OctoForno

[GianniFocaccia]

Re: OctoForno

John, I have been wondering about an issue I see with some of the builds on here. Being a mason by trade, what I see that concerns me is the construction of the entries on some builds. I believe the stronger entry is the type you built, where the arch starts right at the floor. I see some where a short height side wall is built then a shallow arch connects the two short height walls. My thinking is that this could over time collapse. These brick side walls are not tied back into the dome structure itself

Interestingly, I had this same concern and abandoned my original plan which included the conventional 5.5" soldier course in the dome and a four-deep vertical-walled entryway. This was based on my readings of Forces Acting in Arches and Vaults, which can be found here:

Auroville Earth Institute

However, after my I completed the masonry portion of my oven, I totally agree with Stonecutter, and that a number of these forces are not significant, at least in the scale that our ovens occupy.

With zero prior building experience, I tried to apply to my build every sound principle I could learn, including lines of thrust, not only in the dome, but also in the archway design which is also semi-circular. Because of the heatbreak, my entryway is essentially it's own separate, smaller vault, which has no additional buttressing to support the weight of its flue (unlike the oven arch that is tied into the oven itself).

I applaud your interest in applying sound principles in overcoming gravity and predictably, heat transfer. I too, was critical of every element (I could think of) I observed in previous FB builds and tried to envision a better approach. I think this kind of scrutiny is what makes for the evolution of WFO's and with the collective's contributions, result in viable improvements.

[Campmaki]

Re: OctoForno

Interestingly, I had this same concern and abandoned my original plan which included the conventional 5.5" soldier course in the dome and a four-deep vertical-walled entryway. This was based on my readings of Forces Acting in Arches and Vaults, which can be found here:

Auroville Earth Institute

However, after my I completed the masonry portion of my oven, I totally agree with Stonecutter, and that a number of these forces are not significant, at least in the scale that our ovens occupy.

With zero prior building experience, I tried to apply to my build every sound principle I could learn, including lines of thrust, not only in the dome, but also in the archway design which is also semi-circular. Because of the heatbreak, my entryway is essentially it's own separate, smaller vault, which has no additional buttressing to support the weight of its flue (unlike the oven arch that is tied into the oven itself).

I applaud your interest in applying sound principles in overcoming gravity and predictably, heat transfer. I too, was critical of every element (I could think of) I observed in previous FB builds and tried to envision a better approach. I think this kind of scrutiny is what makes for the evolution of WFO's and with the collective's contributions, result in viable improvements.

Thanks to the two of you for your input on the "thrust" issue. I just do not want a failure to occur. I have built plenty of arches during my career as a bricklayer, whether it be stone, brick or even cmu. From veneers on buildings to fireplaces, it seems we always had some sort of "buttressing". In my mind I would go that little extra to support the sidewalls , just to be on the safe side. Just an added note to this subject, On projects with arches, such as a brick veneer, you have brick laid above the arch which adds more support .

[stonecutter]

Re: OctoForno

On projects with arches..... you have brick laid above the arch which adds more support .

This is not a correction, but a clarification for anybody following this or have an interest in arch physics...


The weight of the masonry around an arch does not act in support. It contains load thrust, while the weight above the arch and the thrust line stabilizes the abutment.

The blah,blah,blah aside, from a strictly aesthetic point of view, I like a semi better than a segmental arch any day.

[GianniFocaccia]

Re: OctoForno

The weight of the masonry around an arch does not act in support. It contains load thrust, while the weight above the arch and the thrust line stabilizes the abutment.

Kind of like this? From what I've read, I believe the forces of water pressure on the arc of the dam actually cause it to compress, making it stronger.

from a strictly aesthetic point of view, I like a semi better than a segmental arch any day

Me too!

[stonecutter]

Re: OctoForno

Yep, similar to that....but drier.

[Campmaki]

Re: OctoForno

This is not a correction, but a clarification for anybody following this or have an interest in arch physics...


The weight of the masonry around an arch does not act in support. It contains load thrust, while the weight above the arch and the thrust line stabilizes the abutment.

The blah,blah,blah aside, from a strictly aesthetic point of view, I like a semi better than a segmental arch any day.

Thanks Stonecutter, I also prefer the semicircular arch, but to each his own. Thanks for your thoughts.

[GianniFocaccia]

Re: OctoForno

Just got back from five days in Seattle, where it was clear and beautiful except some near-freezing drizzle on the last day. This was our second year of attending the PAC-12 Conference meet and I am amazed at how beautiful the Pacific Northwest is. Driving around, I kept thinking how nice it would be to gather wood for the oven.

Here are some progress pics of insulation, framing and concrete board install. Many thanks to Stonecutter who set me straight on the use of horizontal nailers, (pic below) the short, angled pieces required to provide backing to screw edges of Durock into.

The 1" insulation was fairly straightforward to install and although time-consuming to custom-fit, was probably much easier than fitting 2"-thick stuff. Like virtually all of the builders here, I secured the blanket with hex net.

The 20-gauge steel studs I got from a drywall distributor for a few cents more than the 25-gauge stuff at Lowes. They were quick and easy to cut (I used my angle grinder with those cheap metal-cutting wheels that smell bad) and after it was all said and done discovered I had not cut or sliced myself once.

The horizontal stud braces are designed to anchor a cleat that will mechanically secure the top of each granite slab in addition to adhesive. I figured this is good insurance since SoCal is a high seismic-activity region and that we literally live on top of the San Andreas fault.

Next up: granite cladding.

John

[texman]

Re: OctoForno

Hey John
Great progress. Did you/will you fill the space around oven with vermicrete or more insulation?

Texman

[ggoose]

Re: OctoForno

Sheez John...I think I saw one of your Durock screws was 1/64th inch out of perfection...better fix that so I can sleep at night

[oasiscdm]

Re: OctoForno

And perfection continues. Looking good John. Your decorative arch how will you go about that?

Am curious about how close you are to the back wall. Seems difficult to get screws in.

[GianniFocaccia]

Re: OctoForno

Thanks, Gene. It's been a lot of fun working on this project, but it just proves that you can be picky and methodical if you take forever to do it.

I do have a question about your build: How has your enclosure vent worked, and now that you've had it awhile, do you think it's absolutely essential? Because it's so dry here I am considering forgoing this element, but, like everything else, don't want to later regret skipping it.

Tex - The plan at this point is to finish the vertical cladding and then yes, void-fill the remainder of the oven with perlite. My guess is it's a tad over-insulating, but with these ovens, is that even possible?

[ggoose]

Re: OctoForno

Project...? How about 'work of art'. You artists always take your sweet time .

My vent was one of those things I thought would be good to circulate air and as well as keep an eye on the inside of the build. Looking back, and forward, if I encounter a problem I'm not sure what good the vent will do me because it is too small to really access/repair anything. So to answer your question directly, I think it could be left out of the design/execution, as the structure will still breathe (not air tight by any stretch), and there is not much inside that would/could fail...perhaps a leaky roof which could be addressed from outside. Aesthetically, the vent detracts from the over all look of 'solidness', plus to really circulate air, one would need a second vent.

gene

[GianniFocaccia]

Re: OctoForno

Thanks. I believe the conventional thought is that a vent allows the moisture from vermicrete insulation to escape, as well as any baking steam that leaks (cracks?) into the enclosure. Since I'm not using any wet insulation and since its predominantly dry here, I think I'll skip the vent, unless advised otherwise.

Besides, like you say, I believe the enclosure is far from airtight, and any moisture that finds its way in can certainly find its way out, especially when the weather gets hot.

I appreciate the kind words, Colin. I have a couple of options regarding the decorative arch. I could cut a semi-circle out of some leftover granite countertop that I plan to use for the landing, but I think I would rather have a little contrast between the arch and countertop.

Also, I like the look of individual bricks mortared into a semi-circular arch. Besides, it gives me one last opportunity to fiddle around cutting bricks.

You know, for as many hours as I've spent thinking about this oven, my inexperience really shone through designing and building my foundation and support stand. The back wall is a mere 9" from the property block wall, which was too close to use my cordless drill on the studs and concrete board. Luckily, I have a small power drill that did the job and installing the granite slab will not need any drilling.

If I had it to do over again, I would still go with the Octogon design, although from some of the language that seeped out when I was battling trying to keep multiple planes of the enclosure frame plumb (at the same time), you'd never know it.

[Texas]

Re: OctoForno

I am looking to do a semicircle arch with a flared vent area. For my 36" oven, I am looking at inner arch of 19" wide, 12" high and my reveal at 1", so the inside of my vent arch (dimensions just outside of the inner arch) would be 21" wide and 13"high and the outside opening of the flared arch would be 24.5" wide and 14.75" high. I was looking at doing 21 arch bricks. Using the numbers from the angelizer, I would mark one end of the brick with those dimensions and the other end of the brick with the dimensions for a 21 brick arch that is the smaller size. Then I would taper the brick from front to back, while making the arch brick shape. Is that a twisted brick? Oasiscdm says you invented the twisted brick, but I don't find any mention of twisted brick on your page.

On page 17, post #167 I think best shown in picture #2, do the first 5 rows or so butt up against the inner arch? Do the small bricks (maybe 3" ish) that are just outside the inner arch (shown in pic #2 with the mortar wedges) mortared to the top side of the inner arch? Do they have an "L" shape or something to help them hang down or are they butt joint too?

Are the dimensions you gave of 13.5"(h) x 22.5"(w) inner arch for the inner arch that is the opening in the dome and tied into each dome layer, or the dimensions of the inside of your flared vent opening - like the arch that forms the reveal?

Are there additional photos/info you can share? Oasiscdm mentioned that you shared a lot of info about the semicircle flared arch.
Thanks a bunch!

[oasiscdm]

Re: OctoForno

Texas

I replied over on my thread to those questions. Hopefully should find your answers there.