Calcium silicate board with clay and sand mortal

Hello Permies

I wish to begin expirementing with Rocket science. I've been on a scavenger hunt for materials and have come by multiple used Calcium silicate boards from the company Skamowall. I've read the data sheet and it says the product has a melting point of 1345 deg C. (2453 ). But i've read comments here saying that the flame path will somehow destroy theese boards anyways. So i was wondering if it would be possible to use theese boards as a casting box for a core and heat riser ( 8 minute riser technique) with maybe 1 inch of clay and sand mortar in the flame path inside a box of calcium silicate board. This technique would make the entire build 5x cheaper in my case. I plan to mark the correct dimension on the board and then basically "fill to here" Is the entirely insane and overly complicated or maybe achievable? initial build is a workshop build.

You could try painting it with Zircon.

Regular clay/sand mix will quickly crack and will probably fall off due to shrinkage and different expansion ratios.
Using zirconium coating could help a little against flame erosion, but the boards are so soft (I have some) that they will be quickly destroyed by loading and cleaning.

Hi Ben;
Welcome to Permies and Welcome to the wonderful world of Rocket Science!

What style of rocket were you thinking of building?  
A traditional J-Tube design or the more recent Batchbox design with its many variants.

There is no good substitute for using heavy full-size firebricks to create your rocket core.
Beyond the core, your choices go up.  
Solid clay brick is very common.
Concrete blocks can be used in certain spots.
55-gallon barrels can be cut length-wise to create a half-barrel bench with no piping.
Stratification chambers (bell) can be built to fit in any location.

Tell us what you have in mind.

Wow! what an overwhelming response! Thank you for all the lovely answers.

I don't know how to use the forum yet, so I'm trying:

There is no good substitute for using heavy full-size firebricks to create your rocket core.
Beyond the core, your choices go up.  
Solid clay brick is very common.
Concrete blocks can be used in certain spots.
55-gallon barrels can be cut length-wise to create a half-barrel bench with no piping.
Stratification chambers (bell) can be built to fit in any location.
Tell us what you have in mind.  

I think Matt Walker disagrees. His designs got me thinking about using these boards. Even though i know it's not CF board.
I think i might want to build em all eventually. I've build several dry stacked J-tubes for now and i think i found a new hobby My heating needs probably suits a 6 inch batch box build from what i've understood. Just so many builds to choose from and so many materials. I like the simplicity of J-tube designs, the complecity of a clean Batch Box build and the ease of mind of just buying a plan. But economy and building time is tight.
Honored to have you answer. I've seen all of your material on stoves

Cristobal Cristo
Post Today 22.33.07     Subject: Calcium silicate board with clay and sand mortal
Regular clay/sand mix will quickly crack and will probably fall off due to shrinkage and different expansion ratios.
Using zirconium coating could help a little against flame erosion, but the boards are so soft (I have some) that they will be quickly destroyed by loading and cleaning.

That's a pity... I've never actually touched the boards. It is my understanding that the same is said about CF board builds. How does the softness compare?

Fox James
Post Today 22.17.59     Subject: Calcium silicate board with clay and sand mortal
You could try painting it with Zircon.

thank you for your response! I'm a YT subscriber of yours You made me fall in love with the idea of J-tubes again again..  not making it easy on me  here

Hi Benjamin, thanks for your support.
You might of watched my zircon videos, Vitcas make a great product and it sets rock hard but it did not stick very well to vermiculite however it might just work on the more porous board you have.
In my case it lasted for a few months before flaking off but on the ceramic fibre boar it is still there!
Generally speaking calcium silicate board deteriorates very quickly in the flame path and is very difficult to fix together!

i had an evening off in the shop and decided to retrofit a L-style rocket of the pieces i had laying around. an old stove, 50 cm of stove pipe, 5 refractory bricks and 50 cm of flexible piping.  I heated the entire shop with this thing by using 30*30cm of 1 inch plywood and heard the rocket and saw the "smokeless" fire. What a night!  I'm hooked for the investment now building something more proper.  

question: does anyone have a clue what this is? insulated brick or just refractory
https://partisalg.dk/produkt/ildfaste-sten-542x492x8cm-pris-kr-200-stk/

That is a refractory tile. apx.  21 x19 x 3 thick
It does not say how high it is rated but probably 2500F +
It would make a fine batchbox roof.

thomas rubino wrote:That is a refractory tile. apx.  21 x19 x 3 thick
It does not say how high it is rated but probably 2500F +
It would make a fine batchbox roof.

Would it be possible to build almost the entire core (except the half brick lifters in the burn tunnel) with the slap?. There's a sale on the slabs now for 40 bucks a piece. :)  I'm thinking of building a 200mm shorty core with a bell and glass top cooker using a scheidel chimney. I alwyays found the whole p-channel apaling anyways.  If the bell is maximum CSA, will it affect draft? I want to build the chimney 1 meter apart from the building because of crazy chimney building regulations. i plan to connect the bell and chimney using ca. 1.5 meter insulated stove pipe with at slight slope. Do i need a bypass for this?
Plans for shorty:
https://donkey32.proboards.com/search/results?captcha_id=captcha_search&what_at_least_one=chimney&who_only_made_by=0&display_as=0&search=Search

Hi Ben;
Yes, you can build with slabs, you will need to cut them in places but that is easy to do with a diamond wheel or a masonry blade.
You will still need some regular-size firebricks and for a Shorty build you will need half a dozen split bricks as well.
An 8" Shorty core is a big one, I just built a 6" Shorty it is plenty big for my home.
Having just built one, I can tell you it is a more complex build than a traditional Batchbox.
The airframe construction for Shorty requires welding and cutting and must be built exactly to specifications.
The door for Shorty is easy and can have a large window.

Your bell needs a bypass, and almost all should have one.
With a 3' horizontal to your outside chimney, you want a steady stream of hot air to get the system moving up and out of your house.
Build your outdoor chimney with a cleanout door you may need to put burning paper in it to start the draft on a cold chimney.
Believe me when I tell you there is nothing worse than a stalled rocket stove venting indoors!

I do not know what a "Sheidel" chimney is.
Only a fire/ heat-rated glass will work anywhere on a rocket.

As far as the P-channel, nobody builds with them anymore.
The floor channel has replaced it.
My quick-change secondary design is easy to make, the 6" riser stub can be plain carbon steel or the RA extreme heat material and swapped out in moments.

Now my two cents worth.
As a first-time builder, a traditional Batchbox is easier to build than a Shorty core, but I just built a Shorty and so can you!
You can study my threads on Shorty construction and airframe construction and build what you feel comfortable building.

he airframe construction for Shorty requires welding and cutting and must be built exactly to specifications.
The door for Shorty is easy and can have a large window.

Is the airframe essential to the build? In the original post by Peter he just stated that the door would need at smaller CSA? Maybe i'm missing something here.

Your bell needs a bypass, and almost all should have one.
With a 3' horizontal to your outside chimney, you want a steady stream of hot air to get the system moving up and out of your house.
Build your outdoor chimney with a cleanout door you may need to put burning paper in it to start the draft on a cold chimney.
Believe me when I tell you there is nothing worse than a stalled rocket stove venting indoors!

the chimney i'm looking at is 3.75 meters tall ø200mm very well insulated chimney . Schiedel is the company name. I'm looking to by this kit used for 400 bucks. What a bargain:
https://www.dba.dk/skorstensroer-helt-nye-skor/id-1113428668/
It's a diy lego like kit, so i can always adjust / make higher if i need more draft.  But because of local regulation i will have to move a window in my roof if i make it 3.76m tall....i know right? So would like to avoid that

As far as the P-channel, nobody builds with them anymore.
The floor channel has replaced it.
My quick-change secondary design is easy to make, the 6" riser stub can be plain carbon steel or the RA extreme heat material and swapped out in moments.

nice! I wasn't aware that this was the case.

Now my two cents worth.
As a first-time builder, a traditional Batchbox is easier to build than a Shorty core, but I just built a Shorty and so can you!
You can study my threads on Shorty construction and airframe construction and build what you feel comfortable building.

I've read the threads. Good read! again: is a steel frame around the whole core essential? I don't understand the purpose of the airframe still.  I would like to make the door Matt walker style (with a fire proof glass off course) without welding because i don't have that skill available in my social circles.. yet!  For support i'm thing to insulate the core (superwool) and add bricks for support in critical areas.

I've added a rough sketch of the room. I'm thinking to make a small height difference in the cooking/ baking area and just leave the bench exposed to the rest of the build with an apropiate CSA. (following the stratification reverse water line of thought). But i would love to be corrected. My reasons for liking shorty is:
refueling posible
low bell makes for higher position of stove - wife aproved and more apropiate for what i want to do with the core. (We're both 1.9m)
batch box advantages

Hi Ben;
Thank you for the nice slice of pie, it is very tasty, and it helps us keep the doors open here at Permies!

Very nice chimney building blocks and at a great price, is it free-standing or braced back to the building?

Unfortunately, yes the airframe is essential to building the Shorty core.
Peter was referring to the door itself being smaller than a door on a traditional Batchbox design, due to the airframe creating a threshold at the front of the box.  
Shorty gets its efficiency from the air being delivered from the front at the top and sides of the firebox.
The original Batchbox design supplied air from the front at the bottom (like a box stove) and then secondary air was supplied at the rear riser port entrance, creating the temperatures required for a complete clean burn.
Without welding equipment and metal fabrication skills having a local shop build the airframe could be expensive.
However, if you had a "new" buddy with those skills it is a fun project, although you will still have to purchase the metal and perhaps the beer they like as well!

The steel frame around the core is not essential but is a good idea.
Without support, even mortared bricks can be accidentally bumped with firewood and dislodged... a teardown of your bell would be required to access the core for repairs...
Imagine that happening mid-winter... your wife would not be a happy camper!
My Shorty core is built with no mortar and uses a Superwool gasket instead.
A frame is required to keep all bricks and gaskets snug when building this way.
My traditional design Batchboxes (I have two) are built dry-stack but with no gaskets and I use angle iron braces at the rear and threaded rods that connect to the front of the stove through the door backing plate to keep them snug.

One factor about Batchboxes that is easy to overlook, is that once warmed up for the winter you only burn them one to three times a day depending on your home and the outside temperature.
So bending down to load the stove is not that bad.

A traditional design Batchbox is a simpler build.
You could have the core at a reasonable height but you would need a brick bell 1' over just your riser, then you can still have the remainder as a bench.

Metal work is required, but the pieces needed are easier to fabricate and the cost would be less.
Even when building Matt's door you will still need a steel backing plate with holes cut in it.

On my website https://dragontechrmh.com/ I offer books on Batchbox core and Batchbox door construction that simplifies things for first-time builders.