Dave and Richard, will try and answer what's come up in the last few posts here
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BIABacus will handle 3 Vessel Brewings and Extract Brews.
The BIABacus can handle 3v and extract brewing as well as BIAB and maxi-BIAB. Note that no other program can actually handle maxi-BIAB. It will not handle partials though.
Extract brewers need to do three things. In Section X, set auto-efficiency to 100%, set Volume Loss from Lauter to 0 and, in Section Y, make sure they put in their potentials for the extracts they are using.
3V brewers just need to change Volume Loss from Lauter to 1 l/kg. Strike Water Adjustment Factor allows for varius mah tun materials etc. Some 'mash' volume warnings won't work well however, a 3V brewer most limiting vessel is usually their kettle so, in most cases, the warnings will work well. Things like mash tun dead space can be worked around if they are even a factor.
As for PLG, most 3V brewers do not use it. The earliest measurement they would make is usually into the kettle. You'll hear of fly spargers taking readings but once again these are after PLG and, in reality, these readings are rarely taken.
ALso, as I mentioned in a post to Richard above, the more sparge water used in the BIABacus, the less that the BIABacus PLG reading can be relied on. However, I still think it would be more reliable than the gravities given in other programs for the simple fact that the BIABacus looks at how much water touches the grain in a brew and alters the EIK accordingly.
Maxi-BIAB Post-Pull Volume
Richard, you wrote, "In terms of the two Maxi-BIAB brews I did using the BIABacus, I was trying to 'pre-calculate' the volume I would have after pulling the bag."
This is really easy as the BIABacus has done most of the work for you already. On a brew where you have either used some water in a sparge and/or added water before the boil, your volume after pulling the bag is VIK less whatever numbers you have typed beside 'Water Used in a Sparge' and 'Water Added Before the Boil' in section W.
If you want to get super precise, then you'll have to do few adjustments for thermal expansion but you shouldn't be going to these extremes.
Respecting and Disrespecting Numbers
I had a look at those links Richard and one thing that worried me was that you were trying to work out why there was a 3% discrepancy between two sets of readings you took. This is totally normal. The smaller the brews, the harder things are to measure and the greater the discrepancy. So, if you were chasing up a 3% discrepancy, don't!!!!!!!!
As I said in my last post here, I mentioned that PLG is not that important. I also said that PLG is exactly the same as the gravity straight after you pull the bag regardless of what type of brew you are doing. Changing the name to AMO which does not include the word gravity probably won't gain anything.
Basically what I am saying here is that it is very important not to get lost in the numbers. They are a tool. Taking measurements pre-boil is okay but making adjustments on these readings is not.
Fast Ways of Checking Efficiency
The BIABacus checks efficiencies for you so my advice is for people to use that. You included a link to checking efficiencies by multiplying the gravity by the volume. We have several posts on this here as well. You've also included a link to a pdf I never finished
. The point about efficiency is that it can be approached from so many different points of views and measurement systems. Any one frame of reference can be written up very simply. It is very hard though to write one article that covers metric brewers, imperial brewers plus the multiple ways in which 'extract potential' of a grain can be laboratory recorded.
The only thing I will say here is that any efficiency figure is alwasy a based on volume and gravity and therefore estimated efficiencies can be compared to actual efficiencies very quickly no matter what units you work in. For example, if the BIABacus said you should expect a VIK of 38.12 l (10.07 Gal) at 1.027, then if you a metric user, you can just multiply 38.12 * 27 = 1,029 'metric' gravity points (there is no such term) or if you are US, 10.07* 27 = 272 gravity points (this is a real term).
Let's say you end up with 40 L (10.57 Gal) at 1.026, then 40 * 26 = 1,040 or, in US, 10.57 * 26 = 275.
1029 versus 1040 tells you all is good as does 272 versus 275. In fact, on a normal brew you should expect larger discrepancies between actuals and estimates.
Hope some of the above gets closer to resolving your question Richard
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Stirring and EIK
Lol on posts made two years ago. That's one of the few ones I have finally book-marked as I got sick of looking it up!
As for stirring and EIK, in some set-ups it may be necessary to stir and in other's not. Lots of things come into play. There are only a few ways questions like this will get answered. For example, we are trying to collect the most primitive mash information in
this thread.
The best way of getting good data though will be if we can write the BIABacus into program form and be able to collect and analyse thousands of actuals in a few seconds.
My personal suspicion for now though is that people with tall narrow kettles will probably find it more necessary to stir than those with wider kettles as in the latter, there is likely to be better circulation. Really don't know though.
PP
).
. I've cracked a beer now and so, as promised, will get stuck into Richard's question on PLG...
I now understand that PLG is not normally used by brewers and that I should not worry about such matters. I will just top up to the VIK mark when doing a MAXI. 
Arrgg, I'm so sorry PP.
My volume could not have been that far off. After taking my refractometer away from my eyes, I must have had a senior moment and recorded a 15.3 brix instead of a 16.3 brix for the PLG. This is where I got off the track. 
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needs to write. The scale and structure of what needs to be written is pretty daunting to be honest and little time has been available so far this year. C'est la vie!