OK. This has been an interesting adventure so far. I have already tested Corten 1.55m steel in the 'Flat-Tiki' and 'Pyramid BBQ Classic'. Folds are essential. I tried to minimise the folds on the end pieces of the FMBK. As it turns out, the top fold has warped but seems to have stabilised after 2 burns. The side panels (with vertical and horizontal top folds) have remained in shape after 2 burns. I found out that the 'Mighty midget panel clamps' can easily blow out if the kiln isn't assembled and disassembled one panel at a time. Besides, 6 inch C clamps (not completely weather proof) are easier to manage and work great most of the time so far - I found a supplier in Melbourne that imports them from China with only 3-4 business days for freight all across Australia.
The first burn was the 'Trough' hybrid mode. The fire was way too big to manage with one person and no machinery (like a front end loader). I just couldn't keep up, and it got so hot that all the feedstock was ashing and it was hot and dangerous to work with. I can't wait to test it in Asia with bamboo,rice hull/husk/straw,coconut husk etc The end pieces may need to be reduced in length (and therefore reducing the overall volume and heat of the fire). The forestry waste I am using is mainly eucalyptus, olive and acacia. It has been dried in my shed for 6 months. I have a lot more of it so when the weather heats up again, I'll be lopping and chainsawing to my heart's content and burn it without drying it for such a long time.
The second burn I reduced the size of the FMBK to roughly a 1600mm square - 2 side panels on opposing sides and the end pieces on the other opposing sides. Note that the end pieces are vertical so it's not a perfect pyramid. I'm still going to call it the 'Forestry' hybrid - close enough - hopefully Kelpie Wilson doesn't mind. I just read research from the Ithaka Institute that describes similar char characteristics for a range of kiln types - so maybe it comes down to choosing a kiln that suits the local materials, fabrication skills, operational skills, feedstock type and processing et al. Anyway, this size is perfect for my feedstock and one man operation. I used a dousing technique I learnt from the 'Flat-Tiki' experiment where I douse the flames at the end of the burn using 1 inch rural PVC pipe attached to an almost full water tank off my drying shed (gravity fed). I then cover the smoldering charcoal with soil then wet the soil afterwards. I'll observe it for about 10 minutes and add extra soil and water from a bucket to put out any remaining smoldering.
So, overall a success for the 'Forestry' hybrid mode. It will take more burns to ensure the Corten steel remains in shape. If you're making biochar this season, happy charring! Will update the blog from time to time to add any extra useful information. Chars!