>Theoretical question: If you had a 48" long KTBH with entry holes on the long edge, and put a follower board in the middle and put a colony in each side, is it likely the two colonies would outgrow the box? (and in what time period? Ok the first year; overflowing the next?)
Why not just pull the end bar in and use the gap as the entrance with no holes? Anyway, the answer is yes. Most likely in the first couple of months. But the answer also depends on the cross section of the hive. To large makes combs hard to handle. The typical comb size in mine is about 100 square inches or less. And the length on mine are about four feet. Mine typically from a package build up, fill the hive and swarm about June with only one in the hive.
>Is a 48" KTBH more than big enough for *one* colony, but potentially not quite big enough for two?
No. It's not really big enough for one unless you harvest frequently, but then again they sometimes don't want to go much more than 48" horizontally.
> Or could you safely stuff two colonies in so long as you're very conscientious about checking for excess honey and removing it to allow more space?
No. There is not enough space for them to have enough stores for winter.
>Thinking on the above, I started up with various "well, you could engineer it so you could add a super over the top of the KTBH..." but that kind of got me into the realms of "wouldn't that just be a funky Warré Hive?"
Yes it would, sort of. Nothing wrong with that...http://www.bushfarms.com/beeshorizontalhives.htmhttp://www.bushfarms.com/images/LongHiveSupered.JPG
>And on that subject, what is the difference between a Langs and a Warré, other than the frames v. top bars and a quilt on top?
Not a lot. Bees fill whatever space you give them.
>I get that TBHs are less stressful on the bees - less intrusive to open up for inspection;
Maybe a little. But not a lot.
> open mesh bottom for mites to drop out of
Most top bar hives don't and I don't see that it accomplishes that at all.
> - but how is a Warré less stressful on the bees?
Most never inspect.
> Don't you have to unpack it all to inspect? Wouldn't the mites just drop into the next box below? Or have I totally missed something?
The Abbe Warre' believed that you needed to hardly ever inspect at all. The smells and warmth of the brood nest were hardly ever to be disrupted. I think the success of the Warre' comes down to clean wax and natural cell size.