Good questions Don
With regard to deferring any dilution until the fermentor, in BIABacus PR 1.3T section W, any value entered in the field "water added to fermentor" also enters that value in "water held back from mash".
The BIABacus can handle a lot more scenarios than any other brewing software at present. In other words, it can handle extract brewing, traditional all-grain brewing and all the dilution scenarios in between however, it's current design works from an initial presumption that most users be doing pure BIAB...
Pure BIAB (the original purpose of BIAB) is to "SMS" brew. SMS means "simultaneous mash and sparge" which also means "full-volume brewing in a single vessel". In other words, pure BIAB is the best way to go if you can so...
When you do any sort of dilution you are
actually holding that back from the mash.
If you do intend to do any full-volume variations (section W), you just enter your planned dilution amount there and the BIABacus does the rest for you. There is one trick though and we can't design it any better in spreadsheet form sorry and that is in Section K...
If you do any
full volume variations in Section W, then you do not fill your kettle with the TWN of Section K. Instead, you fill it with TWN less the 'Water Held Back from Mash" in Section K. When you heat that amount to mash temp, it will be equal the SWN figure in Section K. Go and have a beer and get that clear in your head
. It will take a beer and a bit of slowing down for it to make sense / sink in but I think you are at that level.
Assuming that BIABacus might under-predict my OG would you recommend having a gallon of dilution water pre-boiled/sanitized to save time on brew day?
Yes, I think it is
best practice to do as you say and have dilution water pre-boiled/sanitized. The sanitisation isn't that important though if pitching yeast straight away. (Remember nearly all kit brewers just use tap water). The boiling though will help remove chlorines and, if you can't pitch straight away because your wort is too hot as is often the case, then that boiling will be another bonus.
For the times I've under-shot my OG I believe I have one of two option
You have no options. Those brews are done and dusted and you aren't going to let yourself get in a position of high OG again are you?
If you ever were caught with a low OG again (and were positive about the low OG reading), just leave it. A decent recipe will still produce a great beer even if you are 20% out on your OG. Adding DME prior to your flavour and aroma hops won't work because there is no way yo can no for sure that you actually are dealing with a low gravity brew at that point. Hot samples are just too unreliable to give much weight to. DME is often a very poor quality ingredient. (Many extracts are old etc and will actually taint your beer.)
If your evap rates are fairly predictable, then sure force the BIABacus but don't play with....
Auto-Efficiency. You mention you are getting 65% EIK. Two things. On very high gravity (gravity into kettle) brews you should get low EIK and on very low gravity brews you should get high EIK's.In other words, unless your ten batches had the same OG (and dilutions) then the ten batches mean nothing.
I want to talk more about this 65% EIK you are getting but I would want to see several numbers from these ten batches and I've also run out of steam now
KFL and FPL are quite unpredictable on most systems and recipes I think and don't understand why. For example, I have had more trub on a low hopped beer than a high hopped beer I brewed the next day (or side by side) on the same (or identical) system - figure that out
. The main purpose of KFL and FPL though is to make sure that you allow enough wastage to achieve your desired amount of packaged beer. KFL and FPL do not affect the quality or taste, just the amount of initial ingredients you use. Just be sensible with these. Whilst the next version of the BIABacus fine-tunes these numbers a little, I, personally, don't put much store in KFL and FPL predictions.
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