Mouse guards and chicken wire!

[Steve (The Drone)]

Jim- the national brood chamber and under super remain as-was on the stand. The W.B.C. lifts merely fit over them as an overcoat.

[Jim Norfolk]

Steve I don't think my question was very clear. A National brood box will actually sit on a WBC floor and the lifts fit over. What I meant was they had room to make the WBC box a bit wider and squeeze an extra frame or even two in. Why didn't they?

[Steve (The Drone)]

Good Question! One reason that comes to mind is that when these hives were designed we just had British Black bees which possibly over wintered with smaller colonies and were more frugal with stores. Our mongrels now require a lot more space which is why even National brood chambers are too small. Maybe someone else out there has more info on this?
Steve.