Hansen Horno

[dbhansen]

Re: Hansen Horno

Finally some progress! The hearth is complete. It's a little rough, but it's (mostly) flat and square. I'm glad it will be covered up in the end! The Quikrete was much tougher to work with than the ready-mix that I got delivered for my foundation, but it wouldn't have made financial sense to have it delivered for the hearth.

The grey patches are "Quikrete vinyl concrete patch," which I used to fill a few low spots on the top. The leftover went around the outside edge just to smooth it out a bit. The 2 copper pipes sticking up are for a thermocouple that will go in the middle of the oven floor. The wires will be routed down into the wood storage area and up the other pipe to join the other thermocouple wires coming from around the dome.

The hearth is 4" thick with lots of rebar. The cantilever sticks out 12" at the peak, 4" at the sides. Total dimensions are about 72" x 84" (to peak of cantilever).

Thanks go to Acoma, Ken, and others who inspired me to do the cantilever!

[dbhansen]

Re: Hansen Horno

Score!!! This is a van-load of kiln-dried hardwood that a friend gave me, gratis! Box after box of small slats, almost too nice to burn. Oak, maple, pine, black walnut, mahogany, and probably others. That should keep me in business for a while, and inspire me to get this oven done. But I do some woodworking on the side and it really will make me feel guilty to burn it!

[mfiore]

Re: Hansen Horno

Daren,

Love the cantilever. I'm considering one myself. I'm enjoying your build, I'm right behind you! How late did you wait until pulling the forms?

What do you plan for an insulating layer, vermiculite/concrete or CalSil Board?

[dbhansen]

Re: Hansen Horno

Mike, I waited one full week. I had it covered with plastic on all sides until then. For the insulation, I'm planning on using 2-3" of insulating board, but I haven't decided whether to splurge for the FB Board or go with Insblok-19. I need to decide very soon....

[dbhansen]

Re: Hansen Horno

Here's my template for the 42" oven floor and entryway, and I mocked up the bricks. The template is just heavy poster paper, hopefully rigid enough to transfer to the bricks; I may need to switch to rigid foam or foam-core. I think I'll continue the herringbone pattern into the vent/landing area, like shown.

The vent/landing is 3 brick widths deep and 20" wide at the oven, with a 1/2" reveal on each side, and it angles out 1.25" on each side. I may increase that angle, it looks a little shallow.

Now to concentrate on picking the best bricks for the floor, and getting it level.

I'm not sure if I'll be sanding it or not, but has anyone used a small (5") random orbital sander for the floor? Or would it be best to rent a belt sander?

[CajunKnight]

Re: Hansen Horno

Looks great at this stage. I had to look two or three times at the hearth slab. It looked like it was warped in the pic, but then I saw it was the front curve of the slab. Pictures can play with my eyes sometimes. I am seeing so many great ideas on this forum and cant use all of them. I am glad its going to be a bit longer before I start mine. We have mild winters here so most of my building will be preferred in fall winter and early spring. Summer is just plain hot and muggy here. I really like the herringbone coming out to the landing area.

Now for sanding the orbital will work but the belt will be faster. But be careful with the belt because it can be unforgiving if one gets heavy handed, but you do wood work so you know how to stop that from happening. Work with a dry fireclay mix on top of board to level bricks as much as possible and reduce sanding.

Again it looks great and keep the pics coming.

[SpringJim]

Re: Hansen Horno

DB, What makes you think you need a sander at this stage?

I used a dry sand fireclay mix under the bricks and then just used a rubber hammer to get it level to the touch. (before and after wetting it) I'm not sure I will need any sanding (time will tell) and because the sand/fireclay mixture has no cement, I think I will be able to "touch" it up later if needed.

[dbhansen]

Re: Hansen Horno

DB, What makes you think you need a sander at this stage?

I'm not sure that I'll do any sanding, but I know that's an option to get the floor nice and even. But my bricks seem pretty uniform and smooth, so I'm hoping sanding won't be necessary. Thanks for the input!

[dbhansen]

Re: Hansen Horno

My progress this week has been ordering supplies and arranging my floor bricks. It took me until today to figure out that there's more than one way (or direction, rather) to do the herringbone pattern, and I realized I didn't lay it out the way I wanted (picture 1), so I took the time to re-do it (pic 2). I think the landing area especially will look better.

The 3rd pic shows the proposed floor surface. What do you think - smooth enough? Or will my peel catch on those small ridges? Of course I'll have to reevaulate it after it's laid out on the hearth and not the garage floor.

[dbhansen]

Re: Hansen Horno

I mentioned getting supplies, and this is what I have so far:

• 240 firebricks, in 4 car trips. I "stocked up" because the local supplier is running low and I'm worried their price ($1.37 each) will jump up when they have to get more shipped in from Ohio. Two other local suppliers charge $2.50 each for firebrick. The ones I got have lots of tiny chips and pits and some are even slightly warped - is that normal? I assume perfection is not a reasonable expectation (well, maybe at $2.50!).
• Three 50# bags of HeatStop50 @ $80 each. I had to special-order this, and the shipping adds $30 per bag. Hopefully 3 is enough! I can fill in with the pre-mixed stuff, which everyone carries.
• Four panels of 2" SuperIsol insulation board from Armil CFS. I was almost ready to get some Insblock, but I think SuperIsol is a better insulator and better able to bear weight. I wanted to keep it to 2".
• Oh, and 2 diamond saw blades from Harbor Freight.

And I am soon going to get:

• A 10" tile saw, borrowed (many many thanks, Jim!).
• Four thermocouples (KMQSS-125U-6) and extension wires (TECK10-9) from Omega. I will have one of the thermos custom-made to 8" long, so it fits through my hearth (4"), SuperIsol (2"), and into the firebrick floor (2"). Since they have integrated plugs, the stock 6-incher would be too short, and the 12-incher too long (it would stick out into my wood storage area). $165 total. I still want to talk to someone at Omega to make sure these thermocouples will work best.
• A combination infrared thermometer and thermocouple reader, probably this one.

I went to get some foam-core presentation boards to strenghthen up my floor template (which is currently made of heavy paper), and I was amazed at how expensive they are! Like $8-12 each, even the plain cardboard ones, and I'd need several of them. I think I'll cut up some boxes instead, or get a sheet of pink insulation panel ($6 at Home Depot).

Now to work on thinking of a good excuse for my wife when she sees the credit card bill!

[mfiore]

Re: Hansen Horno

Daren,

Thanks for posting this. Building material options and availability are quite variable in different regions. This summary is helpful.

Thanks

[dbhansen]

Re: Hansen Horno

If only I were closer to Chicago, where I could get the HeatStop for $50/bag and SuperIsol without the freight charge! I almost made the trip, but after looking at tolls, gas, time off work, etc., it just wasn't worth it to me.

Update on the thermocouples: An Omega engineer said the KMQSS probes will be fine, but he suggested a "TJ36-CASS-18U-6" for the floor probe, so I don't have to worry about hitting the connector with a log or something. And I decided to go with only 3 for now: 1 in the floor, 1 in the ambient air in the dome, and 1 between the dome and the insulating blanket.

[dbhansen]

Re: Hansen Horno

Bricks are marked for the oven floor. Next step, cutting.

[mfiore]

Re: Hansen Horno

Daren, thanks for showing the photos of both herringbone arrangements. I don't think I'd have known a difference.

I'm sure this has come up, but when you extend the firebricks out to the hearth entry, is there a problem with them exposed to the elements (rain, freeze, etc.)

[dbhansen]

Re: Hansen Horno

I'm sure this has come up, but when you extend the firebricks out to the hearth entry, is there a problem with them exposed to the elements (rain, freeze, etc.)

Good question, Mike. I didn't consider that. I'd like to hear some opinions on it. Perhaps the landing bricks will need to be sealed somehow to keep ice from getting in there.

The floor is cut! It went faster than I thought (though perhaps my cuts weren't as precise as they could have been). The plan is to put half-high soldiers around the outside of the floor.

Now I'll have to work on mock-ups for the arch and dome.