A new Folly at Full Moon Farm-- build thread

[rwiegand]

So to fit the inner arch to the dome, it should sit with its base (or where a plumb line dropped from the top of the arch) would make a tangent to the outer circle of the dome. Have I got it right?

Or does it need to set back further, as in Version 2 so the tangent is to the inner edge?

[WarEagle90]

Thanks Russell! You're a real treasure to this community!

I'll second that opinion

[rwiegand]

Thanks Russell! You're a real treasure to this community!

[UtahBeehiver]

Tapered inner arch concept can cause major brain cramping to visualize but well worth the effort. I have walked a number of builders through this concept and have never had one say I wish I had not done it. All of a sudden the light bulb will come on..............aaah.

I just walked out to my oven and measured my vent distance 9.5"

[rwiegand]

Yes, I think I see. You want the inside of the inner arch to be a continuous part of the hemisphere of the dome. That would suggest that the stack of bricks that form the reveal for the door should be getting longer as they pile up to allow a perpendicular face for the door to rest against on the outside, but a curved shape on the inside. Hence your earlier comment about wanting longer bricks for the top of the arch. The light (perhaps) begins to dawn. I'm a woodworker and usually pretty good at 3-d thinking, but these intersecting arches are giving me a headache!

I'd better get on with making my IT. I was going to anchor it by drilling a hole through the slab and using a piece of all-thread so I could adjust the base height exactly, putting the pivot point at the final floor level without having to worry about added wooden blocks and false floors. I figure I can use the hole later for a thermocouple.

Russell, looking at you pictures it seems your vent landing is about 11-1/2", is that correct? (A full brick plus a brick on its side, 9" + 2-1/2")

[UtahBeehiver]

From an engineering perspective, there will be an outward load from the dome at the point where the dome and soldier meet vs a full hemisphere dome. Somewhere in one of the posts on the forum there is a white paper on loading aspects of different type of arches..

I cannot tell from the pics, but in order for the dome to meet the arch in the upper courses, the initial arch (at the floor) set back needs to intersect the ID arch of the dome. This is critical in order for the IT to work. I marked up your pic where the dome arch and the floor ID arc should intersect. This is especially important when doing a tapered inner arch.

[rwiegand]

Is my vent landing the right size? Lots of builds seems to have about a brick and a half of depth, but there are also many comments about many ovens having a "too deep" vent landing. Right now I'm at 14" from the front of the oven to the front of the reveal. The FB plans say 8" of depth, but it's hard to see how you then have enough area for the flue, especially if you use a10" clay flue. It might work I guess if the chimney were set back partly over the dome instead of over the vent landing. It would be easy enough to make it smaller now if that's the right thing to do.

There als appears to be divided opinion on the soldier course, with the argument for being better ability to use all of the oven floor with a small vertical height before the dome begins, and the argument against being that it is weaker construction. Have domes actually collapsed or suffered structural damage because of failure of the soldier course? I was going to cut the soldiers down to about 6-3/4" tall, giving me the equivalent of two horizontal bricks above the floor, in the interest of keeping the top of the dome lower.

[rwiegand]

Thanks, I hadn't thought about anchoring the IT other than screwing it to the zipwall sheet I made to lay out the dome and then protect the floor from falling mortar. I'll try to nudge things one way or another for better placement.

I was planning on swapping cut off ends of bricks to make some of the smaller pieces, I just laid it out with full bricks for now to be able to draw the circle.

I guess I should read up on thermal breaks now, I see many people are including them.

[WarEagle90]

Retaining wall looks good. You’ll look back on the time spent doing that and be glad you did. Looking at your floor layout, it appears that the center of the dome falls at the intersection of three bricks or very close to it. You may want to consider laying the floor out in such a manner that the center falls in the center of a single brick. That will allow you to remove the brick and fabricate a wooden replacement to attach your IT to during construction. Just a thought. Looking forward to watching our oven come to life.

[UtahBeehiver]

You can save a few bricks by using surplus of one brick at another location, ie 33 at 44 and 52 at 58 etc. On the CaSi you will have to make the decision on the 55 psi compression rating. $400 delta seems out of wack to me but maybe that is the way it is in MA. Again you should see if any other builders have used this lower compression rated board,

[rwiegand]

So, a bit of a detour the last couple of days. I decided I didn't like the fact that the oven slab is set on a hill and the erosion was beginning to undercut the corner of the slab. Also it was quite a reach from the back side of the oven to the middle of the slab and unlevel to boot, so I decided to build a little retaining wall around the back side and fill it to be approximately level with the oven slab. So, some digging, gravel bed, tamping, concrete interlocking wall blocks and backfill and voila! a level working surface.

With that done I made a cutout of the floor pattern out of a piece of zipwall--should withstand some water exposure, I hope, and laid out the bricks for the floor in preparation for actually cutting something.

Any errors evident in my layout? There are some gaps that approach 2 mm, and some bricks that aren't exactly square.

[rwiegand]

Concrete day! Had a guy with a mix-on-demnad truck come as I needed just under a yard to pour the hearth. As always, a few frantic moments when the concrete truck shows up. I was at his upper limit for being able to pour directly into the form, but we made it, albeit with having to get up on top of the form and encourage the concrete to flow down the chute. No blowouts though, a few voids at the edges I wish I had avoided, but they will end up covered. I figure on just leaving the piers in underneath while I work on the oven unless there is a good reason to pull them out sooner.

[WarEagle90]

Did you tell the inspection team the WFO would be ready for them to try out around the 4th week in November

[rwiegand]

Waiting for the concrete guy to come on Wednesday. Will spend some time running around for materials between now and then. Found bricks at $1.60, which is good for around here.

The inspection team showed up to look at progress--

[rwiegand]

End of the first week of work sees us ready to pour the platform for the oven. The good/bad news is that I am taking a week off for a wood carving class in Indiana, so no progress or postings for the coming week. I will have the local "concrete on demand" guy ready to show up a week from Monday. It seems as if it is going to take an awkward quantity, less than the minimum, but more than I want to mix by hand and lift up on top of the platform. Oh well. At least it's not like the old days when the guy showed up with three yards in the truck and you had to take it no matter if you only needed one.

In a quandry about where to buy ceramic fiber board. The shipping cost for the FB material is high, but the couple of places I've found to buy it locally are even more expensive, and I'm not completely clear that I'm getting something that will work. More research while I'm on the road, it needs to get ordered in the next couple of days. A thousand bucks for insulation (4" underneath, 4" over the dome) is a little breathtaking! Adding more later if I used less and it didn't work out well would be pretty problematic though. I intend to be able to use the oven in Boston winters.

Bought the Harbor Freight brick saw today on a pretty good sale ($209). It's typical "Chicago Electric" crap, but it should last through this job and then I'll try to sell it on CL.

Attached are some pictures with the rebar in place.