Rocket stove under tipi budget build

Hi guys and gals

Long time lurker and YouTube podcast listener!

For reasons we shall not go into in this post I'm now living in a tipi Megahorn 4P by lux with a stove Jack....  roughly 4m x 3m got a cheap multifuel stove and its burning through wood like its money.... well when you pay for your wood I guess it is! My budget is growing tighter with every bag of wood haha

I have been given the opportunity to build a raised floor for the tipi as the ground here is like bog Peat, but its got to be removable with minimal work, so no concrete baee and minimal cob

So I came up with an idea!

If I where to build the raised deck with pallets I where to form a side skirt around the outside of it, and then run ducting in a ladder format in one corner out the other and filled in all the gaps with pea gravel/shingle (more questions to come on this) giving it a fiber board topping and the a thick tarp for water resistance, would this work?

This will be my first RMH

Plan on using 6 inch galv duct, vinegar to remove  nasties
General builders pea gravel 6mm-20mm
I have got what I would assume is a 35 gal drum as its smaller than a 55
I was going to make my own castable refractory core following the Walker stove methods
And I have got ceramic fiber blanket to line the riser
Hoping the fire box will either be flush with the floor or very close s space is a premium in here!


Looking forward to your wisdom and experience

I was going to ask on the castable walker core, do they vibrate the concrete to prevent cracks?

Ted Butrell wrote:I was going to ask on the castable walker core, do they vibrate the concrete to prevent cracks?

From memory I think he does suggest it, recip saw held against the mould does the trick!

Toby Ornot wrote:

Ted Butrell wrote:I was going to ask on the castable walker core, do they vibrate the concrete to prevent cracks?

From memory I think he does suggest it, recip saw held against the mould does the trick!

I think you can also use a drill against the mould.

An oscillating or vibrating sander also works well.

Glenn Herbert wrote:An oscillating or vibrating sander also works well.

Had one fitted to the hopper on my sanblast cabinet worked a treat !

Still nothing on the RMH? Have I got it all that right that none can foresee and issues or has any experience with the way I plan to do it?

Or am I being impatient lol, its chilly and windy on the seaside, just had a whopper of a storm!

What you describe is a version of pebble bed RMH; look into the one built at Wheaton Labs for information on theirs. The big thing I think will be to isolate the pebbles bed from the wet ground. That will quickly steal heat from the mass. Maybe a layer of gravel sloped to drain away from the center, then a tarp for water/vapor resistance, then the pebble bed with embedded ducting. I think it would be important to seal the ducts against flue gas leaks, and have an airtight topping on the bed under the finish flooring.

The ladder style ducting may be problematic, as I understand that any layout with multiple flow paths is likely to have uneven flow, with one path taking more flow than others. If you are okay with possible uneven floor heating, that may not be a big problem. I would definitely arrange it so the flow enters at one end of the ladder and exits at the other end, to make the path lengths and configurations as close to identical as possible.

Sinking the combustion core into the floor will help with flow, as the hot gases will not have to go down as far to get into the floor bed. You want a chimney as well insulated as possible, ideally rising up inside the heated space, to improve the chances of easy starting and good draft.

Hi Glen

Thanks for the reply!

Ok understood the floor is a massive cold heatsink, my plan was to build the entire thing onto of pallets so will be a good 4 inches of free air space between the wet floor and the top of the pallets ( I guess for simplicity sake I should call this the decking)

Would this negate the need for the drainage underneath?

My plan then was to have some sort of insulative board onto of the decking and around the sides of the skirt to form a 10"  deep insulated tub

Insulation would be like this (______________)  then with the bottom layer of gravel, flue sealed with high temp aluminium tape and fire box installed and then the top layer of gravel, followed by  fiber board insulation the kind they use for undefloorheating on this side of the pond

I have use of a smoke generator for testing for air leaks as well

Then to find an airtight thick tarp, maybe like an emergency roof sheet polythene I think they are thick enough to line a stony hole and turn into a pond! That should be a good second safeguard against fumes should they escape

What format would you suggest for the ducting?  I thought maybe a spiral inside to out?

I'm going to look on Amazon for the RMH book now!

Running the flue through the inside is not an issue. Already have a stove Jack fitted

Would a good fiberglass exhauat wrap be good for the  chimney as its probably not going to be that hot at the end?

Will get photos as I go as this might be useful somewhere  else?

Looking into the specific heat capacity of different gravel and it's all quite mind boggling! However I did score 5 10L stainless fire extinguishers to fill with water as a mass (don't worry I'm taking the valves out so they are open to atmosphere;)  AND a pallet of broken soapstone slabs for £25

So my mass is looking promising!!

Thanks again hope I can be of some help on here somewhere!