Hi all

Adam wrote
>
> With the switch to open mesh floors - for Varroa control, we have
> effectively opened 1 "surface" of the hive. I was interested in the
> comments about it being like a hot air balloon, but still am not
convinced -
>  a balloon has a very narrow neck at the bottom and a very high
temperature
> going in. A hive would have much less surface area relative to opening -
so
> would moisture and wind regularly replace this "dead" air inside?
>
I would have thought an open mesh floor and a small heat source in the
centre of an otherwise empty hive would have caused strong convection
currents up the centre of the hive and down the inside of the walls.  On
windy days this pattern would be disturbed and internal air flows would be
unpredictable.  However we have a cluster of bees plugging the centre of the
hive controlling these convection currents.   They have complete control of
their heat generation and packing density and hence would be able to control
their immediate environment without much need to propolise, fan or consume
stores.  I see OMF's as a method of empowering the bees to look after
themselves provided you do not frustrate their efforts by generating your
own draughts by opening the top to cause a chimney effect.  All this assumes
you are working with a single brood box.  Double or triple brood boxes and
especially wrapped hives will alter the dynamics considerably.
I found during the winter of 2002/3 (my first incidentally) that the bees
propolised my top ventilation holes.  I took this as a gentle hint that they
preferred not to have holes in the top.   This winter (2003/4) I
experimented with 11 hives using varying amounts of top insulation and one
with a large ventilation hole and no insulation.  All 11 made it through the
winter and so far they all seem to be strong and free of disease.  I suspect
that if you have the right bees for the locality it's hard to go wrong.
Much of my OMF theory is just armchair beekeeping of course as I have been
building OMF's during the winter to try the system out for the first time
(for me) this coming season.
As for painting the outside I would guess that the amount of moisture
passing through the hive walls would not affect the bees much either way but
would cause most oil based paints to flake off and sealed wood to rot.  If I
fancied coloured hives I would paint them with porous paint to give it a
better chance of staying on.  However, I prefer to use nothing for cedar
hives and a colourless or brown porous preservative on the outside only for
deal and other softwoods.

Kind regards

Steve Rose, Derbyshire England

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