New RMH: Dry out needed to reach full temps?

Hi Everyone,

I made a new RMH this past weekend. Below are my specs followed by my questions:

---I should have all the dimensions correct for the core (H1, H1.5, H3 according to the Wisners).
---The core and riser are made of new, clean firebrick with a thinset of clayslip as recommended.
---5.25 X 5.25 dimensions for the square inches in the core's channel.
---6" duct system, 20' long in mineral soil bed for my attached greenhouse.
---Exhaust vents out the side of the greenhouse.
---Starts up no problem and exhaust moves through the system and ducts wonderfully. However...

The RMH does not heat up like I had hoped. It just gets warm, not hot, and does not convert fully to steam and CO2.

One possible problem: The distance between the riser and the top of the barrel is 2-3", not the recommended .25 of the 6" system which would be 1.5 inches.

QUESTION: How critical is the distance between the riser and the barrel an issue as per the riser getting hot enough to burn the smoke?

The riser is coated in a clayslip-perlite mixture with further insulation of 2 inches of perlite encased in sheet metal.

QUESTION: Does a new, wet RMH need a curing process before it becomes an "adult dragon"?

I've fired up this thing only once thus far. Just one time, so I'm thinking of trying it again before I dismantle it and start all over.

Many thanks to all who might respond to these questions.

Still a novice here, so I'm guessing a bit on this - water in the system (in the mortar, in the cob, wherever it might be) will use up loads of energy in the drying out process. I would expect that until the water has been pushed out, the system is not going to get to its full potential.

I know with my still work in progress RMH, I've been waiting for my perlite and clay heat riser to dry quite a bit before I fire it up, as I don't want steam generated inside the column to blow it apart, as can happen with clay pots in a kiln.

Hi Lowell, congrats on getting it built. I had the same problem with moisture and decided to just give it time. As I was waiting for the bench to dry out I was continually feeding the dragon. It took about a week and a half to dry out the bench and now my core temp ( thermometer stuck into the adobe about 4 ") is consistantly at 115 degrees. One thing that helped was covering the bench in furniture blankets when it was close to being dry. I still didn't have any heat from the bench. After covering, the temps just shot up.Now I can't get the cat off of the thing.

Lowell: Give your stove time to dry out and soon you will be more than happy with it ! I LOVE mine !!! more important , my wife who was VERY skeptical of this project (in her greenhouse ) is also in love with it ! Mass temps in the morning are usually about 80-90 degrees and while running they rise to the 100-130 range ! The air temps in the greenhouse on a 25 degree nite are staying 15-20 degrees warmer than outside after the fire being out for 12 plus hours ! Expect condensation drips, lots of steam out the chimney , but once things start to dry out you will notice that your chimney is only emiting heat shimmers and small amounts of steam yet inside your dragon is roaring and its tee shirt temps in your greenhouse!

I was just about to post a new thread asking about this exact thing - still in the process of building the mass bench for Jerry, our 8" RMH in the sunroom/greenhouse. Jerry's rockety like all get-out, the exhaust has little to no wood smoke odor, and the barrel-top temps are high enough to light paper on fire after about 45 seconds if you're not careful (don't ask how I know this), but the first 5 feet of bench I completed a few days ago are still wet and cool to the touch. I've fed this thing what I figure would be a month or two worth of fuel in the last 3 days trying to get it to dry out, so I'm starting to really get impatient! Are there any tips on getting it to dry out faster? Would covering it with a blanket help on that end or just result in a wet blanket?

Any help would be greatly appreciated - know I shouldn't be but I'm starting to get discouraged

Tristan, don't get discouraged. Don't cover the cob. Keep a fire lit and use a fan on the cob. It will dry out but it takes time. The moving air will help immensely, you'll see it start to dry out on the surface very quickly but the inner core of mass will take time. I stuck a candy thermometer into the bench as far as it would go and left it there to monitor the temps. Finally after about a week the temps started to rise, that's when I put the blankets on. Don't use the blankets until the moisture has evaporated out.

The fan is a no-go since I'm off-grid and running on generator power still (solar just got in, so that's another project for this week) but I'll definitely keep firing it. I used the clay slip method in making the cob rather than the bare-foot tarp dance method, so that's probably part of the problem - A LOT more water in the cob this way I'd imagine, but with the clay soil coming in as frozen chunks, some nearly boiling water to speed things up made more sense. This being the first build of hopefully many, I expect a few things I'll want to do different next time around...For example, next time I will definitely build during the summer months

Another question: with this beast built directly on the bare ground, which stays pretty moist, is it likely to wick moisture up and continue to steam that out or will the cob just dry out and stay dry? I'm wondering if I should have put down a moisture barrier beneath everything before I started to prevent something like that from happening.

Peter Ellis : It has been Ernie Wisners practice to run the RMH as soon as possible, His stated reason for doing so is, if you cob in your barrel, and allow the cob to set and then
build a fire, He expects the Expanding Drum to crack the Cob and or finish cob,

However, with short hot fires the barrel works and sets a grove for itself that the expansion and contraction can occur without major cracks. At Least that is what I Think he said !

Sorry, I did not spot your post sooner, If you have problems please post it here foer your fellow members to SEE ! Thank You ! for the Good of the Craft! BIG AL !