Variable Cell
This attempt to producing variable cell size foundation was a failure.
Drone, large cell and small cell size foundation.
Is it possible to trick bees into building a natural broodnest structure consisting of a variety of cell sizes on a single frame? Would they draw out such a foundation as easily and rapidly as they do natural comb? Would the bees detect and remove mite-infected brood? If it's possible, then all the advantages of a natural broodnest could be realized in standard equipment with its strength, compatibility and flexibility.
The Test
I obtained some drone sized foundation, some large cell foundation and some small cell foundation. I cut a 1 1/2" strip of the drone foundation, a 1 1/2" strip of the large cell foundation and a 5 1/2" strip of small cell foundation to fill out the balance of a deep frame.
Drone foundation was inserted at the frame's top. The large cell foundation was inserted next. It slightly overlapped the bottom edge of the drone foundation. The small cell foundation was inserted last. It slightly overlapped the bottom edge of the large cell foundation. The Y orientation was maintained between the different sized foundations. They were squeezed together where they overlapped.
This hybrid foundation was embedded in a standard frame with the largest cells at the top to mimic how the bees construct natural comb.
A completed test frame.
Four deep frames were prepared and inserted, in various locations, in my small cell hives at the end of June. These hives consisted of 3 deep boxes filled with bees. The yellow sweet clover flow was on. It was a great time to draw out some foundation. One frame was inserted in the center of the broodnest, in the middle box. Another frame was inserted on the edge of the broodnest. Another was inserted above it and another below it. Each frame went in a different hive.
I inspected them several weeks later. This test was a complete flop. The bees worked the drone comb. They wanted larger worker sized cells and drew it out freely. But they made a mess of the small cell size, with lots of odd shapes and transitional areas. Only a few square inches of good small cell comb was found. Everything else was reworked to a larger size. This was the worst case of small cell comb building I've seen. It was so bad that I culled it on the spot. Then realized I hadn't photographed it. Sorry :>(
At least I know what doesn't work :>) It appears location is everything regarding nest structure. The bees aren't easily fooled. But maybe I'm not tricky enough!
Other Options
Worker brood cell sizes aren't distinct but gradually taper from one size to another. In this test, the cell sizes abruptly changed. Maybe the best approach is to heat and stretch some small cell foundation so that a gradient in cell size is more natural. Or a foundation mold could be built using natural broodnest comb as the master.
Another Approach
Different sized comb could be obtained, in standard equipment, by running both large and small cell frames within a hive. Frames with small cell comb would occupy the interior. Frames with large cell comb could be used toward the exterior. When my supply of small cell combs was limited, I ran six small cell frames in the middle of a brood box and four large cell frames on the exterior without loosing mite tolerance. Observations from my top bar hive indicate that four small cell frames should work. Such a small amount of comb could be drawn in five frame nucs and inserted in larger hives.