6 inch J rocket stove from firebrick - a pattern to place them?

Hi,

I am trying to build a rocket stove/s for a stovepipe water jacket and for thermal mass in a greenhouse.  

I have pulled out a pile of fire bricks I got years ago, and am wanting to make a 6inch rocket stove as most of my salvaged pipe is 6inch.  (I do have a smaller amount of 8 inch, so could make a small bell style thermal mass).

75 that are 9 x 4.5 x 3in   or 230 x 115 x 75mm.
I can also get these insulating fire bricks the same size on sale, so if I can keep with this size all the better.
https://thermalnz.co.nz/insulation-brick-jm28.html

5 (two with corners cracked) that are 11.75 x 11.75 x 1.5 inches or 273 x 273 x 37mm  I can't find more of these size online.
12 x 12  x 2 and 13x 13 x 2 inch fire bricks are available, but at $33-46 each compared to $7 each for the other ones.

I have found a few photos of people making J cores with these bricks, but no clear pattern of how to place them.  I am sure it must be out there someone.  Anyone got a link?

Thanks in advance.

I think both of these can help with your build.

This link is to a nicely documented build using hard clay fire bricks 9"x4.5"x2.5" so about 7"x7" riser.  You 9"x4.5"x3" bricks will make a 6"x6" riser when you use the same pinwheel  on edge pattern.  

Pix:
https://permies.com/t/89382/a/70004/4E35A1E4-D63B-4D74-8889-DCBE4F386121.jpeg

From post:
https://permies.com/t/160/89382/RMH-Builders-guide-build-pic

Note:  Uncle Mud did a webinar on greenhouse RMH's:
https://permies.com/w/208519/Heating-Greenhouses-Rocket-Mass-Heaters.

Hope that helps.  Tom