### Author Topic: Earthstone 110 or FGM?  (Read 21620 times)

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#### scott123

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##### Re: Earthstone 110 or FGM?
« Reply #75 on: October 02, 2012, 04:21:41 AM »
Holy Moly way too complicated Lost me on the first X2?  I prefer results

John, buddy, we're talking about wood consumption here, along with peak dome temps. All your beautiful pizza photos prove is that just about any WFO can make stunning pizza.  That's not being argued here.  It wouldn't be easy, but I have no doubt that your stunning pies could be reproduced in a Mugnaini. And yet, no one here would ever recommend a Mugnaini to the original poster.

It's not about whether or not an oven can make great Neapolitan pizza, it's about whether or not it can make great Neapolitan pizza in the easiest and most efficient way possible.  The lower dome of the FGM is a critical part of that equation, but the door height (and potential insert to correct it) is a contributing factor as well.
« Last Edit: October 02, 2012, 04:23:28 AM by scott123 »

#### TXCraig1

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##### Re: Earthstone 110 or FGM?
« Reply #76 on: October 02, 2012, 10:04:20 AM »
According to this calculator, the ideal flow rate for an 8" diameter 2' high chimney at 800F is .05799 m3/s.  In other words, the superheated air volume that we're discussing (0.0454m3) is being replaced every second (give or take). Based on your numbers, for a six hour preheat, the necessary energy to maintain that 1089K temp in that 2" of volume would translate into 81 lb. of wood. Now, this is an ideal flow rate for one chimney.  Even if the chimney is only drawing 1/4 of that, you're still talking 20 lb. of wood.

Scott,
Your calculation represents the amount of wood necessary to maintain the temperature of that 2” if you replaced the air every second with air at 0K. I also think the idea of replacement of that 2” is conceptually wrong. Say you have two ovens identical in every respect except that one has a 2” higher dome.  The flow rate is going to be virtually identical.

Quote
That's a lot of wood. A lot of energy.  If the draw keeps that superheated air in contact with the additional 2" wide surface area for a second (or more), over the course of six (or more) hours, that's a substantial amount of heat transfer, especially considering the convective impact of the perpetually moving air.

You make it sound like if you don’t have “superheated air” on that 2”, the air contacting it will be at ambient temperature. I would think that it would be only marginally cooler than the “superheated air.”   How big do you think the temperature differential is?

I believe the air temperature much smaller factor than the radiant energy coming off the fire with respect to heating the oven. For example, When I bring the fire down and move it from the middle to the left rear, the right side wall is usually about 925-950F. Within 30 minutes, that right wall will have cooled to 875F.
"We make great pizza, with sourdough when we can, commercial yeast when we must, but always great pizza."
Craig's Neapolitan Garage

#### TXCraig1

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##### Re: Earthstone 110 or FGM?
« Reply #77 on: October 02, 2012, 10:12:50 AM »
It's not about whether or not an oven can make great Neapolitan pizza, it's about whether or not it can make great Neapolitan pizza in the easiest and most efficient way possible.  The lower dome of the FGM is a critical part of that equation, but the door height (and potential insert to correct it) is a contributing factor as well.

How do you know that the extra radiant energy put on the pie from the improved view factor of the lower dome doesn't more than compensate for 2" less "superheated air" whatever that is?

How do you know that by restricting the airflow into the FGM as you have proposed, you won't more than offset any gains from the extra "superheated air" with losses in combustion efficiency?

How do you know the energy differential between "superheated air" and the other hot air in the upper part of the oven is even meaningful?
"We make great pizza, with sourdough when we can, commercial yeast when we must, but always great pizza."
Craig's Neapolitan Garage

#### TXCraig1

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##### Re: Earthstone 110 or FGM?
« Reply #78 on: October 02, 2012, 10:18:15 AM »
Scott, you may be right. I'm not trying to be combative. I'm just having a hard time seeing the basis for some of the assumptions that are being made.
"We make great pizza, with sourdough when we can, commercial yeast when we must, but always great pizza."
Craig's Neapolitan Garage

#### scott123

• Guest
##### Re: Earthstone 110 or FGM?
« Reply #79 on: October 02, 2012, 11:43:56 AM »
Your calculation represents the amount of wood necessary to maintain the temperature of that 2” if you replaced the air every second with air at 0K. I also think the idea of replacement of that 2” is conceptually wrong. Say you have two ovens identical in every respect except that one has a 2” higher dome.  The flow rate is going to be virtually identical.

Yes, the 0K was an error. All my figures are pretty rough. It still translates into a lot of wood using ambient temps for the replacement air.

The flow rate will be virtually identical. I'm not talking about two different rates, just two different flow distances. Car A is going 65 mph and Car B is going 65 mph, but Car B (the lower door) is on a slightly longer track.

#### Reep

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##### Re: Earthstone 110 or FGM?
« Reply #80 on: October 02, 2012, 11:55:46 AM »
John, buddy, we're talking about wood consumption here, along with peak dome temps. All your beautiful pizza photos prove is that just about any WFO can make stunning pizza.

Except the OP cares more about making great pies than he does about how much wood he consumes to get the oven up to speed.

#### scott123

• Guest
##### Re: Earthstone 110 or FGM?
« Reply #81 on: October 02, 2012, 12:10:08 PM »
You make it sound like if you don’t have “superheated air” on that 2”, the air contacting it will be at ambient temperature. I would think that it would be only marginally cooler than the “superheated air.”   How big do you think the temperature differential is?

I believe the air temperature much smaller factor than the radiant energy coming off the fire with respect to heating the oven. For example, When I bring the fire down and move it from the middle to the left rear, the right side wall is usually about 925-950F. Within 30 minutes, that right wall will have cooled to 875F.

IR and conduction are big contributors to floor (and, to a certain extent, wall) heat, but dome heat relies a great deal on convection.  By it's nature, a fire, with it's massive amount of rising gases, is a strong convective force. The location of the fire obviously has an impact on that convection, so when you move the fire around temperatures are effected.

When you raise the door, the heat loss isn't going to cause the wall temps to plummet, but the area that isn't exposed to the superheated air isn't going to be as hot as if the door were lower.

#### scott123

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##### Re: Earthstone 110 or FGM?
« Reply #82 on: October 02, 2012, 12:15:15 PM »
Except the OP cares more about making great pies than he does about how much wood he consumes to get the oven up to speed.

The oven you're buying could easily require 8 hours to come up to proper Neapolitan temps. If an insert could trim that to 6 (or less) hours, wouldn't it be worth the effort to fabricate?

#### scott123

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##### Re: Earthstone 110 or FGM?
« Reply #83 on: October 02, 2012, 12:29:13 PM »
How do you know that the extra radiant energy put on the pie from the improved view factor of the lower dome doesn't more than compensate for 2" less "superheated air" whatever that is?

How do you know that by restricting the airflow into the FGM as you have proposed, you won't more than offset any gains from the extra "superheated air" with losses in combustion efficiency?

Combustion is only effected if the fire isn't getting sufficient fresh air.  In theory, as long as you match the dimension of the chimney with the intake opening, combustion should be efficient, but it's not necessary to go that far.  63% has been proven, for centuries, to allow for efficient combustion will keeping the hot air in the oven as long as possible.

The low dome is a critical feature in and of itself and has no correlation to door sizing issues.  One doesn't compensate for the other. Both are important.  When ranking the importance of the features of Neapolitan ovens, I would give a low dome about an 8 out of 10 and a properly sized door about a 3. Most of the high dome ovens have properly sized 63%ish doors and I would never recommend them.  FGM is the clear winner, but it can definitely be improved upon.  Less wood/shorter pre-heats matter.

#### scott123

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##### Re: Earthstone 110 or FGM?
« Reply #84 on: October 02, 2012, 12:45:16 PM »
Scott, you may be right. I'm not trying to be combative. I'm just having a hard time seeing the basis for some of the assumptions that are being made.

No worries, Craig.

Think about a wort chiller.  The more tubing/coils, the further the distance the wort travels through the copper tubing the more energy it gives off to the cooling liquid. A lower door extends the flow distance, leaving more energy in the oven rather than up the chimney. The traditional Neapolitan chimney loop back does the same thing, but on less significant scale. I know you don't believe in the benefits of the looped chimney, and, right now, I'm not entirely certain about the loop either, but the door I believe in.

#### TXCraig1

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##### Re: Earthstone 110 or FGM?
« Reply #85 on: October 02, 2012, 01:36:22 PM »
IR and conduction are big contributors to floor (and, to a certain extent, wall) heat, but dome heat relies a great deal on convection.  By it's nature, a fire, with it's massive amount of rising gases, is a strong convective force. The location of the fire obviously has an impact on that convection, so when you move the fire around temperatures are effected.

When you raise the door, the heat loss isn't going to cause the wall temps to plummet, but the area that isn't exposed to the superheated air isn't going to be as hot as if the door were lower.

I'm still curious how you define "superheated" and what you think the temperature differential is between "superheated" are and the air right under it.
"We make great pizza, with sourdough when we can, commercial yeast when we must, but always great pizza."
Craig's Neapolitan Garage

#### TXCraig1

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##### Re: Earthstone 110 or FGM?
« Reply #86 on: October 02, 2012, 01:57:18 PM »
Combustion is only effected if the fire isn't getting sufficient fresh air.  In theory, as long as you match the dimension of the chimney with the intake opening, combustion should be efficient, but it's not necessary to go that far.  63% has been proven, for centuries, to allow for efficient combustion will keeping the hot air in the oven as long as possible.

There is more to it than that. 1) The size of the fire must also matter. At some point, the door opening will be too small for sufficient air to enter. If the FGM door is ideal as designed, wouldn’t making it smaller result in less efficient combustion or necessitate a smaller fire? 2) Combustion is not the only factor that must be brought into balance. A properly designed oven/chimney system will bring in as much air as needed and no more. Once you go beyond what is necessary for efficient combustion, you are bringing in unnecessary cold air. If you believe you can reduce the size of the FGM door without an adverse effect on combustion efficiency, are you not also saying that the door as designed is too big?

Quote
The low dome is a critical feature in and of itself and has no correlation to door sizing issues.  One doesn't compensate for the other. Both are important.  When ranking the importance of the features of Neapolitan ovens, I would give a low dome about an 8 out of 10 and a properly sized door about a 3. Most of the high dome ovens have properly sized 63%ish doors and I would never recommend them.  FGM is the clear winner, but it can definitely be improved upon.  Less wood/shorter pre-heats matter.

By saying "one doesn't compensate for the other," you are saying that there is only one right way to build an oven.

Why do you rule out the possibility that the lower ceiling of the FGM can get you to the same place as a higher ceiling and 63% door with equal efficiency? Perhaps the low-ceiling design of the FGM inherently lets you burn less wood due to a more efficient heating of the dome by the fire and an enhanced view factor? Just because a 63% door works in a NP oven of traditional proportions doesn’t make it a given that restricting the door opening will increase efficiency. I’m not convinced there won’t be unintended consequences affecting combustion efficiency.
"We make great pizza, with sourdough when we can, commercial yeast when we must, but always great pizza."
Craig's Neapolitan Garage

#### TXCraig1

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• Posts: 19481
• Location: Houston, TX
##### Re: Earthstone 110 or FGM?
« Reply #87 on: October 02, 2012, 01:59:37 PM »
No worries, Craig.

Think about a wort chiller.  The more tubing/coils, the further the distance the wort travels through the copper tubing the more energy it gives off to the cooling liquid. A lower door extends the flow distance, leaving more energy in the oven rather than up the chimney. The traditional Neapolitan chimney loop back does the same thing, but on less significant scale. I know you don't believe in the benefits of the looped chimney, and, right now, I'm not entirely certain about the loop either, but the door I believe in.

I don't disagree with this. I'm simply having trouble believing that the difference will translate into material wood savings.
"We make great pizza, with sourdough when we can, commercial yeast when we must, but always great pizza."
Craig's Neapolitan Garage

#### scott123

• Guest
##### Re: Earthstone 110 or FGM?
« Reply #88 on: October 02, 2012, 02:01:38 PM »
I'm still curious how you define "superheated" and what you think the temperature differential is between "superheated" are and the air right under it.

Actually, I'm using the term 'superheated' because that's what Jeff used on his diagrams and I didn't change it.  It's just hotter air that has risen to the top of the oven.

Think of it this way.  Picture the IR coming off the flame heating the dome, as well as the dome that's in the way of the flame that, in turn, is conducting heat to the bricks around it.  Combine those two forces, accept the fact that they're doing the majority of the work, and then ignore them as if they didn't exist.  What's left is rising hot air- like a hot air balloon. The air at the top of the balloon is the hottest, and gets cooler as you drop.  If you poke a hole in the balloon towards the top, the air will be warmer than if you poke a hole towards the bottom.  If you poke the hole (exhaust) the air closer to the top, the balloon will sink faster than if you poke the hole further down. The higher the hole, the more heat is lost.

A higher dome oven with a 63%ish door would be far easier to test this, but you should be able to prove/disprove this with your Acunto. As the oven pre-heats, take readings of the wall just above the door level and just below. You should see a difference of at least 150 deg.

#### scott123

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##### Re: Earthstone 110 or FGM?
« Reply #89 on: October 02, 2012, 02:27:15 PM »
There is more to it than that. 1) The size of the fire must also matter. At some point, the door opening will be too small for sufficient air to enter. If the FGM door is ideal as designed, wouldn’t making it smaller result in less efficient combustion or necessitate a smaller fire? 2) Combustion is not the only factor that must be brought into balance. A properly designed oven/chimney system will bring in as much air as needed and no more. Once you go beyond what is necessary for efficient combustion, you are bringing in unnecessary cold air. If you believe you can reduce the size of the FGM door without an adverse effect on combustion efficiency, are you not also saying that the door as designed is too big?

By saying "one doesn't compensate for the other," you are saying that there is only one right way to build an oven.

Why do you rule out the possibility that the lower ceiling of the FGM can get you to the same place as a higher ceiling and 63% door with equal efficiency? Perhaps the low-ceiling design of the FGM inherently lets you burn less wood due to a more efficient heating of the dome by the fire and an enhanced view factor? Just because a 63% door works in a NP oven of traditional proportions doesn’t make it a given that restricting the door opening will increase efficiency. I’m not convinced there won’t be unintended consequences affecting combustion efficiency.

The door, as designed, without any question, is too big. At least, it is for efficient Neapolitan pizzamaking.

I think it's important to be aware of the fact that the FGMs were never designed for Neapolitan pizza. They were designed to be used at much lower temperatures for bread- with a pre-heat and then retained heat baking with a closed door. We're taking a tool that was designed for something entirely different and trying to make it work for our needs.  It is only a stroke of luck that, for the sake of fuel efficiency, they made the decision to go with a lower dome.  Their choice of door size has no foundation whatsoever in high oven temperature thermodynamics. The door size decision was most likely based on the need for greater access for loading/unloading bread, as well as the possibility that, at some point, they might have used some kind of shelving system to fit more loaves.  The door size on the FGMs has absolutely nothing to do with efficiency- at least, not within the framework of Neapolitan temperatures. When you get into Neapolitan temps, it's the Neapolitans that have done their homework, not the French. Wood has been a scarce commodity in Naples for quite some time. These ratios (dome height to oven width, door height to dome height) were born out of necessity.  Whatever could produce the characteristically lightning fast bake times while using the least wood won the prize. The fittest ovens survived.  The FGMs didn't grow out of this necessity and thus are a bit wasteful at high temps. To achieve the best possible thermodynamics and fuel efficiency at high temps, there is only one way to build an oven, and the Neapolitans have, to a large extent, figured this out. It's not by chance that all the Neapolitan oven makers use pretty much the same ratios.

We can take this tool that was engineered for bread, and, with a simple insert, make it more Neapolitan pizza friendly.
« Last Edit: October 02, 2012, 02:29:50 PM by scott123 »

#### TXCraig1

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• Location: Houston, TX
##### Re: Earthstone 110 or FGM?
« Reply #90 on: October 02, 2012, 03:59:42 PM »
The door, as designed, without any question, is too big. At least, it is for efficient Neapolitan pizzamaking.

I think it's important to be aware of the fact that the FGMs were never designed for Neapolitan pizza. They were designed to be used at much lower temperatures for bread- with a pre-heat and then retained heat baking with a closed door. We're taking a tool that was designed for something entirely different and trying to make it work for our needs.  It is only a stroke of luck that, for the sake of fuel efficiency, they made the decision to go with a lower dome.  Their choice of door size has no foundation whatsoever in high oven temperature thermodynamics. The door size decision was most likely based on the need for greater access for loading/unloading bread, as well as the possibility that, at some point, they might have used some kind of shelving system to fit more loaves.  The door size on the FGMs has absolutely nothing to do with efficiency- at least, not within the framework of Neapolitan temperatures. When you get into Neapolitan temps, it's the Neapolitans that have done their homework, not the French. Wood has been a scarce commodity in Naples for quite some time. These ratios (dome height to oven width, door height to dome height) were born out of necessity.  Whatever could produce the characteristically lightning fast bake times while using the least wood won the prize. The fittest ovens survived.  The FGMs didn't grow out of this necessity and thus are a bit wasteful at high temps. To achieve the best possible thermodynamics and fuel efficiency at high temps, there is only one way to build an oven, and the Neapolitans have, to a large extent, figured this out. It's not by chance that all the Neapolitan oven makers use pretty much the same ratios.

We can take this tool that was engineered for bread, and, with a simple insert, make it more Neapolitan pizza friendly.

Has someone who owns a FGM told you it is wasteful at high temp?
"We make great pizza, with sourdough when we can, commercial yeast when we must, but always great pizza."
Craig's Neapolitan Garage

#### Reep

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• Location: Thousand Oaks, CA
##### Re: Earthstone 110 or FGM?
« Reply #91 on: October 02, 2012, 04:12:39 PM »
If you poke the hole (exhaust) the air closer to the top, the balloon will sink faster than if you poke the hole further down. The higher the hole, the more heat is lost.

As a former hot air balloon owner I agree this is true, but the inside of the balloon is not in a constant state of convection.  You only heat every once in a while and the rest of the time the air is still.

As the oven pre-heats, take readings of the wall just above the door level and just below. You should see a difference of at least 150 deg.

Also, readings off the wall at different heights do not reflect the temperature of the air at those heights.  You may be right, but this would not be an accurate way to test it.

#### scott123

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##### Re: Earthstone 110 or FGM?
« Reply #92 on: October 02, 2012, 05:32:32 PM »
As a former hot air balloon owner I agree this is true, but the inside of the balloon is not in a constant state of convection.

If you poked a hole in it, it would be

#### Reep

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##### Re: Earthstone 110 or FGM?
« Reply #93 on: October 02, 2012, 05:34:19 PM »
If you poked a hole in it, it would be

Until it hit the ground, then it would be steady state . . . as would I.

#### shuboyje

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##### Re: Earthstone 110 or FGM?
« Reply #94 on: October 02, 2012, 07:09:24 PM »
Mods,
Any chance of splitting this off of Reeps thread?

I've always felt that the oven door is pretty critical.  Thermally speaking it is a masonry black ovens biggest issue.  Think about it, you have a giant gapping hole in the side of the oven you are trying to keep heat inside of, logically that leeds to the fact that as small as possible while still meeting all of it's functional requirements would be ideal.  63% is a good number, it is proven to work, but I don't feel it is the only way to go.  One glaring flaw in the idea behind 63% is the fact that it doesn't take door shape into consideration.  a 63% rectangular opening and a 63% arch are not the same.  Somewhere on FB I have graphics with all the numbers showing this if anybody wants to look them up, lol.  Another point against 63% is the fact the Neapolitans don't use it.  They use one standard door size, which I bet most people who work with a Neapolitan oven daily will tell you is just about the minimum size possible to do everything you need to do though that opening.

So, although 63% is a good rule of thumb, and if building an oven one worth working with, I don't think it's the end all be all some people think.  I've seen many "veteran" members of FB advice people to demolish newly built ovens that do not have 63% doors, because "the oven won't work".  Do I LOVE the door height on FGM ovens?  Certainly not, I'd love to see the standard neapolitan sized door used on all their oven(or really the 18 x 8 arch door I prefer), especially the extended height versions.  Would it ever stop me from recommending an FGM oven?  No way, from everything I have seen these are the best oven kits on the market for Neapolitan pizza, especially the Brick versions.

Can't wait to see the oven Reep, I know you are gonna love it!
-Jeff

#### Pete-zza

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##### Re: Earthstone 110 or FGM?
« Reply #95 on: October 02, 2012, 07:57:57 PM »
Jeff,

At which post would you suggest the split take place, and would all of the posts after that post be included? And what would you suggest the split thread be named?

Peter

#### Reep

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##### Re: Earthstone 110 or FGM?
« Reply #96 on: October 02, 2012, 08:00:18 PM »
Can't wait to see the oven Reep, I know you are gonna love it!

Unfortunately (or fortunately) it is now being built in France.  So, it will be a while.

#### Reep

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##### Re: Earthstone 110 or FGM?
« Reply #97 on: October 02, 2012, 08:01:14 PM »
Jeff,

At which post would you suggest the split take place, and would all of the posts after that post be included? And what would you suggest the split thread be named?

Peter

FWIW, the original issue is resolved and I ordered my oven.  So, you can do whatever you like with the rest of the thread.

#### JConk007

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##### Re: Earthstone 110 or FGM?
« Reply #98 on: October 02, 2012, 08:02:43 PM »
looks like we went off late in Pg 2 early Pg 3?
called
High dome vs. Low dome or does door size matter ?
John
I Love to Flirt with Fire! www.flirtingwithfirepizza.com

#### scott123

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##### Re: Earthstone 110 or FGM?
« Reply #99 on: October 02, 2012, 08:22:54 PM »
Do we really need to put Peter through the extra work of splitting this up?  The topic of the thread is WFO purchasing concerns and everything we've discussed has related to that.  It's been a bit more than Reep asked for, but, as he said, he's gotten the info he needs, has purchased the oven, and, when the oven arrives, he's planning on starting a new thread.

I'm fine with it being split, but I think the thread has pretty much run it's course and splitting it would take some work.
« Last Edit: October 02, 2012, 08:40:41 PM by scott123 »

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