biabacus bug / substitution issue (or my mis-understanding)

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biabacus bug / substitution issue (or my mis-understanding)

Post by jack » 2 years ago

Hi,

I've used the Biabacus successfully for my past 5 AG brews, after advice from Pistol Patch to switch from a 60 to 90 min mash all AOK - if anything, I've been over shooting my OG and the yeast over attenuating, and have hit 6.4% ABV, rather than the estimated 5.3% on the past 3 brews. Zero complaints though, I just need to up my efficiency figures and have been enjoying the higher ABV :)

Anyhow, I started out using just one recipe, and have only changed the hops via the hop substitution area of the Biabacus to get a feel for what hops do what for the same grain bill.

I decided for the next brew to make my own recipe by moving the values from the substitution columns to the original hop bill columns. The same hop AA and weights calculated as 50 IBU's via substitutions, when entered in the original hop bill columns of a new Biabacus comes out as 58.3 IBU's (red in the screenshot). Also, the "Hops you will use" columns are populated and contain greater values in the original hop bill columns, even though not substituting (blue in the screenshot).

Pictures and source docs help at this stage:
biab-substitution1.png
I'm guessing it's a rounding issue maybe, although confused! I guess this means I've been brewing around 10 IBU's higher than planned (although the beer is *excellent* so no complaints there, and this fits nicely with the 6.4% abv I've been hitting).

So my questions are:

1) Is this a bug in the substitution calculations?
2) In the document "test-substituted-to-original", why are there higher suggested hops volumes than the original recipe, even though I am not substituting anything, and should ignore this column?
test-substitutions.xls
test-substituted-to-original.xls
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Last edited by jack on 21 Apr 2015, 02:56, edited 1 time in total.

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Rick
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Post by Rick » 2 years ago

Backing off grain totals, or honing efficiency will change the gravity of the boil. Gravity of boil determines hop utilization in the tinseth formula.

See here ... http://www.howtobrew.com/section1/chapter5-5.html


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Post by jack » 2 years ago

True, however the 2 biabacus files are identical (apart from moving the hop values from the substitution column to the original hop bill column) so unsure how your answer applies to the questions?

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Post by Mad_Scientist » 2 years ago

Post both of your files here. One that is completed (grain and everything) include your actuals and the one you are designing.

MS

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Post by Rick » 2 years ago

Ah, guess I should have looked at the files, eh?

Well, now your "original recipe" VAW is 26.83, because you scaled the last one up from 23L to make 26.83. Change that at the top of sec. D of the new file and your IBU's will get to what they should be.


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Post by jack » 2 years ago

Boom! Got it Rick, many thanks for the help! Been scratching my head over that one...

Thanks again, much appreciated.

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