K79 Oven Build

[david s]

Re: K79 Oven Build

I won't disagree with your measurements TS, but for my ovens the base of the dome is always way cooler than the floor, especially when curing. This is evidenced by the persistent ring of black around the base. Even after fully cured the temperature of the base of my dome, when the whole oven has turned white, is still way lower than that of the floor or the crown of the dome. As thermal expansion is directly related to temperature I conclude that an expanding floor can create pressure on the walls.

[Tscarborough]

Re: K79 Oven Build

I get the same ring, so I understand what you are saying, but other than directly under the fire, the floor, as measured, is always cooler than the walls.

[david s]

Re: K79 Oven Build

Maybe it's because my oven is small, but my fire covers the entire floor and the IR reads higher anywhere on the floor than the base of the dome, when the oven is heating up at around the time the dome clears.

Taking a closer look at your numbers the expansion of both the circumference and that of the floor are both .54% which would suggest that the temperatures of both are the same at time of measurement.

Comparing one oven to another may not be that helpful in drawing conclusions as the relative thickness of wall and floor are likely to be different and give different readings. (My floor and wall thickness are both the same at 50mm.)

[Gulf]

Re: K79 Oven Build

They may have not been reading your thread. I think Gulf and David have a point. I see no compressive load holding in your vent transition bricks. It looks awesome but what is holding them in place when the mortar bond is compromised?

Thank's Les, That is true, although I do try. I think most of us do. My work hours and maybe, the number of builds going on today, have me sometimes just hitting the high spots.

K79, Most of us probably, don't care, if our ovens last 3000 years Your entry/flu may outlast the majority of the builds on this site. My comment was just based on what the "old folks" (which I am becoming nearer to every day ) taught me. That is, "if it will stand up too a dry stack, it will last" .

[stonecutter]

Re: K79 Oven Build

My .02 would be that your vent is fine, especially when you install your flue. With the steel buttresses you could stand on that arch and not blow it out.

As for waiting 28 days...it won't do anything for you. That is a concrete slab number..generally considered the point concrete reaches maximum strength. It has nothing to do with masonry units....fire away.

[Les]

Re: K79 Oven Build

Thank's Les, That is true, although I do try. I think most of us do. My work hours and maybe, the number of builds going on today, have me sometimes just hitting the high spots.

K79, Most of us probably, don't care, if our ovens last 3000 years Your entry/flu may outlast the majority of the builds on this site. My comment was just based on what the "old folks" (which I am becoming nearer to every day ) taught me. That is, "if it will stand up too a dry stack, it will last" .

No Gulf - I was referring to the quote I've seen others that have done it this way and asked prior and nobody mentioned it was an issue

I agree w/ you on the posts - this forum is growing way to big to see and respond to it all. I remember the day when I was watching 1 or 2 builds...

[Sharkey]

Re: K79 Oven Build

That looks fantastic. I think it will be stable enough. Obviously the front is really strong as the bricks are cut to form the collector - no mortar.

When you build up for your flue you could cut some bricks to interlock at the back. Hopefully you can see what I mean in this photo of my build. I interlocked bricks both front and back. The back ones I ground into a curve to fit the flue.

[david s]

Re: K79 Oven Build

K79, it wasn't my intention to alarm you re the inverted arch bricks in your vent, merely curiosity about how you might have set them. I'm sure it will perform ok especially as the vent doesn't get that hot unless you have a raging fire up the chimney. Regarding the lack of a gap between the perimeter of your floor and the base of the dome I don't think you have too much to worry about either because the main reason floor bricks are laid loose is to allow bricks to expand independently. Because of all the gaps between the bricks they should allow enough for the total expansion of the floor.Having said that modular cast oven manufacturers that have floor bricks inside the dome (FB included) all seem to design a gap between the perimeter of the floor and the dome.

In building your oven you want to make it as strong as you can and finished as perfectly as you can. In reality your oven will get dirty and probably develop cracks in places that you made strong.This usually leads to some disappointment initially, but then you get used to your ovens worn in look.

[K79]

Re: K79 Oven Build

So I'm nervous to take the jump to my first fire, but the day is fast approaching. I need to do it next weekend (I have two kids and my wife works every other weekend). What are the thoughts here. First fire up to 300 degrees F and hold it for as long as I can the first time. 350 F the second fire? Seems a little high no?

[david s]

Re: K79 Oven Build

Read the thread on curing in "firing your oven"

[K79]

Re: K79 Oven Build

Read the thread on curing in "firing your oven"

Oh I read that whole thread already. Didn't know if there were any new thoughts on the topic.

[boerwarrior]

Re: K79 Oven Build

K79

I found it hard to keep the oven at a particular temperature - so I based it mostly off the amount of wood. For the first few fires I burnt only kindling - then started progressively adding some bigger logs until about Day 12 when I then fired it up all the way and cleared the dome for the first time. I'm not saying this is the best way but it worked for me!

[K79]

Re: K79 Oven Build

K79

I found it hard to keep the oven at a particular temperature - so I based it mostly off the amount of wood. For the first few fires I burnt only kindling - then started progressively adding some bigger logs until about Day 12 when I then fired it up all the way and cleared the dome for the first time. I'm not saying this is the best way but it worked for me!

How long did you hold your first few fires?

[boerwarrior]

Re: K79 Oven Build

only about an hour or two.. i know that is less than recommended but I figured it wouldn't hurt to start drying it out slowly. I'm also lucky because is has rained here only once in the last 3 months and the relative humidity is generally under 40% all summer.

[david s]

Re: K79 Oven Build

only about an hour or two.. i know that is less than recommended but I figured it wouldn't hurt to start drying it out slowly. I'm also lucky because is has rained here only once in the last 3 months and the relative humidity is generally under 40% all summer.

That's way too much for the first few fires IMO. Start the first one for about 15 mins, then increase daily. Allowing the oven to even out in temp between fires reduces the huge temp difference between the top and bottom of the dome each time. The top of the dome dries first and so will heat up again so much faster which exacerbates the temperature difference and hence the uneven expansion.