# Poppletone's closed-top frame



## little_john (Aug 4, 2014)

I thought that some of you guys might be interested in an unusual closed-top (touching top-bars), open-sided (clearance gaps between side-bars) frame, as used by O.O.Poppleton (1843 - 1917)








The exact position of the two slots is currently unknown - all I know for sure is that they were positioned to be directly above the gap which exists between adjacent combs. To judge the strength and health status of a colony, Poppleton would lift-off the strips of wood he employed to seal those slots, and it was only if he suspected all was not well that he would then proceed to open-up and inspect individual frames - after first blowing smoke through those slots in order to forewarn the bees of his intentions.

Should I ever be tempted to make any closed-top frames myself, then I'd make the frames symmetrical, with four 2" x 3/16" slots (two on each side) positioned such that slots from adjacent frames would coincide to form 3/8" slots. Easy enough to make these days with a table-router which, of course, Poppleton would not have had the luxury of, way back in the late 19th Century.
LJ


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## sparkyApis (Apr 9, 2021)

Just goes to show that there is not much new in beekeeping. When I was planning touching top bars I had a similar idea to provide access to a top feeder. I thought I was being (very) slightly clever at the time, turns out I was recycling a century old idea. Ah well, back to the normal status if not being terribly clever.


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## little_john (Aug 4, 2014)

Hi Sel - LOL - yep, you and me both ... 

This was my 'genious solution' for Top-Bar beekeepers who had difficulty finding a way to feed their colonies:










The above is an array of four Top Bars - the two outers having wedge-shaped starters and have been well-used; the two inners have popsicle-stick starters, and as can be clearly seen have never been used.

The idea being that a plywood 'doughnut' be placed over the hole when it was required for feeding, thusly:










... and an inverted jar feeder placed over that. In theory, should have worked ok - but the bit I overlooked was that retro-fitting slots into existing Top-Bars is not a particularly attractive idea. Much easier to rig up a feeder on the other side of a follower board.

Poppleton's ideas ring true with me too - whether or not I'll adopt the touching top-bars however, is something to be carefully considered. I particularly like the idea of doing away with the Crown Board (Inner Cover) on a Long Hive, but that is offset by the prospect of top-bars being propolised together. Poppleton reckoned that wasn't an issue - I think it might be. Perhaps the best way to resolve the uncertainty is for me to make one set of 14x12-inch frames in my usual manner, with a width of 25mm, then attach each one to a 38mm wide top-bar with slots scalloped-out on either side. Then, in the event of that test falling over, it'll be simple enough to reduce the top-bar width to 25mm, as per normal. On balance, I think it's an idea worth trying-out.
'best
LJ


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## sparkyApis (Apr 9, 2021)

LJ, interesting as always. If we say for the moment that propolisation is not a problem and the feeding issue is readily solvable what other drawbacks are there? Ventilation? Top bars touch but they are by no means airtight, especially ones I may have made, so air could circulate readily. Over on my main thread I talked about problems with spacer strips but I am beginning to think that providing for variable spacing is guilding the lily. I suspect that other handling problems I thought of were more products of my imagination unlikely to occur in reality. What have I missed? Single level hives of course.

Finally, and this is a question, not sarcasm disguised as a question, I am not understanding why retrofitting slots, a 30sec operation on a router table, is harder than changing top bar width?

Sel.


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## GregB (Dec 26, 2017)

sparkyApis said:


> If we say for the moment that propolisation is not a problem and the feeding issue is readily solvable what other drawbacks are there? Ventilation? Top bars touch but they are by no means airtight, especially ones I may have made, so air could circulate readily.


Keep in mind the bees will propolise the bar together to the point of them being air-tight. 
So that is that.
But the ventilation is a non-issue for you with your hive.

In the conditions of mild winter (down under) where emergency feeding with dry feed may not be necessary, I would not be so adamant against the touching top bars.
You can get away with the touching bars, and may even like them.
Certainly, they are less intrusive and help calming down irritable bees - a benefit where it is needed.


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## sparkyApis (Apr 9, 2021)

GregV said:


> Keep in mind the bees will propolise the bar together to the point of them being air-tight


Hi G. I may be reading too much into your word choice but I get the impression that you think this is, or may be, a bad thing. If I have that right then there are two questions which arise.
Are we going to give the bees credit for knowing what they are doing? Is their urge to propolise gaps in conflict with their management of the hive environment?

Sel.


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## GregB (Dec 26, 2017)

sparkyApis said:


> Hi G. I may be reading too much into your word choice but I get the impression that you think this is, or may be, a bad thing. If I have that right then there are two questions which arise.
> Are we going to give the bees credit for knowing what they are doing? Is their urge to propolise gaps in conflict with their management of the hive environment?
> 
> Sel.


Bees will propolise the ceiling above them to make it as airtight as possible.
End of story.
I can post a picture of a used cloth soft covers - I got many around as I use them routinely.

The issue at hand - where is that ceiling demarcation located?
Depending on your hive configuration that maybe all over the place - at the lower edge of the top bars, at the upper edge of the top bars, 1 inch above the top bars, etc....
The bees will react accordingly per what circumstance they are given.
In general the bees want to be able to condition their living envelope however they need - this requires tight envelope (similar to modern houses that also do conditioning).

So, what is the bad thing?
Unsure what you are asking.

I am simply stating the fact.
A fact at hand may be in your favor OR otherwise.
In my particular situation that is _otherwise_ (those touching bars that is).

In fact, in general practice the touching bars produce more inconvenience than help - given the widely available soft covers do everything the touching bars do and you still have additional flexibility with the soft covers.


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## little_john (Aug 4, 2014)

sparkyApis said:


> Finally, and this is a question, not sarcasm disguised as a question


As you guys say (or at least have a reputation for saying) .... "No worries".



> I am not understanding why retrofitting slots, a 30sec operation on a router table, is harder than changing top bar width?


For you and me, sure. But my brilliant plan was intended for Top-Bar beekeepers, many of whom have chosen to run top-bar hives because they are easy to build and with the minimum of woodworking equipment - say with hand tools and maybe a circular saw. From time to time I've read posts where someone enquires from where battens of a particular width may be sourced - suggesting that not even a table saw or plane is available.

I think those of us who have a modest collection of woodworking equipment all too easily forget how desperate life can be for those with virtually nothing with which to build beehives. (And I'm really talking to myself here) It is for such people that the KTBH must present as a heaven-sent opportunity to build a structure adequate enough for the keeping of honey-bees. Certainly, I tend to completely overlook this when voicing my usual negativity towards top-bar hives.



> Are we going to give the bees credit for knowing what they are doing? Is their urge to propolise gaps in conflict with their management of the hive environment?


Although Greg has already replied, I'll stick my oar in on this one ...

What you have touched on is one of the most fundamental issues in beekeeping, and which effectively divides the world of beekeeping into two camps: 'Natural' and 'Conventional' beekeepers. But even amongst some 'Conventional' beekeepers, there is disagreement. It is a huge topic of controversy.

Although not every beekeeper from the North American continent (worded so as to include Canadians) is an advocate, there is nevertheless a marked tendency towards the use of upper hive entrances and upper ventilation. In Britain, the reverse is true (even to the point of some having mesh beehive floors completely open all year round). The British approach is predicated precisely upon the observation you have just made. Both approaches have their advocates, and both approaches have their own compelling logic underpinning them, and this issue is one of those disagreements which looks likely to run-on for ever.

So that covers entrances and ventilation. There is a second issue related to this propolisation observation ... frames. Or rather, the clearances surrounding frames. I've already commented on this in the Latham thread: 

*Langstroth's invention is generally considered to have been the most important development in the history of beekeeping - indeed, one author (Kritsky) considers this to have generated "The Perfect Beehive" - but not everyone would agree.
There was a body of highly experienced beekeepers at around that time who considered Langstroth's invention to be seriously flawed: specifically in regard to the spacing which surrounds the frame which, although very cleverly preventing the bees from sealing those gaps with either comb or propolis, prevents the bees from exhibiting their natural urge to seal the cavity which surrounds their brood nest. Precisely why honey bees are motivated to do this need not concern us - but this particular beehive feature has effectively formed a division between 'Natural' and 'Conventional' beekeepers.*

The desire to seal their cavity with propolis extends not only to the top-bars, but also to the side-bars - initially the upper side-bar regions. Latham attempted to reconcile this urge by making and installing frames with touching top-bars AND side-bars. In a 'Leave-Alone' system this probably doesn't present too much of a problem, but if manipulations are intended, then problems arise - and not just the issue of propolis. Bees have a habit of dashing for a gap when they observe it to be closing, and this tendency frequently results in numerous bees being squashed. Langstroth discovered this problem himself when working with his Huber Hive.

Poppleton appears to have compromised by just using a touching top-bar, with which the problem of bees dashing for a closing gap can more easily be controlled, and where there will no longer be any need to be concerned with what happens below the top-bar when closing-up.

The bottom-line here is that bees love propolis, and beekeepers don't - we *really* don't. You have that pleasure awaiting you ... 
LJ


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## sparkyApis (Apr 9, 2021)

GregV said:


> So, what is the bad thing?


That was the very question I was asking. In my mind, the sequence goes; I said that even with touching top bars there would still be circulation (without commenting on when that may be necessary), you replied that the bees would make them airtight and I gained the impression, quite possibly wrongly, that you thought that this would be a problem in itself. The rest of my post was just trying to clarify that. Sorry for not being clear. I was not trying to lead the topic off into the vexed area of top entrances and the like.

As you have said, soft covers achieve similar results, except perhaps being able to conveniently restrict the open gap when manipulating the frames. I currently have a semi rigid plastic top cover and will be trying waxed cloth when I get some wax. Yes, I know I could buy some, but this is beekeeping the slow way.

Sel.


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## GregB (Dec 26, 2017)

sparkyApis said:


> .......... you replied that the bees would make them airtight and I gained the impression, quite possibly wrongly, that you thought that this would be a problem in itself.
> 
> ........... will be trying waxed cloth when I get some wax. Yes, I know I could buy some, but this is beekeeping the slow way.
> 
> Sel.


Air tight "ceiling" is a non-issue in long hive usually; for sure not with you climate.

You do not need to get "waxed" cloth.
Bees will propolise it quickly for you.
Most any old fabric will do.


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## ursa_minor (Feb 13, 2020)

deleted, I was going off track from the discussion of Poppleton's hive.


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## little_john (Aug 4, 2014)

A small 'top-up' to keep this thread alive ...

I've just uploaded a text file: "Crane on Poppleton.txt" to the usual place. Crane was a beekeeper who was involved in some way with one of Poppleton's yards in 1914. Apparently Poppleton sold-up the following year, so maybe he was in the process of 'winding-down' at that time ? Crane describes the hives he found, and in particular reveals how the frame bottom-bars were configured, so that - with the touching top-bars providing fixed spacings above - the frames were effectively locked into position. An important consideration for a migratory beekeeper.

I also found a few details about Poppleton's life earlier today. His full name was Oscar Ogden Poppleton (1843-1917), who commenced his military career as a private in the 7th Iowa Infantry, rising to the rank of first lieutenant by the end of the Civil War. He later joined the Grand Army of the Republic, rising to the rank of Colonel. For anyone interested in his life, there's a more comprehensive write-up at:
HISTORICAL VIGNETTES: Honey production was once big business in Martin County And for anyone who still believes that horizontal hives are incapable of producing serious quantities of honey - just check out the tonnage figures quoted in that article. 
LJ


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## Gray Goose (Sep 4, 2018)

sparkyApis said:


> Hi G. I may be reading too much into your word choice but I get the impression that you think this is, or may be, a bad thing. If I have that right then there are two questions which arise.
> Are we going to give the bees credit for knowing what they are doing? Is their urge to propolise gaps in conflict with their management of the hive environment?
> 
> Sel.


I would say no to this , they seal where too much air can or will go thru the hive.
the air flow makes the humidity and gas mix and temp harder to control.

their urge is to make the hive more air tight to better allow them to control

of cource this is my opinion.

GG


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## little_john (Aug 4, 2014)

'Morning GG.
I don't have any 'fixed after much contemplation' opinions on this myself, but I'd like to suggest another possible explanation ...

It's generally accepted that Honey-Bees initially evolved in Africa, and only after millions of years did they migrate up into Asia, and then finally across into Europe. Throughout their lengthy initial period of evolution within Africa, efficient water retention would have made the difference between life and death, and so I'm guessing that this is quite possibly the primary reason behind honey-bees wanting to seal their cavities up tight - to preserve moisture - rather than to get out of the wind and rain, and in order to defend their stores, as they do nowadays.

I've often thought about the building materials which bees use: wax and propolis - both of which are perfectly suited for use within a moisture-rich environment. How best could an organism create such a habitat - so necessary for the feeding of exposed and thus vulnerable larvae within the harsh and unforgiving arid African environment - except underground, or by the occupation and sealing-up of some kind of cavity ? And such behaviour - once so essential to self-preservation - quite possibly became 'hard-wired' into the honeybee's behavioural repertoire - remaining there, despite their current environmental conditions having changed out of all recognition from those of Africa.
Well - it's an idea ... 
'best,
LJ


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## GregB (Dec 26, 2017)

little_john said:


> so I'm guessing that this is quite possibly the primary reason behind honey-bees wanting to seal their cavities up tight - to preserve moisture -


+1
This is a very logical idea.
Even in cold climate and in cold season - moisture management is very much critical.
Successful usage of impermeable covers becomes rather common place (now that the proper usage is becoming finaly understood).


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## Gray Goose (Sep 4, 2018)

little_john said:


> 'Morning GG.
> I don't have any 'fixed after much contemplation' opinions on this myself, but I'd like to suggest another possible explanation ...
> 
> It's generally accepted that Honey-Bees initially evolved in Africa, and only after millions of years did they migrate up into Asia, and then finally across into Europe. Throughout their lengthy initial period of evolution within Africa, efficient water retention would have made the difference between life and death, and so I'm guessing that this is quite possibly the primary reason behind honey-bees wanting to seal their cavities up tight - to preserve moisture - rather than to get out of the wind and rain, and in order to defend their stores, as they do nowadays.
> ...


In winter the air can get very dry, any leakage of vapor, and heat, via chimney effect would see a replacement of cold and dry air , so yes Agree hard wired. also some writing out there on gas mix in winter to slow metabolism, this also would work less good with air leaks. I used cloth for inner cover this year as I "ran out of the wood ones, they in a month totally covered the cloth. Also used some made from the refleteix bubble wrap, no propolization. they are working the air flow thing IMO. I had a leak in upstairs barn window but only with a south wind.
As it turned out the south wind on the north garage door created a vacuum in the building, and the water was siphoned in during storms, so the propolis is also a good method to prevent funny water issues and make it rain proof.

GG


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## crofter (May 5, 2011)

I priced some clear vinyl 8 mil film that I will float under much of the area of the burlap and screened bottom of the shavings boxes. Will leave an access area about 10 by 10" that can be uncoverd for viewing and to add sugar or pollen patties if needed without having to lift the whole hive top quilt box. I want to see if leaving the bees a bit more moisture and less air exchange if it will eliminate some of the flying out into the snow that I see in March.

I see Clyderoad and others are having good results with a plastic film under an inner cover of homasote to wick moisture out but with less total air exchange than a whole hive top shavings box creates. I will test the depth of this water one foot at a time though! The suffocation experience with zero top entrance or vent is still a tender area!


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## sparkyApis (Apr 9, 2021)

LJ, a bit of an eye opener is it not? It is making me think more about how to make long hives more transportable should a person ever want to do that. Things like now to make an efficient pallet compatible format for example.
Sel.


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## Gray Goose (Sep 4, 2018)

sparkyApis said:


> LJ, a bit of an eye opener is it not? It is making me think more about how to make long hives more transportable should a person ever want to do that. Things like now to make an efficient pallet compatible format for example.
> Sel.


either 2 big eye bolts for a cable or fork lift capable, Flat bottom, with space for the forks, would fit most fork lifts.
Mine has 2 garrage door handles on each end, 2 guys can move it fine.

GG


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## sparkyApis (Apr 9, 2021)

GG, all good ideas, thanks. It may also be possible with a bit of tweaking to make an efficient fit in a pallet format which would minimise transport issues should anyone want more than one or two. Just need a few minutes with pencil and paper to see if some tweaking here or there would make a difference. Just a bit of an exercise really, I still have no delusions of becoming a commercial keeper with these things.

Sel.


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## Gray Goose (Sep 4, 2018)

sparkyApis said:


> GG, all good ideas, thanks. It may also be possible with a bit of tweaking to make an efficient fit in a pallet format which would minimise transport issues should anyone want more than one or two. Just need a few minutes with pencil and paper to see if some tweaking here or there would make a difference. Just a bit of an exercise really, I still have no delusions of becoming a commercial keeper with these things.
> 
> Sel.


make 3 or 4 have bees in them for 2 or 3 years then, do the mods you find when you have the O Crap why did I , or did I not, do that moments.
So fist ones maybe do not need to much more that the design to prove.

fun project. my 2,, led me to 2 other projects, so this may be the trail to the "promised land" as such one needs only go down it maybe,, not is style is fine.

GG


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## little_john (Aug 4, 2014)

sparkyApis said:


> LJ, a bit of an eye opener is it not?


Poppleton's migratory beekeeping ? Yes indeed - there are lots of eye-openers to be found if a person is able to take their blinkers off. (The sort of 'blinkers' created by the conditioning which results from extended familiarity and a lack of alternatives for comparison) Which is a tough 'ask'. Hope that doesn't sound too pompous ...

I don't know how relevant this is, but as a youngster I had a real problem with the notion of having a 'goal' in life. This problem was caused by my total misunderstanding of what a 'goal' was: I thought it was an 'end-state', and thus vitally important that such a goal be precisely identified from Day One - and it was crucial that no mistake be made when doing this. Now that's one helluva self-imposed burden for any 12 or 14 year-old.
It was only much later in life that I learned what a 'goal' originally was: it was the name given to the post erected at either end of the central 'wall' within the oval track of the Circus Maximus in Rome, which was frequently used for chariot racing. The competitors would aim for one goal, then (quite literally) turn and aim for the other goal. So - goals are thus temporary targets - you aim for one in the full knowledge that having reached it, another goal would be selected, and so on ... This change in comprehension from a finite 'end-state' to 'temporary target' was then of enormous help in steering my way through life. So what has this got to do with beekeeping ?

Well - I've just finished reading a book by Gene Kritsky called 'Quest for the Perfect Hive', and I started reading it with my usual large helping of skepticism, as - yet again - I had pre-judged Kritsky's 'Perfect Hive' as being an end-state: the evolution of one particular hive design - once established, never to be altered. (Sound familiar ?)
But Kritsky was ahead of me on this: over the centuries, as step-wise modifications were made to existing beehives, a 'Perfect Hive' for that particular moment in time was created. Thus there has been a continuous process of beehive development and improvement, that is, until the 1850's when (with the exception of a few mavericks) this process came to an abrupt end. 

The reasons for it stopping are two-fold: unlike the common box-hives which preceded it, the internal components of a Langstroth (later, Root-Heddon) Hive are removable, and thus need to be made with accuracy if they are to fit any given example of that particular design. This in turn led to demands for standardised sizes of frames and the boxes which were to hold them. Ancillary equipment, such as centrifugal extractors, were then designed to accommodate such standardised frames. And before long, a fixed and rigid system of beehive design and equipment had developed, such that the adoption of any contrary designs became virtually impossible. Kritsky calls this "The End of Experimentation".

The second reason for beehive development stopping was the adoption of mass-production manufacturing methods. Prior to the 1850's, and going back over thousands of years, beehives had always been made either by beekeepers themselves, or by artisans - with designs being heavily influenced by locally available materials. When Amos Root set-up his machinery to mass-produce the 'Simplicity-Langstroth' beehive he was not only ensuring the future dominance of one particular hive design, but from that moment onwards in many countries beekeeping would thenceforth be industry-led rather than beekeeper-led.
Some pockets of quite different hive designs remained of course, in Slovenia, Southern Spain, parts of France and Germany, and as we now know thanks to the Internet within the Ukraine and Russia - but in English-speaking countries it would appear that the Root version of the Langstroth Hive became dominant. 

In spite of the comprehensive depth of Kritsky's book, he fails to spot one important trend which ought to have been apparent. He identifies the Kenyan Top-Bar Hive, originating in 1965 from the work of Tredwell and Paterson, as being a major deviation away from the 'standard beehive', but fails to give even a single mention to the hive of Emile Warre, which (imo) falls into much the same category, insomuch as these two hives (and their derivatives) represent a popular shift towards amateur construction, and away from a dependency upon commerical manufacture. The growing interest in Long Hives is yet another example of this.

Having mentioned the recent unpicking of the honey bee genome, Kritsky ends his book with the following words:
*"In spite of high-tech biology, we are keeping our bees in “old” hives. Are we really using “perfect” hives ? Because we have stopped inventing hives, we really do not know. We have nearly forgotten about the old hives and ways of working them. If beekeeping is to survive the challenges of the molecular age, we need to consider the advantages and creative solutions presented by strange old beehives and, as exemplified by the recent innovation of the top-bar hive, use that knowledge to start inventing again. If we do, we may find the next perfect hive."*

"Start inventing" ? - methinks Kritsky has never made a visit to BeeSource.  LOL
LJ


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## GregB (Dec 26, 2017)

little_john said:


> So - goals are thus temporary targets - you aim for one in the full knowledge that having reached it, another goal would be selected, and so on ... This change in comprehension from a finite 'end-state' to 'temporary target' was then of enormous help in steering my way through life. So what has this got to do with beekeeping ?
> ...........................
> "Start inventing" ? - methinks Kritsky has never made a visit to BeeSource


LJ,
You are not affiliated with the software development I figure. 
So - in software (and IT in general) all you have is "good enough, temporary targets".
That is it, speaking of the goals.
Goals are nothing but management tool.

Otherwise, there is exists "the mission" which is never done but rather ongoing for about ever.

So this is a very brief overview of Software Engineering 101 or so about.


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## little_john (Aug 4, 2014)

Hi Greg. 
So there I was in post-War Britain (food rationing was still in place, and plenty of bomb-sites for us youngsters to play on) - can't remember what my exact age was back then, but people were forever telling me that I must have a 'Goal' (singular) in life, but didn't tell me exactly what that was, or how to go about identifying one - so, I had to figure it out for myself. And got it wrong.

I suppose I must have considered a 'goal' as being something like fighting a war: winning being the ultimate 'end-state' objective. Then, once the war was won, everybody packs up and goes home, and conscripted soldiers return to whatever they were doing before the war broke out. The end-state having been achieved - no subsequent goals - that sort of thing.

No such thing as software or IT back then of course, those were the days of crystal sets, valves and typewriters. Transistors were just becoming available for experimenters (if you could afford them) - but no transistor radios at that time, they became available a few years later. The only 'computers' around at that time were slide-rules. 
LJ


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## GregB (Dec 26, 2017)

Right, no computers back then.

I have to say that having the IT as my bread-winning activity for the last 10x(N) years, I was astonished to realize how close the IT and the beekeeping are at their very fundamentals.
This is how I rediscovered this "bee thing".

And this actually suggests of higher and more general order of things that the IT or the beekeeping or <plug something here> simply conform to.

Anywho....
Bee owning is fun as it is a perfect opportunity to keep discovering.... "stuff".


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## sparkyApis (Apr 9, 2021)

That puts me somewhere in the middle I guess. A post-war baby who ended up designing large scale multifactorial breeding programs. Now there is an exercise in diffuse goals and delayed gratification. That got me into writing programs in COBOL to help the data handling requirements of my breeding program. These were run on the government computer in the basement of the treasury building, complete with punched cards, reel to reel tapes and white coated minions. Those were the days. Priorities changed and I have not written a line of code for a couple of decades or longer. Having fun learning about bees though.


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## little_john (Aug 4, 2014)

I don't expect anyone to be bowled over by this, but earlier today I decided to make and try-out a set of Poppleton frames, and have just finished table-routering two dozen top bars for testing.










I'll now proceed to build 14"x 12" deep frames below 22 of them - the remaining two I'll make into partition boards.

Right now I'm not convinced that such frames will be significantly better than frames with standard top-bars - but heck, I'll try anything once. Who knows - it may turn out to be a revelation. 

On the other hand, the bees may well plaster propolis around those slots, especially where the closure strip makes contact with the top-bar. I'll just have to wait and see ...

FWIW - while routering away I kept having a touch of 'deja vu' and it didn't take long to remember where I'd seen a picture of this kind of top-bar before - it was in Dzierzon's 'Rational Beekeeping'. Here's the graphic from his book:








He reckoned number 3 was the best of the bunch, and had this to say about partially touching top-bars:
"The width of a comb-bar must, however, be one and a half inches, as every comb with the space between two combs takes up this room. But in order to be able to take out more conveniently the separate bars carrying the combs - which if pushed closely against one another and cemented together by the bees it would be difficult to separate - and also to enable the bees to get above this set of bars, as well as below a second set fixed lower down in the hive, and to continue the combs there, it is necessary that passages should be left between the separate bars, which may be done by cutting away part of the wood in some places, leaving, however, the full width of one and a half inches here and there that they may rest against one another, and thus retain a firm position. Now, we may either reduce the width of the bars in the middle to one inch, leaving small quarter inch projections at both ends and on both sides, or we may leave them of the full width in the middle, reducing it towards both ends, or leave projections in the middle as well as at both ends, or at once make the comb-bars only one inch wide, and secure the necessary distance of half an inch to make up one and a half inches, by driving in towards each end a pin [...]"

As can be understood from the above, with a bar width of one inch and a spacing of 1.5 inches, the gap between bars is therefore half an inch. Emile Warre specifies 12mm for his hives, which is near enough the same.
I've opted for a 9mm gap (3/8") as Poppleton used - if I should run into problems with that spacing, then it can always be enlarged by 1.5mm each side retrospectively - as it's so much easier to remove material, then trying to add it back on. 
'best,
LJ


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