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  #51  
Old 03-15-2013, 11:58 AM
Tscarborough's Avatar
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Default Re: K79 Oven Build

That is what the specifications are. It is no more likely to crack than home brew, which works fine too.
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  #52  
Old 03-15-2013, 12:56 PM
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Default Re: K79 Oven Build

Quote:
Originally Posted by Tscarborough View Post
I do not see any difference between 2 courses of vertically stacked stretchers and a solider course as as it relates to outward thrust imparted by the dome. Parge the exterior when you are done and it should be GTG.

A sailor course is different though, it has to be reinforced or buttressed.
The difference is that you have a full 7.5" vertical joint with a soldier or sailor course. If the bricks are laid stretcher there is only a 2" vertical join.

Last edited by david s; 03-15-2013 at 01:00 PM.
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  #53  
Old 03-15-2013, 12:59 PM
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Default Re: K79 Oven Build

Cat's out of the bag. I have my degree in civil engineering but my focus is on transportation not structures. I had a structural engineer from our other dept. look at my plans. Basically he told me that there isn't much difference between the soldier's and starting from the bottom using half bricks laid stretcher. The dome's weight will make the bottom brick (whichever way it is placed want to shear out). He wouldn't stamp either plan. One of the weak points is the oven entrance (obviously) since it is a break in the oven dome. Many ideas were thrown about to try and figure out what to do here. We came up with 3 options for this fix. I'm going to incorporate 2 possibly all 3 into the mix (pun intended).

Fix 1. Much like Ken524 did on his build, I'm going to buttress both sides of my oven arch. I'll be using 1 1/2" x 1 1/2" x 1/8" angle iron formed into a triangle and held in place by 2: 1/2" studs drilled into my hearth slab. Some heat transfer here.

Fix 2. Add fiberglass to my high heat mortar for the first 3 rings. This will essentially turn the mortar into a ring. We're dealing with about 1,500 lbs. which isn't that much. (At this amount of load there is some tensile strength to the mortar even without the fiberglass.)

Fix 3. I'm going to wrap at the same elevation as the top of my arch some thin wire about 3 times around my oven. Starting and ending at the back of the oven. The wire will be the thickness of electric fence wire. This wire will be centered on the current ring I'll be working on and will go right over my arch forming a ring. This will work with the buttress and help hold it all together.

When we were all done reviewing the plans we both agreed and it's proven that these ovens have and will last a long time without any of these modifications. But who knows for how long.

Last edited by K79; 03-15-2013 at 01:01 PM.
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  #54  
Old 03-15-2013, 02:01 PM
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Default Re: K79 Oven Build

The fibers are a waste of time, they will burn out the first time you get it to heat.

The wire, etc are also not needed, a simple parge coat will do just as well. The outer arch does need to be buttressed regardless.
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  #55  
Old 03-15-2013, 02:10 PM
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Default Re: K79 Oven Build

Here is something to consider with regard to adding the glass fibers

Strain Point - 825-900 (F)
Annealing - 875-975
Softening - 1175-1250
Kiln Polish-1350-1450
Full Fuse - 1550-1600

They go soft at temps easily seen in your oven so it i agree with Tscar they are a complete waste of effort and time.

Depending on what type of metal you plan to use it will either oxidize in very short order or create internal stress on the structure due to the significant variation in thermal expansion between the metal and the brick and mortar.

Have your structural engineer friends do. A simple expansion calculation for a 1000 f rise on the metal you plan to use, I think they may be shocked as to how much it grows.

The brick and mortar will not expand at a rate even close to the metal.

Chip
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  #56  
Old 03-15-2013, 02:19 PM
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Default Re: K79 Oven Build

And that is for glass fibers, which are not normally used in mortar/concrete anymore, the alkalinity eats them up. Polypropylene fibers are more commonly used now. Coated glass fibers are expensive and will still fail.
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  #57  
Old 03-15-2013, 02:58 PM
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Default Re: K79 Oven Build

Hello K79,
If you do some research, and you probably have, you will find that some of these ovens have lasted for hundreds of years - using even more basic materials and less precise build processes than we are using today.

I suspect there are many Engineers on this forum and more importantly others with years of experience building structures like this. In my experience many projects are over engineered at the expense of the simplicity and beauty of the original design.

You can cut your bricks 6 ways from Sunday and wrap your oven in as many layers of steel wire as you wish...after all it is your project. But don't kid yourself that you are "fixing" or "improving" anything, because there is/was no problem with the standard design in the first place. You are simply adding more complexity, cost and effort for a very minimal increase in overall strength. If you think that is value added activity - have at it. Frankly that's what makes this site so interesting.

I apologize for the snarky tone of this post (criticism can be as hard to give as it is to take) but I think you should be careful not to imply that all of the other ovens documented on this site are structurally unsound. I'll be the first to admit that my own has some serious faults (pun intended) but I'm confident that it will continue to work and remain standing until somebody comes along and decides to tear it down.

I'll go home now and take my happy pills...as it's been a long week (Hopslam anyone?)

Good Luck on the rest of your build.
Sincerely,
AT
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  #58  
Old 03-15-2013, 03:07 PM
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Default Re: K79 Oven Build

This is how I handled it on a sailored course, I did not want to use the insulation as a buttress, I wanted loose fill.



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  #59  
Old 03-15-2013, 03:25 PM
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Default Re: K79 Oven Build

That looks good. I spoke to a mason at the local precast around here and he said not to worry about any of that stuff too. Basically keep the joints as small as possible and neck down the height of the soldiers and no fiberglass in the mortar.
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  #60  
Old 03-15-2013, 04:54 PM
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Default Re: K79 Oven Build

Quote:
Originally Posted by Tscarborough View Post
This is how I handled it on a sailored course, I did not want to use the insulation as a buttress, I wanted loose fill.



Hi T,

Wonder why no one has tried loose filled, before, please keep us posted. P or V??
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