Pizza Bob's 42" Build

[Millstone Man]

Re: Pizza Bob's 42" Build

Well done! Your keystone gives inspiration to all of us who follow.

[John K]

Re: Pizza Bob's 42" Build

Congrats Bob!! The Key stone turned out great.
Now to the vent construction!!

cheers

[dsgreco]

Re: Pizza Bob's 42" Build

Really looks great. Nothing like getting that keystone in. Have fun with the vent and chimney.

[WoodchuckDad]

Re: Pizza Bob's 42" Build

That looks awesome. ....I have to get off my butt and get outside and work on mine.

[Dino_Pizza]

Re: Pizza Bob's 42" Build

Well done Bob, congratulations. Just a few more pieces to cut for the vent and you'll be through with cutting firebrick. As dsgreco says above, the vent and chimney can be fun.
-Dino

[fxpose]

Re: Pizza Bob's 42" Build

Congratulations, Bob!!!

George

[KraemerBAC]

Re: Pizza Bob's 42" Build

Congrats,

It looks great

Peter

[pizza_bob]

Re: Pizza Bob's 42" Build

Thank you everyone for the compliments. Hopefully I'll have pictures of the vent and chimney soon.

Well done Bob, congratulations. Just a few more pieces to cut for the vent and you'll be through with cutting firebrick. As dsgreco says above, the vent and chimney can be fun.
-Dino

So how much "fun" is the vent/chimney area??? I've seen so many different approaches. I need to select one and move forward with it. I have room to go with a 8.5" x 18" flue. This sounds HUGE but based on my understanding - bigger is better??? If I use the 1/10 ratio (oven opening to flue effective area ratio) then my flue only needs to be a 5" diameter which seems really small for a 42" oven. Let the "fun" begin...

[Tscarborough]

Re: Pizza Bob's 42" Build

Bigger is not better or the rule of thumb would be "bigger is better". The 10% rule works, and when I am called out to diagnose a smoker, 7 times out of 10 it is incorrect flue size, too small mostly, but sometimes too big. The other 30% consists of 25% chimney placement or height, and the remaining 5% are tear it down and hire a real mason.

(fireplaces, not ovens)

[pizza_bob]

Re: Pizza Bob's 42" Build

Bigger is not better or the rule of thumb would be "bigger is better". The 10% rule works, and when I am called out to diagnose a smoker, 7 times out of 10 it is incorrect flue size, too small mostly, but sometimes too big. The other 30% consists of 25% chimney placement or height, and the remaining 5% are tear it down and hire a real mason.

(fireplaces, not ovens)

Thanks Tscarborough.
My oven opening is approximately 250 square inches. 1/10th of this is 25 square inches. So if I go with a rectangular flue from Superior Clay (Superior Clay Flue Liners) the closest standard size (with out going undersize) would be the 4.5" x 13" which hs an effective flue area of 34 square inches. This seems like an awfully small flue compared to some that I have seen. If I went with the round flue it would be a 6" diameter.

Thanks again for all your help!

~Bob

[Tscarborough]

Re: Pizza Bob's 42" Build

Truthfully, I was a little wary of applying the ROT to my oven, since it only called for an 8x8 and my stack is only 3 foot tall. My instinct was a 13x13, but in practice, I have not had a wisp of smoke out of the front arch and it sucks like a well, golfballs and hose type of mind picture.

FYI round or square will always perfom better than rectangles.

[pizza_bob]

Re: Pizza Bob's 42" Build

Truthfully, I was a little wary of applying the ROT to my oven, since it only called for an 8x8 and my stack is only 3 foot tall. My instinct was a 13x13, but in practice, I have not had a wisp of smoke out of the front arch and it sucks like a well, golfballs and hose type of mind picture.

FYI round or square will always perfom better than rectangles.

Is that because the corners of the rectangular opening develop "eddy currents"? I wonder why the square wouldn't behave similar to the rectangle.

[pizza_bob]

Re: Pizza Bob's 42" Build

I am finishing my oven and having second thoughts about using a clay flue coming out the front of the oven. I decided I like the hipped style roof but if the flue came straight up it wouldn't look right. I decided to layout a stainless flue that has a 30 degree bend to it. I believe 30 degrees is the maximum bend allowed by code for residential building codes (wood stoves). Someone told me it's because an angle steeper than that would be too difficult to get a cleaning brush through. I think it must be code like that for draft purposes too - which is my concern with the venting system shown below.


Any advice on using a 30 degree bend? Will this draft properly? I can probably go less than 30 degrees but then the structure gets taller.
I also decided to call it quits on my "mason career". I was originally planning on a sheetmetal framed cement board enclosure with a stone veneer finish but decided to higher a "real mason" instead. He came out and gave me a quote to build a complete stone structure, with the hipped roof shown in the image below, around the entire pizza oven. He'll leave me plenty of room between the dome and the stone enclosure to get 2" of ceramic blanket and 4" of loose vermiculite at the soldier course. The loose vermiculite thickness will obviously increase as it approaches the top of the dome. I'm not sure if loose vermiculite is acceptable around the stainless flue. Any advice on that?

Thanks,
Bob

[Fairview WFO]

Re: Pizza Bob's 42" Build

Bob, you are correct in that two 30 degree bends are all that's allowed by code. Below is a pic of what that looks like from my construction. It does get rather tall if your trying to get the chimney to the back of the structure. I have a 36" dia oven with a 6" flue and have no issues drafting with this angle. I imagine you could go 60 degrees and have no drafting problems if you had enough chimney height in total, but that wouldn't be code. I filled the entire cavity around mine with perlite or vermiculite, so you should be ok as that stuff can handle the heat, and when using a class A chimeny pipe you don't get much heat transfer to the outer pipe anyway. If you are using a single wall, well that's going to get hot and is not per code, if your worried about that. The other thing to consider is the cost...this setup will set you back almost a grand!

[pizza_bob]

Re: Pizza Bob's 42" Build

The other thing to consider is the cost...this setup will set you back almost a grand!

Whoa! $1000??
It looks like your vent ran past the center of the oven and to the back. How tall is the top of the 2nd bend where the straight portion starts from the top of your dome? I plan on using the double walled pipe. Is it heavy? It looks like you supported it against the blocks. I planned on using sheetmeatal supports that are anchored to my structural concrete layer but I wasn't sure how heavy thissystem is.

Your oven looks great!

Thanks for all the info and pix!

Best Regards,
Bob