Want Second Opinions before I start

[shuboyje]

Hey Everybody,

As with every project I undertake, this has been a long and bumpy road in the design phase, but I finally have a solution I am happy with, and have built my stand and poured my insulation. I'll be ready to start brick work this weekend but have a few things I want second opinions on.

My main issue is space width-wise. Due to this I'm building a small 30" low dome oven and even to fit that I am making it 3" of thermal mass. Here are my questions.

1. I plan to build my soldier course using full fire bricks standing on end with the 4.5" wide face looking inward. This will only give my 2.5" of thermal mass in this course. Should I make up the extra half inch with mortar, and if so should I leave expansion joints in this big ring of mortar around my entire soldier course?

2. The normal plans call for 4.5" of thermal mass in the dome and 2.5" in the floor. If I build my floor using 2.5" of thermal mass, but only have 3" in the dome, am I gonna throw the oven out of balance? Should I build my floor using half thickness bricks?

3. Making my oven with 3" of thermal mass means I can get 3 pieces out of each fire brick. Should I use the inner piece that does not have a "factory" finish on it? I know generally one using 4.5" bricks one would put the factory end on the inside of the oven.

I think this covers it for now. Thanks in advance for any advice.
-Jeff

[stidik]

Re: Want Second Opinions before I start

Jeff,
1. Due to outward thrust, or hoop stress, from the dome, I would consider making the soldier course wider than the rest of the dome. Consider a width of at least 3.5".
2. I don't think that your oven would be out of thermal balance if constructed the way you propose.
3. If you have a factory finish then obviously use it on the inside of the oven, but I would not hesitate to use a brick without a factory finish to face the inside of the oven.

Best of luck,
Stephen

[dmun]

Re: Want Second Opinions before I start

Should I build my floor using half thickness bricks?

I wouldn't suggest using splits for the oven floor. I think that would be a problem as far as floor stability. My whole oven is 2.5 inches thick, firebricks on edge, and while I may not have as much heat retention as other makers, my oven works fine. Modular ovens are all about two inches thick, top and bottom.

I'd vote for more insulation instead of added thermal mass if it were up to me.

[Nev Grady]

Re: Want Second Opinions before I start

Hi Jeff,
Whilst the theory behind your oven design may be OK you haven't said what you want or expect your oven to do. Low thermal mass with sufficient insulation is OK if you're just using it for a single session of pizzas or cooking other things. If you're like me and will just use your oven at weekends, a high thermal mass with efficient insulation will make the oven more versatile and will give you the opportunity of bread baking the following day and cooking your Sunday joint and all the trimmings!

You need to decide what you want out of it.

Nev

[shuboyje]

Re: Want Second Opinions before I start

Thanks for all the input so far.

I should have clarified that I have a plan to re-enforce the soldier course, so outward thrust should not be an issue. I also should have pointed out that the 30" oven with 3" thermal mass was designed to allow 6 inches for insulation. I plan to use loose vermiculite, but worst case scenario I can add so ceramic mats, but with 6 inches I think I have plenty of space.

As for what I want, Pizza is number one, then the ability to do a little bit of bread(a few loaves), and the ability to maybe roast a small turkey. I think with 3" I can do that, even if not all in one firing, but tell me if I am wrong.

[stidik]

Re: Want Second Opinions before I start

I think that you are correct, that your oven will be able to perform the above goals.
Best of luck
Stephen

[DrakeRemoray]

Re: Want Second Opinions before I start

You are planning 6" of loose insulation on each side? Frankly, I would make the oven wide by 8", cut the insulation down to 2" of blanket on each side. 30" is a very small oven. You can still add loose insulation. The only place you will be tight is on the sides where the dome is the widest.

[shuboyje]

Re: Want Second Opinions before I start

Just wanted to update this. So far so good, most everything has gone well, and I am keeping on my schedule even though I've been working long hours and saturdays. I got my oven floor done friday, the soldier course done by sunday, and just finished the "buttress". I was even lucky enough to have my brother-in-law who is a very experience civil engineer look over my "buttress" and find it more then suitable for the force it will be supporting. Guess this means it is time to start the dome tomorrow, wish me luck!

[mfiore]

Re: Want Second Opinions before I start

good luck! Post some photos along the way!

[shuboyje]

Re: Want Second Opinions before I start

Well, here is what I have as of the end of work tonight. As you can see being a sheetmetal worker has it's up side, and me and a friend custom build the stack today.

[MK1]

Re: Want Second Opinions before I start

Looks great. Can't wait to see the next set of photos.

Mark

[stidik]

Re: Want Second Opinions before I start

Your vent and stack looks great. My vent was made from 22 gauge stainless steel, which I did not trust to hold up for many years, so I opted not to enclose it in the stucco.
Good luck,
Stephen

[shuboyje]

Re: Want Second Opinions before I start

Well, last night was the first big fire in the oven, sadly it was a spurt of the moment fire at 11 pm after I was away all weekend so I did not cook on it, but I am thrilled with the ovens performance, it is everything I had hoped for. It took about 1.5 hours to get up to temp as it drove out the last bit of water, but once it did I threw on a few more small pieces of wood and the oven hit 1000F and stayed there for over an hour with no more additions. The outside of the enclosure never went over ambient temp. Today I'm gonna make up a batch of Mozz to prepare for what the next few days holds. I hope everyone who's done this is as happy with their oven as I am at this point!

PS. With no door it was still 550 5 hours later and 350 12 hours later at the top center of the dome.

[Neil2]

Re: Want Second Opinions before I start

Consider that sheet metal to be a form and cast reftractory material on to it. At the temperatures you will be running, the sheet metal will rust out in a year or two.