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Lilydale 42" build, Yarra Valley, Victoria, Australia - Forno Bravo Forum: The Wood-Fired Oven Community

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Lilydale 42" build, Yarra Valley, Victoria, Australia

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  • Lilydale 42" build, Yarra Valley, Victoria, Australia

    Hello from Lilydale which lies in the Yarra Valley on the outskirts east of Melbourne, Australia.
    This forum is a wonderful resource and thanks to the Forno Bravo team.

    Our build is about to commence. There has been a wait for ’straight’ fire bricks and this has allowed some sensible planning rather than what would have been a ‘bull at a gate’ approach.

    This 42” (110cm) oven will have the following specs:

    1. Concrete blockwork base; Dry stacked hollow blocks , concrete filled/reinforced at least at the corners (pic). Base brickwork ‘bagged’ with sand, cement lime at 6:1:1

    2. 90mm concrete suspended slab with F62 mesh, 25mm bottom cover. Some addition reo in critical areas (pic). Thankfully my neighbour Pierre offered small Kubota 4WD tractor with front bucket to move concrete from Mini-mix to the oven site. Don’t know what we would have done otherwise. The concrete quantity was 0.5 cubic metre.

    3. 40mm thickness perlite cement (5:1). Exfoliators in Melbourne supply a wonderful product called ‘Premium Lite Fill (fine)’ which is perlite that has been treated to make it waterproof. This is easy to work with, has good compressive strength and is not at all ‘crumbly’.
    We mixed 100 litre bag of LiteFill perlite with 20kg bag GP Portland cement and it made 75litre finished volume (ie 25% compaction).
    One reason for using this thin perlite layer was to prevent any water damage to the Calcium Silicate sheet directly above.

    4. 50mm Calcium Silicate sheet beneath the hearth.

    5. 75mm thick hearth using herringbone pattern and the standard 230x115x75 firebrick.

    6. Hearth protected during construction using 19mm particle board (yellow tongue; waterproof)

    7. Dome made from ‘dry stacked’ tapered fire brick (230x115x75/63mm). These are the same cost as ‘straight’ bricks. Bricks supplied by Melbourne Fire Bricks. They specialise in supplies for DIY Forno Bravo Pompeii ovens. Refractory mortar only required at the back of and between adjacent bricks, but no mortar on the inside face.

    8. The bottom course will be ‘half bricks’ on edge. These will have 13 degree angle cut at their top face to take the second row of bricks which will be tapered bricks (cut in half).

    9. Dome will be constructed using wood arch guide (pic). An indispensable tool was made but it was soon realised the centre of the arch is below the hearth level and this would have required many adjustments to the tool. Further, as tapered bricks are being used, there will be no need to ‘clamp’ each brick in position. The arch guide is notched to indicate each brick course.

    10. Today, a polystyrene dome’ form’ was made (pic). Brickie’s sand and the arch form were used to make the form for the form(!) We used polystyrene because it was at hand, but one could just as easily use a thin layer of concrete/chicken wire or a’ lightweight model’ using the ‘LiteFill Perlite/cement mix reinforced with chicken wire. But the styrene worked a treat and the whole construction of this form took just a few hours.

    11. Both entry arches will be made from the tapered bricks. The arch is rather flat but should be OK?

    12. Flue’ entry’ will be the full width of the entry arch and 115mm deep. This will taper up to a 3 foot long 8” stainless round flue

    We are cutting the bricks using a cheap diamond wheel ‘tile’ saw ($99 at Bunnings). A bit dinky and the 35mm max cut requires bricks to be’ turned over’. The wheel supplied lasted 50 bricks! Maybe a proper brick saw would have been the better option, to be sold at the end of the project. Persevering….!!

    I wonder if a tungsten blade might do the job as the diamond blades are expensive and fragile. Intend giving this a try and will report on success or otherwise. Has anyone tried this?

    Someone else suggested a hacksaw and water. This actually works (!) but is hard Yakka if a lot of cuts are required. But could be useful for some fiddly cuts at the entrance.
    Some extra pics will be attached to next post.
    Attached Files

  • #2
    Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

    couple more pics.
    Andrew
    Attached Files

    Comment


    • #3
      Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

      Originally posted by andyshak View Post
      I wonder if a tungsten blade might do the job as the diamond blades are expensive and fragile. Intend giving this a try and will report on success or otherwise. Has anyone tried this?
      Welcome Andy.

      The diamonds in a diamond saw are held in a tungsten matrix so I doubt your plan will work.
      For a good diamond blade you have to spend good money, I mean like $30 for a 9" grinder disc.

      Also, with you having tapered bricks you would have been better of building a barrel oven.
      The English language was invented by people who couldnt spell.

      My Build.

      Books.

      Comment


      • #4
        Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

        [QUOTE=andyshak;126494]
        3. 40mm thickness perlite cement (5:1)..
        We mixed 100 litre bag of LiteFill perlite with 20kg bag GP Portland cement

        The perlcrete ratios suggested are by volume not by weight so you have ended up with a leaner mix. The considerable amount of compaction is probably due to mixing which tends to break down the perlite grains. I read somewhere that it should not be mixed for longer than 2 mins. The extra compaction should compensate for the leaner mix. I'm sure you'll be OK.
        I like the idea of minimal mortar which will allow the oven to move.
        Look forward to seeing the rest of the build.
        Dave
        Kindled with zeal and fired with passion.

        Comment


        • #5
          Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

          just replied but it was lost in cyberspace. Try again.

          Also, with you having tapered bricks you would have been better of building a barrel oven

          Hi; tapered bricks would be ideal for barrel. But for an igloo, it means that little or no mortar is required between each horizontal brick course. No wedging and no need to use the indispensible tool.

          The firebricks seem not so much different to sandstone which is quarried using tungsten blades and water. Came across blades called 'Rotary Hacksaw' today and will give one a fly.

          Thanks Dave; We mixed 5:1 by volume. It just worked out that we needed ONE 100 litre bag of perlite and ONE 20kg bag cement. We had no idea of quantities at the beginning and this will allow more confident ordering in the future. But it has gone off like a rock and the cement content could be reduced I think, even under the hearth.

          This 'LiteFill' perlite is different to normal perlite as each particle has been sealed. We mixed quickly and as gently as we could. LiteFill Perlite can take the place of sand to make a lightweight render and we intend finishing the outside of the dome using this.

          Spent the day sourcing thermocouples here in Melbourne it seems Jaycar have some that look OK and not too pricey. They have the readers too but a digital multimeter can also be used.

          Just realised today the mushroom styrene form will need to be cut in half at the end to remove. Should have cast in two parts.
          Jumping at shadows now and can't wait to get the straight bricks so we can start laying and work off some of this planning tension.

          Thanks,
          Andrew

          Comment


          • #6
            Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

            "Thanks Dave; We mixed 5:1 by volume. It just worked out that we needed ONE 100 litre bag of perlite and ONE 20kg bag cement. We had no idea of quantities at the beginning and this will allow more confident ordering in the future. But it has gone off like a rock and the cement content could be reduced I think, even under the hearth."


            Something is not right here. A 20Kg bag of cement takes up 13 L therefore 13: 100 = 7.7:1
            Maybe they ripped you off and there wasn't really 100 L of perlite. No matter it will work OK.

            I can't get the silicon coated stuff up here, wish I could, the normal stuff takes up tons of water and takes ages to dry.
            Kindled with zeal and fired with passion.

            Comment


            • #7
              Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

              I was measuring and Molly was counting. Not my fault!
              You are right of course about the density of the cement bag. IMO, it also went looser in the bucket than in the bag. But whatever, it is EASILY strong enough for the base. As mentioned, it is like a rock. Probably we'll go for a very lean mix for the shell...say 15:1. But we'll experiment a bit first.
              Andrew

              Comment


              • #8
                Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

                Finally obtained the straight bricks and CaSi board. The bricks are not all the same size and the Silicate board, being cut to 50mm thickness from a thicker board, is a bit wonky.
                Spent yesterday deciding how to do the entry arch; should it be cut to the interior curve of the dome or just have vertical sides?
                With no brick saw (just a small tiling saw), the former option was problematic. Tried 'sculpting' the bricks using bench grinder; while this was moderately successful we finally opted for the vertical soldiers at the entry.
                Tried to think of the drawbacks; eg. more difficult to remove ash? Are we missing something?
                Spent 4 hours with my neighbour Pierre, trying to nut out the angles where the dome meets the arch. We both retired defeated!

                With head still hurting from trying to visualise those compound joints, laid the silicate board and herringbone floor later in the day. The floor is a little skewed.....damned hard to get the 45 degree just right, especially when the reference points are knocked over! Decided to leave as is.... a sort of tribute to the imperfections of DIY.

                Today, laid the first 'base course'. Now we are celebrating the successful completion of the first compound joint where the second course meets the arch. Wasn't so difficult after all. The joint was cut using an angle grinder with diamond blade and 'cleaned up' using a bench grinder. The inside face of the bricks for the second course are being 'tapered' using the tile saw.

                We are mixing the mortar very wet and runny. This has led to minor shrinkage cracking of some of the wider joints but I am not so worried about that. Is this blissful ignorance? There will be no mortar joints inside the dome so this cracking will not be visible. We could have used castable to fill the larger voids...if we had any!

                Really looking forward to tomorrow. Lovely weather here in Melbourne.
                Attached Files

                Comment


                • #9
                  Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

                  I wouldnt have put that cracked brick in, last pic first course.
                  The English language was invented by people who couldnt spell.

                  My Build.

                  Books.

                  Comment


                  • #10
                    Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

                    Thanks Al, good spotting.
                    Did an extraction then an implant today on that cracked brick and then completed second and third courses. Luckily that mortar takes some time to harden.

                    The hands are a bit sore; burnt from the mortar or just handling the bricks. Will try to get some decent rubber gloves or use disposable kitchen gloves under the leather gloves.

                    Tomorrow hoping to get the arch completed. Better make use of this glorious weather.

                    Bought a 'turbo' diamond dry saw and it works wonderfully.
                    The tapered bricks working well, however cutting the additional taper to get rid of the 'V' takes some time.

                    Andrew
                    Attached Files

                    Comment


                    • #11
                      Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

                      You need to not do a straight continuous joint as in the 4th pic right hand side, as it is a weak spot.
                      The English language was invented by people who couldnt spell.

                      My Build.

                      Books.

                      Comment


                      • #12
                        Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

                        Thanks Al. Yes, I said to Molly that might get a comment but I was too lazy to cut and then taper a half brick. Will definitely bond the brickwork at that point in the next course. There is also a structural discontinuity at the connection to the vertical entry to the, arch, just near this point. We have a vertical one but others have an angled one if the back of the arch bricks are bevelled.

                        The brickwork for an igloo is a little unusual. I was wondering if any forum members have suffered serious structural damage due to such things or any other cause. Perhaps the igloo is inherently a forgiving and structurally sound shape...at least I hope so.

                        And I was also wondering what leads to firebrick cracking and how to prevent that. For example, is the distribution of mortar between brick courses a factor, causing localised stress concentrations. Or is it related to quality of firebricks. You have picked up hairline cracks in our bricks...there are many like that but you can only see them some of the internal cracks when they are cut.

                        This is a bit of a ramble...sorry about that.
                        Thanks again.
                        Andrew

                        Comment


                        • #13
                          Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

                          Aimed to complete the fourth course and the arch today....and failed.
                          Heard somewhere that one should set aside one day a week in which to 'fail' and that this was good practice for personal development. Say, 'fail' to get up early one day a week. Well today was such a day despite the best of intentions.

                          We are buiding this dome using tapered bricks (75/63mm taper). We very carefully laid the tapered bricks out on the floor to determine the best curve and geometry. Then a curved wood form guide was made.

                          Well today a fatal error in this approach was discovered.
                          This has led to the postulating of the
                          FIRST LAW OF TAPERED BRICK DOME CONSTRUCTION,
                          and this is:

                          "The radius described by tapered bricks stacked in an arch is greater than that described by the same bricks stacked in a dome"

                          In other words, the tapered bricks were not conforming to our wood form guide.
                          But there was a silver lining to the gathering dark clouds. We had deliberately planned for the dome to be a bit higher and were targeting an opening/dome height ratio of 59%. We had read somewhere in the forum that an 'allowable' range is 59-63%. Well, our discovery today has led us to modify the form guide and we will now get the 63% ration that everyone seems to accept as ideal.

                          But these setbacks we can do without and hope for plain sailing from now on.
                          The next fifth course will introduce the spectre of gravity and it must be decided if we will use the styrene 'mushroom' form we made or persist with the wood guide.

                          My fear of the styrene mushroom form is that it may be difficult to accurately align the face of the bricks and one could not see the finished interior face until the form is removed. Has anyone some advice here?

                          Being still hot and bothered, I am happy to say it is 'beer o'clock'. Cheers.
                          Andrew
                          Attached Files

                          Comment


                          • #14
                            Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

                            I went with an indespensible tool and would do that or your wood form for the "next time" It was great to clean off the interior bricks from my sloppy mortar work, as it was being constructed. Also vertical alignment issues show up easily and with the correct consistency of mortar, the set time is relatively quick, allowing for the next brick placement in a few seconds.
                            Your build looks great! Keep up the superior work!
                            Build Thread:http://www.fornobravo.com/forum/f8/i...ome-15521.html
                            Photos: http://groups.yahoo.com/group/brick-...67884/pic/list
                            Oven Blog: http://johns-brickoven.blogspot.com/...ven-folly.html

                            Comment


                            • #15
                              Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

                              Thanks John. We will stick with the wood form and alter as required as the build proceeds.
                              I have been considering the entrance 'tunnel' and am trying to make it as shallow as possible. At the moment it will be ONE brick deep; i.e. 9" from the outer face of the internal arch; then some sort of shallow 5mm metal facade such as Scotty's on the Sunshine Coast). Am thinking about knocking off another inch to reduce that to 8". My aim is to maximise the accessibility to the oven. Am I worrying too much about this? (Molly thinks so!).
                              Andrew

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