OctoForno

[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

[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.

[stonecutter]

Re: OctoForno

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

[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

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.

[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 .

[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.

[stonecutter]

Re: OctoForno

I guess I was not giving my full thought on this issue. I think the shorter side walls need to backed up with at least a 4 inch block. there might not be an issue when using a metal chimney, but what about a clay flue liner. This adds some extra weight and downward pressure to the arch.

If the spans were greater than 24", had tall piers, and have 12" flues maybe, but the outer arch you are concerned about doesn't carry 100% of the load anyway. With the oven opening arch as part of the system, strength is further gained by the vent being constructed in a way so that it functions like a vault, even though it technically isn't one. It provides plenty of structural mass to support itself, and a few flues.

BTW, I was talking about loading the arch with several clay flues, not metal ones.

Just so I'm clear, I am not saying a segmental arch is as strong as a semicircular one. Only that building an abutment ( or buttressing as referred to on the forum) is not necessary in most cases and is over building. It's not a design flaw to omit it, but it is good insurance, and there is nothing wrong with that.

[Campmaki]

Re: OctoForno

You mean a semicircular arch, Colin

The height of the pier which a segmental arch springs from is the real point of weakness. Most of the segmental arches built on here have sufficient thickness/ height ratio in the pier to worry about hinge failure, because the don't support that much load weight. A lot of builds here have buttressed the pier, creating and abutment, removing any possibility of overloading the arch.

I guess I was not giving my full thought on this issue. I think the shorter side walls need to backed up with at least a 4 inch block. there might not be an issue when using a metal chimney, but what about a clay flue liner. This adds some extra weight and downward pressure to the arch.

[stonecutter]

Re: OctoForno

there seems to be an echo

Like the information I too built the same type of arch as John. We discussed this a bit a hemispherical arch is much stronger for those reasons you have highlighted.

You mean a semicircular arch, Colin

The height of the pier which a segmental arch springs from is the real point of weakness. Most of the segmental arches built on here have sufficient thickness/ height ratio in the pier to worry about hinge failure, because the don't support that much load weight. A lot of builds here have buttressed the pier, creating and abutment, removing any possibility of overloading the arch.

[oasiscdm]

Re: OctoForno

there seems to be an echo

Like the information I too built the same type of arch as John. We discussed this a bit a hemispherical arch is much stronger for those reasons you have highlighted.

[Campmaki]

Re: OctoForno

[QUOTE=Campmaki;168640]Abutments
An arch abutment can be a column, wall or combination of wall and shelf angle. Failure of an abutment occurs
from excessive lateral movement of the abutment or exceeding the flexural, compressive or shear strength of the
abutment. Lateral movement of the abutment is due to the horizontal thrust of the arch. Thrust develops in all
arches and the thrust force is greater for flatter arches. The thrust should be resisted so that lateral movement of
the abutment does not cause failure in the arch. If the abutment is formed by a combination of brickwork and a
non-masonry structural member, rigidity of the non-masonry structural member and rigidity of the ties are very
important. Adjustable ties or single or double wire ties are recommended. Corrugated ties should not be used in
this application because they do not provide adequate axial stiffness. Consult Technical Notes 31A for further
discussion of abutment and tie stiffness requirements.[

[Campmaki]

Re: OctoForno

I guess I just figured that one out!!!!

Abutments
An arch abutment can be a column, wall or combination of wall and shelf angle. Failure of an abutment occurs
from excessive lateral movement of the abutment or exceeding the flexural, compressive or shear strength of the
abutment. Lateral movement of the abutment is due to the horizontal thrust of the arch. Thrust develops in all
arches and the thrust force is greater for flatter arches. The thrust should be resisted so that lateral movement of
the abutment does not cause failure in the arch. If the abutment is formed by a combination of brickwork and a
non-masonry structural member, rigidity of the non-masonry structural member and rigidity of the ties are very
important. Adjustable ties or single or double wire ties are recommended. Corrugated ties should not be used in
this application because they do not provide adequate axial stiffness. Consult Technical Notes 31A for further
discussion of abutment and tie stiffness requirements.

[Campmaki]

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. Just thought I would pick your brain a little. Here is another issue , have not yet figured out how to make my messages get in the forum. Thanks again for any help

I guess I just figured that one out!!!!

[Campmaki]

Re: OctoForno

Hello All,

Glad to be back after all these months considering my company closed its CA offices (laying everyone off) and then I hit a bit of a rough patch with my health which initially landed me in the ER. Feeling much better now, but getting old is really getting old and I'm still in my fifties!

Fortunately, I can report I'm on the homestretch on my oven (and now fully-cured dome ). I have completed the entryway save for the last two leveling courses. The welding of my custom-designed flue (by a family member) got derailed but is now at a commercial fabricator who promised it to me last week and now says hopefully day after tomorrow.

I really struggled with an approach to constructing my flared entry and integrating a 13.5"(h) x 22.5"(w) inner arch with a 12.5"(h) x 26"(w) outer arch. I finally got it figured out and kicked myself for not attacking it sooner because it really wasn't that difficult a job, just time-consuming. All in all, it was a fun part of the project.

Anyway, here's some pics and a profile of my vent. I really wanted the vent architecture to be totally seamless to give the oven exhaust every opportunity to go up rather than out the front of the oven. Hence the trapezoidal shape and an outer arch that is an inch lower than the inner arch. I think it came out okay.

I'll report back when I get my flue installed and hopefully a first fire (really?) video a week later.

John

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. Just thought I would pick your brain a little. Here is another issue , have not yet figured out how to make my messages get in the forum. Thanks again for any help