[GregV]

Scroll down for photos and diagrams:
http://бортникъ.рф/ylei-krilatskiy.htm

Sizes are metric.
Total areas of the opening (as depicted) ~85cm^2

 

[BernhardHeuvel]

Which you can buy as well, called Happykeeper.

https://www.apiservices.biz/en/happykeeper

A good friend of mine uses and likes them. The idea is to let the varroa mites drop out of the hive through the bottom, without using a mesh, because a mesh is too airy. Too much ventilation. My friend uses it as a double bottom, to prevent the bees from building burr comb in the deep floor he uses. Mesh at the very bottom, happykeeper directly below the frames. There is a slot at the entrance, so bees can pass up.

Doesn't help too much with varroa though.

 

[little_john]

Good links, guys.

I've been looking for a possible alternative to a steel mesh floor for a while - think I'll try something along these lines - more for gentle ventilation, rather than as an anti-Varroa measure.
LJ

 

[GregV]

Good links, guys.

I've been looking for a possible alternative to a steel mesh floor for a while - think I'll try something along these lines - more for gentle ventilation, rather than as an anti-Varroa measure.
LJ

The "anti-Varroa" intent of the thing is not deserving the attention IMO, and I don't even care for that "mite-control" idea (marginal even if true).

The combination of ventilation, ease of cleanup from outside/below, and thermal mass of the wood are more useful to me.
This is, essentially, the same old notorious rack below the nest.

A consideration though - mice could gnaw thru such floor if made too easy for them.

 

[rwlaw]

Quite a few years ago, there was a few guys on here making the basically the same thing w/ PVC pipe, I haven’t seen any such designs since.

 

[little_john]

Weather was kind today so I started work on a prototype 'cavity base', which will have a slatted floor with a removable slatted-rack over it. The 'slatted floor' being an alternative to a mesh floor, as I have far more wood in the form of battens than I have metal mesh. This initial prototype will have rectangular battens presenting a flat upper surface, rather than triangles or tubes.

Being curious as to how much ventilation such a 'slatted floor' will provide, I ran the numbers: with 3mm gaps it'll provide the equivalent of a one square inch open hole, spread evenly across a floor 18 inches square. That, of course, assumes that the slots remain open and don't get clogged with debris from above. Only time and a 'bee test' will reveal that. Here's hoping ...
LJ