Some thoughts (take them or leave them):
After much though and research, and realizing that my woodworking skills are average at best, I've decided on the 8 frame medium detailed at Honey Run Apiaries.
LINK to PDF of Plans
Probably a good choice. I don't recommend anything smaller than 3 deep frames or 4 medium frames. Personally I don't really like anything larger than 6 medium frames, just due to the weight of the item, but this size should work nicely for you. The single frame thickness is key, in my opinion, to truly maximizing the value you get from an observation hive (and really seeing everything that happens). The design also doesn't call for many complex joints or cuts, which is good for a modest woodworker.
My question is ...Is it really necessary to build the outer frame with 2X4's? . . . I'm thinking 1X4's would make it a lot less bulky looking, not to mention a bit lighter...but just want to make sure it's still structurally sound.
I'd recommend against going with 1x4's. Two concerns I get. First, you are using but joints in the corners, not complex joints (which is fine). A screw put into end grain doesn't provide fantastic hold as is. Now add into the fact that you cut down the thickness of the wood by half, reducing the surface area that will be glued, and it's a significantly weaker joint. In addition, this thing should be about 5 feet tall I think, with only a little bit of support in the middle. A 1" thick board (which is really .75" thick) and 5 feet long can really bend considerably. A 2" thick board (which is really 1.5" thick) will also bend, but much less so. Trust me when I say this, you don't want any of these boards to bend or shift when you are moving this thing from it's stable spot to outdoors for maintenance . . . TRUST ME!
One of my designs had a think peice of wood on the side rails. I had to throw it into a car to take the hive to an outyard to stock it before taking it back home (which really wasn't a good idea anyway). I hit a bump in the road, the wood flexed, popped out of the locking mechanism that was holding it in place, and the hive burst open. While I was on a highway, in an enclosed car.
Your situation isn't as extreme, I know, but the same thing could happen when you move it outside to do maintenance. You'll need two people to move it (it will be heavy, regardless of whether you use 1" or 2" wood), and if you lay it on it's side (any side) the wood may flex some.
Not to say you can't use 1" thick wood. Looks like you already chose that. But just test it out before you put bees in it. If it seems to flex a little, glue another 1" thick board to the outside. My take on it at least.
Also, I'm toying with the idea of leaving off the jar feeder, since I'm trying not to feed unless absolutely necessary...in an emergency I'd simply insert a frame of honey instead.
I'd change your thought process post haste. You need a jar feeder. You need a feeder of some kind. Even if you hope to never use it, have it anyway.
Observation hive colonies can't really regulate brood or temps like they can in a normal colony. As a result, they are very "boom" or "bust". The issues an observation hive encounters are the same issues a normal colony encounters, only it has a much quicker effect on the colony overall, for one because their configuration is different, but mainly because their population is smaller. I've seen Observation Hives crash in a matter of days, for a variety of reasons. One of a few being not enough stores. So you need to be able to feed them at the moment you notice a problem, and not later, as the weather may not be right for you to take them outside and do the work you need to (or you don't have time because of work, or you don't have a second person around to help you move the hive). While a normal hive will hang in there for a few days for you to get around to it, an Observation Hive won't always. They'll just swarm, abscond, die, get infested with SHB (or wax moths occasionally) all because you didn't get around to it that day.
Get a feeder. You won't regret it.
Issue #1, The current design that I'm following calls for the frames of the doors to butt up against the inside frame when the doors or shut. I see two potential problems there, First, a lot of smashed bees when closing the door, and second, an invitation for them to propolize the seam. a 7/8" door frame is what is currently called for and would fit flush. What would be the problem or drawback to making my door frame 1/2" wide, assuming it'll be structurally sound, thus leaving 3/8" (bee space) between the inside frame and door frame when shut???
By saying the inside frame is butted up against the frame of the door, I'm assuming you are referring to the "self spacing" portions of the end bars on the frames, right?
If so, this is exactly what you want. As tight of a fit in this spot, the better (believe it or not). This will literally hold the frame in place as you move the whole observation hive inside or out. Larger and it will shift when you move it. When that happens, it's impossible to correct. You can lose an entire side of one frame, as the bee space becomes too small, and it gets infested with SHB as they can't clean it out. The other side then becomes too thick, and bee space is not right, and the bees build wax on the frame. A disaster (again, I know from personal experience).
The key in a good observation hive is two fold:
1. The frame of the door butts up tight to the self spacing portion of the frame end bars (and you can put vasaline on the door frame or end bars before you close it, which cuts down considerably on propolis), and
2. The glass of the door (or window) recessed away from the door itself. If not (like if you took a sheet of glass and just screwed it to the side of the observation hive) the bee space is off.
Remember to maintain the right bee space from GLASS TO GLASS! That's 1 3/4" from my perspective (talked about this issue in Post #9 here: http://forum.beemaster.com/index.php/topic,30161.0.html
). Some observation hives are slightly more, others slightly less. Mike Bush talks about this somewhere on his website, and opinions vary, but 1 3/4" from glass to glass appears to work best for me.
Issue #2, This design doesn't have a screen bottom with an accessible clean out drawer or compartment...I had not planned on putting one either, but could possibly still modify mid project to accommodate one...but would prefer not to! Is this a mistake and this is really needed, or is it more of a "nice to have", but not a must?
Not a must at all. I've had it in some, not in others. I haven't really noticed any difference. In my last build, I had a slide out drawer so I could do mite counts. I don't think I ever really did. It ends up making a compartment that the bees can't access and clean, so you have to (more work for you). Without the screen, the bees will clean it out when they need to.
I've seen, occasionally, when things get really bad, they may not clean out the bottom right away. But that's really just an indication to you that something is going on that might require your intervention.
As long as the ventilation in the hive is correct, you don't need a screened bottom. Proper vent holes are, however, necessary.
Let me know if any of it wasn't clear. I'll see if I can help in any way possible.