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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='color:#1F497D;mso-fareast-language:EN-US'>Dear Vincent<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D'>>The question was prompted by the overall need to stop the heat in the firebox from reaching the foundation (made of clay) and burning it up.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Something you can try is the system used in the StOvs Cooker from Senegal. When you visited (in the past) the bioenergylists.org website there used to be a background picture showing a strange stove in a cutaway drawing. I am not sure if you ever noticed it. That was a StOvs cooker. It is made of thin concrete with a clay combustion chamber and had to protect the cement portion at the bottom of the chamber. In order to do that a circular depression was made with a supporting ring upon which sits a fired clay disk – something really cheap and easy to make locally for a few cents (or less).<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>The disk sits under the combustion chamber and is free floating, meaning not held in position with some clay or anything – just sitting there with an airspace underneath and some form of supports on the side/lip.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>This is replaceable and creates a hot surface to help burn the char that is otherwise smothered in the ash. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>In Indonesia this disk is often used in improved stoves however they perforate it and allow air in below the floor which also means having a cleanout for ash. This provides ‘under air’ to the char and again helps burn it reducing fuel consumption. One such stove is the Jolentho Stove which can have 2 or 3 pots, a chimney and comes in various sizes up to ‘huge’. The disks (if perforated) tend to be quite thick and not of very suitable clay but that is another story (clay selection).<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>The Jolentho stove is built in with clay. Here are the components which are supplied to the builder:<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><img width=454 height=416 id="Picture_x0020_1" src="cid:image001.jpg@01CF1B4B.86A52220"><span style='color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>The right hand one has the perforated disk at the bottom of the combustion chamber. A side-access us constructed in the floor and even has an air controller. Stick fuel is bed into the right side as viewed from this angle.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>The point is that having a loose disk of clay is a pretty good way to limit heat going down. Air under a hot surface is a really good insulator. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Crispin<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p></div></body></html>