Curing, Cracks & Other Kentucky Conundrums

[oventhusiast]

Re: Curing, Cracks & Other Kentucky Conundrums

Hi Ken,
Sorry to see those cracks in the vent opening but I think Frances has a point about the arch. I'm not at all qualified as an engineer but after reading about your problem I went into the photo galleries and looked at photos of other arches. I found that the arches vary in the number of bricks used to span the arch. Maybe some one else here is more qualified in explaining this (I'm sure), but it looks to me that your arch is more shallow than some others and because of that, you needed to use more bricks to make the span, which would transfer the weight to the widest parts of your curve. Anybody out there see what I'm seeing or am I off base here?
Rick

[Ken524]

Re: Curing, Cracks & Other Kentucky Conundrums

...from a gut feeling I would have thought that a full rounded archway is structurally stronger than one with a flattened rounded top

You are correct! It's a lot stronger.

[Ken524]

Re: Curing, Cracks & Other Kentucky Conundrums

Rick,

Thanks for the thoughts. I think you and Frances may be on to something.

I'm going to let my repair sit another day or two before firing again. If it fails, I have an idea for a replacement that incorporates all three observations made by Wade, Frances and Rick.

Thanks for the input!!!

[wlively]

Re: Curing, Cracks & Other Kentucky Conundrums

You guys are right about a taller arch being stronger. But, we are not talking about alot of weight to support here. The picture posted is having to support a very tall wall. My arch looks to be pretty close to Ken's as far as arc height and it is fine.

[gjbingham]

Re: Curing, Cracks & Other Kentucky Conundrums

Ken,
Sorry to hear about your setback.

I think the theory of the outward force of the dome expansion is correct too. It sounds like the sag of the arch is a secondary failure, occurring after the original problem of the dome's expansion forces causing the mortar debonding. If you're not seeing any tilt in the vent walls, then I would guess the weight of the arch and vent is probably not the real problem.

The question might be how to minimize the foreward stress on the arches caused by the dome's expansion. Hmmmm......... I'll keep thinking about it.

I'm going to go out and look at mine. I haven't noticed any cracks yet. Maybe I'm just not looking hard enough.

George

[Ken524]

Re: Curing, Cracks & Other Kentucky Conundrums

Ken,
I think the theory of the outward force of the dome expansion is correct too. It sounds like the sag of the arch is a secondary failure, occurring after the original problem of the dome's expansion forces causing the mortar debonding.

That's exactly what I'm seeing. I think that's a good analysis.

If you're not seeing any tilt in the vent walls, then I would guess the weight of the arch and vent is probably not the real problem.

The left vent wall must be moving slightly during heat-up/cool-down causing the mortar debonding from the arch. Before I fire back up, I'll start taking measurements of everything to see if I can figure out what's moving and where so I can quantify exactly what's happening.

I'm going to go out and look at mine. I haven't noticed any cracks yet. Maybe I'm just not looking hard enough.

We all will have cracks (some small/insignificant and some big) With that much heat, mass and mortar, something has to give somewhere.

[Hendo]

Re: Curing, Cracks & Other Kentucky Conundrums

Don't know if this is any help (well, it isn't in this case, but maybe in general) but from a gut feeling I would have thought that a full rounded archway is structurally stronger than one with a flattened rounded top, which a lot of people seem to be building at the moment. Or not?

Frances, Wade, Ken, George et al,

There?s also some useful information in the link in my post at
http://www.fornobravo.com/forum/f8/o...html#post13952

Although the article focuses mainly on semi-circular arches, you can see that for a ?segmental arch? (about half-way down on the left) the direction of thrust meets the arch support at the top of the support, rather than on the floor like a semi-circular arch. If we extend these lines of thrust for our ?flattened rounded top? oven openings, in most cases they would end up in space very quickly, unless some kind of solid buttressing is employed to contain the line of thrust all the way to the floor. While I?m no expert, common sense tells me that the ramifications for stresses and consequential movement would be way greater than for a semi-circular arch.

Paul.

[Ken524]

Re: Curing, Cracks & Other Kentucky Conundrums

Finally got a break in the weather to do my first test fire after repair.

I did a 2-3 hour slow burn today with damp wood (thanks to the recent rain). This worked well. I didn't want a really hot fire, just warm saturating heat. So far so good. No cracks, but again, I didn't get close to burning off any carbon on the dome.

Heat underneath the floor??? After 2-3 hours of low temp fire I felt the underside of the hearth (the roof of the storage area). The concrete felt warm to the touch. Not hot, but pretty warm. Is this normal??. Because of the problems I've been having, I'm getting paranoid and am worried the Kaowool boards I used underneath aren't cutting the mustard.

I'm guessing one of three things,
1. The boards are a little moist and all is well;
2. A warm hearth is normal and all is well;
3. I've created the Heat Sink From Hell and my daughter's Easy-Bake Oven will cook better pizza.

How warm does the underside of your hearth get??

[Ken524]

Re: Curing, Cracks & Other Kentucky Conundrums

I did another burn today. I really cranked it up and was able to get the top 4-5 courses white. At one point I reached in the oven to add some wood; upon pulling out my arm I noticed my right hand and wrist no longer had hair. I was pretty happy with the heat being generated .

My repaired mortar joints came through like champs. Jahysea, your suggestion of grinding out the mortar and remortaring appears to be the correct prescription. Thank you!

I noticed one hairline crack in an adjacent joint, but it never opened up. I'm thinking the oven may be about finished moving/shifting around so I'll add some reinforcement to the top of that joint and call it fixed.

We have a winter storm forecast here in Kentucky this weekend (finally!!), after that I'll add the vermiculite and continue work on the enclosure.

Thanks again for everyone's advice. It was all very helpful.

[dmun]

Re: Curing, Cracks & Other Kentucky Conundrums

Heat underneath the floor??? After 2-3 hours of low temp fire I felt the underside of the hearth (the roof of the storage area). The concrete felt warm to the touch. Not hot, but pretty warm. Is this normal??. Because of the problems I've been having, I'm getting paranoid and am worried the Kaowool boards I used underneath aren't cutting the mustard.

I'm guessing one of three things,
1. The boards are a little moist and all is well;
2. A warm hearth is normal and all is well;
3. I've created the Heat Sink From Hell and my daughter's Easy-Bake Oven will cook better pizza.

How warm does the underside of your hearth get??

I fired this afternoon, to cook pizza at 6, raked out the fire and baked a pie after dinner. At 11, the oven with the door on is still at 350f, and the underside of the slab is just lukewarm. 2.5" insblock19 here. I suspect that your insulation is still a little damp.

[Ken524]

Re: Curing, Cracks & Other Kentucky Conundrums

I suspect that your insulation is still a little damp.

I'm pretty sure that is what's going on. The Kaowool board was pretty damp during the build and the weather has been really humid lately. I've just scratched the surface with fire.

Thanks for the feedback.

[RTflorida]

Re: Curing, Cracks & Other Kentucky Conundrums

OK, I have to ask.....has anyone actually tried making a tiny pizza in an Easy Bake Oven? Come on, be honest. All of us are guilty of putting unusual things in our sister's, neighbor's, or daughter's Easy Bakes...Has pizza been tried???

RT

[Ken524]

Re: Curing, Cracks & Other Kentucky Conundrums

Thanks for the laugh, RT. I'm sure there's an Easy-Bake oven forum somewhere where they whip up gourmet dishes with those things.
"Thanksgiving Dinner - All from our Easy Bake Oven!"

[asudavew]

Re: Curing, Cracks & Other Kentucky Conundrums

Here' a link for yins!
It's Ken's deep dish easybake pizza.

Ken's Deep Dish Pizza Mix

Funny his name is Ken... could Ken be posing on another site?

Notice the 2 tbls of flour.

[asudavew]

Re: Curing, Cracks & Other Kentucky Conundrums

Uno mas


Easy Bake Oven Recipes