Can you direct me to Styrofoam forming Dir.?

[Marcel]

I have been advised to form my dome as a parabolic? hyperbolic? 3D shape.
I plan to use styrofoam or solid insulation sheets and interlock them as several have done; placing the 1/2 firebricks as concentric reducing circumference courses.

I will try to pack construction sand between the vanes although others have had satisfactory results omitting this step, but to quote (or misquote?) a famous bulider, overdo it or don't do it

My question is two-fold:

1- I have seen images of the vanes but not on how the template was made to scribe that profile. Can you specify the URL where that procedure is started? ___

2- If you know of no relevant photo images on-line, can you describe how I should draw the correct parabolic? curve for a 42 inch diameter oven? ___

Thanks,

Marcel
marceld@efn.org

[paulages]

marcel,
all i did was lay out my bricks on a piece of board (in hindsight i would have done this straight onto a piece of styrofoam), with the 42" edges marked (representing the inside edge of my walls/diameter of the floor), and an 18" mark in the middle, telling me roughly how high i wanted the center of the dome.
then i just layed bricks out, starting with the first vertical course, until i had figured out a number of bricks that would fit in the desired dimensions. then i played with this shape until i got something a liked ( i was shooting for a slightly flatter top), which ended up being 17.5" high, with the parabolic shape you can see in this picture.



then, i just traced the inside line of the bricks. i measured in 21" from the edge, put a square on it, and only cut out half of the template, so that the dome would be perfectly symmetrical all the way around. i then used this half-template to remake the first two full templates. to put these first 2 vanes together, i just slotted one halfway down the center, and the other halfway up, and then slid them onto each other.

.

filling the cores with sand seems like it would be helpful, as there were places toward the middle where gravity started showing its presence, but the vanes hadn't closed in enough to completely hold them. but i bet they'll be hard to tear apart. the styrofoam is easy to break apart when you can bend it, but i'm not so sure with it sandwiched in tightly. i found it easy to just keep making the same template (cutting a bit off of the inside edge each time to allow it to fit between the previous vanes) over and over until it seemed pretty solid. i did 16 vanes, but where's the limit?