Top Bars expand past the end of the hive

[TX Ashurst]

As a woodworker I am very aware of the iron-clad rule that "wood moves". So I am embarassed to admit that I did not consider it when I built my TBHs. I built Tanzanian (straight-sided) hives and for my own reasons I joined the ends so that they sit about 3/4" above the sides. I carefully measured the width of 30 top bars and made the sides exactly that long, but I didn't consider that wood moves. In fact, wood moves back and forth laterally as it absorbs/releases moisture, but is pretty stable lengthwise. Since the top bars are laid in place side by side, they move considerably along the length of the hive. When I put the first hive out at the farm, on my first return trip the top bars were wedged tight into place and it was devilishly hard to get one out. I consider myself lucky that it didn't rain and the top bars didn't build up enough pressure to break the hives apart (which has happened to a lot of well-made but poorly-designed furniture). When I put the bars back, I found that I could leave one top bar out entirely and the rest fit quite nicely. The next week, it was tight again. That time I left the last top bar sitting in place on its side to fill the gap, and it has been fairly stable since then. So the top bars expanded the width of about 1.5 top bars over a hive with 30 top bars, or 5%. Yes, wood moves.

I still have both ends higher than the sides, and it is still a problem because it's difficult to keep the end sealed up tight when a top bar is too wide or too narrow to fit the last gap. I toyed with the idea of putting a strip of sheet metal across the ends of my hives so the top bars could slide over it when they want to expand. I will probably do that next year, but for now I have a follower board (actually just cardboard) in place so the bees don't have to defend such a large hive.

Any hives I build from now on, I will be sure to make the back end at the same height as the sides so that the bars can slide over them when they want to.

[drobbins]

WOW
that's a lot
I was a metal worker when I was young and as long as you weren't working with real close tolerances you could count on it to stay where you put it.
switching to woodworking requires a lot of rethinking.

I was planning on making a follower board which is actually a box that could server as a feeder.
Make it so a couple of inverted mason jars will fit inside.

Dave

[BerkeyDavid]

Tex
Yes the moisture in a hive really moves them laterally. I had the same problem. It gets worse over time. If you can just cut down one side (away from entrance) it will give you some slop. really gets crazy when y ou start moving different width top bars around.

[Michael Bush]

On my KTBH I leave the gap at the front (which is my entrance) and put them tight to the back. On my TTBH I can leave a gap at either end and usually do. The front gap is the entrance. The back gap is covered by the covers. They don't have to come out perfect. And they never will. [img]smile.gif[/img]

[Scot Mc Pherson]

My hives have a cleat in front to push the bars up against as I prefer the tightness up front in the brood nest where comb spacing is most important. The back of the hive is flush with the sides, and the last two topbars are really just covers for the back. The outer cover of the hive has cleats on the front and back and I push the cover against the last topbar to push all forward tightly. Then expansion can push the cover back as much as it likes, but the cover will keep it all from getting "loose".

[jim b]

I'm thinking the next one i build will have the sides extending out beyond the ends to leave me a place to hang any bars removed from the hive. Any thoughts on whether this is a good idea, or the other kind?-j

[Scot Mc Pherson]

I just go ahead and put the extra 2 or 3 top bars ontop of the hive. They won't have comb in them anyway if you manage your hives properly.

When I get to the broodnest I go ahead and pick up the extra bars again, and put them 'behind' where I am working. When I am putting hive back together I put them back 'infront' of where I am working again. Then when I get to the last bars, I go ahead and pick them up from where I put them last and pop them back into place. I know its a burden, but sure is a lot easier than figuring out some contraption to hold empty topbars.

Also when the sun is REALLY high in the summer, the the extra topbars provide a modicum of extra shade ontop.