Building in Central Florida, Question about insulation beneath cooking floor

[DrakeRemoray]

Re: Building in Central Florida, Question about insulation beneath cooking floor

Door is probably better a little too wide than too tall...

[glowthb]

Re: Building in Central Florida, Question about insulation beneath cooking floor

Neil,

The full width of the opening may be +/- 23 inches, but the measurement of the inside dimensions at the reveal is 20 inches and the height will be 12.5 in accordance with the FB plans for the 42 inch oven.

I originally planned to build the interior height to the 21 inches but I am reducing it to 19 inches high. I will not get to the dome for another week or so due to schedule. Any thoughts on the 19 inch interior height vs. 21 please let me know if you think its a problem. No particular reason why I am reducing it other than 21 inches looks awefully high and unnecessary. If there is a thermal dynamics reason let me know.

[mklingles]

Re: Building in Central Florida, Question about insulation beneath cooking floor

My dome is 18" high inside. Door is 12" high and 19" wide. Heats well in 1 1/2 hrs. I have lots of thermal couples so I am sure I'm soaking the heat through the floor and dome. You'll be fine.

I can't think of a valid thermodynamic reason for a high dome. A high dome would have more thermal mass then a low dome (assuming both are 4 1/2" high). But you could thicken the walls of a low dome.

A high dome allows a higher door which allows larger items into your oven.

I'm very happy with my dimensions which are vary close to yours.

[Dino_Pizza]

Re: Building in Central Florida, Question about insulation beneath cooking floor

I agree, 19" dome height is fine. I think it's a great goal. I found it's hard to keep to a lower dome height: the mortar kind of gets out of control and the height creeps up a bit but a 'flat-ish' dome is ideal. It directs the radiant heat down to the oven floor where you want it. And 19" is still plenty tall for casserols or even vertical beer-can chicken.

However, in your last pic, I counted 5 high side arch wall bricks. Most seem to be 3 or 4 hight at most. Are you using an iron "L" bracket/header across the top or still going for an arch? My oven opening is 12.1" in the center and 8.5" at the sides. Just wondering.

Your brick work looks really good, your going to have really nice oven.

take care, Dino

[glowthb]

Re: Building in Central Florida, Question about insulation beneath cooking floor

Thank you all for input.

Dino, Yes. I did use 2" angle iron to bridge the opening opting for the safer easier newbie design. I ground down the 5th course and bricks as needed to accommodate the iron and bring the top of the reveal in at just a hair over the 12.5 inch height after mortaring.

Additionally I will cut off that 5th course at the front back down to only 4 courses bringing the front opening down to 12 inches, 1/2 inch lower than the reveal height. Regarding this, is 1/2 inch enough to trap the smoke forcing it up and out the chimney? I am using 8 inch Duratech system for the chimney.

Thanks again.

[glowthb]

Re: Building in Central Florida, Question about insulation beneath cooking floor

Minor correction needed here regarding number of bricks at the oven opening. I actually added a 6th course to the height of the opening. The fire bricks here in Central Florida, for what ever reason, are coming in at +/- 2.25 inches high and not 2.5. The top of the 5th brick is right at 12 inches if you are looking at the photo with the level across the top.

[Neil2]

Re: Building in Central Florida, Question about insulation beneath cooking floor

The "magic" ratio for door height to inside dome height is 63% which is pretty much what you have achieved.

Your height to radius ratio is about 90% which is in the optimum range for an elliptical oven.

I still think your door opening is a bit wider than typical, but this is something that is very easy to modify if you find you are having problems with it once you get your oven working.

[glowthb]

Re: Building in Central Florida, Question about insulation beneath cooking floor

Neil,

Thank you for reading through and providing input. It is reassuring to know it is on track to optimal engineering standards.

I agree, narrowing opening should not be an issue if necessary. Going wider however...another story.

Hopefully I should get to the dome this week...under the lights.

Thanks again.

[efleifel]

Re: Building in Central Florida, Question about insulation beneath cooking floor

Good morning glowthb,

Please excuse my ignorance, but I cannot find the link or photos of your oven, but reading some of the posts above, they seem to have seen some.
Cheers

Eddie

[glowthb]

Re: Building in Central Florida, Question about insulation beneath cooking floor

Efleifel...are they not showing on previous pages?

Here are the latest as I am getting (hoping) to close the dome.

A couple of lessons learned to relay to someone taking this on:

1. Bricks cut in half are heavy. Your ability to keep them from sliding with fresh mortar gets more difficult as the angle increases.

2. Styrofoam vanes are nice, but make sure you have enough to provide support to help with the issue above.

3. Shimming Bricks from the inside quickly causes problems getting off the gradual dome igloo you are "curving" in to shape.

Recommendations:

1. Styrofoam vanes are fine but get some cardboard to cover the top half or so?the area when your bricks start hitting more than 55 or so degrees.
2. At that same point start considering cutting those half bricks in half so the mortar is not pulling all the weight.
3. Avoid shimming from the inside. If your bricks are sliding and there is not a vane to catch it, it is time evenly cover those vanes with cardboard. This helps keep the uniformity you are looking for. Shims may help in that one spot, but the next course may be off.
4. Finally, as you get to the top, the need for custom cutting bricks to fit is necessary. Using squares to form a circle gets harder as that circle gets smaller.

Others may not have experienced the above but something to consider as you move forward.

[efleifel]

Re: Building in Central Florida, Question about insulation beneath cooking floor

Hi,

I can see the 3 pictures now but not in the previous posts. Looks very good.
I had to do the same thing when I was using the styrofoam, I used card- board to hold the bricks as well. Unfortuantely I could not do anything with the oven today, I was planning to build the front arch and the vent this weekend, but the weather was windy, and then started raining. Hopefully next weekend.
Cheers

Eddie

[glowthb]

Re: Building in Central Florida, Question about insulation beneath cooking floor

Well I got the dome closed this weekend. As the opening got smaller, the brick work got sloppier but I am sure the Heatstop50 will compensate for it, okay, fingers crossed a bit. It seems very solid.

As you can see, another issue with the styrofoam ribs is you cannot clean off the excess mortar as you go so there is some clean-up work to get done next weekend. Thank goodness for a skinny 18 year old son. He is already on task to climb in and clean it up.

To add some additional "grab" on the Duratch plate, I used some half inch "metal cloth" bolted around the four sides of the plate to grab into the mortar.

[glowthb]

Re: Building in Central Florida, Question about insulation beneath cooking floor

Not the prettiest entrance but will be enclosed anyway in a gable house design.

[efleifel]

Re: Building in Central Florida, Question about insulation beneath cooking floor

WOW, You have done a lot, and it does looks good, you are just being mosdest. I did nothing this weekend.
I agree it did get sloppier as we close the dome. I also found that I had to go in and mortar the gaps from the inside.
Cheers

Eddie

[Neil2]

Re: Building in Central Florida, Question about insulation beneath cooking floor

"If your bricks are sliding and there is not a vane to catch it, "

I bought a package of cheap chopsticks and cut them up to bridge between the Styrofoam vanes at that point. They can be pressed into the styrofoam to maintain the exact shape. This also allows some access to the inside joint as you go for cleaning up the mortar.

I'm a great believer in he stryrofoam vane/formwork approach. Once set up, there is no guesswork - you know the dome shape is going to come out exactly as designed.

I can't see from your photos, but I also cut sizable 6-8 inch half circle "mouse holes" in the bottoms of the vanes to facilitate air circulation (and dropped tool retrieval).