These are plans to build a Kenyan insert for a British National brood box and assume the dimensions found here:
This was designed to accept the same follower boards and 17-inch top bars as Phil Chandler's horizontal top bar hive. Several BN brood boxes could be modified to form a Warré-like vertical top bar hive or it could be used to super a Chandler hive. It could also be used as a bait hive or nuc.
The first step is to make new top side rails that will hold the top bars and support slanted (Kenyan) Masonite sides. A table saw will be required. Cross cut a piece of 4x4 (3-1/2-inch square) to 16-5/8 inches and rip according to the following profile:
Save the piece shown shaded in the bottom left-hand corner. It will be trimmed to 3/4-inch high and glued to the top of the new rail to form a lip that will enclose the top bars. The slanted cut is made by raising the blade and rotating it 24.5 degrees. Note that you may need to flip the piece and make a second pass if your table saw does not raise high enough. The triangular piece that is removed will be flipped over and used on the bottom of the Masonite side panel.
Here's an end view that shows the new side rails fitted into the exisiting BN rebates and Masonite side panels attached.
The triangular pieces cut from the 4x4 are flipped upside-down and attached to the bottom outside (the non-shiny side) of 12 x 16-5/8 panels of 1/8-inch Masonite - also called hardboard or tempered hardboard - with water-proof wood glue and one-inch wood screws. The Masonite panels should now stand on a flat surface at a 114.5-degree angle. The new side rails are placed in the existing rebates of the British National and the tops of the Masonite panels attached with glue and screws with the shiny (tempered) sides in. The bottoms of the panels should be 5 inches apart. Insure the flat side of the triangular blocks are resting on a level surface while attaching to the side rails. New end rails are cut from 3/4-inch stock and are 2-7/8 x 18-1/8 inches. These are attached to the side rails with glue and 1-1/2-inch wood screws. To make the insert permanant you could drive 1-1/2-inch wood screws through the ends of the BN into the bottom blocks. Flip the whole box upside-down and fill the dead space between the original BN sides and the slanted sides with wood chips and staple a fine mesh screen over the opening. This will help insulate the hive and absorb moisture from the box below when supering. A shallow BN honey super could also be bottomed with mesh and filled with wood chips to make a quilt box. The original floors and roofs can be used as is. Orient the box on the floor so that the entrance is perpindicular to the top bars. This will allow the bees to better ventilate between combs.
Here's a top view showing the hive filled with 11 top bars and two half-inch follower boards (shaded and labeled "F").
The follower boards are made by following pages 7-12 of Phil's free hive plans found here:
Note that the center 5 bars (numbered 4-8) have 1/2-inch holes drilled between them to serve as bee passages when supering. These can be covered with narrow strips of Masonite when starting with one box and uncovered when a super is added. Insure that the holes are within the center five inches of the top bars if supering with an identically modified box. This area is shown with dotted lines in the top view.
Anybody want to try this and post some pictures? I imagine that British Nationals may be hard to find in the US.