The slatted rack

Here's piece of kit I made for the first time last spring.  It is a slatted rack and acts as a spacer below the brood box and above the floor.  I first read about slatted racks on Rusty Burlew's blog on Honey Bee Suite (https://honeybeesuite.com/blog/).  Slatted racks are in common use in the United States and are commercially available for 8, 9, and 10 frame Langstroth hives (which have top bee space).

The modified British National Hive is built with bottom bee space but there is a lot of extra space (usually around 30mm) below the brood frames above the floor.  Some bees build comb on the bottom of the brood frames, often filling it with drone brood or using it to hide queen cells.  

The advantages of a slatted rack are:

1. It stops the bees building comb on the bottom of the brood frames as it restores bee space below the frames.  This is especially useful for colonies on double brood as it makes it easy to swap frames around with scraping the extra comb off the bottom of the frames.
2. It is said to keep the hive cooler in summer and warmer in winter.
3. It reduces draughts, especially around the bottoms of the brood frames.
4. It provides more room for the bees to hang out, reducing congestion in a large colony and perhaps reducing the tendency to swarm.
5. It moves the brood nest a bit farther from the entrance and encourages the queen to lay right to the bottom of the frame.

I couldn't find any plans for a slatted rack to fit a National hive so I adapted those I found for the Langstroth.  In essence it is an eke 50mm deep which carries 11 slats which are spaced to be below each brood frame.  So the outside dimension is 460 x 460mm.  The slats are 18mm wide and are spaced every 36mm to match the Hoffman frames above, so the spaces are 18mm as well.  Easy.  It is important that the slats line up with the frames above so the varroa mites that fall will pass through to the mesh floor below.  As a National brood box will take 11 frames plus a dummy board the slats are spaced from one side and are therefore asymmetrical.  (I keep my dummy boards on the south side of my hives - the hives face east - so the slats are spaced that way.)

At the front of the slatted rack there is a shelf about 100mm wide which is said to reduce draughts through the entrance, although I don't know if it makes much difference if there is a mesh floor.  I made the front, back and sides of the rack from western red cedar (some of it recycled from a restoration of the greenhouse) and the shelf and slats from pine.

This is the underside.  I don't think the depth of the slats is critical but mine are 44mm, so slightly less than the 50mm of the frame.

Because the National hive has bottom bee space, one very important modification I made was to put the slats and shelf flush with the top of the rack (in the Langstroth version they are recessed to provide the bee space).

You can find instructions for making a Langstroth slatted rack here, all dimensions in old-fashioned inches.

The rack stays in position all year round.  Here is my first one, nearly a year later.

I have now made three more and will fit them to my other three hives at the first inspection this spring.

You can watch a YouTube video of bees on the underside of a slatted rack here.