As simple as possible?
(M) While setting up my first course of dome bricks I wondered about the rationale for changing the plane of orientation for only that bottom course.
(M) I couldn't understand why that would be necessary since the 4.5" depth was a constant in every course ring, irrespective of the plane of orientation.
(M) I temporarily set up a few bricks with the "traditional" orientation of the first course that is placed on it's 2.5" edge, and is 4.5" deep. That first image is a front view.
(M) The second picture shows a similar sized front view arc of a 42" circle but this time the first course is oriented the same as every other course in the dome, i.e., lying on one of it's two 4.5" sides and also being 4.5" deep.
(M) In that 2nd picture you'll see one errant 1/2 brick, purposely butted against the first 2 courses. Its there to show that 2 bricks of 2.5" are 1/2" taller than the "traditional" orientation of the first row. I make this as a positive argument in favor of all bricks having the same orientation. The additional 1/2" will provide that much more height to the desired parabola profile.
(M) The third picture shows the back of the "traditional" orientation. Note that the support areas of the top of the first row are not equally distributed; some bricks have almost no support from the bricks left and right, and some are supported almost entirely by just one brick. I realize that mortar will fill those voids, but in terms of balance I suspect that a uniform orientation will help the Newbie to consistently place his bricks in a staggered pattern, with the distribution as uniform as the eye can make them.
(M) The fourth picture shows the back of the proposed new orientation. If you compare this fourth picture with picture #3 you'll notice the even supports offered by a consistent orientation.
My arguments in favor of the new orientation are four-fold:
1- It simplifies instruction for the Newbie. S/he doesn't have to try to figure out what is meant by "side", "short", "long", etc. All that builder needs to know is that every brick lays on it's 4.5 by 4.5 side with the rough cut facing out for the mortar cladding.
2- It is inherently more stable as there is almost twice the surface area on the hearth floor in that orientation as in the "traditional" orientation.
3- The added 1/2" (presupposes the same size circumference for the first two courses) works in favor of a higher parabola.
4- It is easier for an unskilled mason to see how to place the bricks when viewed from the back.
My argument against this arrangement is that the first course will not be as smooth a curve. That shouldn't really matter as every subsequent course on even the "traditional" orientation will be a more "angular" curve.
(M) A final image, #05, shows the split level insulating hearth concrete.
(M) Einstien said that "Everything should be made as simple as possible; .... but no simpler!" Is this simpler than possible?
It appears we're at the same stage. I'll try posting my pics tomorrow.
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