Saint Helena Oven

[Marcel]

Can neither recommend nor discourage a beach ball.

(M) James wrote, in part:

"Does that seem to be the "best practice" (my old IT days showing through) method for the last few chains? Marcel, does that work for you, or are you ready to recommend the beach ball? "

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(M) In general, I'd like to see the plans include *many* optional approaches. I realize that we're not "skinning a cat" but I have seen a great variety of methods and materials. I would favor a basic recommended set of instructions with footnotes indicating a special section where alternatives could be viewed.

(M) Your "" makes me wonder if you are speaking tongue in cheek or just being friendly. I'll assume the latter and say that I have not used a beach ball but if I were to build another oven, that would be something I'd certainly try.

(M) Without having had actual "hands on" experience using any particular technique or material, I'm reluctant to take a pro or a con position. I tried balloons and had trouble with them popping so I figure a beach ball is far tougher, bigger (so it eliminates the need for styrofoam vanes) and a virtually perfect sphere. The builder could see the first 6? chains on the inside and only later employ the ball.

(M) I know that somewhere on this site there is a successful build using a beach ball. I could probably find the reference if anyone requests it. Beyond that, I'll stick with my old cliche' adage in red of Albert Einstein

Ciao,

Marcel

[jahysea]

Good idea

Well.... I have a old circular saw long ago designated solely for dusty crud work like cutting stucco with a masonry blade.

But. I'm cutting an arc. If it were made of wood I'd use a jigwaw. The rounded cut would be pretty tough with the circular saw alone. You gave me a great idea though. I'll vacate most of the cut with straight strips with the circular saw. Then I'll use my wet saw without the table and free hand the arc. It just has to be round enough to mortar.

Or I'll do as David suggested and use a diamond wheel on the grinder. Nice to have options.

Not having seen the materials yet, but knowing the sections are only 1' in length, how do they join together? Are they fluted to overlap each other I wonder, or are they straight and I will just mortar them together? If the latter, I suspect they will need additional support, which I can provide as they go through the roof.

You are correct in pointing out the force on the outside of the arch walls. Big cathedrals in Europe like the one in Lincoln England have giant extensions with piles of masonry outside along the walls (not sure of the architectural term) to keep the weight of the roof from pushing the wall outward and over.

I could easily make a little brick wall on either side of the arch tunnel walls. If I placed it on top of the concrete I just poured I'd be pretty confident they will never move. And nobody would ever see them as they will be inside the walls.

[maver]

flut tile

Ouch, I was planning to do it with the $5 abrasive masonry wheel.

Oh well, more tools. Hopefully my grinder is beefy enough for a diamond blade.

If you are concerned about the quality of your grinder consider purchasing a blade for a circular saw, if you have one. It would be easier with a circular saw to obtain a straight cut, plus you will have the ability to set a shallow depth of cut and make a few passes.

I would also suggest you consider buttressing the sides of your front arch (where you placed the metal stud next to the arch or, if there is room, behind it). I don't know anything about calculating load bearing for an arch, but I do know that the force of your arch as designed will push out on the sides of your entry. I think a few bricks mortared onto the side in that area would be wise for a masonry chimney.

[jahysea]

Began metal walls

I also started the metal walls today. Got 2 done in a couple hours, the metal isn't as hard to deal with as I feared. I bought an abrasive metal blade for my chop saw but never bothered to dig the chop saw out, it wasn't that rough cutting the studs with my shiny new tin snips.

I did the back wall and one side wall. I also anchored the base trays into the fresh concrete mentioned in my previous post.

Weather and family fun permitting I should be able to finish all 4 walls and possibly the stringers for the roofing over the long weekend.

I plan to stucco the exterior and use spanish tile on the roof, to match our home.

[jahysea]

6 drying fires.. Cracks and arch movement

Well, 7 days after finishing the dome I lit the first tiny fire. I've then lit 2 per day, one at night and one before leaving for work.

Some settling happened and a few no big deal cracks in the dome. I've sealed the dome cracks with some chimney stuff like caulk that says it is tested to 2000 degrees.

The bigger issue is that the arches in the front developed some cracks. I've realized that the base bricks have moved outward. They are "mortared" to the vermiculite/portland 8" shelf with just 50/50 sand firedust, which isn't very sticky, even when well cured.

I've taken the front arch partially apart and will remortar it after addressing the spreading.

I all along intended to pour concrete in front of the oven as a base for the granite tile shelf that will span the entire front (got to have a place to set your glass of wine while playing with the fire). I decided to extend that concrete base to wrap around the bricks at the oven mouth so that the concrete could hold those bricks from sliding outward.

So I formed it all in 2" high and poured concrete today. No rebar. I realize that the concrete will steal thermal mass from the oven slightly, but the tunnel opening on my oven is about 15 inches deep and the concrete butts up to only the outer 9 inches or so. I think I can live with that. The infrared indicates those bricks don't get real hot anyway.

The pictures probably tell a better story. The first one is of the spreading the arch base did. The rest show the concrete forms and concrete.

I'll reassemble the arch when I add the chimney.

[jahysea]

Make sure you have an diamond blade for your angle grinder - that stuff is HARD

Ouch, I was planning to do it with the $5 abrasive masonry wheel.

Oh well, more tools. Hopefully my grinder is beefy enough for a diamond blade.

[dmun]

Make sure you have an diamond blade for your angle grinder - that stuff is HARD

[jahysea]

Good advice, particuarly given the cost of metal venting. I found some clay liner I can use, in Newcastle CA. That's about 90 miles away, but fortunately my parents are coming for Thanksgiving and my father lives 5 miles from Newcastle. He's bringing me 6 8"x14"x1" flue pipe sections. I shouldn't need that many, but I'm going to try to use the grinder to cut the bottom pipe to fit the arch.

[maver]

If you are looking for flu tile, Superior Clay is the company, their website lists dealers who carry it. Flu tiles are cheap - if it helps solve your problem it could be worth the effort to find it because it might save a lot of work.

[jahysea]

One guy on this forum used crushed firebrick in his cast and said it worked well. Did you keep all the dust from cutting your firebricks? I saved mine in case I end up casting something.

Well I thought someone might ask me that. I was way too industrious, I cleaned up the whole job site after finishing the dome, so those scraps are gone. I've already thought about how easy it would have been to crush them into something like pea gravel.....

I think I'm going to do as Maver suggested and brick up a transition to a flue pipe flange. I can't find any small clay flue liner, not that I've looked incredibly hard. I'm told a woodstove place here in Napa carries stainless chimney parts, or possibly I will order from fornobravo.com.

I did order cooking tools from fornobravo.com and it seemed like they arrived the next day, so I recommend the service to those out there that have needs.

[redbricknick]

One guy on this forum used crushed firebrick in his cast and said it worked well. Did you keep all the dust from cutting your firebricks? I saved mine in case I end up casting something.

[maver]

That opening looks pretty close to the size of a rectangular flu tile (in width), why not make a transition from a few bricks, or use splits if you intend a lighter metal chimney? Nice looking arches. I think Alf has suggested in the past that the venturi effect of a narrow opening with a bigger vent area can help with draw. Look at the way a "smoke chamber" in a rumford fireplace is designed. Setting a flu tile on your opening with the front inner edge flush with the front of your opening would achieve this. Alternatively, look at Dmum's pictures for creating a tapered vent with two cut refractory flu tiles. The idea is also used in the "BIA Rumsford Plans", which you should be able to easily find with Google.

[jahysea]

Front Arch/Vent opening

I finished a second arch in front of the oven, with a vent opening in it. I used the same form as the first arch, and used shorter bricks for the 5 center/top bricks in the arch to leave a gap for the chimney vent.

I think I will cast a vent, but I'm struggling with the recipe to use. I cannot find "refractory concrete" but I'm sure some combo similar to the mortar I used, mixed with something like gravel or crushed firebrick would work? Any suggestions out there, other than "find refractory concrete?"

[jahysea]

Flashing

Using inexpensive, and somewhat flexible aluminum flashing to smooth out the top of the form for the last few chains seems to be a good idea. JC, if it's OK with you, I'm going to add your photos to the standard set of plans, and update the text.

Does that seem to be the "best practice" (my old IT days showing through) method for the last few chains? Marcel, does that work for you, or are you ready to recommend the beach ball?

Patrick, it seems as though we should start the process of reaching consensus on some of these more tricky areas, which would make it easier to finalize and produce a PDF set of plans. What do you think?

Let me know what you recent builders think.
James

Using the forms did give a sense of comfort all the way up the sides. Let me know if you want higher resolution pictures James. I should have taken more shots of those steps, I think all the ones I have are posted in low res.

[jahysea]

Mortar Recipe

Hey mate, what recipe did you use for your refractory mortar? I can't find heat stop in Los Angeles. Anyone used furnace cement? The black stuff?

Hi, I used a recipe I found here in the forum. 3 parts sand, 1 part portland cement, 1 part lime, 1 part fireclay

there are some recipes here:

http://www.fornobravo.com/forum/showthread.php?t=914

I mixed all my mortar with a cordless drill, thus far one of the handiest tools for this job.