Hi Scot,
It's been quite interesting exchanging ideas about the natural behavior seen in our tbhs. What we've both seen has been quite consistent, yet our ideas about management are different. I think the different seasonal dynamics between Wyoming and Florida account for most of it.
Over the last few years, I've been selling and giving away most of my beekeeping stuff. I'm down to just a couple of tbhs and a half dozen Langs which I will probably liquidate, next year, before moving to Florida the following year.
I just haven't found any easy way to consistently expand the broodnest core in a tbh. It seems the bees know when it's large enough and aren't easily tricked into building a larger broodnest core. As you noted, they will trail it out at the bottom of the honey storage combs behind the broodnest area. That behavior is more predominate in a shallower tbh, but is still seen in a deeper one as well.
I think is has to do with a repeating structure I've seen in the honey storage area but haven't mentioned until now. In a horizontal hive, the repeating unit will occupy about half the volume or number of top bars as the original broodnest. The front of it consists of a couple of storage combs consisting of storage and a little drone comb. Then, the rate of change in cell sizes will mirror the rear half of the broodnest. The actual cell sizes will be much larger, but the amount and rate of change will be just about the same. If additional space is available, the pattern is repeated again. It's very easy to see in long, shallow tbhs.
The actual pattern is very hard to see in the comb itself, as the organization and actual cell size location, in the honey storage area, is very chaotic and not consistent from comb to comb. But when the combs are measured and the summary results are plotted, this pattern is obvious. The rate of change, in the amounts of the different cell sizes, mirrors the rate of change in the rear half of the broodnest core, except the cell sizes are much larger.
Another way to think about it is like this: In the honey storage area, storage cell size replace drone cell sizes, drone cell size replace the larger worker cell sizes, and large worker cell size replace the small cell sizes seen in the broodnest. The left-right comb orientation, seen in the broodnest is lost. And the comb tends to consists of patches of different cell size. But the larger cells are generally found at the top of each comb and the worker cell sizes at the bottom.
Take a look at the bar graphs at:
http://bwrangler.litarium.com/natural-comb/
This season, I tried an interesting experiment. One of my tbhs failed due to queen problems. So I took the broodnest core comb and placed it behind the original broodnest in another tbh. That provided twice the broodnest volume compared to what the bees bees would normally construct.
How's that for easily expanding a tbh broodnest :>)))
Would the bees operate within the original broodnest core volume and treat the additional broodnest comb as honey storage? Or would they treat the expanded broodnest as a very large broodnest?
Preliminary results indicate they choose the latter. Those behaviors associated with just the broodnest core, occured on all those additional combs. I will report more later.
Regards
Dennis