Pros and Cons of a Soldier Course and Spreadsheet IT questions

[ML38]

I'm about to start my dome on my 39" oven.

I was going to have a soldier course of a half brick on edge but while fooling around with deejayoh's spreadsheet I realized that if I just start out with first course like all the other courses (on top of oven floor). the calculator shows 9-10 less bricks being needed. So I ask the experts:

- What's the benefit of a soldier course vs all courses being brick height of 2.5 in? Just aesthetics?

While I'm on the subject of the spreadsheet, I posted a couple questions to the original thread without response but it's 5 years old so I'll try here too.

My IT is adjustable so with every course, I can measure so it is exactly 19.5 inches from the center of the floor even though the pivot point is above that.

- If I make this adjustment, couldn't I make the 'Distance from IT Pivot to Dome Floor' value 0.0?

Lastly, I liked the idea of reducing the size of the brick from course to course so the joints are staggered so I used Column R to calculate the inside top dimension and then used that as the outside bottom of the next course. When I did this, the Side angle dropped so that it starts at 0.1 for course 1 and gradually increases until it reaches 4.9 on course 11.

- Does this sound right? Original values in spreadsheet use 4.9 for all the courses except for the first couple which are 5.5 (this really confuses me because the side angle increasing as you go up makes sense to me)

- Are you just saving yourself some adjustments as you go by using 4.9 for all the courses?

The other confusing equation is for brick count of each course. The equation uses the Outer Radius.

- Isn't it the Inner Radius driving the brick count considering the inner is where the bricks are edge to edge plus joint thickness?

I may be missing something so please correct me if I did. Below is the screen capture showing what my side angle and inner and outer brick widths would be.

Thanks

Marc

[SableSprings]

By using a soldier course, you give yourself more working/baking/fire room on the sides. If you just had 2.5" on the sides, you'd be hard pressed to actually make use of a pretty significant portion of your cooking surface. When doing pizza, you want a fire on the back or side that curls up toward the dome top to give you some good extra radiant heat on the pizza top...even then most of us do a little doming just before bringing it out of the oven. With a "shorter" side wall, your fire has to be more out toward the center to get proper air & flow for the dome fire/heat curl. Although there's nothing wrong with doing all the courses with the header orientation...it's just a bit limiting (IMHO).

On your IT, you should take out the center brick in your floor and that way set your IT down so the pivot point is flush with the floor. This was a great innovation brought into the forum by Gulf and his build of the Mississippi Queen (It's in the Hidden Treasures thread https://community.fornobravo.com/for...n-the-archives ). Using his method, you don't have to do readjustments on the IT length for compensating a "high" pivot point.

Sorry, but I built my dome before that great spreadsheet calculator from Deejayoh was available ...so I can't offer any insight or advice. I'm sure there will be comments to follow from people who know.

Looking forward to your build.

[ML38]

By using a soldier course, you give yourself more working/baking/fire room on the sides. If you just had 2.5" on the sides, you'd be hard pressed to actually make use of a pretty significant portion of your cooking surface.
Looking forward to your build.

Thanks for the input Mike. Great point about having more room with a soldier course.

Since my IT is so easily adjustable I'll just measure often and pretty sure it should be fine. I'll get a build thread going soon. I cut all my soldier bricks today but not sure when I'll get a chance to start mortaring in bricks. Hopefully soon.

[david s]

A disadvantage of using a soldier course is that the base of the dome is its weakest point. Think of a boiled egg when you cut the shell in half. One piece cast domes usually suffer from a vertical crack starting at the base and running vertically. Placing a tall vertical mortar joint at the base is the equivalent of laying coinciding joints on the first and second courses. It probably doesn't matter that much, the Italians have been building ovens like that for years, however two courses laid flat with their inner faces remaining vertical would achieve the same effect.

[ML38]

Thanks David. I had planned on only a 1/2 brick soldier course , not a full vertical brick. I'll stick with that and given how many builders on this site have done the same I'm not too worried but I did consider doing exactly what you suggest with two flat vertical courses. Still might. Haven't mortared anything yet

[MarkDLxu]

A disadvantage of using a soldier course is that the base of the dome is its weakest point. Think of a boiled egg when you cut the shell in half. One piece cast domes usually suffer from a vertical crack starting at the base and running vertically. Placing a tall vertical mortar joint at the base is the equivalent of laying coinciding joints on the first and second courses. It probably doesn't matter that much, the Italians have been building ovens like that for years, however two courses laid flat with their inner faces remaining vertical would achieve the same effect.

Hi David, what about to put a first soldier course cut on top by angle equal to the 2nd course ?

[david s]

You can see from your drawing how the weight of the dome on the bottom brick will create significant outward thrust. I think you need either a steel band bracing around the first course or buttressing outside it. Alternatively, and simpler, just build a hemisphere. I read from your first post that you intend to lay the bricks on edge. This only gives you (presumably) 3" thick walls. While this is adequate re enough thermal mass in the dome it does not provide enough structural bond at the mortar joint. For the same reason brick walls are not laid on edge as it's not strong enough. Remember that thermal expansion can break the mortar joint bond. Other builders of brick ovens have tried less than 4" thick walls and found them inadequate.

[MarkDLxu]

Even if I’m still curious about this solution, I’ve understood the message !
david s Thanks for have saved me money and time to rebuild it!