39 inch Corner Build

[Gulf]

JR,

Sorry for the late reply. Things got busy for me yesterday, then there were errands and appointments today. I had a little problem understanding your last drawing. And I may be my misunderstanding the size of the anchor plate. Regardless, I agree that 7" to 8" would be fairly easy to transition. Back, a page or two ago, I was thinking that you were contemplating a (1 brick) 9" depth entry. That would have made the opening (front to back) some where in the 4 to 5" range. That would have been a different ball game . With a (brick and a half) 13.5" depth entry, you should have plenty of room for a full 8" opening. A full 8" opening leaves 5.5". That's 2.75" each (front and back) to complete the entry arch and form the entry to flu opening. It can be done with a 12" (brick and a half) depth entry imo.

If I'm missing something, please correct me .

[JRPizza]

No, you hit it on the head. I was thinking of 3" as a minimum for arch width/depth, but as we know the smaller the difference the smaller the effect and an additional 1/4 inch probably is nothing. If I stay with a 13.5 depth plus decorative arch I will be right at the width and end of my hearth which I can make work and look good. So whether I do a 7 and open up to 8 or make it 8 I kind of have an idea now. I'm laying out the differences between the serpentine transition and a rectangular opening that I frame up like you did. Either way by the time I start putting mortar to brick I think I will feel pretty good about the direction I'm going in.

[Gulf]

Great!

I feel better now, anyway .

If you think about it this way: There are a lot of successful entries with the arch not completed in the back. That is not in my philosophy of brick work, but I can not argue with the "run time" that they have shown. The back portion of the arch gets all the heat. The front portion of the arch only receives cool air. Those two columns of hot and cool air are mixed in the flue or smoke chamber (if it is included). Your build, with a double wall SS flue will not put much weight on the entry. So, going from 3" to 2.75" or even 2" should not be a problem imo.

I'm real in interested in the "serpentine transition" that you have in mind . I'm looking forward to your ideas.

[JRPizza]

Well, I may not be using the proper term by serpentine, but it seemed like an appropriate name for the transitions made by reversing the tapered arch bricks part way up so the fat edge of the brick is inside the arch and the narrow outside like the attached pictures of Amac's and Yorkshireknight's vents. This should give an "S" shape and with the proper number of bricks bring the surface of the top brick to a horizontal position like I sketched in post #87. I plan on tapering up a bunch of bricks then laying them out to see if I can make that type of transition work. If not, I'll fall back to the type of transition that Dino showed in the 3rd picture, which I think is similar to what you did but I had trouble seeing exactly how you transitioned from arch opening to vent.

[JRPizza]

The other question I had is I am planning on building the vent and arches out of the same low density firebrick as I used for the dome and inner arch. I am going to have a roof structure over the oven but the bricks will be exposed to moisture in the air and they are quite absorbent. I think using exposed firebrick has been done by many in their builds - should I be using a different type of brick here? Deejayoh said in post #88 that I should be covering the firebrick with something - is that necessary?

[david s]

How come you used low density firebricks? Apart from insulating fire bricks having very little thermal mass, they also abrade really easily if touched with tools or bits of wood.

[JRPizza]

How come you used low density firebricks? Apart from insulating fire bricks having very little thermal mass, they also abrade really easily if touched with tools or bits of wood.

David, I guess it's getting late - the proper term would have been "low duty firebrick". Per the Pompeii plans -
"Low duty firebrick. This is the basic fireplace firebrick stocked by many masonry supply stores. They have a lower alumina content than a medium duty firebrick (around 30%), they have more non-refractory impurities, and they are less dense. That said, low duty firebricks are a good choice for building a Pompeii Oven...."

[david s]

David, I guess it's getting late - the proper term would have been "low duty firebrick". Per the Pompeii plans -
"Low duty firebrick. This is the basic fireplace firebrick stocked by many masonry supply stores. They have a lower alumina content than a medium duty firebrick (around 30%), they have more non-refractory impurities, and they are less dense. That said, low duty firebricks are a good choice for building a Pompeii Oven...."

Ah, ok I thought you meant insulating firebricks. Low duty bricks are fine for the temps we fire to.

[Gulf]

JR,
"Serpentine" is OK. I did not know what to call that arch, either. I referred to it back in post 90 as an "S Curve". I don't think that there has been an accepted name for it on this forum. I had searched before for the name of it. The closest that I could come up with, then and now, is an "Ogee".

Aside from the fact that fire brick are porous and absorb water, I like the idea of using firebrick for the entry, if they are available and affordable. The entry gets hot too when firing. During the hot summer months, It would also get uncomfortable for someone standing there tending the oven. By insulating from and covering the entry, the oven tender can at least can step to the side to find some comfort.

[JRPizza]

I started cutting tapered bricks for the arches today so I can play with the different layouts. Because I have a 10" saw and can't cut through the full 4.5 inch height of the brick I have to make cuts from each end. I was stuck trying to fixture the bricks so I made a model and 3D printed a fixture to put on my cutting table. I move the adjustable stop (with yellow handle) so that when I push the fixture against it I can index the lower edge of the brick against the lip (to the left) and make all my first cuts on the thick end of the brick. Then I rotate the fixture 180 degrees and index it so the blade will complete the cut from the other side. With two adjustments I can make my tapered cuts and have them be relatively repeatable. Probably lots of ways to do these cuts but I wasted a few bricks before I came up with this fixture.

[JRPizza]

JR,
"Serpentine" is OK. I did not know what to call that arch, either. I referred to it back in post 90 as an "S Curve". I don't think that there has been an accepted name for it on this forum. I had searched before for the name of it. The closest that I could come up with, then and now, is an "Ogee".

Maybe Serpentine will catch on for that type of transition then. If I build one I'll call it that - I think the term fits the design and I like it's descriptiveness https://en.wikipedia.org/wiki/Serpentine_shape

[DavidApp]

Hello JR

The entry into my smoke box is 4" x 11".

Some smoke escapes on each side at times. You can see some of it being drawn back in from the front of the oven. The entry should have been wider to catch all the smoke in the type of entry I used.

David

[JRPizza]

Thanks for the measurements - BTW, I really like what you did to finish off your igloo! We want to do something other than stucco and will file pics of yours for inspiration.

[JRPizza]

I was playing with the serpentine arch layout today. Placed some tapered arch bricks in position to see how they looked and what kind of dimensions the natural curves might yield. I am going for a 1.5" reveal, so I'll be working with a 11.25" radius. If I do four bricks along the arch then reverse 4 bricks, I'll have a flat top with what I think is 9" minimum width. I might go as small of an opening depth of 6", so I'd have at least 54 sq-in at the top (63 if I go 7" deep) to mate with the 50" area of an 8" SS vent. I didn't measure, but I think the vent would be about 16" wide at the bottom, which at 6" deep would give me 96 square inches at the beginning of the "funnel". I'm starting to be able to visualize how to proceed and I think the serpentine is the way I'm going to build. Time to start cutting some arch forms.

[JRPizza]

Question for those of you that built in a heat break and used a gasket/rope material. How much bigger than your gap was your nominal rope diameter? I was looking at Rutland Grapho-Glass and it comes in quite a variety of diameters. I understand when you can pull on the rope it gets thinner so you can insert it into the gap - for about a 1/4 inch air gap how fat of a rope should I be looking at?