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42" build in McPherson KS

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  • SableSprings
    replied
    Seth, here's my take on your questions:

    Insulation: The goal of your insulation is to totally isolate the heated oven bricks from the stand and any other outside contact. There would be no problem having the CaSi board extend a bit further to "connect" with the upper dome blanket. Just be very aware of providing a moisture barrier and moisture escape route for all insulation (top and bottom). Water seeping in along the perimeter of the dome's outside base is one of the top problems for a WFO that is not in a permanent, roofed enclosure

    Opening: The opening width is not as important as the ratio of opening height to inner dome height (remember the magic 63%). The biggest decisions for me were 1) making sure I could fit a full sheet pan easily into the oven and 2) what worked out simply by the brick dimensions I was using to do my build

    Landing: Best practices indicates putting an insulated gap around the oven opening and front arch set(s). The base insulation would not need to extend further than this gap. For a lot of people it is just more convenient to extend the insulation out to make the landing bricks the same level as the cooking floor. If your landing extends out a brick or two from the opening, then your plan sounds great. The bricks outside the oven on the landing can get plenty warm, but I seriously doubt there will be any issues for you (and it will look great with that front brick edging )

    Hope that helps.

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  • slschoming
    replied
    Earlier this week I picked up my insulation for under the floor and about 140 firebricks (enough to get started). Next week I will start cutting the insulation and floor bricks. I have changed plans since I started.... I will be building a 42" internal diameter oven so my insulation footprint will be a circle with a 51" diameter connected to a rectangle for under the landing. However, I have a few more questions before I get started.

    Insulation Question
    I was curious if there is any benefit in having the floor insulation extend another 2 inches beyond the outer layer of firebrick so that the bottom of the 2" insulation blanket is resting on CaSi board. Has anyone done this? Or is it better to overlap the other way, having the blanket extend below the bottom firebrick enough that there is no heat sink?

    Opening Question
    I think I read somewhere that a good opening for a 42" is around 20" - 22"? Is this a decision that should be made based on science, or is it mostly personal preference?

    Landing Question
    Since I started planning a 36" oven my hearth is probably a little smaller than the average 42" oven hearth. I am going to be extending my landing all the way to the front edge of the hearth and will be utilizing every last inch of space that I have.. That being said, how much of the landing should be above insulation? I am currently planning to run my insulation 4 inches short of the front edge of the hearth so that I can put a full brick down (stretcher orientation) between the edge of the hearth and the insulation. I am open to suggestions.

    Thanks!
    Last edited by slschoming; 06-20-2019, 08:30 AM.

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  • SableSprings
    replied
    Seth, as Russell noted, even with the non-absorbing Foamglas underneath your CaSi board, having the mosaic tile sheets allows any water that seeps in underneath the oven, a clear path drain out the weep holes. That's why setting the sheets upside down (with the webbing up) works...you get little channels for any water to flow out to the weep holes. Also gives you little air channels to help dry out any moisture wicking up from the concrete. As with the weep holes, in your case with the Foamglas under the CaSi it's just cheap, extra insurance...just make sure you set the mosaic tiles so weep holes are not covered. Also don't forget to cover the lower (underneath) weep hole openings with some pieces of insect screen (metal if possible). Silicone seal will hold little squares of screen nicely and keep any critters from looking for a new home in your insulation layers. I'm not fond of the plastic screen materials, seems like the bugs often just chew through it too easily.

    Good luck and glad to hear you're back working on the oven!

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  • slschoming
    replied
    UtahBeehiver I have 2 weep holes located along the perimeter of where the insulation will sit. I was previously planning to put my CaSi board on some sheets of mosaic tiles to keep it up off the (potential) water. Now that I'm planning to put a layer of foamglas under the CaSi I'm curious if I still need the mosaic tile.

    The current plan is to have an exposed dome that I will eventually finish with remnant brick like cobblerdave 's oven.
    Last edited by slschoming; 04-16-2019, 11:04 AM.

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  • UtahBeehiver
    replied
    Are you enclosing the oven or not? Open ovens are prone to having water come in from the hearth. A weep hole would be cheap insurance in case any water works its way in. Even though the FoamGlas will not absorb water it would be advantageous to have any water that migrates in able to egress out.

    Leave a comment:


  • slschoming
    replied
    I just ordered enough CaSi and Foamglas to do a 2" layer of each. Should arrive to the warehouse next week and then I will have to find the time to drive 3 hours round trip to pick it up...

    For those with weepholes and Foamglas.. Is laying a sheet of mosaic tiles underneath overkill now that I am using foamglas as my bottom layer, or is it still advised?

    My kids are starting to question whether I am going to really get this thing done:

    "Dad, when are you going to start working on the pizza oven again?"

    "What if you mess up and can't fix it?"

    Leave a comment:


  • slschoming
    replied
    Michael Harrington Thanks, but CoastPizza pointed me to a place nearby that has both foamglas and CaSi board. 70 miles away so I can drive down there.

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  • Michael Harrington
    replied
    I bought 12 18x24 sheets of 1.5 foam glass on ebay 72..00 including shipping the peices arrived with a few dings and some rounded corners over all good shape. I don't know if you could use this instead let me know I can give link he said he had15 left.

    Leave a comment:


  • david s
    replied
    Originally posted by UtahBeehiver View Post
    Most like will work but to ensure, get the "K" value of the material, should be around 0.5) at 500 F (Standard Units) or 0.079 at 260 C (Metric Units), also need compression strength of at least 75 PSI with 5% compression.
    That board has pretty much the same density as 10;1 vermicrete which is considered too weak to support the weight of an oven. There are tons of different products out there, even under the same brand name. My calsil board has a density of 350 kg/m3, considerably more than the product you’re looking at. Make sure it has the compressive strength Russell has already posted.
    Last edited by david s; 04-04-2019, 12:35 PM.

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  • slschoming
    replied
    Shipping that stuff to Kansas doubles the price... $213 worth of insulation ships for $207.. I might be going back to vermicrete...

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  • UtahBeehiver
    replied
    If DJ used the board, then great, as long as it is the same product.

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  • deejayoh
    replied
    I used the McGill's CF board. Its been great for 4+ years. Can't beat the price either.

    1" layers are great, you can stagger the seams

    Leave a comment:


  • slschoming
    replied
    I sent the manufacturer an email and am now waiting on a response regarding the K value. I searched the forums and it looks like others have used this CF board. In the meantime, I noticed that the 2" variety is out of stock, but I can get the same volume in 1" board for the same cost. Is it acceptable to do two layers of 1" board in place of one layer of 2"?

    Leave a comment:


  • UtahBeehiver
    replied
    Most like will work but to ensure, get the "K" value of the material, should be around 0.5) at 500 F (Standard Units) or 0.079 at 260 C (Metric Units), also need compression strength of at least 75 PSI with 5% compression.

    Leave a comment:


  • slschoming
    replied
    When I hung things up for the winter I was planning to use vermiculite as my insulation layer. I have thought about it over the winter and have sort of shifted gears. I am now planning to purchase some CF board and blanket. It will save me some space and will be easier to put a rigid piece of CF board on top of a sheet of tiles for my weep hole drain channels.

    This is the board I plan to buy. I get confused when people start talking about CF board specs, so I am sorry for this uneducated question. Does this seem like it will do the trick for insulation under my firebrick floor?

    https://www.mcgillswarehouse.com/hf1...0kgm3-d1af10df

    Leave a comment:

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