Converting a Box Cooker to Have
Round Inner Walls
my SBC to round inner walls was easy, here are the steps for anyone wishing to
- Cut a long rectangle of smooth, flexible card (not corrugated or stiff),
its width being the height of the inside of the SBC, plus about 1/2 inch for
- Mark, cut and fold tabs along both sides.
- Bend it into a cylinder, overlap the ends sufficiently so that it makes
the biggest cylinder that will fit into the SBC and glue together.
- From stiff card, cut a square the same size and shape as the outside
dimensions of the top of the SBC. Cut a circle out of the middle the same
diameter as the cylinder of flexible card.
- Using the tabs, glue the cylinder to the card top made in step 4.
- Insert cylinder into existing SBC. It should just touch the flat inner
walls and rest on the oven floor. Glue it all together.
- Glue aluminum foil over the insides and floor.
- Make a cross out of two intersecting cardboard strips, glue them in the
centre of the floor of the oven. This makes a stand that raises the black pot
above the floor. Besides raising the pot to a warmer part of the oven (small
gain), it increases the surface area of the pot which 'sees' the sun (larger
There may be significant temperature gains to be had with:
- Adjusting ratio of pot size to crude focal beam width.
- Making the inner sides into a section of a cone.
- Using a reflective hemisphere for the inner walls and floor.
I shall probably try these all in time but as my modified SBC stands right
now it is the best one I've ever built. I would like to hear results from anyone
else who tries out this design, I feel that there is room for even greater