iCan Model II
This innovation in secondary air is what makes this a model II iCan. This design eliminates rings of holes around the entire circumference.
This variation in secondary air uses only three sets of 4 holes made at intervals equal to 1/3 the circumference of the iCan. Thus they are centered at 120 degree intervals.
While I started with 7/32 secondary air holes, as in the Basic Student iCan, subsequent testing indicated that full 1/4 inch secondary air was a better choice. You can easily test this for yourself.
Other sizes of iCans will require other secondary air hole patterns and hole sizes.
Update: Try placing the 12 secondary air holes used above on a sine wave curve that wraps once around the can. I use a curve with a total of two maximums and two minimums. I place the holes at a fixed and equal distance. On a can of this size, the height of the band the curve fits in is about 4CM from min to max. The results with a 50 gram fule load are very interesting, both when the iCan is used alone and when it is used with the draft enhancer. More to come on this.