The Dragonfly Den in Retrospect, June 2009-May 2012

[SableSprings]

1 September 2009

Final oven specs - Oven opening is 19" wide and 11.75" high. Internal dome reaches 20" high at the peak so the oven's door height to dome height ratio is a little low at just under 59% (instead of the target 63%). The widest point inside the oven is 39" and from the cooking door brick to the back wall is 42". It's 11" of landing from the inner door line to the ash slot. The ash slot is 22" wide by 3.5" with another 12" of landing in front of the ash slot provided by the bullnose bricks.

We decided the first curing fire warranted a party. Twelve of our friends were able to come down for an impromptu toast to the first fire in the oven. One of our friends brought some white lightning to start the brief newspaper fire and to share with the gathered guest glasses. Fed the fire twisted sections of newspaper slowly for about 15 minutes to see if my low door height to dome height ratio would draw and breath properly. No problems with the draw once I took off the chimney cap. Put another section of flue pipe on top to improve the draw (and primarily to expel the smoke slightly above the crowd).

Home made whole wheat bread crisped with olive oil and salt & pepper, chunks of Parmesan cheese and some Peppadew (sweet peppers) for snacking while the fire burned. Brownies for dessert after the "fire ceremony".

Over the next week or so, it will probably just be me and my Black Butte Porter tending the curing fires.

[SableSprings]

Tried to put a thin layer of clay on the outer dome to smooth it out...waste of time for me. Decided to use 10:1 perlcrete for my top insulation. Made a quick form around the insulation base, leaving a couple of inches gap. Put some heavy wire mesh in place around the dome base form and placed a piece of ½" leaning rebar to provide additional lateral support/strength for the front arches. Used two bags of standard redi-mix concrete to set the wire and rebar into place. Once the concrete had set, I bent and cut the wire mesh up and over the dome.

I planned for the wire mesh to be in the outer third of the dome's perlcrete insulation layer. I spread a layer of diatomaceous earth (D.E.) over the dome and planned to spread some of it between each layer of the perlcrete (and the firebrick) as I mixed and applied it. My understanding was that the D.E. would give the firebrick dome some slip from the outer insulation dome...hopefully reducing or eliminating major cracking. I then simply braced pieces of plywood vertical to the outer surfaces of the lower base form. Used up one 94# bag of redi-mix and two big bags of perlite mixing 5 wheelbarrows full of the perlcrete insulation. I ran out of perlite before I was able to close the top.

We had to leave for a month, so I covered the open area of the dome with a tarp and put a canopy over it (double protection from Oregon rains). Ordered three more big bags of perlite hopefully to arrive by the time we returned.

[david s]

Tried to put a thin layer of clay on the outer dome to smooth it out...waste of time for me. Decided to use 10:1 perlcrete for my top insulation. Made a quick form around the insulation base, leaving a couple of inches gap. Put some heavy wire mesh in place around the dome base form and placed a piece of ½" leaning rebar to provide additional lateral support/strength for the front arches. Used two bags of standard redi-mix concrete to set the wire and rebar into place. Once the concrete had set, I bent and cut the wire mesh up and over the dome.

I planned for the wire mesh to be in the outer third of the dome’s perlcrete insulation layer. I spread a layer of diatomaceous earth (D.E.) over the dome and planned to spread some of it between each layer of the perlcrete (and the firebrick) as I mixed and applied it. My understanding was that the D.E. would give the firebrick dome some slip from the outer insulation dome...hopefully reducing or eliminating major cracking. I then simply braced pieces of plywood vertical to the outer surfaces of the lower base form. Used up one 94# bag of redi-mix and two big bags of perlite mixing 5 wheelbarrows full of the perlcrete insulation. I ran out of perlite before I was able to close the top.

We had to leave for a month, so I covered the open area of the dome with a tarp and put a canopy over it (double protection from Oregon rains). Ordered three more big bags of perlite hopefully to arrive by the time we returned.

I doubt whether having steel mesh in a weak 10:1 vermicrete mix achieves much. It is also a lot of extra work to get it to conform to a spherical surface. The vermicrete only needs to be firm enough to act as a substrate to apply the outer render/stucco coat onto. Having steel in that layer also increases the conductivity reducing the insulating capacity in that layer. I don't think it is a problem, just a waste of exta labour. Could be wrong, have been before.

[SableSprings]

You're absolutely correct David...it was a lot of work and didn't gain me anything in the long run. At the time, with my limited experience I thought I would be able to get the perlcrete to hold better on the vertical sides with the mesh firmly in place. It didn't work very well and that's why I went with the outer plywood--to create a consistent width of insulation on the sides and to keep the wet perlcrete from sloughing off while it cured. I thought the mesh being embedded in perlcrete several inches away from the oven wouldn't be a conductor or a problem for the oven. On hindsight, I definitely would have skipped the mesh.

At the time I was starting the outer insulation cladding, I had decided not to stucco the outside. I was going to be building a permanent structure over the oven to protect it from the elements, and I fancied the look of the half barrel brick exterior. Since I had built the "sorta dome" for the advantages it would provide for my baking options, my intent was to create a brick "barrel" facade on the outside of the oven to give me a particular (and different) look to the oven. Addition of the plywood forms to contain the perlcrete while it cured on the sides would create a nice clean vertical wall that, hopefully would be beneficial to laying the facade bricks. I'll try to be showing what & how I got the barrel look with the dome functionality as I continue to document my build.

Incidentally as of last Friday's bake, we've put 4,100 pounds of dough (counting pizza, buns, bread sticks, biscotti, cookies, flatbreads, and regular bread loaves) through the oven since the fall of 2009. That dough total includes the 2,746 loaves of bread that I've made...1,877 (68.4%) given to mostly to friends, neighbors, and local police & fire departments. It's been a terrific, relatively inexpensive retirement hobby...and yes, I keep track of everything on Excel spreadsheets! (What can I say, I'm a retired CIS instructor...)

[SableSprings]

30 October 2009

Picked up three more bags (4 cu ft/bag) of perlite and two 94# bags of Portland cement to finish the dome insulation. Talked to a local metal shop guy about making a stainless steel fire door. Preliminary design called for a "thin box" with handles that would double as stands and a 2" box chamber to contain insulation material. He said he’d create a removable cap for it so I could fill/refill it with perlite for insulation.

Finished the insulation cap on the dome. I estimate between 4"-5" on the sides and probably a little thicker on top. Picked up my fire door and was really happy with what he’d created. Door is rather heavy (about 18# when filled with perlite), but the handles he designed and welded on make it really stable. Cap is held in place with stainless steel hex screws and the door fits perfectly flush against the oven’s reveal. The two pictures below show the door standing on some brick pieces--as I was seeing if air flow underneath was better than just around the sides (when the door was sitting on the landing a few inches from the reveal--see note below).

Continued with some higher end curing fires to finish drying the outer perlcrete cladding insulation. Had the first pizza on November 19, 2009 – five months from the foundation ground breaking. Even Hamelman’s pre-ferment (2-day process) pizza dough could not make that first pizza of ours look good......however, I’ll always remember how good it tasted and the satisfaction of knowing my oven was a success.

Note: I now just stand the door 2"--3" away from the reveal when I light the fire the night before my baking day. Only coals left in the morning and generally the dome has cleared and needs to equalize and cool down to under 600F for my bread baking. I generally bake my breads now around 2:30 in the afternoon and at about 575F in the chamber.

[SableSprings]

As winter and the rains approached, I started covering the dome with a tarp and put a cap on the flue pipe. We were leaving for a while so I took the chimney cap off and placed a canopy over the whole structure. Big windstorm took the canopy off and over the fence even though the legs were weighed down with cement blocks. At that point, I decided I needed to construct a temporary, but more stable cover for the oven until I could build the larger den enclosure. Built the faux chimney up a few more levels with hollow bricks to make sure the flue pipe would not get knocked about in the wind.

Used a piece of angle iron and some mortar fill across the back side to provide a level area over the curved insulation for the first course of bricks there. I left some air gaps in the angle iron's support mortar, so any moisture remaining in the dome or insulation would be able to escape up the faux chimney space. Although it doesn't show here, there is a 12" flue pipe that has the working 8" flue nested inside...shows in a later picture I'll post. Once the faux chimney extended above the intended "temporary" roof line, I started creating the frame for the temp. structure.

[SableSprings]

The frame and temporary oven cover is starting to look like a homeless shelter . I even had some half sheet pans positioned to the sides of the chimney before I figured out how to flash it with the rest of the metal roofing. (Fourth picture shows how I put up some roof edge flashing into the chimney brick mortar to provide a good drip zone around the chimney.) I was pretty concerned that a freak wind would take off the shaky structure, so that’s where the nylon rope and cement blocks came in. Problem was that the metal roof and the big swings in day/night temperatures in our winter caused a LOT of condensation and consequent dripping onto oven. I mean it all got sopping wet within a week...never saw that coming!

Ripped the metal off and put down a plywood roof, some Tyvek house wrap on top of that, and then replaced the metal roofing sheets. We had some pretty nice weather and the perlcrete seemed to dry out pretty quickly. Put some pink fiberglass insulation between the roof and the dome mostly because I had it laying around and then tacked up some plywood sides for further protection. Counted on that to get me through the remaining wet months.

I kept firing the oven at least once a week when we were home until the more permanent den structure was built. Any residual moisture in the perlcrete dried out pretty well with the improved cover and somewhat consistent firings.

[SableSprings]

9 March 2010

Brother-in-law Jerry came in to be the “contractor” for the den. Put the posts up around the perimeter of the foundation slab, framed it up, made our trusses, and set the window & door frames to have screen insets to keep out the unwelcome flies, yellow jackets, and mosquitoes.

The most difficult fitting was for the chimney stack, but like my other brother in law (the mason) noted it’s like putting socks on a chicken -- you do what's needed to make it work.

[SableSprings]

Bought 12' sheets of metal roofing for the den structure. Put roofing asphalt on the roof plywood and then used screws to attach the metal roofing sheets. I considered having some custom flashing made for the chimney (estimate of $200-$300) but ultimately (being extremely frugal) I just cut pieces out of some extra material to guide water away from the chimney opening. During the build I continued to work on baking bread in the oven.

Ripped some tongue & groove cedar pieces from a neighbor's house for insect screen frames. Stretched screen from 48" wide rolls across each window frame, cut, and tacked into place with hardware staples. After the screen was secure, we screwed the cedar pieces into the frame outline and in doing so, double anchored the screen panels. The French Doors were done in two pieces (top & bottom on each door).

The Umpqua Community College (UCC) welding instructor I’d contacted about building carts for the bays returned my call and said they had the bay cart frames ready to "check for size". I borrowed a pickup and brought the two carts home to see if they fit (or more correctly, if I'd measured it right). The carts are a student's final project in the class, so it's really a nice dynamic with getting everything "perfect".

[SableSprings]

Cart frames fit nicely into the stand bays, so I took the frames back to the college to have the tops, ends, and handles welded on.

Now that the oven was under the permanent, roofed structure -- I removed the temporary, first winter cover. On the left side of the oven stand, I had to do a minor fill. When we poured the top slab, the left side form board started to move out and the Ready-Mix operator "tapped it" with his hip to put it back over the blocks. He just tapped it a bit too hard and it was only a cosmetic fix that I made here.

I wished I had removed the temporary roof before we enclosed it in the den...certainly was a lot more difficult doing the demolition at this point. Next I needed to figure out the easiest way to turn the exterior dome into an apparent half-barrel shape...time for more pencils, paper & beer.

[SableSprings]

So, in order to create the look of a half-barrel oven from my short beavertail dome, I needed to add a barrel facade. I could only imagine doing it in brick, but I didn’t want so much weight on my stand. I decided that I would cut bricks lengthwise for a brick barrel classic look. I thought the easiest way to approach this would be to place a piece of cement board on each side, up to the halfway point where the barrel started to curve over the top.

I cut some hollow bricks lengthwise and used them to set the cement board vertically against the oven sides. Once I mortared these base bricks into place, the actual laying of the barrel walls was pretty easy to do...just set each brick half up against the board and presto -- straight & perfectly vertical . I did put in a few little pieces of pink fiberglass between the perlcrete sided and the cement board to allow for a little air flow (and to allow a little expansion room for the contained dome...if necessary during firing).

When I got to the top curve, I put some pink insulation over the top to act as a cushion and to let some air flow between the oven and the brick facade. I inserted some metal lath between the perlcrete and cement board. The lath was curved up and over the dome where it went into the other perlcrete/cement board. Obviously, the front and the back of the lath needed some extra support where the dome curved down (and the barrel would not )...a couple of brick chips strategically placed did the trick.

Once I cut the single line of bricks to start the top curve on each side, I was simply planning to alternately lay split brick courses up from each side. Hopefully I'd meet in the middle up on top and not have to cut slivers of bricks to "span the gap" (also the top I figured would be where the joints would be least visible).

[SableSprings]

The mortar grabbed the lath nicely and I only did a few courses on each side at a time to let the mortar set. (Otherwise, the lath tended to “pucker” with the weight of the bricks pushing down on the more extreme dome curves.) Note the piece of angle iron protruding along the back sides of the false brick chimney. This was used to set the back bricks of the chimney level across the back of the curved dome. I cut the excess angle iron ends off as I approached putting in the final top courses.

I extended a couple bricks along the front buttress posts to give myself 2 small shelves on each side of the oven opening. After I finished the half-barrel top facade, I folded the lath down in the back. I cut and put in another piece of cement board, then mortared it and the folded lath into position to protect the backside perlcrete. Sorry, never took a picture back there...no one except me has ever seen it...

I was pleased with the look I got with the facade and am still happy I didn't actually build the half-barrel style oven. I love the look of a brick half-barrel oven, but prefer the variation on the Pompeii dome for the types of baking I do.

The welding instructor that was supervising the bay cart final construction, remembered I wanted a lighter weight cooking door. He made me the cooking door shown on the left side of the "finished" oven (in front of the flowers). It has a small metal dragonfly cutout (matches the ones that will be on the bay carts) mounted over an old style welding tool handle. I simply painted the dragonfly cutout with white high temp paint and the rest of the cooking door with black high temp paint. You can partially see my stainless steel firing door in position at the oven opening.

[SableSprings]

Some pictures of my cooking door since it has turned out to be extremely useful for me. I can easily lift and move it with one hand and the handle stays cool enough to work with even when I'm running a pretty hot oven. As I mentioned previously, the black and white is simply high temperature BBQ paint. The dragonfly cutout was made from a photo of a dragonfly I took at the river in front of our house. My UCC welding instructor friend, took the picture, made it into a silhouette, then cut it out with the plasma cutter in the welding shop. I still am humbled that my friend made this as a gift for us and the oven.

[SableSprings]

Bay carts are completed. My friend, the welding instructor at Umpqua Community College, took the dragonfly picture silhouette mentioned in the last post and made two large cutouts with the plasma cutter. The welding student (these carts were his term project) mounted one of these cutouts on each end of the carts...very cool. I had him make and attach his initials on the cart ends as well.

Took the carts out to a local company that does power coating and they did the basic carts in black with the dragonfly silhouettes in off white. (And now you know why we call this The Dragonfly Den.) I was ecstatic when I saw the finished carts. I secured some “railings” inside the bays so the carts wouldn’t scrape when I moved them in & out. The left hand cart works great for a prep table and cooking item storage, while the right cart base is used for wood storage. The right side’s top is where I deliver pizzas to cutting boards for serving or where I cool hot loaves of bread. Both carts can be pushed in flush with the bays and really makes closing up the den pretty easy.

We had added a lower guide rail system to the original plan to keep the carts centered while moving them in & out of the bays. Unfortunately, I had measured the heights to achieve maximum use of the bay and adding the rails raised the right side cart too high to fit into the opening...hence the use of the side rails in both bays.

The large dragonfly on the chimney was an art piece we bought in Idaho on a trip back east. The curved metal container under the ash slot in front is an old tire bath. They used them to find leaks in tires in "the old days". It fit perfectly beneath my ash slot, so I just used a concrete block to lift it up into place fairly tightly. Now I just pull the ash and coals directly into the slot, everything drops into the container, and I'm ready to bake.

[SableSprings]

Since the carts are done, I decided it was time to finish the area behind the oven. Bought some plywood sheets and started to screw them into the posts around the backside. OOPS! I was able to get behind the oven before, but by adding the sheets of plywood--getting behind the oven was no longer an option for me. I’m not that big, but essentially I was unable to even get a power screwdriver in position to attach the plywood below the stand level. A few, less often used phrases and words were used ...but that didn't help either ...so I attached on the upper portion of the plywood sheets as best as I could and then took some pieces of 2x4s, cut them to just fit in the gap, and then pushed them down to the base of the stand along the back wall to actually wedge the lower margins of the plywood tight against the structure posts...sorry, no pictures here ‘cause I was (still am) too embarrassed .

My next goal was to build a woodshed. Laid down some landscape fabric and had 11 yards of 3/4" minus gravel delivered and dropped on the fabric. Spread fabric and gravel around the side of the den where we expected people to park. I then ran fabric/gravel down a path to where I wanted to build the woodshed. Staked out the woodshed dimensions I wanted and put in posts, secured with quickset concrete in the holes. Again fabric and gravel down before building the simple structure. Wind is generally from the southwest, so I put the open side to the northeast. Pallets will go down on the gravel and wood on top. I hope to fit about three cords of split wood and some yard tools in the shed.

Good to have the wood under cover but I’d forgotten how much work shoveling and moving 11 yards of gravel would be ...definitely time for a long shower and a cold beer after each of the days I was shoveling and spreading it.