Quite often I see discussions pop up regarding one top-bar hive length or another, and which is best. My hives, based on Wyatt Mangum’s design, are three feet in length. I see that a lot of other people advocate Michael Bush’s recommendation of a 4 foot hive.
After much reading to see if there was a “best” length I realized that even hives of the same length may have very different volumes due to the height and widths of their ends. When I did the calculations I found that most of the most commonly recommended hives have pretty similar volumes despite their difference in length.
By my calculations
A 3 foot Wyatt Mangum design has 69 liters of volume.
A 4 foot Michael Bush design has 72 liters of volume.
So while there is a 25% difference in length, there is only a 3% difference in volume.
A Top-Bar Hive’s Volume Is More Important Than Its Length
I ran the numbers on several other noted top bar beekeepers and found that nearly all of the recommended hive dimensions yielded a volume somewhere between 70 and 80 liters – only a 14% difference between the smallest and largest. Now when I build my hives I keep them in that range. It’s worth noting that a double deep Langstroth is about 85 liters.
When I started beekeeping I started with a top-bar hive. While far less common than the traditional Langstroth box style hive, I figured it would be less expensive to build (around $50 as compared to $200) and if I didn’t like beekeeping, I wouldn’t have invested a lot, so no big deal. I picked up Wyatt Mangum’s book and got started. It turns out I love it and have been at it for years.
In a top-bar hive, bees attach their comb directly to the bars which form the roof of the hive. Because of this, the bees can pass around the sides of the comb but not over the top. Beekeepers that use Langstroth style hives will often say that top-bar hives are unsuitable for the overwintering of bees because when the cluster reaches the top of the comb they will run out of food stores because they can’t pass over the top and move to the next comb. Of course this is how the cluster moves from comb to comb in a Langstroth hive so if that is your only experience keeping bees I guess it’s a reasonable assumption.
In truth, while in a top-bar hive the bees normally can’t pass over the top of the comb, a strong colony will just pass around one side or the other – so normally not being able to pass over the top hasn’t been a big deal in my top-bar beekeeping experience.