Read this article carefully. It clarifies a lot of misconceptions about how to use Top Bar Hives. TBH’s have a reputation for mis-shapen combs and poor temperature control, this explains some ways these can come about.
A comparison between Hunneybun’s side-entrance TBH and my own end-entrance ones (see post below, “A Queen cell discovered”) clarifies several issues with TBH hive design. The comb structure is very different between them – where my TBH’s have “perfect” combs hers vary in thickness along the bar, being thin at one end and thick at the other. Her hive is essentially identical to mine, apart from the position of the entrances, providing an excellent controlled experiment with one major variable – but dramatically visible differences.
The thickness along the bars in her hive varied so much that we were unable to optimise the spacing between bars. There were either huge gaps at one end or combs almost touching at the other. We eventually realised this was because bees consider the entrance to be the front of the nest, no matter what direction the combs / bars run in and had built their nest “sideways” in her side-entrance hive:
The colony always builds brood comb near the entrance, as that minimises the distance required for the most common task of trucking food to the young. Excess food is stored at the back of the nest, away from the entrance. This may not be where the beekeeper assumes the back is!
With end entrances, I have never seen variable-width comb. Brood comb is thinner than honeycomb, but both are a consistent thickness. One only needs two sizes of spacer between bars.
(When I began beekeeping, I didn’t realise the importance of spacers between bars. So I got bridging and weird shapes between combs. Once I understood about spacing, this problem vanished.)
Because the colony in the the side entrance hive was small (originally a cast), they had not reached the ends of the hive and it was easy to spot the radial building pattern. But the cross-section of the hive, between the two follower boards, is rectangular. This leaves large volumes of empty air to heat, which isn’t optimal for winter. This may explain some of the temperature control problems (chilled brood and overwintering issues) reported by some TBH users.
In my experience, the only downside of end entrances is that you need to move a few more more bars if you wish to inspect the brood area. But as I am a moderately low intervention beekeeper, and I’m a lot faster now I’m more confident, and one can often move several bars at a time, it doesn’t take much longer. And if I need to medicate the nest, say with icing sugar, I simply remove a spacer and sprinkle it down there without needing to move lots of bars.