Lilydale 42" build, Yarra Valley, Victoria, Australia

[Aegis]

Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

Nice work so far! Beautiful mortar joints and your transition seems very smooth.
As far as the flue goes the wider the bottom and funnel effect you can get the better you will be. I used 8" square flue, which I angle cut to piece together a funnel, and I made the brick transition area wider at the bottom and came up to the funnel. Then it was the 8" flue up from that point. I have never had smoke coming out of the front of the oven, it all goes up the flue. I am extremely happy with how this turned out. Thanks to the people who did this before me that I copied!

John

Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

Completed sixth and seventh courses today.
During laying the sixth, was hit by a major downpour which made things a bit tricky.
Thinking about going to quarter bricks for the next courses as the gaps under the centre of each brick is growing. Can't use thirds as the bricks have already been cut into halves!
Removed the arch support today. The arch, with no mortar, is still standing. Molly not convinced though and mutters about unnecessary 'risk taking'.
As others have mentioned, getting sick of cutting and then grinding. My advice; try to get proper good brick saw and life will be so much easier.

The flue opening is planned to be wide and narrow. Hoping to gain a 'venturi effect' as adopted on most traditional fireplace flues. Does anyone have thoughts about this?

Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

forgot to upload the pics....maybe need a day off.

Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

Fifth course completed today. The dome just cut across the corners of the arch; not in a major way. From now on I think we will dispense with the dome form guide and just press ahead.
After completing the next course we will remove the temporary wooden arch formwork. The arch bricks have no mortar between them at all and Molly does not think the arch will hold up.
Defying gravity so far but the next courses will test.
Andrew

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

[Aegis]

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!

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

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

[brickie in oz]

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.

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

[brickie in oz]

Re: Lilydale 42" build, Yarra Valley, Victoria, Australia

I wouldnt have put that cracked brick in, last pic first course.

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.

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

[david s]

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.

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