Building outdoors on ground in tropics

[Johnnycantplaytoday]

Hi Dave,

Thinks for that. Don't know what happened to the photos I attached. They were there yesterday. The others are still there. Does that mean no one can see them anymore. Should I put them back up again. Is there a limit to the amount of photos and should I create an "Album" instead. Sorry, this is the 1st forum I've ever signed up to so not sure on the way to go.

Regards

JB

[david s]

I think the limit is 5, if posting more you need to link it to something outside the forum.

[UtahBeehiver]

Also, the size cannot exceed abt 1.2 mg per pic.

[Johnnycantplaytoday]

Hi Dave and Utah,

Thanks for that, I checked last night and there was still 6 photos there in post #12, but just now there are no photos. Wierd. I will add a couple to this post so you can see what I'm up too.

Managed to sneak home an hour early yesterday and put down a 2nd layer of 5:1 Vermicrete flooring. This now brings the floor to about 180mm (7 in) thickness.

I also purchased some 300x460x50 Kiln/Firebricks for the base/hearth instead of using the 230x115x35 Firebricks that I already had.


So onto a couple more questions. (They just keep appearing out of nowhere!!) Hopefully I've run out.

1. I've found a supplier down the road that sells Ciment Fondo. I thought I might use this instead of Portland Cement in my 3:1:1:1 homebrew mix because of the better heat properties but after some research and it seems that not many people recommend this for various reasons. Is the standard homebrew recipe better/stronger than using a Ciment Fondu recipe. Seems like the Ciment Fondu is a good product but more trouble than it's worth.

2. In regards to the flue placement, just want to confirm that the entrance to the flue is just outside the door external to the hot chamber. See pikkie below.



Thanks as always.

JB

[david s]

1. Use the Cement Fondu if you want, but it does have drawbacks. Firstly price, secondly it goes off really fast being far more temperature dependant than portland cement, in this weather you will need to ensure a cool barrow and spade as well as using chilled water for mixing. Also if adding lime to the mix it acts as an accelerant on calcium aluminate cements further reducing working time.
2. That design does not allow smoke collection and results in lots of smoke escaping out the front especially on light up. Better to do it this way.(attached drawing) Note you can set the flue pipe well back making the entry quite shallow and easier to work.



A better explanation is this pic on the following post
#2

[UtahBeehiver]

You can also install a vent at the apex of the dome using a breather vent with a pvc or brass bushing that is available at any auto parts store, they are about $5 US so maybe $10 AUS. Some builders just plug the bushing and open up when they fire or after a long period of non use while they fire.

[UtahBeehiver]

I can't see the drainage holes in the front so if not there you will need to get some in the concrete since the pcrete is sitting in a basin so to speak and you need to get any water a way from it.

[Johnnycantplaytoday]

Thanks Dave and Russell.

Sorry for late reply, been out of town for a couple days for work.

Hey Russell, checked out your oven and I love the copper sheeting. Looks awesome, and Dave, I like your photo where your guarding the beer. It's a tough job, but you can never be to complacent!

As for my build, I do have a drain hole in the lower left corner about 22-25mm in size. The "basin" also has a 60-70mm crossfall from the rear right to the bottom left corner. Refer pikkie below. When it's all finished and has the pavers set around it, I expect there will be very little water getting in there. So hopefully I should be fine and the oven base stays dry..

For the flue. It seems like I should make up some kind of antichamber (flue gallery?). Was thinking of something around 300mm wide, 200mm deep and tapered to 100mm high before the flue sits in and have the taper start right next to the oven chamber door frame where the smoke comes out..Not quite as high as yours Dave but hopefully should still do the job (or not!)

Dave, I know you said I didn't need it, but I couldn't help myself, I poured a 25mm thick homebrew base to lay the floor bricks onto. Did this for a few reasons.

1. I figured if it all went pear shaped, I could remove the floor firebricks and the homebrew base and replace later with 25-30mm vermicrete base and place the floor firebricks back on top of that, so no real loss.

2. I wanted to see the best way to mix the homebrew with the S.S. needles and the poly proplylene fibres so that it was thoroughly mixed. I ended up putting all the ingredients into the cement mixer minus 2 parts of the sand. ie 1:1:1:1 . I was going to mix it and then put it in a wheelbarrow and then shovel mix in the water and remaining sand but because of the ton of dust coming out I decided to add heaps of water to get it into a slurry and let this mix for 20 minutes or so until all the fibres looked like they were starting to separate and mix well. Occasionally I had to get the spade in there to get some mix off the off the back of the mixer, but eventually I had a really nice "wet" mortar sloppy looking material. I then slowly added the remaining 2 parts sand to dry it up and ended up with a fairly good thoroughly mixed product, though perhaps not as dry as it should be for casting but nevertheless good for putting on the bottom of the oven floor as a base.

3. I thought I'd see of the extra volume of heat absorbing material would keep the heat in the oven a lot longer. Testing to come later.

4. I wanted to see how well the S.S. needles held together the homebrew even though it is only 25-30mm thick under the stresses of heating and cooling.

5. I didn't put any homebrew in the retaining wall cutout, I filled that up to height with some 5:1 vermicrete and will rest the firebrick tile straight across the 15-20mm airgap from the main floor onto this. I figured an airgap would probably help a bit to keep the temperature down a bit on the rock retaining wall.


I've also attached a photo below showing the S.S. needles. Wasn't what I was expecting. I was expecting I guess a box full of little shiny sharp needles. These look like shavings of some sort. Do they look the same as yours Dave?

metal

Anyways, A thunderstorm is happening overhead so I've had to put down the tools and retire to the aircon and bar facilities to see out the rest of the day.

Thanks and Cheers.

JB

[david s]

Hi John.
Those ss fibres you have are the same as the ones I use. The min is 2% of the dry weight of castable. 4% starts to make placement difficult so go for 3% Those other fibres you have look like the correct ones. Test by placing a very small amount on a saucer(when your wife’s not around) in your oven set at 160C to check if they melt. I think 20 mins mixing is overkill. Because of the clay in the mix I’ve found an electric mixer unsuitable and prefer mixing by hand with spade and barrow where you can see more easily what’s going on and feel the consistency. Because the fine polypropelyne fibres are so thin you need less of them than you’d think. For a batch of 20 litres or so you only need a small handful.

20 mm rain down here last night, very welcome.
Cheers,
Dave

[UtahBeehiver]

On the melt extract fibers, why don't you post where you got them so other Aussie cast builders can source them unless they came from the same place David S gets his (Antec). I know this is common question for on where to buy the fibers in your end of the world.

[david s]

On the melt extract fibers, why don't you post where you got them so other Aussie cast builders can source them unless they came from the same place David S gets his (Antec). I know this is common question for on where to buy the fibers in your end of the world.

Here you go.
http://antec.com.au/

[Johnnycantplaytoday]

Hi Guys,

Havn't had a chance to do much the last couple weeks. But back on the tools the last few nights and have managed to make the formwork for the entrance to the oven. Man, took a lot longer than I thought. Decided at last minute to add a 2nd door to the very front of the oven to keep out rain and leaves.

So trying to get everything ready for a Saturday morning dome build. I think I have everything under control.

Dave, does the flue "chamber" look OK to you?.

Any tips on the homebrew and putting it on. I am going to make a wooden trowel with a 950mm radius to help with the dome shape and some 60mm spacers/packers to help keep tabs on the thickness of the dome. Apart from that I'm basically going to just wing it.

Any suggestion as to which way to lay the cement on eg start by completing a circuit around the entire base and then slowly build up layer by layer until you get to the top.(horizontal rings) I was thinking of this one.

Or start at rear of dome and work your way vertically (bottom to top to bottom) along to the front of the build.(vertical rings)

I've also seen where some people start at the top and work their way down.

Anyway, will let you know how it all goes.

Thanks as always

JB

[david s]

That looks ok. I can’t tell from the pic what material you’ve used for the mould, but it needs to be something that can be easily removed from the inside. You should paint on a release agent to the mould surface. I use 50/50 motor oil and kero applied lightly. When doing the casting for the hole into which the flue will go you need to make it slightly loose so the expanding ss won’t crack the casting during firing. If casting around the the flue pipe wrap some cardboard around it, then some cling wrap and remove both after casting. Your fluepipe is actually upside down the crimped end should be at the top to fit inside the rain cap.
When casting over the dome start at the bottom and wriggle the mix against the mould so there are no voids against the surface. Work all the way around making a flat ledge at the top so you can see how thick you are making the layer. Once all the way around you can then build up on the flat ledge you’ve made to go higher, all the way around again. It gets easier as the walls begin to lean in. Cover the damp sand with thin strips of wet newspaper so the mix won’t pick up sand against the surface.

[Johnnycantplaytoday]

Hi Dave,

Thanks for that, I was going to put some vegetable oil over the formwork to help stop the concrete sticking. Also the flue is just sitting there for the photo, the round discs of timber will be the actual flue opening and I made that about 6mm bigger than the flue. Was going to put wet paper over the sand and maybe some clingwrap over that to keep the moisture in the sand. Will try to make the sandcastle dome this afternoon and the actual concrete dome 1st thing in the morning. So hoping clingwrap stops the sand drying out overnight and becoming loose. The actual mould is made from timber and soft plastic wrap around. It's made to separate in three stages, the flue pops out at the top, the main centre structure will be propped up around 5mm, so I can tap it down 5mm and then pull it forwards out the front and after that's out, the flue gallery has a handle built inside it that I can pull straight down and then out the front opening. So hopefully Fingers crossed the mould will come out as planned.

If not, I always have my backup plan of a large hammer and/or blowtorch!!

Thanks again,

JB

[david s]

Sounds all good to go.