After reading all the post on TBHs I constructed a version to put the wild bees into. (If you go to bee forum you can read my post on how that went) Basically I built the top bars out of scrap popular and the hive out of scrap rough cut ceder. I made it so that it would fit medium frames in case I need to install a bee package or I can use the perma comb for the honey flow. The side bars are added to maintain bee space on the sides and give a little strength to the comb. I did run a kerf down the center. I also used a router to cut a 1/2 a bee space on each edge to form a full bee space between each top bar. I realize this hive does not keep in the simplicity of a tru TBH but it does not have the complexity of a reagular hive and frames.
Wish I had gotten the bees into it so I could give you an update on how it works.
Do you have frames with bottoms? The bottom bar is essential to tying the comb into the frame and having it stay. Otherwise the strings will cut into the comb and it will fall out.
As far as using it as a top bar hive, do the sides stay pretty straight on the frames? It would seem a bit flimsy until the comb ties it together.
I would be curious how it works. If the sides stay pretty well they may give a lot of support.
I was going to use capture frames and slowly replace them with the frames shown. Another reason why I wanted the hive to be able to accept medium frames. As for how straight the side bars stayed, they were fairly consistent. They sit in a dado cut on the end of the top bars. If anyone is interested, and I get a little time, I can post dimensional pictures to the web for everyone to look at.
Well, if they stay straight and provide some beespace there, I think they will add a lot of strength. I like them better than the center one that Topbarguy used.