Author Topic: Forno Napoletano - made in Germany  (Read 4050 times)

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scott123

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Re: Forno Napoletano - made in Germany
« Reply #20 on: March 05, 2014, 04:27:44 PM »
In that style the insulation is the reinforcing.  You and your date can dance on top of it.

Tom, insulation provides compressive force, not flexural, correct?  Unless there's something providing an opposing force- unless there's something present for the insulation to compress against, it will bend and fail.

On Gene's oven, you used plenty of insulation, right?  Why did Gene's oven require wire for reinforcing when it had that much insulation?



Offline meatboy

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Re: Forno Napoletano - made in Germany
« Reply #21 on: March 05, 2014, 04:38:42 PM »
...I have seen a lot of neapolitan oven build pictures and none of the 'top-builder' uses an extra attachment. But in most cases the dome is build on top the soldiers, and with my physical understanding the force is not moving outwards but downwards in that case?!

Offline JConk007

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Re: Forno Napoletano - made in Germany
« Reply #22 on: March 05, 2014, 06:47:23 PM »
The angle cut on the soldier course also helps with the forces correct? Or is that opposite ? Personally I think you will be just fine ! And I hope you are around her for 5 years so we can prove it , ;) crank it up !
John
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Offline stonecutter

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Re: Forno Napoletano - made in Germany
« Reply #23 on: March 05, 2014, 07:07:50 PM »
I sat and stood on top of my unreinforced barrel, along with a load of bricks and mortar when I was building the chimney, it isn't going anywhere.

In that style the insulation is the reinforcing.  You and your date can dance on top of it.

Same here, when I was framing the roof of the enclosure.   To a certain extent, loading a dome enhances the strength of it.
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Offline stonecutter

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Re: Forno Napoletano - made in Germany
« Reply #24 on: March 05, 2014, 07:14:48 PM »
The angle cut on the soldier course also helps with the forces correct? Or is that opposite ?

The angle cut provides a better set for the first course of the dome bricks....the same thing as a springer in an arch.
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Offline stonecutter

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Re: Forno Napoletano - made in Germany
« Reply #25 on: March 05, 2014, 07:43:04 PM »
...I have seen a lot of neapolitan oven build pictures and none of the 'top-builder' uses an extra attachment. But in most cases the dome is build on top the soldiers, and with my physical understanding the force is not moving outwards but downwards in that case?!

The flatter the dome is, the greater the lateral thrust.  But it is contained with sufficient thickness of the brick and cladding.  For a dome of 39", he has plenty of support within the brick, especially more so with 5" cladding.
« Last Edit: March 05, 2014, 07:57:03 PM by stonecutter »
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scott123

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Re: Forno Napoletano - made in Germany
« Reply #26 on: March 05, 2014, 08:02:38 PM »
The flatter the dome is, the greater the lateral thrust.  But it is contained with sufficient thickness of the brick and cladding.  For a dome of 39", he has plenty of support with the 5" cladding.

While I'm relatively certain that 5" of solid concrete would provide the necessary mass to counter the lateral thrust, I don't think 5" of vermicrete

For the outer insulation I opted for light concrete from Vermiculite-Perlite and cement 4:1, and sufficiently incorporated wireframe.
On the side I have at least 12.5 cm, on the dome over 20cm.

performs the same purpose.

Now, I just noticed that his soldiers face in by their sides and not their faces, which puts 4.5" of solid brick/mortar into the wall, so if you want to say that a 4.5" wall is sufficient mass to counteract the lateral thrust, I'll  defer to your judgement, but I have a hard time seeing vermicrete contributing much opposing lateral thrust in this equation.
« Last Edit: March 05, 2014, 08:08:51 PM by scott123 »

Offline stonecutter

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Re: Forno Napoletano - made in Germany
« Reply #27 on: March 05, 2014, 08:30:58 PM »
While I'm relatively certain that 5" of solid concrete would provide the necessary mass to counter the lateral thrust, I don't think 5" of vermicrete

performs the same purpose.

Now, I just noticed that his soldiers face in by their sides and not their faces, which puts 4.5" of solid brick/mortar into the wall, so if you want to say that a 4.5" wall is sufficient mass to counteract the lateral thrust, I'll  defer to your judgement, but I have a hard time seeing vermicrete contributing much opposing lateral thrust in this equation.

Masonry nomenclature -  If the base course was oriented width side facing in, that is called a sailor course.

  4.5" of masonry is doing most all the work, so in this case the cladding is pretty much insulation.  Though at 4:1 it leans toward reinforcement especially now  with the addition of the wire.  It will most certainly contribute some tensile strength to the structure during thermal expansion.
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scott123

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Re: Forno Napoletano - made in Germany
« Reply #28 on: March 05, 2014, 08:47:35 PM »
Sailor course. Got it.  I know I've read that before, but it didn't stick.

It's the mass of the wall and insulation that creates friction with the floor, which, in turn produces opposition to the lateral thrust.  It's an oversimplification, but, since vermiculite and perlite are basically massless, the insulation is providing the equivalent mass of about 1 more inch- for a total of about 5.5" of masonry.

With an oven with this dome construction, dome height and interior diameter, in your opinion, theoretically speaking, what's the minimum width of masonry that would counteract the lateral forces?

Offline Tscarborough

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Re: Forno Napoletano - made in Germany
« Reply #29 on: March 05, 2014, 08:54:33 PM »
Scott, Neapolitan ovens use a medium density insulation between the oven walls and the outer stucco/tile surface (which acts as a monocoque structure) and that is more than enough to support another of the same oven sitting (evenly) on top..


Offline shuboyje

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Re: Forno Napoletano - made in Germany
« Reply #30 on: March 05, 2014, 08:59:37 PM »
...I have seen a lot of neapolitan oven build pictures and none of the 'top-builder' uses an extra attachment. But in most cases the dome is build on top the soldiers, and with my physical understanding the force is not moving outwards but downwards in that case?!

There are two factors that make this possible in traditional Neapolitan ovens.  They do not use a true insulation, they use "european" style insulators like Tuff and Expanded clay which are much more thermally conductive then true insulators used in America, but also much stronger.  They then place a thick stucco shell outside of this that ends up serving a structural purpose.  If I recall correctly Tom estimated the stucco on Craig's Acunto to be 1" thick(?). 

I personally have a steel harness on my oven, and would have one on any oven I built, but in truth the outward thrust is not much.  I build lower more aggressive domes then anyone else I've seen, and still have temporarily "buttressed" my 42" oven with a nylon ratchet strap that had a knot tied in it.  It didn't budge and was like that for months. 

The bigger problem I have personally had with an oven constructed like this in the past was thermal expansion destroying the stucco.  There is no expansion gasket, and the stucco ends up cracked, the oven get's wet, and it's all downhill.  It was so extreme on my oven that the cracks would go from hair line at ambient temp to 1/4" wide at pizza temperature. 
-Jeff

Offline Tscarborough

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Re: Forno Napoletano - made in Germany
« Reply #31 on: March 05, 2014, 09:15:00 PM »
Exactly, shuboyje, that is the weakness of the Neapolitan oven.  Here is a in-my-head calculation of the outward forces exerted by a low dome:

42" oven=3.14159*42=132.4"circumference.  132.4x3"(thickness of the brick for a chamfered sailor course)=397 SqIn of bearing surface
42x42=1764/144=12.25 SqFt for the dome (being generous)
12.25*4.5=100 firebrick, more or less, times 8#=800# for the dome.
800/397=2.01 PSI on the sailor course.


The mortar shear strength is a factor or two greater than this and if you clad it with 1/4" of refractory cement, you get another factor of strength.  It ain't going anywhere.

If Neapolitans used loose fill the efficiency would ratchet way up.
« Last Edit: March 05, 2014, 09:18:01 PM by Tscarborough »

Offline dheeraj

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Re: Forno Napoletano - made in Germany
« Reply #32 on: March 05, 2014, 09:31:30 PM »
Manuel, what method did you use to counteract the outward lateral force of the low dome?
hi scott could you please tell how to counteract the outward lateral force of the low dome, maybe i could use it as i am in the process of making my oven ("900 degree" thats my threads)

Offline stonecutter

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Re: Forno Napoletano - made in Germany
« Reply #33 on: March 05, 2014, 10:29:39 PM »

With an oven with this dome construction, dome height and interior diameter, in your opinion, theoretically speaking, what's the minimum width of masonry that would counteract the lateral forces?

Just under 4"...give or take.
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Offline Sirius

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Re: Forno Napoletano - made in Germany
« Reply #34 on: March 06, 2014, 06:06:13 AM »
Looks like a 1 to 1 Acunto Clon! Echt gut gemacht!

Offline meatboy

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Re: Forno Napoletano - made in Germany
« Reply #35 on: March 06, 2014, 07:06:22 AM »
[...]
The mortar shear strength is a factor or two greater than this and if you clad it with 1/4" of refractory cement, you get another factor of strength.  It ain't going anywhere.

If Neapolitans used loose fill the efficiency would ratchet way up.

Have I understood you correctly that a loose filling will rise the efficiency?
As shown in the picture (i have borrowed from Visciano) the loose fill is better than mixing it up with clay?

Offline Tscarborough

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Re: Forno Napoletano - made in Germany
« Reply #36 on: March 06, 2014, 07:39:46 AM »
Loose fill is certainly better, and finer is better than granular.  The idea is to trap air and reduce the density.

Offline meatboy

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Re: Forno Napoletano - made in Germany
« Reply #37 on: March 06, 2014, 07:43:18 AM »
thank you so much sir - that makes my plans much easier :) :D

Offline meatboy

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Re: Forno Napoletano - made in Germany
« Reply #38 on: March 13, 2014, 05:26:31 PM »
...this oven is awesome!
I was invited by Balilla-vero today and we had a great day. It was almost a 600 kilometer drive but worth every one of it! Thank you so much for your company!

We made a lot of pies. I made two batches of dough. Both 63% hydrated one with 1.5% Ischia Starter, the other with 0.16% Cake Yeast (fermentation was 20/9 for the Ischia, 14/9 for the yeast batch).

The floor temp was 499°C (930°F), baking times around 50 seconds

Offline stonecutter

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Re: Forno Napoletano - made in Germany
« Reply #39 on: March 13, 2014, 10:16:20 PM »
Real beauties there...nice to see another successful build too.
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When we build, let us think that we build for ever.
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