I have been using vertical entrance bottom boards for close to 10 years now and am very happy with them. Small hive beetles are not an issue in our climate, so I can't give any thoughts on that. I have recently did away with the rear vent holes as they just propolis them anyway and I have reduced the entrance to 6" wide. Also staple a piece of Reflectix under the bottom to improve insulation. Note the pictures show wooden hive, but I use beemax exclusively.
The advantages of the vertical entrance are:
1. Greatly reduces the draft on the bottom of the brood nest. With a standard Langstroth bottom board, the queen rarely, if ever, lays eggs on the bottom of the frames. With the vertical entrance there is no wind blowing directly into the brood area. It also creates hydraulic resistance for heat loss as validated by Derek Mitchell using computational fluid dynamics. Derek continues to do great research on the thermal properties of bee nests. His original paper,
Ratios of colony mass to thermal conductance of tree and man-made nest enclosures of Apis mellifera: implications for survival, clustering, humidity regulation and Varroa destructor, is
here. Warmer and moister brood chambers can also help with varroa control.
Temperature seems to have more of an impact on Varroa reproduction than most people thought. While 95?F is ?brood nest temperature,? that temperature fluctuates some with climatic conditions. By carefully controlling temperature, Varroa were found to reproduce best at 93?F. Performance was a bit worse at 88-91 and 95?. At the lower than brood nest temperatures, the post-capping period is extended about one day per 2?F. At higher temperatures the post-capping period is not shortened significantly. However, at ?brood nest? and higher temperatures, mite reproduction drops way off. In the same study it was shown that 53% of the mites on brood held at 59-68% RH (normal) reproduced normally but at humilities of 79-85% only 2% of the mites reproduced. Hot, humid brood nests are tough on Varroa. Studies of Apis cerana brood nests showed drone brood is reared at 92?F (perfect for Varroa) and worker brood is incubated at 96-98?F (too hot for Varroa). Purposely cooling the brood nest in Apis mellifera colonies by using a ?thin? hive lid, open bottom board, simulative feeding to spread brood out, and splitting the brood nest with frames of foundation doubled the numbers of mites on the bees.
The antivarroa bottom board must never be used with its bottom hole opened as this leads to a lowering of cluster temperature resulting in ideal conditions for varroa development. As confirmed in 2000, this situation not only negated the beneficial effects of the bottom board, it also resulted in a net increase in the mite infestation rate (29.2% more varroa mites, non significant) as compared to the control group.
2. Helps with robbing. Most robbers seem to prefer direct entrance into a hive, that is why robber screen (relocate entrance) work so well. With the vertical entrance, guard bees can not only patrol the horizontal landing area, but can also guard the actual entrance gap from above as well. Guarding from above provides a distinct advantage of intruders coming up from below.
3. Built in mouse guard. Preparing hives for winter is often a daunting task and often we run short on time. Never miss getting mouse guards on again. You fight to hard to keep your bees alive, don?t fall victim to mice killing a colony over the winter.
4.Vertical entrance provides drainage and air circulation during winter months even in heavy snow areas.
Topic: Please post your bottom board idea's.. (Read 1537 times)