I've been studying rocket heaters/stoves for about 8 months now, and have built 8 using different methods. I first started with a 4 in square tube k awsome stove, but alot of what I've learned is not right, I've learned making a slushy mix of fire clay and water then dipping fiberglass in it is better than messing with the perlite concrete mix, j type isn't the best , no nd for second air, for small homes going below 4 in is just fine,
