. In this way the oven is resting on each layer and is self supporting.
This is all in the instruction... best off print a copy and much easier to break them into sections and refer back as you need.
Regards cobbler dave

[dmun]

Re: Tanzania/Canada

First course consider standing the bricks on there end to start... why it gives you more usable room as the first 11 INCH( thats you brick lenght?) is vertical wall not an angled one you can get dishes etc closer.

Think carefully before doing this. It's been suggested that full brick height soldier courses cause too much side thrust without buttressing. It may be a coincidence, but our one recorded oven collapse had a full brick soldier course (as well as questionable mortar)

[SteveS]

Re: Tanzania/Canada

Hi dmun,

As I had posted earlier....

"The dome bricks that I am using are 11 inches long. I am going to cut them in half for my first upright coarse. Thinking I should cut them on a bit of an angle so my second flat coarse will start on more of a correct angle toward the top of the dome."

I am still going with this plan which will put my first coarse at approx. 5 1/2 inches high. Now I can make an angle cut when I cut these 11" bricks in half so the second flat laid coarse lays at the correct angle. This will result in very little mortar used. From what I've read this is a good thing....right?

Cheers, SteveS.

[cobblerdave]

Re: Tanzania/Canada

Dear SteveS
Yes check that thread out but I dont think you"ll find the same conditions he used a filler type morter and the part built thing collapsed in freezing conditions not what you could expect in africa....
Dumn well he's not a moderater for nothing see what he thinks

Regards Cobblerdave

PS the bloke that posted his failed oven GUTSIE or what

[dmun]

Re: Tanzania/Canada

I am still going with this plan which will put my first coarse at approx. 5 1/2 inches high.

Yes, this is perfectly sound. Some people cut the bricks in half on an angle to match the tilt of the first course of flat bricks.

[AndrewL]

Re: Tanzania/Canada

Hey,
Great thread. Wish I had found the discussion earlier,... I have seen glass bottles used to insulate hearths for cob ovens. You might consider using bottles to insulate your dome?
Hope it's going well.
A.

[david s]

Re: Tanzania/Canada

Be careful with the bottles for insulation idea around the dome. There is a chance that with all the moisture around them they could explode with steam pressure. I think that is why the glass is usually crushed for under floor insulation. If you have access to that pumice it should work pretty well if you crush it up and add 1 part cement for every 10 parts pumice, using it much like vermiculite.I'd guess you'd need about a 5" layer.

[david s]

Re: Tanzania/Canada

Steve,
I missed your reference to filling the brick cavities with sand in an attempt to increase their density. Although sand is quite heavy it is a poor conductor of heat (K value 0.15_0.25) This is because of all the airspaces surrounding the grains of sand. You d to fill these, probably with an equal amount of clay or maybe that anthills. Then it becomes a good conductor with a K value like brick (1.3)

[SteveS]

Re: Tanzania/Canada

Hello All,

I am continuing this thread in OVEN CONSTRUCTION where I probably should have started it in the first place. I had hoped to move the whole thread there but wasn't able to get help on that one (might not be permitted I guess). I have posted some updated pictures of my progress there and asked for some more advice. So sorry for any inconvience with the move!

Cheers, SteveS.