I measured the cell size in my top bar hive today. Generally I tend not to swap combs around very much in it. The measurements were made, where they could be, top right, middle, bottom left and from the front of the hive to the back. 16 combs had been drawn on which no 14 was drone. There were occasional patches on the others also. Sometimes I wasn't able to measure cell size because of the wrinkled honey cappings.  The top bars are 17" long and the hive is hemi-cylindrical so the maximum depth is 8.5" - beespace.  The shape meant that generally there wasn't much difference between middle and bottom left. The measuring tool was a piece of card with a truncated wedge shaped quadrilateral cut from it to measure across 5 cells.

 

The average top right was 5.37mm; middle 5.25; bottom left 5.25.  Front to back, bar 1= 5.1, 2 = 5.17, 3 = 5.1. 4 = 5.2. 5 = 5.43, 6 = 5.2, 7 = 5.2. 8 = 5.37, 9 = 5.37, 10 = 5.33, 11 = 5.4, 12 = 5.5, 13 = 5.4, 14 = drone, 15 = 5.23, 16 = 5.2.  The smallest size was 5.1 and the largest (excluding drone) 5.6 mm.

 

The comb was drawn from either a bead of wax drawn along the centre underside of the bars or from the footprint of an earlier comb. 

 

As can be seen from this single sample, cell size is greater aloft than alow.  A smoothed graph from front to rear shows smaller cells at the front (warm way) gently rising to a rather flat peak at comb 12  and then diminishing by comb 16 almost to the number first thought of.  The downward curve seems smoother than the upward one.

 

Not a lot can be learnt from a single sample, so over to you chaps and girls to do some measurements of your own.

 

Chris