1 to 2 vessels migration

[FunkedOut]

I need a hand wrapping my head around moving from single vessel BIAB to a 2 vessel rig.
Particularly setting up the mash profile in BeerSmith.
Not sure if this a process misunderstanding or a software misunderstanding.
Let me explain what's got me confused...

I took a recipe from a recent brew and changed the mash profile from a BIAB single infusion, to a single infusion, no sparge, no mash out profile that came as a sample.
I can see where the Total Water Needed field increased by exactly the amount of difference in the grain absorption rates.
What confuses me is that the calculated/estimated post mash gravity and pre-boil gravity don't change.
In my mind, there is wort left in the grain, not water.

If I mashed this BIAB-style, then lifted the bag out and and squeezed until exactly 0.586 fl.oz. of wort was left in the bag per every oz. of grain (BS default for BIAB), my mind tells me that the wort left in the grain in the bag shares the same SG as the wort in the kettle.
Many times, I've lifted the bag, stirred well, measured the gravity, then squeezed the bag for another half gallon, stirred and measured the same gravity.

So If I now mash this same grist, with the increased amount of water described above, in a mash tun with false bottom, full volume, and simply drain.
I'll take a leap of faith here (since I've never done it) and assume that the grain will hang on to 0.96 fl.oz of wort for every oz of grain (BS default for non-BIAB).
My mind tells me that I have diluted this wort by the water addition and the gravity should be lower. Something like this:

(BIAB Volume of Water)*(BIAB Post Mash Gravity) = (nonBIAB Volume of Water)*(nonBIAB Post Mash Gravity)

However, BS doesn't change its estimated power mash gravity or pre-boil volume when switching from BIAB mash profiles to nonBIAB mash profiles.

Am I doing something wrong in BS?
Or is my mind playing tricks on me with regard to the added water = dilution concept?

Thanks for reading all that.

 

[pricelessbrewing]

If I'm understanding the question correctly, my interpretation is that because beersmith works on a fixed brewhouse efficiency, then any changes in water volumes don't matter as far as gravities are concerned because the input efficiency hasn't changed.

In real life, this isn't correct, which is why my software seperates it into input conversion efficiency which is almost always a constant value +- 1-2 % unless there's issues like changing grain mill or not enough diastatic power in a recipe...

In real life, using more water means your mash gravity goes down. But using the fixed brewhouse means that using more water, but the same brewhouse gives a higher conversion % which is a strange expectation IMO.

If your only change is grain absorption, 0.08 to 0.125 gal/lb, then I would expect a 5-7% lower brewhouse efficiency for a typical 1.060 recipe.

 

[Smellyglove]

I bet your predicted mash efficiency has changed. You have to manipulate this number to mirror your real life mash efficiency by adjusting your BH-efficiency. All losses will be the same.

 

[Setsumi]

a BIAB single infusion, to a single infusion, no sparge, no mash out profile that came as a sample

This seems the same to me.

 

[pricelessbrewing]

@Setsy

a BIAB single infusion, to a single infusion, no sparge, no mash out profile that came as a sample

This seems the same to me.

Beersmith has two global values for grain absorption rates, in fl oz/oz under settings / advanced IIRC. The only two differences between those two profiles is that the first one uses the BIAB absorption rate, and the second one uses the default absorption rate, roughly equivalent to 0.08 gal/lb and 0.125 gal/lb respectively.

 

[FunkedOut]

@pricelessbrewing your 1st post is exactly in line with what I've settled on. 5% real world is what I was expecting. Seems like no sparge is less efficient than BIAB. I plan to batch sparge to make up what I'll lose and then some.
I need to give your software a test drive.

I bet your predicted mash efficiency has changed. You have to manipulate this number to mirror your real life mash efficiency by adjusting your BH-efficiency. All losses will be the same.

It does not. That's what I was expecting too.

a BIAB single infusion, to a single infusion, no sparge, no mash out profile that came as a sample

This seems the same to me.

The lifting of the bag out of the wort creates an inherent squeezing effect thanks to gravity and geometry. This effect is not there when the grains are simply drained in a tun. This is why there are two absorption rates for the software.

@Setsy

Beersmith has two global values for grain absorption rates, in fl oz/oz under settings / advanced IIRC. The only two differences between those two profiles is that the first one uses the BIAB absorption rate, and the second one uses the default absorption rate, roughly equivalent to 0.08 gal/lb and 0.125 gal/lb respectively.

Beersmith's default values are 0.960 fl oz/oz and 0.586 fl oz/oz (BIAB).
These rates work out to exactly 0.120 gal/lb and 0.07325 gal/lb.