Warning: Science Content..... I'm going to experiment with adding some forced air to my temperature control system. Several weeks ago, I wrestled with a large wind storm and even with the plywood shelter, I still had problems. I placed a box fan in front of the firebox, and the issue calmed a bit. This got me thinking about adding a dc fan to control system. However, I still like the idea of the rotating damper, and wanted to add the fan only for rapid increases. For example, if I don't monitor my fuel well, and have to add fresh lump to the box, it takes some time to heat up again. The fan should resolve this. To aid in the control (and this is where the "science content" warning applies....turn away if your brain gets sore easily ) I added the ability to "overlap" the percentage of use between a primary and secondary damper. In my case, I'm going to have the primary control operate the rotating damper, and the secondary control operate the fan. From the illustration below you can see that I am going to start with about 75% overlap. This means that the secondary damper overlaps the primary damper on the last 75%. So the primary damper can operate up to about 40-50% will little or no help from the fan. As the control gets higher, the fan RPMs start to increase to the point of.......well, possibly melting the fire box (let's hope not). I'm going to start extensive tests during the Christmas break, but issues I'm sure I will be dealing with are: 1.) fan will I'm sure blow ash into the smoking chamber. That will need to be dealt with. 2.) ????.....ideas from you guys....what do you think?