Dadant originally settled on 38 mm because he was convinced it reduced swarming. He was correct, but the way it works can be a problem depending on local nectar flows. Dadant was trying to deal with colonies that built up to a spring peak several weeks before the main flow in his area. 38mm frames force the winter cluster to cover less total comb area which can delay spring buildup by 3 to 4 weeks. Thus the reduced swarming tendency.
Areas with heavy early flows have the opposite problem. Bees tend to build up to their spring peak several weeks after start of the main flow. 38mm frames exacerbate this timing delaying the peak even further. A prime example in your region would be canola which blooms very early and produces the main crop for many beekeepers. For these areas, 32mm frames make more sense. Narrower frames reduce bee space between combs to a size that will fit only 2 bees in a layer as compared to 3 or 4 bees in a layer with 38mm. The cluster can cover more comb surface and therefore spring buildup is 2 to 4 weeks earlier than other frame designs.
When I built my square Dadant hives, I made all of the frames with end bars just under 32mm. The only issue I have, and one I expected based on experience, is that the bees often rework comb into drone cells. I deal with this by installing a single shallow frame in each hive so the bees can build drone comb off the bottom of the frame. This satisfies the drone comb urge which prevents reworking full size frames from worker into drone cells.
Below is some info I wrote several years ago and have posted on beesource in response to questions about narrow frames. Reading it carefully will save a lot of frustration when it comes to frame spacing. I made a few minor updates to include square Dadant hive conditions.
There have been several articles published over the years advocating variants of the standard measurements of a frame. The January 1995 Bee Culture article titled Bee Space discussed using narrow gauge frames and referenced an article in the January 1977 issue. I first subscribed to Gleanings in Bee Culture in 1977. The article by Charles Koover plus financial restrictions inspired me to manufacture equipment, including narrow gauge frames. I went through three frame designs before I settled on the correct modifications. I have approximately 20 hive bodies using the narrow frames and have used them for 32 years. I also have used standard frames extensively for comparison. Here are my conclusions regarding narrow gauge frames.
Narrow gauge frames tend to bow and warp more easily during construction. This is because all the measurements for frame joints have to be reduced. The frame must be carefully cut to precise dimensions and assembled to hang straight and free. I glue and nail all frames to achieve this goal.
A comb which is even slightly bowed is unacceptable. The frames must be wired to obtain perfectly straight combs. Combs built in unwired frames will result in one side being deep and the other shallow. The bees will only raise brood in the deep side. Pins and other methods do not support the foundation adequately to prevent this bowing. Newer molded plastic foundation will hang straight if properly attached at the top of the frame. Plastic core foundations like duragilt tend to bow too much over time
Drone cells cannot be permitted because they will usually be at the frame's top or bottom edge. When a comb is removed from the hive body, bees will be crushed potentially killing the queen and causing excessive stinging because of the alarm pheromone released by the crushed bees. I renew the combs after about 5 years of use by cutting out the old comb and putting in new foundation. I use slatted rack bottom boards to reduce comb chewing and removal in the critical areas of the frame. The result is solid worker cell size combs which are easy to handle.
Narrow gauge frames in supers for honey production are useless because uncapping is almost impossible. I use and prefer 9 frames in a honey super or 12 frames in a Dadant super. The narrow gauge frames can be spaced to give this density. The advantage obtained with narrow gauge frames in a super is that uncapping is easier because there are almost no low spots in the comb surface.
The structure of the winter cluster is different on narrow guage frames. There is room for only two layers of bees between the combs as compared with three layers in 35mm Langstroth frames. A winter cluster on narrow frames is therefore slightly larger for a given number of bees than in standard frames. This is especially important in early spring when brood rearing begins because the cluster covers more comb surface. This allows brood rearing to expand earlier.
Narrow frames full of honey weigh less than wider frames because the combs are thinner. The combination of expanded winter cluster and lower hive body weight will result in a colony that starves out in the early spring. This should be addressed either by leaving more frames of honey for winter or by early spring feeding.
Spring buildup with narrow gauge frames is only slightly improved in my area because of weather conditions. The first pollen from willow is in mid February. The main flow starts about April 20th and peaks from the first to the twentieth of May. This means I have 9 weeks for spring buildup from the first incoming pollen to the start of the main nectar flow. With such a long buildup period, swarming is a significant problem whether using narrow or standard frames
The primary advantage under these conditions is that two deep Langstroth hive bodies can contain the brood of the most prolific queen. I have had up to 18 frames of brood, larvae, and eggs from an exceptional queen. The two outside frames in the hive body were full of pollen and honey and all 9 inner frames were at least 70 percent full of brood. With standard frames, this amount of brood would partially occupy 3 hive bodies, but with narrow gauge frames, only two hive bodies are required. A single square Dadant hive body has roughly the same total brood area as 2 Langstroth hive bodies.
One significant advantage is that when made to the correct dimensions, bridge and brace comb is almost nonexistent. Please note that some bee strains are excessive at building bridge and brace comb. The narrow gauge frames will reduce, but not eliminate this tendency in these strains.
Would I recommend a wholesale change to narrow gauge frames? No, but only because bees on them are less forgiving of human errors. They have slight advantages over standard frames in daily operation.
The standard hive body with standard 35mm frames has been proven in over 100 years of beekeeping. The only impetus that would cause us to change the size hive and frame we use today would be a dramatic change in the way we keep bees. Examples of such dramatic changes could be found in the operations of migratory beekeepers using pallet systems. They could use a square hive more effectively than the rectangular ones we use today. Also, if queens are bred to be more prolific with resultant higher honey production, the standard hive body and frame will show serious limitations.
