Flue w/sonotubes as forms?

[fxpose]

If I can't find a clay flue in my area I'm thinking of forming my own using 2 sonotubes (8" inside of a 10" = 1" wall thickness). It will be reinforced with thin rebars or wired mesh.
How practical is this and what should I form it with?

[kebwi]

I'm loving this thread! I would love to know more about this possibility. How do you hope to keep the metal mesh in the middle of the one-inch thick wall while you pour it? You wouldn't want it to get push to the side of course.

[dmun]

I cast ordinary concrete around a sonotube for a non-flue purpose. It was hard to get the tube out after the concrete set. I'd suggest a parting agent like aluminum foil on the inner tube. The cardbord tubes get wet and swell, which is actually a benefit for exterior tubes, the inner ones not-so-much.

Castable refractory concrete ordinarily uses stainless steel needles instead of a grid type mesh.

It seems to me that by the time you buy the pair of sonotubes, the castable, the needles, and engineer a way to keep the tubes properly spaced, you'd be better off doing a special order of flue tiles, which are cheap as dirt.

[fxpose]

I had a couple of design possibilities in mind, one of which was the naked clay flue look.

My other choice was a stuccoed flue, contoured all the way to the top. In this case I was looking at the possibility of using an inexpensive single walled 8" metal stove pipe, putting a 12" diameter sonotube over it and filling the 2" space around the stove pipe with vermiculate cement. And then this chimney will be rendered in stucco as the rest of the oven.

[dmun]

Upon reflection, you could burn the inner sonotube out. It'd be a bit smokey, but there's no reason it wouldn't work.

[castiron]

Here's a couple of pictures of a build I found.I'm hoping to incorporate this into my design..Seems like a good concept....Just pour refractory concrete....

[Archena]

Use wire and a fairly dry mix (which you will have to shake the heck out of). Wire is just easier to work with and you don't have to tie it together. A wet mix and you'll have trouble with the bottom of the form leaking.

This isn't exactly what you're talking about but his experience might help (that and how cn you go wrong with a homemade forge link? ). Baby Furnace - The Artful Bodger's Home Foundry

[dmun]

I'm studying those forms, and I can't figure out what they're building. Is it a particle accelerator?

[Archena]

A cannon or a submarine?

Seriously, looks like a squirrel tail - the box is the form. Why the heck it's so big is beyond me (but since I'm usually wrong, what the hey?).

[castiron]

Here is another picture of the flue system on top of this oven with the forms removed...I guess everyone has there own way of doing an oven.This particular oven I found and the finished oven looks very nice.I am building my final oven in it's final location this Summer and I like to get ideas from all sources...