I'm back

[Amusinglisa]

1. Red brick is ok
2/3. You could use vermicrete, but a high proportion of vermiculite is very weak. I cast the front decorative arch in my builds in concrete, but replace half the aggregate in the mix with vermiculite and use plenty of random fibres for reinforcement. Actually I do it in two layers with the side facing the heat having a higher than 50% proportion and the outer layer lower than 50% that way the inner layer is more insulative and the outer layer stronger.
4. Always

Thank you, david (especially for #4).

what kind of fibers do you use in the cement? Would you mind sharing the proportions?

What do you recommend using for material to make the mold?

[david s]

Thank you, david (especially for #4).

what kind of fibers do you use in the cement? Would you mind sharing the proportions?

What do you recommend using for material to make the mold?

I use AR (alkaline resistant) 18mm fibreglass random fibres

Inner face 0.50 L 7mm aggregate, 2.0 L vermiculite/perlite,1.25 L sand 0.75 L portland cement
Outer face 2.0 L aggregate, 0.50 L vermiculite/perlite, 1.25 L sand, 0.75 L portland cement

I use some sheet steel well oiled see pic. The bottom plate is 3 mm acrylic.
I should also add that in my build my outer decorative arch is separated from the flue gallery by an 8mm expansion joint filled with CF blanket sealed with 5:1 vermicrete.

[Amusinglisa]

Could you please come be my new friend? =)

[david s]

Could you please come be my new friend? =)

Sure, but judging by those legs, I'm way too old for you.

[Amusinglisa]

Bahahahahahaha!!! Those belong to my kiddo.

[Amusinglisa]

OK. We have done a change of design plans for the final sculpture and I will be using a header for my outer arch to make arch, chimney and arbor all work nicely together. Stay tuned. This is going to get a little crazy!!

[Amusinglisa]

Do I need to do the stretcher/header thing for the sides?

I decided to stop letting the tile/brick saw stop scaring me today and am ready to cut some more if that would be better!

[SableSprings]

Do I need to do the stretcher/header thing for the sides?

I decided to stop letting the tile/brick saw stop scaring me today and am ready to cut some more if that would be better!

The side buttressing is usually only necessary when you start applying more weight at the top of the arch. The weight is transferred down to the base. The taller/straighter side arches need more and higher buttressing because the outward force press is greatest higher up the arch curve. Don't know yet what your "this is going to get crazy" means in terms of the arch. Do remember that the angle iron is going to expand/contract at a different rate than the surrounding brick, so if that area is going to get hot there will be some movement along the metal/brick interface...

It looks like you will be directing some of the arch/hood weight back towards the dome with the angle iron, but I'm an "over builder" and would still look at a stack of stretchers on the sides of the arch in your picture.

As noted in an earlier post, if you have a vault (smoke hood) that funnels into a squirrel tail chimney, most of the weight will be on that pipe/dome interface. Solves two problems for you, gets your chimney venting away from the roof line and moves the weight load to the dome instead of directly above the outside/vault arch. Your arch brick cuts look great and I assume you allowed some mortar spacing between the bricks when you did the dry fit.

Glad you're getting some quality time with the tile/brick saw...it's actually pretty satisfying work (although a bit dusty at times ). Keep posting...

[Amusinglisa]

OK, Mike -- Not sure if you can get where we are headed from here unless you know my place is named "LazyBones." I was planning on holding off on more photos till we get finished, but I'm just too excited!

I am thinking I will let go of this monster chimney pipe -- it will work, but I don't see getting a bend into it to make that squirrel tail happen.

Here's the crazy:

[Amusinglisa]

OK. I am having a horrible time with the outside arch. Making small batches of mortarso I can try cockamaimie ideas and let them set before taking them down.

the good news is that I am taking them down and so far, they are not falling...

Three questions:

1. does the outside arch have to be fire brick? Can it be redbrick? My guess is that I would rather have it pretty dang heat tolerant - just incase. THIS is not part of the project I want to revisit.

2. can I cast the front arch in vermicrete? I am hoping that because I will rake the pipe and its weight will be supported mostly by the dome, it might work...?

3.Can I cast thewhole front arch in vermicrete?

4. Is it beer o'clock yet???

I am having a bit of a panic because I am realizing that I asked about the front arch twice when I meant to ask if I can cast the entire *vent* in vermiculete -- which Ihave now done and I am hoping is not a huge mistake.

If so, I need to take it down before I do my outer layer over the blanket...

[david s]

The flue gallery still gets pretty hot and beyond the capacity for Portland cement to cope with IMO. Vermicrete also weakens the concrete mix made with it and the entry is an area that needs some strength as it gets bashed with wood and tools. The higher the proportion of vermiculite or perlite in the mix the weaker it will be. A far better solution is to use castable refractory which uses calcium aluminate cement which has a far greater tolerance of heat.

[Amusinglisa]

If the vermicrete I put up today is holding its firm in the morning, could I coat the inside with catsable refractory (I'll have to find the recipe)? Would homebrew work?

[david s]

That might work, but as it's a thin layer it will have a greater tendency to flake off or fracture more easily from impact. Castable refractory would be better, homebrew second best.

[Amusinglisa]

Is castable refractory something I buy or is there a recipe somewhere? I'm not finding a recipe. Any help would be very appreciated.

[UtahBeehiver]

The castable David is talking about is typically a proprietary product you buy. Any refractory supplier or perhaps a fire place store will carry it, be sure to get dense not insulating. Home brew is the same as the home brew you have been using for mortar. 3 sand, 1 lime, 1 portland, 1 fireclay.