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]

Re: Flue w/sonotubes as forms?

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]

Re: Flue w/sonotubes as forms?

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]

Re: Flue w/sonotubes as forms?

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]

Re: Flue w/sonotubes as forms?

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]

Re: Flue w/sonotubes as forms?

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]

Re: Flue w/sonotubes as forms?

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]

Re: Flue w/sonotubes as forms?

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

[Archena]

Re: Flue w/sonotubes as forms?

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]

Re: Flue w/sonotubes as forms?

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...

[dmun]

Re: Flue w/sonotubes as forms?

Okay, so now i start to see, it vents from the front of the oven chamber, and has a ninety degree redirect to the back. I'm just scratching my head over this one. This is what Lord Grimthorpe once referred to as "the strange propensity of mankind for taking more trouble to do wrong than it would be to do right"

[Tscarborough]

Re: Flue w/sonotubes as forms?

Apparently to get it away from the eaves. It can't draw well, though.

[castiron]

Re: Flue w/sonotubes as forms?

This particular build was done by a fellow named Doug.here is a link to his build. I think he knows what his doing as I think that the oven came out looking very nice.I like the fact that as long as you follow the basic principals of building oven chamber the rest can be left up to your imagination.Here is a picture of the completed oven... ..Marian & Doug's Pizza Oven

[dmun]

Re: Flue w/sonotubes as forms?

It's a perfectly good looking enclosure, but the two ninety degree bends in the flue are a real problem. Chimney code calls for no more than two angles, no more than thirty degrees. It's a barrel vault, so obviously they are interested in retained heat cooking for large amounts of bread, but they have this big uninsulated place in the middle of their dome. Also, having the vent inside the cooking chamber, rather than in the entry, has proved problematic again and again.

Good thing they have that dark slate cladding over the door, that will help mask the smoke stains.

[Tscarborough]

Re: Flue w/sonotubes as forms?

Just to add to what Dmun said, the concept of using the flue gases to heat the masonry is a great idea for masonry heaters and fireplaces, but since the cooking is done after the charging fire is complete, it is kind of pointless for pizza or bread.

The danger of using flues over 30 degrees is a potential buildup of flammable soot which can catch on fire and destroy the appliance, plus draw issues.