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-   -   Castable - How thin can you go? (http://www.fornobravo.com/forum/f9/castable-how-thin-can-you-go-18976.html)

mikku 02-20-2013 03:39 AM

Castable - How thin can you go?
 
Does anybody know how thin a dome can be cast and still work?

cobblerdave 02-20-2013 03:55 AM

Re: Castable - How thin can you go?
 
Gudday
Difine "work" in relationship to "dome"

Regards dave

david s 02-20-2013 03:57 AM

Re: Castable - How thin can you go?
 
Probably depends on your castable, whether or not you are using SS needle reinforcement, the size of the cast pieces and method of placement. IMO 2" is ok if done properly. Also depends what you mean by failure. Hairline cracks, decent sized cracks? Because the dome is a self supporting structure, even if it cracks severely into a number of bits it will still stand up.
Try making one half as thick as you dare and report back.

mikku 02-20-2013 04:35 AM

Re: Castable - How thin can you go?
 
Quote:

Originally Posted by cobblerdave (Post 146020)
Gudday
Difine "work" in relationship to "dome"

Regards dave

1) Dome to maintain integrity through repeated heat/cooling cycles.
2) Self supporting- at high temps for pizza making/low mass application.
3) Self supporting- moderate temps-for breads/general oven use where "additional mass would be added" to outer surface of dome. But basically same dome as for (2)
3a) Mass to be determined- right now unknown.

4) Assumption- aside for additional thermal mass, no other weights need to be calculated, outer render to be precast--inner void filled with loosefill or ????

A starting place anyway for this discussion.

mikku 02-20-2013 04:56 AM

Re: Castable - How thin can you go?
 
Quote:

Originally Posted by david s (Post 146021)
Probably depends on your castable, whether or not you are using SS needle reinforcement, the size of the cast pieces and method of placement. IMO 2" is ok if done properly. Also depends what you mean by failure. Hairline cracks, decent sized cracks? Because the dome is a self supporting structure, even if it cracks severely into a number of bits it will still stand up.
Try making one half as thick as you dare and report back.

Thank you david s for checking in--by your threads you have experience in casting.

I was hoping for something in 3/4" to 1" range. I suppose a parameter must be set for oven size to begin with.

What size would be attractive to a small household- with 1 to 2 children?

Something to think about, to gain strength.. would ribs or sections with a thicker cross section allow for thinner builds?

A dome cast as a single section preferable.

I would assume "a pourable type castable" preferable to trowel type. But pourable by design has larger aggregate. Assuming that many manufacturers have similar products. (trowelable AGC is OK min thickness 20mm).

(The reason for even thinking about this is because I noticed how strong even a 6mm thick section of my render was today---I had to grind off some of my bad work, and the diamond cutter was singing to me--like it was hitting steel).

Thoughts- thin, affordable, portable. :)

This one-- think it through first, then make it! If it doesn't perform, adjust and try again. If the casting is thin enough, the cost is of little significance.

cobblerdave 02-20-2013 05:41 AM

Re: Castable - How thin can you go?
 
Gudday
Just a thought but most cast ovens I have come across are 2 in thick, in fact from what I know ,same again for the clay/sand shell of a cob oven.
The forno oven a 1/2 brick 4in thick. Is this just the "overkill" that makes the forno oven a robust construction or just a convenient size being a 1/2 brick?

Regards dave

mikku 02-20-2013 06:18 AM

Re: Castable - How thin can you go?
 
I thought someone made an oven using pavers, something like 1 1/2" thick. But these would be a bunch of segments, held together with a refractory mortar.

I would like to imagine much thinner. Everyone knows how strong an egg shell is and how thin it is.

Someone with some math skills should be able to predict at least a range of thicknesses--even though they are not commercially available.

I thought I saw a thread about a rocket stove pizza oven that used a flower pot dome. Instead of looking for the best pot, I thought it would be better to design a dome with the proper ratios in mind. But just thinner than the conventional.

It seems like the most difficult task is making a dome with the right dimensions to work. Additional mass can be added; different insulations used; and all the rest which I consider "decoration" added to suit the end user. (To clarify better-"an operating oven-including opening,landing,transition,chimney etc all included as proper design for dome). Design features I consider decoration-brick,stone,plaster,stucco,other cladding etc. These are reflections of the owners personality.

stonecutter 02-20-2013 10:15 AM

Re: Castable - How thin can you go?
 
Quote:

Originally Posted by mikku (Post 146032)
I thought someone made an oven using pavers, something like 1 1/2" thick. But these would be a bunch of segments, held together with a refractory mortar.

I would like to imagine much thinner. Everyone knows how strong an egg shell is and how thin it is.

My question would be why would you want to? With a super thin shell you would have to have recharge your fire constantly to maintain temperature, even with good insulation. Also what advantages would you have by making a thin walled oven? IMO, nowhere near enough to offset the inefficiencies.

interesting concept though.

Tscarborough 02-20-2013 10:19 AM

Re: Castable - How thin can you go?
 
Normally, concrete is getting dicey at at 3". Using additives and fibers you can get that down to an inch, but those are for non-refractory applications. I would say that less than 3" without SS fibers is pushing it for a refractory situation.

mikku 02-20-2013 02:43 PM

Re: Castable - How thin can you go?
 
Quote:

Originally Posted by stonecutter (Post 146045)
My question would be why would you want to? With a super thin shell you would have to have recharge your fire constantly to maintain temperature, even with good insulation. Also what advantages would you have by making a thin walled oven? IMO, nowhere near enough to offset the inefficiencies.

interesting concept though.

I guess main reason, portability.

Same reason for "Weber" type BBQ grills, people cannot always stay at one location forever or have the inclination to create monuments.

So a day at the beach could include baking a pizza, just throw the portable oven in the car along with the rest of the stuff... Get to your destination--assemble some KD parts--add some "mass" readily available--i.e. beach sand, stone rubble, whatever. Light it up with "twigs", heat beads, and enjoy.. When you leave, return the "re-usables" to their original location. Only difference, they got heated up a little once.

Same concept for renter or apartment dweller. Make your oven portable enough that you can take it with you when you relocate--like a favorite chair, TV, etc... that you and a friend can easily get into a car or pickup and set-up again at your new digs.

The point is "scale", why does an oven need to resemble a garage, interstate tunnel, stadium or cathedral with flying buttresses? Thought there would be some middle ground to explore so more people could enjoy a WFO.

I guess part of this discussion needs to define what are the essential components of a WFO?

Which traditional parts are superfluous and gaudy.

What would a bare bones oven look like? Its design should reflect its function.


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