K79 Oven Build

[stonecutter]

Re: K79 Oven Build

Some progress. I can't wait for this weather to break !

Looking good! Are you getting rid of that sliver on the first course?

[stonecutter]

Re: K79 Oven Build

With a front flued oven I don't believe it is.

I agree. An outdoor chimney doesn't function like one for an indoor FP/stove...too many dynamics outside. It's more about giving smoke a place to go besides the front opening.

[K79]

Re: K79 Oven Build

Looking good! Are you getting rid of that sliver on the first course?

Yes I'll be getting rid of that. I wiped out all of the firebrick at my local yard. Waiting on more brick

[K79]

Re: K79 Oven Build

Ok all, I'm hoping to resolve my chimney/vent/flue issues today so I can finalize my foundation pad and block wall design.

I understand that 15% of my oven opening is the minimum size I want for my flue. My oven opening is 208sqin. Therefore I need a minimum of 31.2sqin of vent opening. A 6" ss chimney only gives me 28.27sqin. A 7" ss chimney gives me 38.48sqin. So I can go with either a 7" or an 8". Now I'm trying to figure out what my anchor plate is going to rest on. I've been looking at Ken524's design and this is where I get a little confused (unless I'm trying to go by the books too much).

Ken's oven is 42" (btw, thanks for letting me use your oven as a guinea pig Ken)
In view one (and I'm assuming some numbers here but I think I'm close) Ken's flue vent starts 9 bricks wide and looks to be 1/2 brick in width. This gives a flue vent area of 83.25sqin. at the bottom. It then tapers to 5 bricks wide at the top giving about 46.25 sqin (view 2). Now in View 3 Ken builds a "landing" for his anchor plate and now makes the opening only 4 bricks wide giving about 37sqin of flue vent for his 8" ss chimney which can handle 50.26sqin. (view 4).

This is what confuses me. Shouldn't the opening under his anchor plate be 50.26 sqin to maximize the effectiveness of his 8" chimney. Since a 7" chimney can handle just over 38sqin would that have been a better fit????

[david s]

Re: K79 Oven Build

Actually a bit of restriction can be a good thing because it creates a Venturi effect and increases the velocity of the flow in that area.

[UtahBeehiver]

Re: K79 Oven Build

K79 Maybe this will help. This is how I fasten my anchor plate. First two pics are looking at the bottom. I cut out the bricks to inset the anchor plate. This was the top my chimney. There are other pics on my picassa album.

[K79]

Re: K79 Oven Build

K79 Maybe this will help. This is how I fasten my anchor plate. First two pics are looking at the bottom. I cut out the bricks to inset the anchor plate. This was the top my chimney. There are other pics on my picassa album.

That's awesome. The only issue I have is space. How long is your vent landing? Must have used a brick and a half at least. I'll take a look at your album. How did you make those nice round cuts in the brick? If I build mine like Ken's that would leave me just under 3/4" in front of my chimney to put my 1/2" concrete board. Your method the firebrick would be sticking out beyond my concrete board. hmmmm

[UtahBeehiver]

Re: K79 Oven Build

Mine is an exposed igloo and not enclosed so space was not an issue. Landing is about 14-15". I cut small sections/slivers out of the brick alot of feathering like you did on the floor arch then took and angle grinder with a cupped diamond wheel to finish final shape.

[Ken524]

Re: K79 Oven Build

Shouldn't the opening under his anchor plate be 50.26 sqin to maximize the effectiveness of his 8" chimney. Since a 7" chimney can handle just over 38sqin would that have been a better fit????

To be honest, I didn't do any "flue math" when I built my vent. That's way above my knowledge base.

After spending years as a kid playing with campfires and lighting fireplaces, I was reasonably sure that if I gave the heat a fairly simple, direct path, physics would take care of the rest.

Actually a bit of restriction can be a good thing because it creates a Venturi effect and increases the velocity of the flow in that area.

I can, without a doubt, confirm this. I never get smoke out the front of the oven. When the chimney heats up after a couple of minutes, the smoke is literally sucked out of the oven. It's fun to see it accelerate through the flue. There are some serious convective forces at work.

If you are sweating over a few sq. inches, relax and don't get too caught up in the math; we aren't building cooling towers for nuclear reactors . Give yourself a reasonably sized vent opening and it'll work (as it has for thousands of years).

[K79]

Re: K79 Oven Build

Updated Photos. I need more bricks:

[K79]

Re: K79 Oven Build

Hello All,

I'm wondering about my 3" of Fiber Blanket that I'm going to wrap my oven in once the dome is complete. Do I wrap it and compress it with chicken wire to hold in place or should I make sure not to compress it against the oven dome? Since I'm doing an enclosure and burying it in vermiculite I don't need to put anything else over it correct?

[deejayoh]

Re: K79 Oven Build

If you are doing a housing, you don't need to wrap it with chicken wire, and I don't think you want to compress it (not that you could compress it much anyway). I found that a spool of rebar wire worked really well to anchor it to the dome. I wrapped a ring around the bottom of the dome, and then criss-crossed wire from that to hold the insulation in place. It doesn't take too much pressure to hold it.

[K79]

Re: K79 Oven Build

Ok, I know I'm definitely thinking ahead here but your first fire and your subsequent ones to help cure the dome; shouldn't those be done before the insulation blanket goes on? I just watched two new video's on YouTube where they were done after the blanket was put on and one after the stucco was put on.

I now know that I've been worrying too much about mortar joints. Both ovens in the video's I watched had mortar joints well over an inch !!! I'm still aiming for my 1/8" mortar joints

[Laurentius]

Re: K79 Oven Build

Hi K79,

I start curing mine a week before I insulated. I also it to sun and wind dry a week before the first curing fire, I wanted to drive as much moisture out, before insulation. Firing does not effect the drying of the stucco, because a well insulated oven's exterior doesn't above ambient temperture.

[mrchipster]

Re: K79 Oven Build

Ok, I know I'm definitely thinking ahead here but your first fire and your subsequent ones to help cure the dome; shouldn't those be done before the insulation blanket goes on? I just watched two new video's on YouTube where they were done after the blanket was put on and one after the stucco was put on.

I now know that I've been worrying too much about mortar joints. Both ovens in the video's I watched had mortar joints well over an inch !!! I'm still aiming for my 1/8" mortar joints

I think pre drying is a good idea less chance for trapped moisture.

Oh, by the way most of us have tools we use to build our ovens but for the life of me I cannot figure out what you are using the bicycle pump and tree trimmer for...

Chip