THE FOLLOWING WAS UPDATED ON APRIL 08, 2014.
I made some improvements to the design of my ventilator rim (a.k.a. a ventilation eke). It’s still cheap and easy to make and should do a fine job at improving the ventilation of any Langstroth hive. First, I cut four pieces of wood for the front, back and sides of the rim. Here’s a shot of the side pieces:
Here’s a shot of the front and back pieces:
Note all the measurements are written on the wood — in both Metric and Imperial. The red line on the wood indicates how far the telescoping top cover will hang down over the rim. The ventilation holes are subsequently drilled below that line. I happen to have a 1.5-inch drill bit, but 2-inch-wide holes would probably work too; even 1-inch-wide holes (though you might want to drill up to four holes in the sides if they’re that small). Notice that the holes are drilled at an angle to minimize the chances of sideways rain from getting in. Here’s a straight on close up of one of the holes that sort of illustrates the angle of the hole (the hole from the outside is angled up so rain is less likely to drip down into the hive):
Behind each hole, I stapled on some screen or mesh. I don’t know the size of the holes in the screen. It doesn’t matter as long as wind can blow through and predator insects like wasps can’t get in.
So I took those pieces of wood and stuck them together with 2-inch-long brass screws, pre-drilling the holes first with a thin drill bit. You could probably use a hammer and nails, too, if you know how to swing a hammer. Note that the front and back pieces go between the side pieces.
Also note that the front of the rim doesn’t have any holes drilled in it.
That’s because sometimes bees returning to the hive get confused and will try to enter the hive through whatever hole they can find. But when the hole has a screen on the other side, they can’t always figure out what to do next, and they just sit there trying to get in until they die. So don’t drill holes in the front.
I don’t remember the cost of the lumber, but it wasn’t much, maybe $10 tops. The brass screws were cheap, too, because I bought them from a wholesaler. I didn’t use any fancy tools to make the rim. A hand-held jig saw, a power drill (which can also double as a power screw driver), and a cheap power screw driver. I didn’t use carpenters glue, though I probably should have. Then there’s the screen which cost about $5 for a 20-foot roll, something like that. I used a deep super to figure out the dimensions. I used the super as a workbench, too, for the drilling and the sawing. I didn’t use a T-square or anything like that to ensure right-angles. It might be a little rough around the edges, but as far as I can tell, the rim works. One aspect of the design I was careful about was making sure it was flat on the bottom. If one side happened to be even a fraction of an inch higher than the other sides, it could leave enough space for rain to seep in. I can’t think of anything else to say about it. Hopefully I’m not overlooking some glaring flaw in the design. Here’s the rim ventilating away on one our nucs.
Placed on top of the inner cover, the holes in the rim should provide adequate ventilation in the summer to reduce moisture in the hive, thus accelerating the honey curing process when honey supers on installed. The added ventilation also makes it easier for the bees to regulate the temperature of the hive for brood rearing. The rim is high enough so that the lip of the telescoping top cover doesn’t block the holes, and the holes are angled down so rain is less likely to get in. I’m still new at this beekeeping game, but it looks like a well designed ventilation aid to me.
P.S.: Check out this comment from Rusty for a detailed explanation of hive ventilation (reproduced in a full post on her website: Physics for beekeepers: How does ventilation increase honey production?).
ADDENDUM (Jan. 15/14): This ventilation rim can be converted into a winter moisture quilt by stapling fabric across the bottom. See what I’m talking about at Honey Bee Suite.
ADDENDUM (April 08/14): Remember to paint the outside of any rims. Moisture in the form of wind-driven rain or fog will easily seep into the hive if the rims aren’t painted.