insulate or thermal mass around fire box?

I have been reading for a couple weeks and looking at plans online and there seems to be LOTS of different methods to make a rocket stove, especially if they are USED for different purposes. So I wanted to clarify my understanding before I start building the three rocket stoves I have in my near future.

First stove I want to make is a portable cook stove. Can in a Can, L shaped inner chamber. I have seen MANY different construction methods and wondered which is better and why?
Loose rock : https://hemetsunshine.wordpress.com/2012/04/08/inside-a-tin-can-rocket-stove/
Sand : https://hemetsunshine.wordpress.com/2012/04/08/inside-a-tin-can-rocket-stove/
Fiberglass : http://www.thebugoutbagguide.com/category/urban-wilderness-survival/page/3/ as shown in step 5 of the construction
or something else ??

Second stove I want will be for semi-permanant cooking on a deck or patio simular to https://www.pinterest.com/pin/178877416424224159/ but maybe separate wood feed and air inlet. Again I don't know which insulation to use.

Third will be last build and will be the most ambitious. Much larger Mass Heater and I know I would want to have a LOT of thermal mass warm up ... Hex shaped cord wall building with a central rocket stove with a small under ground "exhaust" tunnel to the bench that goes all the way around the hex interior and up above the roof line at the end.. plans will begin after I figure out what works best for the first two and play a bit with stacked fire bricks and such.

I should build the first one this weekend ..second will be after the end of the month when I get some cash.
dmac257

For a L or J tube rocket, you need insulation for best results.

So, sand, when well dried acts as insulation, but also as a thermal mass. Third world techniques use cob, with straw manure, wood dust or shavings, ashes etc. You can use rockwool too, not glasswool. Kaowool, superwool. Insulating firebricks. Air entrained concrete (siporex), perlite, vermiculite, lava rocks, expanded clay balls.


And for your second one, separating the wood feed from the air inlet has been done, but i've never heard anybody having good results with it.

It's early yet for details of your third system, but you need to keep in mind that there is a limit to the length of horizontal flue you can run through the mass benches. For an 8" system, that is about 50', minus 5' for every 90 degree bend. You will not have enough length to run even halfway around any but the smallest of houses. I would suggest identifying the main gathering space and put your bench there, while keeping it open to the rest of the space for radiant and convective heat flow. The RMH generally wants to be near the center of the whole house, unless there is a zone that benefits from staying cooler.

Glenn Herbert wrote:It's early yet for details of your third system, but you need to keep in mind that there is a limit to the length of horizontal flue you can run through the mass benches. For an 8" system, that is about 50', minus 5' for every 90 degree bend. You will not have enough length to run even halfway around any but the smallest of houses. I would suggest identifying the main gathering space and put your bench there, while keeping it open to the rest of the space for radiant and convective heat flow. The RMH generally wants to be near the center of the whole house, unless there is a zone that benefits from staying cooler.

I attempted to post a reply to this yesterday but for some reason it didn't show up .. initial plan was central RMH with a bench around the entire building but your comment about the limit to length has me re-thinking the "plan". this will be a small 2-4 person weekend hunting cabin. Cord construction, Hex building, 8 feet per side, with entrance on one side. Now thinking to place the RMH on opposite wall from the door and SPLIT the flue under the bell through TWO benches on either side of the Hex. If i keep the total CSA of both benches' flue same as the combined riser it should work right? something like this:

and i had another question .. you said "length of horizontal flue" .. what qualifies as horizontal .. I was thinking if the first section from the bell is under the bench and the two 90 degree elbows also raise the second half of the flue about 10 inches above the level of the first it might help with draft .. again still brainstorming till i play with smaller versions
dmac257

Donald MacRae : Small hunting cabin you only should need a 6'' system to heat the whole place that would give you about 30 Vertical feet and You
are using 6 elbows per each 1/2 -

This has been tried and Always always always one of the two horizontal chimneys will dominate and the other chimney will not ' Draw '

New would-be Rocketeers need to view the Rocket mass heater for what it is , not what it isn't - a Regular Wood stove ! The idea of the Thermal mass

is to be located in the heart of your structure as close to your elbow as possible, this way tending the Rocket is an automatic function prompted by
visual and Audible clues, with no-more thought given to Tending it than you would take in adjusting a pair of reading glasses on your nose !

With a Central location and feeding for 1-2 hours to receive 20 -40 hours of heat is exactly like having a well endowed bank account that you make small
regular deposits of Short fine split wood and receive Automatic disbursements of Heat, soothing bone warning heat sit on it, put your feed up on it, or curl
up on it its always there, want a warm up on your coffee its right there on top of your barrel that can be used for cooking too !

Here is a link to a RMH that is completely contained in the footprint of the Rocket Burner base with Barrel and the cob Thermal mass the size of a small
daybed / lounge and final vertical chimney your RHM needs will take about 3/4 of that space ! Link below :



https://youtu.be/Vddj8dOvtCg


For the Craft ! big AL

"WARNING !" Please be advised "KAOWOOL" is as dangerous as asbestos. The tiny ceramic strands that make up the wool have little barbs on them that make them impossible for your body to expel. This was told to me by an insulator supervisor that worked in the power plant where I worked. He died a few years later from his exposure to asbestos during his early years in the trade.