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Materials Questions  RSS feed

 
Posts: 52
Location: Shenandoah Valley
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Hello all,

I'm excited to almost begin my stove construction!

I have a few questions:

1. Has anyone ever used "cement board"? It's fire proof drywall like material. I plan to use it between the wood floor and the combustion unit, and possibly on the ceiling above the combustion unit. Maybe also in the headers in the pictures attached in the subsequent post.

2. I was able to get some 3" rock wool insulation. Should I strip it down to 1"? Also, how should I hold it together? Also see photo in subsequent post.

Thanks!

Adam
image.jpg
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Cement Board
 
Adam Jonathan
Posts: 52
Location: Shenandoah Valley
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Rock wool and location of bench photos
image.jpg
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Rock Wool (3" thick)
image.jpg
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Location of thermal battery
 
pollinator
Posts: 4154
Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''
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Adam Jonathan : Cement board has a very useful place in your construction, First I want to send you off to look at some eye candy, a series of 19 short video clips,
approximately 3/8ths of a professionally shot DVD showing an upscale build by ernie and erica Wisner our Rocket and Wood Stoves moderators here at Permies.com

During the prep work over the existing wood floor the DVD shows them laying down bricks to create air conduction channels,and then using large Concrete pavers
over the top of that, your Cement board is equally able to bridge the gaps created, but will not substitute for the additional mass needed to handle the heat energy
load radiating down through the rocket mass heaters RMHs Burner Base from the Combustion Core ( the Burn Tunnel and bottom of the Heat Riser ). If a picture is
worth a 1000 words this free look at the Heart of the build is priceless !

Click on the link below and find and click on the playlist marked rocket mass heater Scenes, relax, and enjoy !

http://www.youtube.com/user/villagevideoorg/playlists

The 3'' rock wool insulation will work well for you with a thickness of 1.5 inches or more and can ether be held in place with Chicken fencing wire or Hardware cloth,
a frend uses romex staples the kind used to secure electrical wire to 2 X 4s to meet code and catches both ends of the wrapping material, by bending the staple legs
in towards the center creating a ''heavy-duty paperclip'' shape .

The goal here is not to see how much you can use, but rather to securely but loosely hold the batting in shape and leave about 2'' of airspace between the outside of
the batting and the inside of your metal drum !

You have definitely created a High ceiling condition and on that basis alone I will recommend a 8'' rocket system, we will need ether sketches or several more pictures
to assist us to locate a good location for your RMH, Remember we are retro-fitting a special type of wood space heater into an existing structure and some trade offs
will probably need to be made !

I expect that the original floor joists in good condition will be more than adequate to support the floor loading of 2 -2.5 tons spread over the RMHs Foot print, this would
be similar loading to a waterbed !

So that when you come here for help from your Fellow Members and Rocketeers, we need to be using the same words to describe the RMHs sizes, shapes, materials,
and the orientation of its parts to themselves and the whole. If you have not already done so please goto Rocketstoves.com to Download your PDF Copy of the
3rd Edition of Rocket Mass Heaters. This is 'The Book', with well over 100,000 RMHs built World Wide, most have followed this book closely, and 95% Of the
First Builds (that worked ) were made from 'The Book', Rocket Mass Heaters will save you time, money and Frustration ink your build, and more than pay for
itself due to your late start !

For the Good of the Craft! Big AL !
 
Adam Jonathan
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Location: Shenandoah Valley
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Al, thanks! I've watched those videos, read the book and watched the 4-part DVD.

Do you think I should add a layer of perlite & clay slip on top of the cement board under the combustion unit?
 
allen lumley
pollinator
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Adam : Go back and count the layers including the concrete pavers, I know this seems like a lot but remember the operating temperature in the Burn Tunnel,
and the Heat Riser is 2,000 degreesF, there is actually a question about the effectiveness of the Aluminum foil at that location, but you need a non flammable
sheeting to contain the insulation you will need for safety ! In this location only more is actually more !

For the Good of the Craft, Think like Fire! Flow like a gas! Don't be the Marshmallow! Your comments/ questions are Solicited and Welcome Big AL
 
gardener
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Location: Southern alps, on the French side of the french /italian border 5000ft high Southern alpine climate.
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Adam Jonathan wrote:Al, thanks! I've watched those videos, read the book and watched the 4-part DVD.

Do you think I should add a layer of perlite & clay slip on top of the cement board under the combustion unit?



You need far more than that.

I would say a good layer of air entrained concrete blocks. 8 inches i'd say! Or the same in clay perlite.
 
Adam Jonathan
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Based off of the research I did, the cement board and perlite (2") would be sufficient. Can anyone else either confirm or correct the previous comment. Just want to make sure I'm on the right track.

Cheers,

Adam
 
Satamax Antone
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Adam, you have a wood floor under there, do you understand "better safe than sorry"?
 
Adam Jonathan
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So, my revised plan is to put the following layers on top of the wood floors:

1. Cinder block that was once in a chimney (about 6" thick);

2. 1/2" Cement board (in picture above);

3. 2" clay-perlite mixture;

4. Fire brick base layer for combustion unit.

Any comments?
 
allen lumley
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Adam : We are getting closer, go back to the village video's film clips review the number of layers as shown in the Video clips #13 and #17, merely increasing the depth
of your air channels will not substitute for Increased insulation/mass !

To use an example from another part of the stove, if you had two RMHs completely Identical, except for the size of the Barrels over top of Your Heat Risers, they both
have to radiate off the same amount of Heat Energy for the heat pump to work !

Counter- intuitively, the smaller barrel with its smaller surface area to volume will radiate off that heat at a HIGHER Temperature than the larger 55 gal drum!

This is also why when the family 4-yr-old is tired, and wants up in your lap, they are such a great cuddle, with their lower surface area to mass -in order to maintain
98.6ºF they have to radiate off their heat load at a noticeably higher Temp !

The direct effect of the insulation is reducing the loss of heat needed at Your Core to raise the Combustion Temperatures and Efficiencies !

We need to look at the RMHs Burner base with its air channels separately from the RMHs Body! Also we have to understand the affect that thermal conductivity has on
Final surface temperatures !

In the Burner body we want mass everywhere. The more mass we have1) The more surface area we have, and ultimately 2)more control over the Surface Temperature
that that mass radiates its heat off at !

Think of it like throwing the 'Proverbial Stone in the Water' and looking at the ripples. as the ripples spread out they become wider and shallower.

This is very close to what happens when High Temperature heat energy leaves the Combustion core area of the RMH Burner body, and what happens within the Large
Thermal Mass Storage battery. High temperature at the cores and safer surface temperatures at the surface of our monolithic structure !

If necessary we will simply add more bricks at your burner base even if we have to make them like adobe, In everything we do we must strive to be safe First !

I think I have fully answerd your question from yesterday at 6 :16 PM For the Good of the Craft ! Big AL

 
Adam Jonathan
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allen lumley wrote:If necessary we will simply add more bricks at your burner base even if we have to make them like adobe, In everything we do we must strive to be safe First !



Thanks Al!

To clarify, I would use the following items on top of the wood floor:

1. cinderblock described above;
2. Cement board described above;
3. perlite-clay mixture;
4. Layer of brick below base layer of fire brick; and
5. First layer of fire brick for the burn chamber.

Does #4 need to be fire brick, or can traditional brick suffice in this case?

Cheers,
 
gardener
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Substituting more perlite-clay mix for the layer of brick just below your burner floor brick would substantially increase the insulation while also reducing the mass to be heated from the combustion zone. You would want to make sure the top of the perlite-clay was dead level and smooth for easiest laying of the firebrick floor.
 
allen lumley
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Adam Jonathan wrote:

allen lumley wrote:If necessary we will simply add more bricks at your burner base even if we have to make them like adobe, In everything we do we must strive to be safe First !



Thanks Al!

To clarify, I would use the following items on top of the wood floor:

1. cinderblock described above;
2. Cement board described above;
3. perlite-clay mixture;
4. Layer of brick below base layer of fire brick; and
5. First layer of fire brick for the burn chamber.

Does #4 need to be fire brick, or can traditional brick suffice in this case?

Cheers,



This is a hard concept to wrap your head around, while there are places to apply the insulation on the outside of a structure, this is not one of those times,

By placing a well packed clay slip perlite layer directly below the Fire brick floor of your burn tunnel you accomplish TWO very important things! 1) You raise
the Final combustion temperature of the Burn Tunnel, While increasing the speed at which it happens,* and 2) It retards the transfer of heat towards the
surface structure which in this case is the under side of the RMHs Burner Base, Because of the flammability of the floor that you are building on, we need
further protection in that area !

While we can not expect a Perlite and Clay slip tower to be a stable mass no matter how well we buttress it, we can halve multiple layers of 2'' Perlite and
Clay Slip in place for protection SO-

1) Cinder blocks
2a) Cement board hardy backer board !
3) packed perlite and clay slip with brick borders
2b)Cement board - - - -
4)Layer of clean brick dressed with clay slip to promote a true level surface
5)packed perlite and clay slips/ brick borders
6)Floor layer of Fire brick surrounded with Perlite and clay slip then encased in Cob, followed with Structural cob !

This is still very close to 8'' of total material, If necessary we can make the # 4 layer out of structural cob or cob and sawdust !
 
Adam Jonathan
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Could a layer of rock wool insulation fill in for number 3?
 
Adam Jonathan
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Progress photos!
image.jpg
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Cinder block
 
allen lumley
pollinator
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Adam : No ! The rock wool can take the heat just fine but will loose most of its insulate ability if it is compressed, it is the air trapped in theRock Wool that gives it
the ability to BE Insulative ! Some how the Web at an earlier e-mail of at least thousand words !

Start trying to locate urbanite or old brick, slate ,shale, any rock with cleavable lines, you may find an old Highway rock cut hillside stacked with split rock with 2
sides nearly parallel, are there no more Old abandoned tobacco drying kilns with firebrick the size of dinner pails ! often when they got tore down they just got
dumped into or pushed into the closest gully !

95% of the Material in any rocket mass heater RMH canbe scrounged, look harder ! Big AL
 
Adam Jonathan
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Cement board with brick border, clay perlite inside border, and cement border on top of sandwich.
image.jpg
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Adam Jonathan
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Dry run first layer of brick.
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[Thumbnail for image.jpg]
 
Adam Jonathan
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Another few questions:

I have the border built for the last layer of clay-perlite (see attached).

1. Do I put fire brick under the center of the tall part of the J?

2. How long does clay slip take to dry? We're having cold weather with no heating yet.
image.jpg
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allen lumley
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Adam : in the entire rest of the build of the Combustion Core, the feed tube, the Burn Tunnel and the Heat Riser, the only part where I would consider using red brick
and not fire brick is at the near side of the Feed tube, that being the near side as you stand in front of it and feed it!

From the point that you make up your bed of clay slip/'perlite the job of the clay slip is to not to hold the bricks to gather but to keep them apart !this helps to keep things
plumb and level. dry stack your bricks several times and take pictures to prove to your self you are doing it as well as you Can !

The inside of the combustion zone should be smooth as possible, the bricks set in order with the smoothest sides in towards the fire, if you have to make the choice in the
burn tunnel Err on the side of taller, not wider ! Keep going, the fire will dry the Cob and the Clay slip !

If you do not know what a running bond is> google search ''running bond pictures'' . Everything now is running bond and plumb and level ! Big AL1
 
Adam Jonathan
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Thanks Al! Some day I need to buy you a beer!
 
Brace yourself while corporate america tries to sell us its things. Some day they will chill and use tiny ads.
What would you cook first in a rocket oven?
https://permies.com/t/89866/cook-rocket-oven
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