Screened bottom board

[LizzieBee]

I just purchased a screened bottom board and switched it out with my solid bottom board last Thursday. I slid a tray with a graph underneath it, and then sprinkled the bees with powdered sugar. I came back a couple hours later and pulled the tray out. No varroa mites or other pests. Today I pulled the tray out. I didn't see any varroa mites, or other pests. But there was a lot of pollen that has fallen through the screen. I picked most of it off cause I felt sorry that it fell through the screen to be used for nothing and placed it next to their entrance. Most of it fell off but some bees came over and started eating it. It was about half a teaspoon of pollen. Does anyone else find that a lot of pollen is falling through their screened bottom board? Also, a couple of bees flew underneath and hung under the screen, as if they thought that was the entrance. I moved them and slid a thin wooden board into place underneath the screen.

thanks for your advice in advance!
Lizzie

[Van, Arkansas, USA]

{Does anyone else find that a lot of pollen is falling through their screened bottom board? }

Yes, my bees drop pollen all the time.  I use screen bottom boards also. I have tried 4 different manufactures and some definitely allow bees to get under the screen.  Freeman is a type of bottom board built specifically with beetles in mind, they are built tight not allowing the bees to get under the screen.  The Freeman Bottom Board is also the most expensive, patented so twice the price of the loosely built brands.
Blessings

[Acebird]

The bees should not be allowed below the screen.  It defeats the primary purpose of the screen, removing varroa from the hive.  It can cause problems get bees lost because they think they are at the entrance.

[LizzieBee]

My bees cannot get to the underside of the screen unless I do not have the tray in place. In this case, while I had it removed and was evaluating it, a few bees began flying underneath the screen.

[paus]

I have had all of the above problems.  I make my own double screen bottom board.  They are bee proof and catch lots of SHB.  I have started using a board with only the back third screened.  I am making a beetle bait from commercial and my mixture with shortening, a dab of honey, the bait, and sweepings from the bottom board and boric acid.  There is a tray between the screens with this bait in a throwaway aluminum tray. seems to work for SHB.

[cao]

Does anyone else find that a lot of pollen is falling through their screened bottom board?

That happens all the time.  Don't feel too bad the bees will typically bring in more pollen than they need.  That's how pollen traps work.

I have started using a board with only the back third screened. 

I've thought about that too, having a hybrid bottom board.  Haven't done it yet.  I was thinking about just having the back corners screened since that the corners is where the bees chase the SHBs to usually.

[BeeMaster2]

I run all screened bottom boards in my hives. Some hives drop lots of pollen and others do not drop any. It seems like the stronger the hive, the less they drop. Some of my 5 stack hives keep clean trays for weeks at a time.
Jim

[little john]

The bees should not be allowed below the screen.  It defeats the primary purpose of the screen, removing varroa from the hive.  It can cause problems get bees lost because they think they are at the entrance.

Yet another common beekeeping myth ...

OMFs are not a new idea, but have been around for about a century and a half, their main reason for use being to promote good wintering under harsh conditions.

When they were first advocated in the U.K. as an aid in the fight against varroa, many beekeepers were frightened to use them because they thought the bees would winter badly, even though they had been used successfully for many years in quite cold climates.

http://www.dave-cushman.net/bee/open_mesh_floors.html

LJ

[BeeMaster2]

Good post LJ. I did not know that they have been around for 150 years. I put a board under my OMF swarm trap white it is set. Then when I have to move it a can just remove the board and keep them from overheating during the trip.
Jim

[Acebird]

Yet another common beekeeping myth ...

There is no myth.  Many things are made for one purpose and used for another.  SBB are only used for TEMPORARY ventilation.  That doesn't mean you can't run them wide open all winter long.  I used to do that.  I have never heard of any migratory beekeeper using SBB for ventilation and they run hives thousands of miles across the USA.  When they are used for varroa inspection or control you defeat the purpose of the screen if you let the bees get to the tray where the varroa fall.  They just jump back on the bees.  Using a SBB for winter ventilation is completely unnecessary in the Utica area.  All it will do is burn up honey and bees.  It doesn't mean they won't make it.

[eltalia]

Good post LJ. I did not know that they have been around for 150 years. I put a board under my OMF swarm trap white it is set. Then when I have to move it a can just remove the board and keep them from overheating during the trip.
Jim

Same thing different design was the "Ventilated Bottom Board" sold standard with a startup 'kit'
here in the '60s/'70s. Aside from the poor design in being made from Masonite (compacted fibre)
they became known for their use as safe harbour by pests, ants, cockroaches, wax moths, frogs
loved them. Never used again in any colony I fostered since the mid70s, ventilation in summer
was something to be monitored up until the early eighties when I began playing with alternatives
to finally settle on screened penetrations to the super/supers eventually developing thatto be a single
50mm penetration to the top super. All boxes own the modification with control being done by bees,

Bill

[Acebird]

All boxes own the modification with control being done by bees,

If I could shout out a message to all newbies this would be the number one message.
Well done Bill.

[eltalia]

All boxes own the modification with control being done by bees,

If I could shout out a message to all newbies this would be the number one message.
Well done Bill.

Brian,
There is a caveat to my 'advice' as learnt(ed) for NH colonys, particulary those in high
 humidty temperate areas of the British Isles and Ireland.
Being there would be times when sudden higher moisture content within the hive body
 *may be* exhausted through an OMF when the cluster cannot break to open a closed
 vent penetration, or open one further.
For those periods in time an OMF *may* prove advantagous, however the beekeeper
 would need to be on the ball to adjust OMF exhausting as that ventilation may well
 then rob the hive body of generated heat, knocking the cluster off.
Where history has shown such to happen I would be revisiting the method applied to
 deny condensation buildup in a hive body during wintering.

Bill

[little john]

There appears to be a failure to appreciate how Open Mesh Floors work with regard to ventilation.

Whilst it is true that (generally speaking) moist air is lighter than dry air (which is why we have clouds up there in the sky), and that warm, moist air is doubly so - it is also the case that moist air can be heavier than dry air, and so 'fall out' through the open floor of a beehive.  So - how is it possible for moist air to be both heavier AND lighter than dry air ?  The answer lies in timing.

Anyone who experienced life before the invention of electrical refrigerators may remember the primitive cooling devices that were available back then - which relied upon the evaporation of water from a porous surface to cool the contents within.  That process is known as evaporative cooling, and occurs when water changes from a liquid state into it's vapour phase.  Such cooling renders the molecules of moist air denser and thus heavier than the dry air which surrounds it and so will descend.  If it's passage downwards remains unimpeded, then that moist air will exit the hive through the Open Mesh and be exchanged with drier air pulled up through it.

However, in the absence of an Open Mesh Floor where such an exchange of air no longer takes place, then cool moist air will begin to adopt the temperature of the surrounding dry air by thermal exchange.  Once that moist air has warmed, it will then begin to rise - and exit the hive through an upper opening, assuming one has been provided.  If not, then the warm moist air will start to condense-out upon any cool surface present.

Thus, moist air can exit a hive either through an upper OR a lower aperture.  The Open Mesh Floor as used in the cool to bleak conditions of Britain confers an advantage by enabling the upper part of a hive to remain fully sealed (and invariably insulated) and thus retain heat.  In much warmer parts of the world this may confer a disadvantage, in which case upper entrances would be more effective.
LJ

[BeeMaster2]

LJ,
In some of our desert climates they put swamp coolers in the ceiling of houses to work just as you mentioned.
I don?t know if they were ever built but Popular Mechanics once had a article that they were going to build these tall towers over shopping areas, with the doors wide open, where all they do is pump water up to the top and drip the water over porous membranes.  As the air goes through the membrane it cools and drops down the tower, once this starts, it provides cool air in the shopping area below.
Jim

[Acebird]

The answer lies in timing.

However, in the absence of an Open Mesh Floor where such an exchange of air no longer takes place,

LJ this is an assumption not a fact.  If a solid bottom board was used it would go out the lower entrance.  The timing question is how long does this transfer take?  When beekeepers talk about ventilation needs of the hive are they referring to 3 air changes a minute or 1 air change an hour.  I think it is more the latter because I have experienced no negative effects through the winter by closing off my screen bottom boards.  More then enough air changes occur with just the front entrance and a small top vent.

[paus]

I agree with ACE  I have placed a board in the bottom screen in the winter and I have left hives with nothing but the oil pan in bottom there was no difference.  I have started using screened top boards and I placed a cloth over the top screen no difference but I did too few to make a legitimate observation.  Several Beeks in my club never close the bottom screen.  This is in NE Texas.

[little john]

I give up ...

I've tried my best to explain why both Upper and Lower Entrances will work - depending upon climate.

I've tried my best to explain why beekeepers in some parts of the world swear BY Open Mesh Floors, and yet why others swear AT them.

Only to be met by the predictable objections of the forum's Naysayer who wants to be presented with some mythical entity called 'facts' rather than a reasoned explanation based upon the physics involved, and my knowledge of the industries which use these self-same principles.

I really can't be bothered to argue about this anymore - it's just too much hard work battling against ignorance.  But what I would say now is: "OK - then YOU find a better explanation".
 
LJ

[Acebird]

I am sorry you feel differences of opinions as ignorance when it differs from your opinion.

[eltalia]

I am sorry you feel differences of opinions as ignorance when it differs from your opinion.

One.
LJ presents an explanation formed around science (physics) in a situation specific
to a contained living organism. Factual devolvement of elements present could not
meet the criteria of "opinion".
Two.
"Ignorance" is a strong word to describe what is really scarcity, the spotty presence
or absence of scientific principle I would suggest the majority of beekeepers own or
indeed would comprehend/retain when explained.

Where contributors do not own solid understanding of thermodynamics,
the laws around entrophy, enthalpy and temperature pressure relationships  for set
volumes the 'discussion' always defaults to "this works for me".
That outcome *is* opinion, and in the situation the thread topic forms from Lizzie's
questions, wholly irrelevant.

I'd be only too happy to build a new topic in the Development subforum for those who
would wish to air the application of science in maintaining ambient conditions within
the bounds of an artifical beehive.

Bill

[Acebird]

Bill there is a whole lot of science that goes into forecasting weather and still their track record here is about 50%.  I would suggest to the forecasters to read the Farmers Almanac and bring their numbers up 10% but that would be believing in ignorance.

[eltalia]

Bill there is a whole lot of science that goes into forecasting weather and still their track record here is about 50%.  I would suggest to the forecasters to read the Farmers Almanac and bring their numbers up 10% but that would be believing in ignorance.

I understand it was LJ who first used rain/moist warm air as an analogy however it is a very
long stretch to join weather as a "living organism" as you appear to attempt, and whilst we
(b'keeps) entertain such fancifullness there always will be 10 answers to one question - or
whatever numbers are flavour of the day. :-((

The whole of the answer to hive body environments lies in science.
The prime being physics, well known.
The secondary being bee biology, also well known yet rarely understood.

As put, both can be aired in a specific topic, elsewhere.

Bill

[Dustymunky]

If anyone is in Portland, OR area I will gladly give you 3 slightly used SBB.  I dont use them anymore. I dont think bees like that much ventilation. I also think it causes the bees headaches when paired with bottom entrance. Bees are forced to walk across the screen to exit and enter. Their feet are like little grappling hooks and just watching them it looks like they struggle to walk on the screen.

[little john]

FWIW - earlier I said the issue was down to timing.  By 'timing' I was referring of course to the physical characteristics of a molecule of air - and thus it's behaviour - changing over a period of time: at first it's made heavier than air due to evaporative cooling; later - if it still remained within the cavity - it would begin to warm, and eventually become lighter by virtue of this, such that it would then ascend.

(Paragraph deleted by admin) PM sent.


However - let's take a look at an example of such passive gaseous exchange:
During winter, the front entrances of even my largest beehives consist of 2x 22mm diameter holes.  If you run the figures, that's 1.18 sq.in.  On some hives - notably those few I still have with solid floors - the entrances have been reduced by the bees with propolis to between 12 and 15mm diameter.  Staying with the higher figure, that's 0.55 sq.in.

The OMF's I use have an area of 290 sq.in.  That give us a comparative surface area ratio of between 300 and 530 to 1.

(Paragraph deleted)

But I will not enter into pointless discussions about this issue anymore, as I have far more important things to be doing with my time.  My over-winter losses have been 0% for many years now, and I no longer see either chalk brood or nosema.

Cordially yours,
LJ

[BeeMaster2]

This board is not here to insult other members. I have removed the insulting paragraphs. I would have removed the entire reply but there is good info here. There is no need to throw the insults, just state your case.
Jim

[Acebird]

The prime being physics, well known.
The secondary being bee biology, also well known yet rarely understood.

I think you have them reversed Bill.  However, both are sciences with boo coo variables.
I have read that bees control the hive environment to 50-60% RH.  It is easy for me to understand how they do that when it is 20% outside the hive.  I can't figure out how they do it when it is 80% outside the hive.  We do it in our homes with a condenser.

[BeeMaster2]

Ace,
I would like to know the same thing. 85% RH is our low during the day. 95 to 98 at night.

[eltalia]

@Acebird
"boo coo variables" is not something in my vocab archive Brian,
a tag eyed with suspicion rising only.
It is easy enough to cherrypick an element of ambient to
then argue around an individual's understanding of
componentry... pointless though without the deeper knowledge
of basics being apparent at the start.

As put, if genuine interest on the whole of the topic spurs
the topic elsewhere I am happy to build that and not hijack this
thread.

Bill

[Acebird]

As put, if genuine interest on the whole of the topic spurs
the topic elsewhere I am happy to build that and not hijack this
thread.

Bill

One only needs to start a new topic and that can be answered.

[eltalia]

As put, if genuine interest on the whole of the topic spurs
the topic elsewhere I am happy to build that and not hijack this
thread.

Bill

One only needs to start a new topic and that can be answered.

Wellll, off you go Brian...get to it to "just do it".
My post (#19) even hands you the topic banner, in plain english. :-))

Bill