I dont know, but after reading several similiar posts, I have decided to not try out topbars for myself. Tillie, a well respected member on here, was at one time about to light a match under hers I think. Ill just continue to intersperse some foundationless frames for my natural comb pleasure. Are you using some type of starter strip on your top bars?
VolunteerK9, I strongly encourage you to give TBH a try despite what you've heard (Tillie, too! Try it again!). I installed my first TBH with packaged bees in April. Two of my first-year-beekeeping mentees did the same. Each of us also installed packages in several Langstroth hives, and I have to say that all the TBHs are way outperforming those bees in Langs. It surprises me that they're doing so well because I half expected not to like the TBH experience. But I do. Each of us quickly constructed another TBH and plan to increase TBHs in the beeyards in coming years. We're all hooked.
I followed Michael Bush's suggestions for modifying the TBH plans found on his website...this modification not only allows me to exchange top bars (which are 19"...same as Lang frames) with Lang frames when necessary, but the additional width has kept the bees (so far) from attaching comb to the sides.
Suggested-modification thread: http://forum.beemaster.com/index.php/topic,30309.msg256048.html#msg256048
I'm a sucker for ugly, so I'm thrilled that I can make my TBHs from inexpensive cedar fencing and used corrugated aluminum from an old barn roof for a lid.
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