I think oven mass needs to be brought back up.

[asudavew]

In the following thread Dmun raised some valuable questions about oven construction, more specifically the overall mass of the oven.

I wish I would of found this one before construction....

If I had to build my oven again, I would probably opt for thinner walls and more insulation.

I'm putting a link to his original thread, because I think it might be of value to new builders and it needs a bump up!

http://www.fornobravo.com/forum/f8/p...thick-215.html (Pompeii oven - too thick?)

Happy Reading,

Dave

[RCLake]

Dave
I think you have hit on a great historic moment. The pioneers of this forum. They not only challenged conventional wisdom but established a forum that have given us hope and inspiration to build our own WFO. I first wanted only a smoker to do BBQ and came across the bread making oven - the barrel type with lots of cladding and was sold. Finding this site, I was skeptical, it wouldn't keep its heat. It didn't take that long until I was sold on the round oven. So thank you, the pioneers of this forum from 2005.

By the way Dave, do you have to much time on your hands to find this historical background?

[Ken524]

Dave,

That's an interesting thread. You've been firing your oven pretty regularly now. For what reasons do you wish you had a lower mass?

Sounds like I may be glad I didn't add a coat of mortar to the outside of the dome.

[asudavew]

Originally Posted by Ken524

Dave,

That's an interesting thread. You've been firing your oven pretty regularly now. For what reasons do you wish you had a lower mass?

Sounds like I may be glad I didn't add a coat of mortar to the outside of the dome.

Well... mainly it's the heat up times and the amount of wood required.
it can take upwards of 1.5 to 2 hours.

I think it would be nice to fire it up in 45 minutes....
Now on the other hand... I do have really good heat retention for the next day.

Trade offs... Just life I suppose.

Maybe I will have to build another....!!!!!! Low mass.

So I can have either/or.!
Now I may be on to something!

DAve

[asudavew]

Originally Posted by RCLake

Dave
I think you have hit on a great historic moment. The pioneers of this forum. They not only challenged conventional wisdom but established a forum that have given us hope and inspiration to build our own WFO. ?

I appreciate them everyday!

By the way Dave, do you have to much time on your hands to find this historical background?

Actually, I'm an accountant for an electric utility.
At the first of the month I am busy closing the previous month's books.
That usually takes 2 weeks.
The last two weeks of the month, I am looking for anything to do... Hence my fascination with Forno Bravo.

I did get a promotion .. effective on April 1st next year. So I may not have as much time... but until then.. I guess everyone is stuck with me!

How's the build coming along for you?

[Dutchoven]

Dave
This topic has been discussed several times and i think it will come up many times more. It was briefly mentioned on that thread about structural stability when using thinner walls. Less mass less time to heat up yes but, brickwork has to be spot on because the line of thrust has to fall within the inner 1/3 of the thickness of the brick...on a 2.5 inch thickness that leaves only a little space. I suggested on an earlier thread(one that I can't find right now) that the lower courses(1-3) be comprised of 6 inch units created, then through the middle courses go to the bricks cut in half 4.5 inch units and then the last 3 or four courses go to 3 inch units. This design would load the haunches of the dome and thin out the upper level of the oven to(in theory) shorten heat up time. As for thickness of the floor, to me it would be a personal choice...my oven floor thickness is about 4.5 inches...pompeii plans give you 2.5 to 3 inches the other option is brick splits which are 1.25 inches and will on average cost at least double what a standard firebrick is(that is what it was here $1.02 versus $2.08 per)
Dutch

[dmun]

I have a really low mass oven. It's composed of bricks set on edge, or a 2.25 inch thickness. I have a lot of insulation, but it's not of uniform thickness, because I designed a couple of voids through the oven enclosure for another purpose. As I stated in the thread you dug up, I wanted just enough thermal mass to cook a turkey, and just last month I passed that milestone with flying colors.

In the end, I decided that the thin oven was going to work because it was the same thickness as a pre-fab oven (How thick?). Building an oven that thin requires some finesse, and might promote cracking, but I'm now convinced that almost all ovens crack. I have a bunch of hairlines, but I didn't stress about it because all my bricks are angle cut, and couldn't fall in short of an east coast earthquake.

Remember that when I started researching this, the vermiculite layer was BELOW the support slab, which you heated up in its entirety everytime you fired the oven. I read about paulages pouring his entire winters wood supply into the oven trying to get it up to temperature.

Now most builders use cal-sil or ceramic fiber block directly under their cooking floor. Right there you have a hundred percent beter insulated oven than that first generation. If you ask me now, I don't know if the thin dome is worth the extra work. How fast your dome is ready for pizza is a function of a bunch of things, including how good and how dry your firewood is, and what the exterior temps are. In any event, I'm glad I did the geodesic dome. It's neat to look at, and impresses folks with how crazy I am.

[RTflorida]

Interesting.
I'm taking the lazy approach in asking (I don't want to go back through your entire oven building thread) "how thick is your dome"?
I did the standard 1/2 brick thickness with 1/2"-3/4" mortar cladding before insulation. It has never taken more than an hour to go all white. This past Sunday morning I fired it during the coldest (sorry it really doesn't get cold here in Tampa) and windiest conditions yet - 45-50 degrees and 20-30 mph constant winds, and it was still white in the usual 45 minutes and equalized within the hour. Must be my 2" blanket and 3 1/2" of perlcrete.
Are you sure you are not losing heat from going a little light on insulation? Just a thought.

RT

[Frances]

This is an interesting thread!

...a couple of days ago I mentioned on another thread that I'm glad not to have added any additional mass to the outside of my oven. The half bricks are quite enough to go along with.

When I heat my oven its really great for pizzas, gets white quite fast (under an hour), but then tends to equalise at at around 190 C (375 F), which is not really enough for bread etc. At the same time I think the insulation is quite impressive, because two days later with below freezing temps outside the oven is still at 50 C (over 120 F). So what it needs is longer heat up times. From what I've heard, Dave's insulation is even better.

Which is fine, all I'm saying is the oven certainly doesn't need MORE mass (which has also been discussed a lot recently). If in doubt, leave the cladding out.

On the other hand, after reading this link (which Hendo originally found), I wouldn't dare go with thinner walls. It may be an advantage for experienced or gifted builders, but certainly not for me...

Auroville Earth Institute is a research, design and developing agency for vaulted structures, construction of various Vaults, Arches, Domes (VAD).

[dmun]

Originally Posted by Frances

On the other hand, after reading this link (which Hendo originally found), I wouldn't dare go with thinner walls. It may be an advantage for experienced or gifted builders, but certainly not for me...

Auroville Earth Institute is a research, design and developing agency for vaulted structures, construction of various Vaults, Arches, Domes (VAD).

This is the first time I've seen that. Everyone building a dome should read that page.

At the end, there is an interesting condemnation of cement-based mortars. Of course these folks are working with compressed earth blocks, or adobe.