"Open the Sides of the Broodnest" - Steps:
1. Several weeks before swarm season, move each outside frame up into a new box and alternate them with new frames, directly above the Broodnest.
2. Insert a new frame on each outside edge of the Broodnest. (So that a Brood frame is only on one side of the new frame.)
3. Check them in 2-3 weeks and repeat if comb in the frames has been mostly drawn.
When to "Open the Sides of the Broodnest"
1. When daily maximum temperatures start getting to 15°C /60°F or above and the weather forecast looks good for the next week.
2. When Drone brood is being raised.
3. When you see a large number of young bees starting to do orientation flights in the afternoons. (Think - wax makers!)
4. When a good deal of pollen is being brought in.
"Opening the Sides of the Broodnest" is done when a beekeeper doesn't have spare drawn comb.
Why do you need spare drawn comb?
Swarm prevention is best done by giving a bee hive plenty of spare drawn comb and breaking up any solid bands of capped honey. The idea is to make sure that there is not a solid honey dome, as the bees want to set a boundary for the nest so that they can fill it up and swarm. Even the gap between boxes can be seen as a boundary, so frames they are using need to be moved.
Typically swarm prevention is done by Supering early and Reversing or Checkerboarding.
When bees are preparing to swarm, they don't make wax, but rather "save it up" for when they find a new home and need to build new comb.
"Opening the Sides" is all about triggering wax production before swarm season and then maintaining wax production into the main flow. So the bees build more comb for raising brood and storing nectar and also use up incoming nectar to max the wax.
As swarm preparation takes a few weeks, "Opening the Sides" is best done at least 4 weeks before swarm season. Several weeks beforehand is best.
The new frames should have only a strip of foundation as a comb guide. I would have no more than half a sheet of foundation on a new frame at most. There must be a HOLE close to the broodnest. The hole in the broodnest is what triggers comb building, (to fill the hole).
The "Sides" of the Broodnest/Cluster are opened up, rather than inserting frames into the Broodnest, so that the cluster is not forced to heat a larger area than what they are used to. Doing that can set back brood rearing and cause issues such as chilled brood if cold weather sets in at this stage of the season.
Bees will often build mostly drone comb before swarm season if the frame is completely foundationless. But with the foundation strip it ends up being about 2/3 worker to 1/3 drone comb. (Comb support helps. Such as wire, fishing line, or in my case I use thin bamboo skewers.)
Having some extra spare drawn comb will also really help with the bees moving into a new box quicker.
The hive should have a few frames with some capped honey, at least on the top corners. I prefer not to feed, but if they haven't got enough stores you may need to, as they will use up all their stores trying to fill the hole(s) with comb. Make sure you leave them some stores close to the broodnest in case bad weather sets in.
Also see: http://www.beesource.com/forums/show...-the-Broodnest