type M masonry mortar

Hi all, thank you for all the info and helpful posts. I just test fired my 8" system last evening and it works GREAT. Now I just have to add the mass.

My question, I have on hand 4 bags of Type M mortar, can I use it perhaps on the bottom layer of the bench to mortar in rocks, or any part of the bench out past about 8 feet from the rocket?

Allen I apologize for asking this on the other thread

I just installed 30 feet of exhaust duct work and lit her up. It's been burning about 15 minutes and the ducts are too hot to leave my hand on, including the 5 foot vertical up to and into the old inside house chimney. Will the mass cool off that hot exhaust?

I just posted over on donkeys board so here is that update:

Just a note on how I used the M strength mortar. I mixed 2 shovels of fire clay, 12 to 14 shovels of sand depending on how the mix looked and 1 PINT of M strength mortar. That little bit of M firmed up the mix and it would dry out on the surface over night, it did away with the sandy, easily eroded, texture of the original mix.

I've been running the rocket hard, (14 to 18 hours per day for the last 6 days) to dry every thing out, there is a little cracking around the barrel, manifold and feed tube where I used just fire clay and sand but not a single crack in the 16 foot field stone bench. The rocks get to hot to hold my hand on, on the first 16 foot run and about 1/3 of the way back on the return run to the open 5 foot duct running up and into the vertical chimney.

I can put my hand on that 5 foot piece of open duct but am not able to leave it on there very long.

I am heating a 1400 sq. foot basement and the gas furnace for the whole house is running about 1/3 the time it normally runs in these below zero F temperatures. I am going to install a 24" by 24" floor grate about 3' off to the side of the barrel and pull all that excess barrel heat upstairs with an existing large ceiling fan turned on in reverse, I am quite sure that the gas furnace won't be needed at all. I've all ready turned it down from it's normal 68F setting to 63F and it's still very comfy upstairs because of the heated floor.

I would say this heater is greatly exceeding my expectations. At first it would burn back up the feed tube and had a lazy burn but after raising the barrel 2.5" and tweaking the manifold and feed tube, stand back.

Even though the fire still creeps up the feed tube, all the gases and smoke are sucked back into the burn tunnel, I can have fuel, (softwood, spruce), sticking 10" above the feed tube without any problems.

I very much want to thank all of you for all the info I have gotten through this board and the Premies board.

Your generous sharing of knowledge is greatly appreciated.

Willie from Lily....the goofy one