rocket mass stove with ONLY cob?

[philippeelskens]

Hi,
I'm new to this forum, so this question might have been asked and answered already...
Can I build a rocket mass stove by using ONLY cob, so no metal components...? I would just sculpt it, so with just my hands as molds...
Thanks for the answers!

[pinhead]

You can, though without insulation it isn't a "proper" RMH and won't perform nearly as well.

BUT!

It's best to build without metal components, anyway; metal is doomed inside the flame path (burn tunnel and heat riser).

[philippeelskens]

Thanks for the answer!
Ok, I've been doing some more research, and as you said, I do need insulation! What I am wondering now is, what material do I use best for the heat riser if metal is no good? The insulation I would use is perlite, which is not firm enough to form the heat riser, am I correct? I also assume that making the heat riser out of cob, and insulating that with perlite would not be ideal... since I would use up to much unnecessary space between the heat riser and the insulation... Just an assumption though, no idea if this is correct...?

[patamos]

Form heat riser with perlite clay combo. or vermiculite clay horse manure combo. Use a plastic pipe as the inner form, then slide it out when mix is wet. You can smear the inner surface with clay and fine sand to help hold things together but may not be necessary.

Lots of info on these threads. Donkey has written a fair bit about all locally harvested materials and techniques

enjoy

[esbjornaneer]

Happy to have found Donkey's cob post.
Thank you Pat