Nathan's 36" SoCal WFO build

[DavidApp]

Re: Nathan's 36" SoCal WFO build

Hello Nathan

Someone suggested to me that I put a sheet of plastic over the oven to see if there is any moisture being driven off. The steam will condense on the plastic. It was cold here when I was doing my first fires so I am not sure if the plastic trick would work when it is warmer. It may be that it collects the small amounts of steam that is invisible and concentrates it.

I did notice a big variation in the dome temperature top to bottom at first. Seems that the lower parts may be wetter because as you build water gets splashed on the lower sections and water does run down hill.
So check the temp. Dome, mid dome and just above the soldier level looking for the temperatures to be similar. Things seemed to even out after I had my door to keep the heat in the oven.

David

[n8huntsman]

Re: Nathan's 36" SoCal WFO build

I was at 300?F last night for 6 hours and saw zero steam. I then took it to 350 today again with no steam. But I did see a hairline crack open up in the mortar joint but no smoke escaping. The piece of 2x4 was dying down so I tossed another in and as others have done, spiked the temp to 550. I let that die down and haven't seen any ill effects and still zero steam. The dome did sit for 38 days in the California sun. Tomorrow I think I'll take it to 450 and immediately back down to get back on track unless someone thinks I can skip that since I accidently cleared that step today. I don't have insulation on so the outside is only measuring 170 with the infrared, even while the inside was 550. Is that indicative of anything?

[david s]

Re: Nathan's 36" SoCal WFO build

Curing is a dumb term to use IMO because it gets confused with holding in moisture to enhance the strength of concrete or mortar. When you begin to slowly raise the temperature using fire all you are doing is driving out the water which is exactly the opposite. This needs to be done slowly or steam spalling will result. I don't think it really matters that much if it is done continuously or ramped up and down. You need to do it carefully because the top will dry first and it's temperature will be way hotter than the bottom. This leads to uneven expansion which is stressfull to your refractory materials. Allowing the oven to cool brings the temperature of all of the oven back to the same temperature. If left longer some of the water will also migrate back to the dryer parts of the oven so you can then start increasing the temperature again. If you see steam you are going at it too fast, back off. For the temperatures we fire to there are not really any chemical changes taking place in the refractory we are really only removing mechanical water.

[n8huntsman]

Re: Nathan's 36" SoCal WFO build

Im a little confused about curing. I've read two different things. One said to get it up to the temp and keep it there for at least six hours, let it come down and move to the next temp, again holding it for six hours.
The other said to just bring it up to the temp, and let it cool back down, then move on to the next temp.
How long did you guys maintain each temp in the process?

[DavidApp]

Re: Nathan's 36" SoCal WFO build

Looking good.
Take the first fires very slow. These ovens seem to draw very well and the fire can get big and bad very easily. Don't ask how I know.

I did use Muriatic acid to clean up the vent area brickwork but I would think that the fumes would be too much for you to get inside the dome and clean it the same way. My vent area brickwork had some mortar residue that would not wipe off. I had let it get too dry before I wiped. The fumes were pretty bad.

David

[Greenman]

Re: Nathan's 36" SoCal WFO build

If push came to shove it could be helped by an injection of air directed upwards at some point in the chimney. It would be simpler than in line fans etc.

[rodeair]

Re: Nathan's 36" SoCal WFO build

n8 .. first class job you have going on there. As far as the chimney stuff, as far as I know, U.S. codes don't allow 45 degree bends, thus Canada. I'm in the same boat with trying to figure out the exhaust system. If you can figure out how to shy away from large bends, it would be better. If not there is always the option of an electric blower to help flow if it becomes necessary. The blower would be mounted at the top if I have it figured right. Good luck, nice work!!

[n8huntsman]

Starting the entry arch

I lost a couple weeks due to being out of town for work but I’m back at it. I should finish up the last of the brick work this weekend. I got the chimney parts on order from Canada. Two 45’s, an 8″ and a 36″ section, base plate, bracket, and cap. Came to almost $1000 with shipping! Surprisingly that was cheaper than it would have been in the US due to our current exchange rate. Then it will be time to cure, insulate, and stucco. I can almost smell the pizza!

Couple questions:
Do most of you clean the inside with sulfuric (muriatic) acid to make things pretty?

Do I need to worry about curing the vent arch even though it wont be as hot because of the thermal break? If not, I can start curing now while I finish the arch. The dome has been sitting in the California heat for over a month already.

[n8huntsman]

Re: Nathan's 36" SoCal WFO build

So I got the chimney laid out but even with a 30? elbow, I don't have the height to clear the roof. I see in the Canadian Duratech catalog they have 45's, part number 8dtc-e45ss, but I can't find any source for them online. Anybody know how I can get ahold of these? I'll have to make some calls tomorrow and see if I can find them.

[n8huntsman]

Re: Nathan's 36" SoCal WFO build

...what is "regular stainless"? What it chromium and nickel content? The first element provides a heat-resistant steel, the second prevents rust when exposed to acids (formed in the combustion process) and moisture.

By regular stainless I was referring to 18-8, 18% Cr, 8% Ni. This is the most common type. That's what the .125" plate is made from, probably 302 but possibly 316, I didn't check it. It's on the cold side of the thermal break. The .012" piece is made from an alloy, Inconel 718, to handle the higher temps. 18-8 has issues with carbide precipitation at high temps and I had the Inconel available so I used it. At the temps we're at, carbide precipitation probably isn't an issue, but like I said, I had the material available.

[valentin]

Re: Nathan's 36" SoCal WFO build

You have done a lot since I visited this forum. And what is "regular stainless"? What it chromium and nickel content? The first element provides a heat-resistant steel, the second prevents rust when exposed to acids (formed in the combustion process) and moisture.

[DavidApp]

Re: Nathan's 36" SoCal WFO build

Have you taken a look at Rodeair"s a "Pensacola Build".

He is doing the same type of thing and has what appears to be an interesting solution.

David

[david s]

Re: Nathan's 36" SoCal WFO build

That's good reassurance regarding the arch. Thanks.
Somewhere along the journey my dimensions between the roof and oven drifted a little and my chimney is now off by about 8", interfering with the roof. I need an offset so I have two options.
1.) Use a short section, about 36", angled back 15? off the top of the arch, then a 15? elbow, and another 24" section extending above the roof.
2.) Come off the top of the arch directly into two 45's to create and offset then continue straight up. Not sure how you connect an elbow to the mounting plate or if that can even be done?

Which method do you guys think would be the best aesthetically and structurally?

Thanks

I use the two 45 degree bends. It means buying two bends rather than than one, but looks better IMO.

If you angle the pipe straight back off the top of the arch you may have trouble because when you cut it at an angle it will make an oval rather than a circle and the oval will increase the entry depth required. You may also have more difficulty attaching it to the top of the entry. A 15 degree bend may not be readily available and you may have to get one specially fabricated.

[n8huntsman]

Re: Nathan's 36" SoCal WFO build

That seems like a pretty good advancement on the heat break. I don't think you'll have any trouble with your entry arch. It's an arch... They're pretty strong. I would be cool if you thought about how your door mates with that stainless break. You could get a really good seal on that if you built it that way.

That's good reassurance regarding the arch. Thanks.
Somewhere along the journey my dimensions between the roof and oven drifted a little and my chimney is now off by about 8", interfering with the roof. I need an offset so I have two options.
1.) Use a short section, about 36", angled back 15? off the top of the arch, then a 15? elbow, and another 24" section extending above the roof.
2.) Come off the top of the arch directly into two 45's to create and offset then continue straight up. Not sure how you connect an elbow to the mounting plate or if that can even be done?

Which method do you guys think would be the best aesthetically and structurally?

Thanks

[deejayoh]

Re: Nathan's 36" SoCal WFO build

That seems like a pretty good advancement on the heat break. I don't think you'll have any trouble with your entry arch. It's an arch... They're pretty strong. I would be cool if you thought about how your door mates with that stainless break. You could get a really good seal on that if you built it that way.