Silence is Golden
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Gerry Parent wrote:Hi Bart and BIG Welcome to Permies!
So glad to hear your going to start a RMH build in Italy. Lots to learn and wish you well on your adventure.
Due to your warmish climate, you probably want to concentrate on mass vs instant heat, so eliminating the barrel is probably a good idea.
Its always a good idea to have insulation under the core. This helps to keep the heat directed towards the fire burning hot and clean while also not transfering it down into the earth where it will forever suck it away.
Vermiculite panels could work, although I've never used them so don't know for sure. Another option people have used quite often is perlite mixed with a little clay slip tamped flat as a pad. Elevating the pad and leaving an air space is particularly good as well.
The heat riser must be insulated as this is where a lot of the gasses are burned up to produce a clean exhaust.
A "5 minute riser" in my opinion is a great way to go. An 8" steel pipe lined with morgan superwool.
Lots of options for metal over the heat riser to cap off the top of your brick work: iron skillets or griddle, cut off steel barrel top, high heat ceramic glass even a manhole cover would work. Although its metal, most of the oxygen has been burned off by then so oxidation and spalling is kept to a minimum.
Your larger 8" chimney will work just fine. No need to replace it. If it was the opposite direction, it would have been a constriction and therefore a problem.
Here is a link that will show some examples of the manifold area:
Flue-exhaust-transition-plenum-pictures
Bart Leynen wrote:
1) So, I found some perlite, I bought a bag of 100 litres but I haven't been able to find the ultra fine powder I have seen the Wisners use in the project from the first DVD.
Bart Leynen wrote: They call it 'argilla espansiva', which means "expansive clay". Can I use it in the cobb and in the clay mortar for the firebricks in the heat riser?
Bart Leynen wrote:I also wonder how one can stabilize the perlite layer that comes under the fire tunnel and heat riser. That wasn't shown in the video. It has to be 100% solid and level for the fire tunnel to be built on top of it.
Bart Leynen wrote: 2) Durablankets, which seem really convenient and were also used in the video on the DVD, are hard to come by but I have found something else which I can order online here in Italy. It is a ceramic fiber with aluminum and silicium and can tolerate temperatures as high as 2000 °F so that already ticks another box. My question regards the thickness of the material. DO I need 1 inch thick, or will 0,5 inch be enough?
Bart Leynen wrote:3) One more question regards the liquid they dip the firebricks in before they put them on top of each other to make the heat riser? Is that just water mixed with fire clay? That's my mission for tomorrow: find a place where they sell fireclay. So far it seems like they don't have fire clay powder, but there's a local store where they sold me the firebricks, maybe I will have more luck there. They sold me some refractory cement last week but I have read it is far from ideal.
Silence is Golden
For all your RMH needs:
dragontechrmh.com
Gerry Parent wrote:
Bart Leynen wrote:
1) So, I found some perlite, I bought a bag of 100 litres but I haven't been able to find the ultra fine powder I have seen the Wisners use in the project from the first DVD.
Actually, what you show in your picture of the perlite looks just fine. You don't want the ultra fine powder (if there even is such a thing).
Bart Leynen wrote: They call it 'argilla espansiva', which means "expansive clay". Can I use it in the cobb and in the clay mortar for the firebricks in the heat riser?
If you can't find any natural sourced clay in the hills, stick with fireclay for all your RMH work and you won't have any issues.
Bart Leynen wrote:I also wonder how one can stabilize the perlite layer that comes under the fire tunnel and heat riser. That wasn't shown in the video. It has to be 100% solid and level for the fire tunnel to be built on top of it.
With your fireclay, you want to add enough water to it so its the consistency of a milkshake. This is what is called clay slip. Add this to your perlite and mix it in well....but just enough so that it will clump together and hold its shape but will still easily pop apart when lightly squeezed. Too wet and you loose a lot of the insulation value of the perlite, as clay is not an insulator, only a binding agent.
Bart Leynen wrote: 2) Durablankets, which seem really convenient and were also used in the video on the DVD, are hard to come by but I have found something else which I can order online here in Italy. It is a ceramic fiber with aluminum and silicium and can tolerate temperatures as high as 2000 °F so that already ticks another box. My question regards the thickness of the material. DO I need 1 inch thick, or will 0,5 inch be enough?
Not sure which ceramic fiber blanket your looking at but the safest one to use that has next to no health concerns (no more than standard fiberglass insulation) is called Morgan superwool. Working-Morgan-Superwool-ceramic-blanket
1" thick is a good size to work with. Half inch is a bit too thin for insulation and structure.
Bart Leynen wrote:3) One more question regards the liquid they dip the firebricks in before they put them on top of each other to make the heat riser? Is that just water mixed with fire clay? That's my mission for tomorrow: find a place where they sell fireclay. So far it seems like they don't have fire clay powder, but there's a local store where they sold me the firebricks, maybe I will have more luck there. They sold me some refractory cement last week but I have read it is far from ideal.
Yes, clay slip is what they dip the bricks in. Just on the edges and just enough to help temporarily stick them together, help seal the air gaps and level out any irregularities in the bricks so they don't wobble. Refractory cement is a one way deal. Clay is so much more forgiving and much nicer to work with. No gloves needed and if you want to modify your stove in the future, you just wet it down and it easily comes apart.
Silence is Golden
For all your RMH needs:
dragontechrmh.com
Gerry Parent wrote: Bert, the clay slip / perlite mix needs to be kept as dry as possible - just wet enough to barely hold itself together when squeezed together with your hand into a ball. If you were to then squeeze it with two fingers, it should pop apart.
Secondly, it doesn’t really harden but rather dry enough to handle gently.
This soft delicate nature makes it very insulative. Surprisingly though it will hold up a core when the weight is distributed over it.
You could add an external source of heat to help it dry faster but adding minimal water to it at the very start is key.
Silence is Golden
For all your RMH needs:
dragontechrmh.com
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