After loading up the The Pit with wood we set fire to it.
The airducts seemed to work really well, and within 20 minutes we had a raging fire.
Covering over the The Pit with tin, I left the airducts open, and allowed it to vent through the gap in the tin sheeting.
After 8 hours we opened it to have a look
the fotos for this are terrible and show nothing but a black hole and smoke. so you don't get to see them.
The wood wasn't fully burnt, but there was a significant charcoal cunks in there. we covered it over again to head back the following eve.