Ceramic wool for heat riser questions

I just recently saw a rocket stove heater using a ceramic blanket for the heat riser. I really wanna try this now and see how it works. I intend to line an 8 inch stove pipe with the ceramic wool and then wire the stove in a few spots with stainless steel wire just as added insurance so it doesnt pop open. I want a 6 inch system and doing the math I would need an 18 inch heat riser. I also noticed the stove pipe and the ceramic blanket are both 24". Would the extra 6 inches in riser length effect the stove negatively? I hear its nasty stuff to work with so I dont wanna mess with it any more then necessary. Anyone have a favorite video on assembling the burn chamber out of firebrick? Thank you for your time.

Hi Jason, are you building a J style configuration? if so, using the 1,2,4  formula the heat riser for a 6” system needs to be 24” long making a total hight of 32” from the burn tunnel base.
If you can make it longer that is good and maybe very slightly shorter will suffice but 24” is the recommended.
The ceramic fibre is easy to use and I don’t think there is any proven evidence of any extreme  danger but it would be sensible to use a mask while working with it.

Hi Jason;
Yup, ceramic blanket is the newest thing to build risers from. However 18" is very short for a riser.
When it comes to risers , taller is better.
My 8" risers run from 48"-54" tall.
As far as it being nasty to work with, if you buy Morgan Super wool ceramic blanket, it is completely safe, to handle or breathe.
If you buy the cheap ceramic blanket then it is extremely hazardous to  breathe and horribly itchy to handle.
A full tyvec suit and a respirator are highly recommended if you choose to use the cheaper product.


Now about cores.   Plenty of posts  in the rocket mass heater forum have photo's and descriptions on how to build a core.
I will cross post for you to that forum as well.
Do you have a copy of the RMH builders guide? Readily available on Amazon. It will tell you exactly how to lay out a core.
When building a rocket the core dimensions need to be followed exactly or your rocket will fizzle on the launch pad.
Are you aware of ceramic fiber boards to build a core ? They are what the innovators use these days.
Otherwise you will want split fire brick and insulated or heavy fire brick to build a core.
A 50# sack of Lincoln fire clay is handy to have as well.

Welcome to the wonderful world of rocket science!
Our cheerful and knowledgeable staff of rocket scientists are eagerly awaiting your questions.

Jason,   Kirk "Donkey" Mobert has put out a video series on an 8" RMH build that could be useful to you: RMH build video

Note: Its an 8" system he's building but it gives you an idea of how he goes about building it with brick.

The evidence reported here:
http://donkey32.proboards.com/thread/1845/scandal
says an 18" riser would be fine, and 24" just fine as well.
It presumed a full height chimney,  not a short hidden one.

Hi William, do you think that applies to a standard j tube design, it seem that thread applies to batch box designs and that has since developed  onto the shoebox design?
It would be fantastic if one could build a standard J tube with a short riser as it would then all fit inside one drums ?
I have done my own experiments, although only  on a basic level, and found performance (ie barrel top temp) dropped considerably with shorter risers .

Fox,  I just don't know.
J tubes require more tending and have less power,  so I hardly ever think about building them.
I'm not even sure if anyone has built a J tube with a ceramic wool riser.

In the link that William provided, the fourth post by the user Shilo said: "after a lot of work and dozens of tests, the simple bottom line is you can do a batch box with just 40-50cm riser."

William Bronson said: "I'm not even sure if anyone has built a J tube with a ceramic wool riser."
Our forum leader Thomas Rubino has built one and he describes it here: Baby-Dragon-Roars

I also used one in my own 6”  J tube.
I did some experimentation and settled on a 24” riser with 2” of fibre inside a 10” stainless tube.

Plenty of healthy new questions for sure. I ordered some fiber blanket last night. 1"x48"x60". Definitely going with a higher heat riser. I plan on letting the barrel height dictate the height of my riser. I'm reading that 11-1200 degrees is hot enough to consume all the smoke and gases. Not looking for 2000+ degrees. I'd like to shoot for 12-1500 degrees. The cost of the fire brick has me slowed right now. And yes thinking a J tube design that can be modified to burn sticks of wood or pellets. Would the fiber board be suitable for a burn chamber? Not seeing any ceramic fiberboard locally. Should I try for a rounded burn tunnel or is brick square straight to a tube fine? I can already see I'll be building a few of these.

Hi Jason;
Excellent choice on ordering the CF blanket. You won't be sorry.
On a J tube rocket, in the lower portion of the riser, temperatures of 1200-1500 F are very obtainable.

Not recommended to build a rounded J tube, there is no performance gain.
Straight and square with brick is good. Size must be exact, and maintained.
Ceramic fiber board is most easily acquired from sellers on Ebay.
Search for a Masonry supply store. There you will find firebrick , full size and split (1/2) size.  .
You will be wanting Fireclay, #50 sacks run from $7- 20. The masonry supply should carry this as well.
Plain old clay bricks will be needed ,used or new.

Last, I suggest again finding a copy of the RMH builders guide!  

The riser I'm hoping will be 6 inches. 1 inch lining of wool inside an 8 inch pipe. So the burn chamber and tunnel need to be 6 inches as well right? I'll look into the book. Thank you for your time. I really appreciate it.

Jason;  Build size on a 6" J tube is actually 5.5" x 5.5" square.    
8" pipe with 1" cf blanket is perfect as your riser.

There are different styles of rmh , J tube or batch box.  
A standard piped mass or a brick bell.
You can read all about them at the rmh forum.

What did you have in mind for your rocket?

First one I'm building is more for my dad. He wants to save money on wood and add an emergency heat source. The thing I'll need to discuss with him is the mass he intends on using. He has plenty of red brick for a stove so thinking brick bell chamber idea. The one thing we are mulling over is heat storage ideas. I do have a nice length of 3/4" copper pipe for water. The garage is the only suitable place for it since the basement floors. so the next project is how to get the heat from the stove into the house.