gt40's Pompeii Oven 42" build log

[shuboyje]

Re: gt40's Pompeii Oven 42" build log

Without a specialized coating I think board is a poor choice for the top of your vent. It will be in contact with fire and moisture laden corrosive flue gases. I'm building a similar vent(eventually) on my new oven and will be using either a dense castable or pieces cut out of a flue liner for this.

[david s]

Re: gt40's Pompeii Oven 42" build log

I'd be concerned about the heat loss from the top of your dome into the flue area when doing retained heat cooking. Wouldn"t it be better to insulate over the dome first, then run your flue over the top of the insulation.

[gt40]

Re: gt40's Pompeii Oven 42" build log

Without a specialized coating I think board is a poor choice for the top of your vent. It will be in contact with fire and moisture laden corrosive flue gases. I'm building a similar vent(eventually) on my new oven and will be using either a dense castable or pieces cut out of a flue liner for this.

Interesting point. I was going to coat the fiberboard with refactory paste. I will look into the durability of the fiber board. I may just put a plate of 321 stainless on the top and then put the fiber board on top of that.

I'd be concerned about the heat loss from the top of your dome into the flue area when doing retained heat cooking. Wouldn"t it be better to insulate over the dome first, then run your flue over the top of the insulation.

I was actually thinking the super heated gases recirculating over part of the dome would be more efficient and better than sending them straight up and out. I will wrap everything in fiber blanket in any case.

[david s]

Re: gt40's Pompeii Oven 42" build log

"I was actually thinking the super heated gases recirculating over part of the dome would be more efficient and better than sending them straight up and out. I will wrap everything in fiber blanket in any case."[/QUOTE]

Yes, this would be so, but once the fire is out and your door is on for roasting or baking, cool air is going up your flue over the uninsulated dome. In the usual set up it doesn't matter if the flue is cooling because it is isolated from the actual oven.

[gt40]

Re: gt40's Pompeii Oven 42" build log

"I was actually thinking the super heated gases recirculating over part of the dome would be more efficient and better than sending them straight up and out. I will wrap everything in fiber blanket in any case."

Yes, this would be so, but once the fire is out and your door is on for roasting or baking, cool air is going up your flue over the uninsulated dome. In the usual set up it doesn't matter if the flue is cooling because it is isolated from the actual oven.[/QUOTE]

Your point is interesting. This stuff is more complicated than it seems. I am not an engineer or anything but I was thinking that the whole flue channel and bottom part of the chimney wrapped in fiber blanket would give enough insulation + the chamber would be sealed with the door.



I hadn't thought much about the channel sucking air through it and cooling the dome through the unexposed portion. Unless I have a fan blowing air through the channel with the door closed, I am hoping the insulation on top of the channel will do its part. I will finish building it and report back before I permanently enclose my dome. I can always convert it to a traditional chimney.

On the other hand, this design may provide increased draw and faster heat up times

Pic so far:

[shuboyje]

Re: gt40's Pompeii Oven 42" build log

What you are building is very similar to the traditional vent on ovens built in Naples. They claim an experienced oven builder can tell when the flue is not constructed this way just from watching the oven fire. I guess you and I will both know soon enough how well it works. I have my old oven with a straight up vent to compare it to.

Last point is that I would consider a additional chain of bricks at the front if it fits your enclosure. It will create more of a smoke chamber and better airflow which should lessen the amount of smoke that goes out the front on startup. The traditional vents are very high in front and I assume this is the reason why.

[brickie in oz]

Re: gt40's Pompeii Oven 42" build log

I hadn't thought much about the channel sucking air through it

You could always incorporate a damper into the front of the flue to shut it off.

[gt40]

Re: gt40's Pompeii Oven 42" build log

What you are building is very similar to the traditional vent on ovens built in Naples. They claim an experienced oven builder can tell when the flue is not constructed this way just from watching the oven fire. I guess you and I will both know soon enough how well it works. I have my old oven with a straight up vent to compare it to.

Last point is that I would consider a additional chain of bricks at the front if it fits your enclosure. It will create more of a smoke chamber and better airflow which should lessen the amount of smoke that goes out the front on startup. The traditional vents are very high in front and I assume this is the reason why.

I am taking your advice and putting a second row on front and the whole channel half brick height to increase volume

You could always incorporate a damper into the front of the flue to shut it off.

Any suggestions on design?

[shuboyje]

Re: gt40's Pompeii Oven 42" build log

I hope your chain holds up better then my stainless cable did. I just finished demolition on the old oven and was very disappointed to see the status of the cable. All there broke clean at the same spot, must be the result of some uneven thermal expansion. Even then the remaining cable was corroded stretched and brittle. Oddly enough my 16 gauge black iron vent was in perfect condition as was the angle iron that framed the door and connected the cable together. Live and learn. Luckily I was already planning on using multiple methods on the new oven and am confident it will be fine.

[brickie in oz]

Re: gt40's Pompeii Oven 42" build log

Any suggestions on design?

If you have a ceramic workshop or suppliers in your area get some kiln shelving cut to size, its not dear and will last for ever.

[david s]

Re: gt40's Pompeii Oven 42" build log

until you drop it.

[gt40]

Re: gt40's Pompeii Oven 42" build log

until you drop it.

After some measuring, my arches are pretty identical so I will try making a 5" thick door out of stainless sheet and filling it with ceramic fiber. It should block air into the oven and the flue by plugging the arch area.

[david s]

Re: gt40's Pompeii Oven 42" build log

I think that should work, but it will make the door kind of bulky. If your inner arch is the same width and height as the outer one won't there be sealing problems?

[Cheesesteak]

Re: gt40's Pompeii Oven 42" build log

Heck - I think it's a great idea.

I have a simpler solution to propose to you . . . .

I think I'd add a couple of inches of perlcrete / vermicrete on top of the dome in the chimney area - and then build your same chase on top of that. That way - there'd be an insulating later between the the dome and chase. You could parge a thin layer of mortar on top of the perlcrete to seal it up if you wanted to . . .

Heck - you could just fill that existing cavity you've constructed with perlcrete and then build your chimney chase on top of that.

Just a suggestion to avoid construing dampers and complicated mechanical equipment for the oven . . .

[shuboyje]

Re: gt40's Pompeii Oven 42" build log

In this type of design the heat of the dome is supposed to increase the draw pretty dramatically, so the insulation would be a problem. I think the simple solution would be to cut a piece of ceramic fiber blanket to fit the cavity and slide it in fron the front if you feel the need for lots of retained heat.