Hot day today in Adelaide, humid and 42 degrees C forecast, bees getting busy cooling hive. Wanted to know how much airflow is generated, feather gives a good idea , surprised me the amount shifted. 
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Hi Anthony, what I have done is hold a strip of light plastic down the front to see the inflow on the other side…and then move it across to see the outflow. This is one reason I think the wider entrance (like yours) might better allow for the circulation of air. With my narrower entrance hives, the bees can’t seem to organise the ventilation as well.
First photo shows wider entrance and the second shows the struggle with the narrower entrance. I have two with the narrow entrance and both are identical with bees coming out to cool. They tend to fan out one side of the wider entrance and the other side has air drawing in. These photos were taken just now- and it is a bottler in Tassie today too.
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Hi Dan, I’ve changed my entrance reducer strategy. I’m reducing my entrances in the middle so that I have one small entrance on each side for the purpose you are talking about.
Also it reduces the buildup of rubbish (chalk brood mummies etc) in the corner behind the entrance reducer, assuming that the entrance reducer is on one side, as some are.
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Hi Jeff…yeah, good idea probably. This issue has me in two minds, as the "best " entrance size is supposed to be the 15cm2 one, but you have bees landing and leaving and ventilating all in that small space…it just doesn’t seem to work well. I’ve just looked at the hives again, and the two smaller entrance ones are struggling and putting a lot of energy into cooling. The wide one looks quite normal. It is about 34 here at the moment which is really hot for here, and will go higher.
Do you find the bees leave one side free for air intake and fan outwards on the other?
No Dan, I haven’t looked all that close. I just set them up & move on to other things. Bees are fairly forgiving of what we present them with. They adjust their airflow accordingly.
I got the idea to place a middle entrance reducer after a newbee brought his brood box for me to put a colony into. He built it himself & placed a center entrance reducer after something that he read on the internet. I didn’t need any convincing to do that myself. I think it’s a great idea.
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Thanks Jeff…
Next time you are about to work the hives, please take a peek at the entrance area for me and let me know if there seems to be any ordered process going on with ventilation.
Hi @Dan2, I have checked the airflow across the width of entrance , it looks like the whole entrance acts as the outlet. I have a slatted bottom rack and screened bottom board with corflute removed, and SBB opening closed off with timber. The video shows what I mean, the airflow inlet I am supposing is the open bottom.
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that’s excellent Anthony. I like the feather on the stick idea.
Boy you guys have it hot in SA at the moment.
We got to 36 . As Jeff said the bees are adaptable and I found they went under the hive -between the concrete and the box and all around the back of it in the shade.
Yeah, I’ll do that. Not many of my hive’s entrances are set up like that yet. It goes back to what I said about the bees being forgiving of what we give them. It hasn’t been a priority of mine lately, I’ve been more concerned about swarm prevention & a bit of a current nice honey flow has kept me busy for a while.
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I made this reducer for my flow hive for all the reasons Jeff has mentioned but also thinking it would help combat the chalk brood that has started in my hive.
From what I’ve learned on this forum cold brood will result in chalk brood so as most of the brood on a new hive is located on the central frames that is the area I’m trying to keep warmer.
The mummies appears to be slowing up but it has been around 40c for the last few days so I’m not sure if my reducer has helped or not
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This topic only lasted a couple of day but I think it is important for us bee keepers in a hot climate. I recently, maybe a few months ago, made up new brood boxes and put a closure 1/2 way across the entrance but still maintained the same area of entrance.
That has certainly allowed for more air flow for the bees to fan cool air into the hive and I have even seen bees now fanning air out of the ‘air discharge’ side on a very hot day.
I think us bee keepers in hot climates should at least consider a duel bottom entrance as a positive benefit to our bees.
Regards to all
Erm…
Put the reducer in the middle having entrances on either side?
My strong colonys have no reducer year round yet beard like crazy summertime. I really want to trial a slatted rack but havnt gotten round to making one as they are not available here commercially as ‘commercial beekeepers don’t use them so they’re not needed’…
I really think there’s a market for a hobby beekeeping shop that can cater for our whims. 
Anyway @Peter48, a slatted rack may be a good men’s shed project also. 
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Much better than a salted rat… Sorry, in-joke. 
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Maybe I didn’t explain well enough, unless the hive has a full width entrance, the middle piece is equivalent to what is taken off the end pieces of the entrance, the entrance remains the same dimension in its open area, but the air flow through the entrances are better as there is no vortex of still air half way across a single entrance. The vortex is the same as in a cyclone with the still air in the centre, but of course in this case the air is moving horizontally through the entrance.
It will only bee in mid Summer heats that I will see the benefit, at the moment the highest temp at a hive has been 42c, but based on physics it will work, how much is the unknown, and I think that will variable with less bees fanning.
Cheers