Ok, I've been watching videos of horizontal hives and I am intrigued... I like the fact that you don't have to stir the whole nest up if you just want to rob some honey or check a frame or 2. Seems much less disruptive than unstacking their house, tipping them everywhich way, stacking them on the ground in the wrong order, shaking some out on the ground in the process... My only question is if it would be possible to put a queen excluder in one to keep her to one end of the hive so you know you have pure honey on the other end. Then you could possibly make a hybrid hive with flow frames on the honey end and normal ones on the brood end for even easier honey harvest. Could even possibly make it so the flow frames drain down under the hive and make another box under the hive to put the jars in so you could crack the frame and walk away without worrying about a ton of bugs getting in the jars.
I’ve never used one... so take this with a grain of salt ...
But I have intended to build one and try it, and over the years I have read a ton about them from those that have kept them on beek forums... and I’ve talked with beek friends that have had or still have horz. hives...
Many folks build giant coffin length boxes that are unrealistic as far as the queens ability to fill it with brood and/or their local nectar flow’s allowing the bees to fill it with honey...
And it’s common to hear that the bees don’t store honey sideways very well... at least not without some frame management from the beek... so there is a risk of the queen becoming honey bound if the beek doesn’t keep up...
Where they seem to work well is where you shuffle honey filled frames to the outside and replace with empty frames, and then remove the filled frames once capped...
so the honey collection is a bit more like the warre hive in that you take a bit here and there, rather than all at once...
But the idea of getting the bees to stack honey into ten or twenty frames to one end in the same way that they fill supers vertically in a Lang’s hive, seems to be difficult to achieve... at least for most folks in a temperate climate with a fairly long growing season...
And there are proven strategies for shuffling frames in a horz hive particularly in fall and then again in spring... but I forget what those are at the moment
As for queen excluders, I think I’ve seen people use a standard excluder built in a custom frame in a horz hive, but more often a divider board is used with honey frames on the other side... the queen is unlikely to move to the outside of the brood frames across the divider than she is to move up into a honey super on a Lang’s hive... so a traditional queen excluder is probably not needed in a horz hive
I don’t have any experience with ‘flow’ frames... they seemed like a ‘gimmick’ to me but maybe there is something to them, I don’t know?
In any case, I’d still like to build a horz hive one of these days, just to put some theory into practice...
Be sure to pay attention to folks on the internet that have been running a horz for multiple seasons vs. all the internet ‘look at my new horz hive’ information ... I think they can work, but not really any better than a vertical hive... other than the point you make about not disturbing the brood nest as much