I think I've read through all of the RSMH links on permies.com, I've listened to the RSMH podcasts, and I've read "Rocket Mass Heaters" by Ianto Evans. They have provided great information to build a permanent RSMH. But when (not if), we have the expected economic collapse, my plan is to take my family and all my preparedness stuff and head out to a friend's ~80 acres about 130 miles away. The only thing there right now is an open barn, so we'll be staying in a 16' x 32' canvas wall tent. We may need to be in it over winter, so I'd like my family to be warm enough.
Consequently, I want to build a temporary RSMH in the tent that can be dismantled easily and be moved to a more permanent location as circumstances allow. The RSMH will be in the tent on the left about five feet from the door on the left side of the tent and four feet away from the wall on the back side. The 6" vent will be on the ground, come 2-3 feet to the center of the tent then go down the middle of the tent and out of the tent on the right, about 28-29' total length. It will have about six inches of various sizes of rock covering the vent pipe all around it all the way out of the tent, and held in place by chicken wire that is staked to the ground on either side of the rock. I know Paul used a wood box to hold the pebbles in place in his portable rocket mass heater, but I thought the use of chicken wire to hold larger rocks in place would allow better transfer of heat to tent occupants and take up less room.
I have questions about some things I'm not sure of and would appreciate some direction from the RSMH gurus:
1) Since I will need to be able to move everything easily, I don't want to use mortar on the feed tube, burn tunnel, and heat riser. What can I do to prevent smoke from leaking out between the bricks of the feed tube and burn tunnel? Can I wrap them in rock wool and cover that with chicken wire staked to the ground, or can I place rocks over the rock wool to hold it in place? Or can I use mortar and still be able to break the bricks apart fairly easily without breaking the bricks?
2) My heat riser needs insulation, but a perlite/clay mixture will be more permanent and make it too difficult to take apart. On page 94 of Rocket Mass Heaters, 3rd edition, it shows a refractory wool blanket as the insulation in a wire mesh cage. Rock Wool would do the same thing as I understand it. But doesn't the fire get so hot that it would destroy the wire mesh fairly quickly? If so, is there any way to hold the rock wool in place without it being permanent? If not, how can I insulate the heat riser well enough without it being permanent?
3) Will I have to use cob to seal the manifold so there are no leaks, or is there another way that will allow the system to be disassembled easily?
4) Since the vent will be on the ground, does the exhaust end of my vent pipe need to go vertical at all after exiting the tent or can it stay horizontal if it goes out of the tent far enough?
5) If it does need to go vertical again, how high should it go?
6) If it can stay horizontal, how far is far enough out of the tent?
7) Should I place some rocks under the whole length of the vent pipe to absorb heat also, instead of just on the sides and on top of it?
Is a standard vent cap a good way to block the wind from pushing air back through the system, or is there a better way?
1) Use fireclay for mortar in your temporary build; it will seal the cracks, but come apart easily and brush or wash off of the firebricks. You want a thin slip so the joints are as thin as possible.
2) Chicken wire to hold the rock wool in place around the riser will be fine. The outside of the riser will not get hot enough to damage it.
3) Cob will be the easiest and best way to seal the manifold and around the barrel. It will break away fairly easily and be completely reuseable.
4, 5, 6) Unless you have a 100% reliable prevailing wind, you will need to have a vertical chimney that rises above the top of your tent by 2 feet or more. It will work best if the vertical chimney is inside the tent, exiting at the top. It will be cool enough that you can make a fairly simple collar to shed water.
7) Yes, gravel and rocks under the duct as well as sides and top will be good to keep from trying to heat the ground.
Yes, a vent cap will be good to keep water from falling down as well as reduce gusts backdrafting.
Location: Upstate NY, zone 5
posted 5 years ago
If you make a perlite/clay heat riser with an outer form of sheetmetal (ducting), it will be durable enough to move from your temporary build to a permanent one. I have one that has survived several car trips and a couple of setups so far, and is still in fine shape.
You should build one at you bug out spot now. Check out Matt Walkers stuff, he has a great out door bench system.
Size it as a sleeping platform, include cooking utility , show up and pitch the tent right over it.
You may want another in case your bug out plans change, but the matirials are so cheap, I cant see not making one at your planned hide out.