BeerSmith OG Calculation Off?

trav77 said:

I put my new eBIAB system through its first brew yesterday and everything went smooth. Hit all my numbers except the OG, which is what I don't understand.

Est Mash Eff = 74.5%
Meas Mash Eff = 72.2%

Est Pre-Boil Vol = 7.38 gal
Measured Boil vol = 7.4 gal

Est Pre-Boil Gravity = 1.043
Meas Pre-Boil Grav = 1.042

Boil Off = 1.06 gal
Post Boil = 6.32 gal
Trub Loss = 0.53 gal

Are these the predicted values or your actual values. How much do they differ?

Cooling Loss = 0.25 gal
Batch Vol (into the fermenter) = 5.55 gal

Again, how is this different from your planned volume (batch size)

Est OG = 1.053 (?)

I hit all of these number almost dead on but my measured OG was 1.048 not 1.053. Quite certain it was well mixed and I didn't pull a stratified sample.

Even if I did, BS's estimated numbers don't make sense to me. It should be a simple concentration ratio between pre (1) and post (2) boil, no?

If I just use BS's estimated numbers:

C1V1 = C2V2
(43)(7.38) = C2(6.32+0.53)
C2 = 46

So my OG should have been 1.046 (which is much closer to my 1.048... especially when the simple equation above doesn't take into account the volume of the hops/trub itself). In any case, I can't see how it should have been 1.053

Any thoughts?

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laredo7mm said:

With all the people that use BeerSmith I doubt it is an issue with the software. More likely an issue with the user not putting in accurate values or measurement errors.

If your numbers above are correct, here is what I calculate: 7.4 gallons pre-boil at 1.042. 7.4 gallons is the hot volume, so cold it would be 7.12 gallons. 7.12 x 42 points = 298.8. 7.12 - 1.06 boil off = 6.06 gallons.

298.8 points / 6.06 gallons = 49.3 points or 1.049 post boil.

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Oginme said:

Exactly. I had first come up with similar number, but looking at the equipment profile and full recipe may give some insight or may point to an error which can be reported to Brad.

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laredo7mm said:

If your numbers above are correct, here is what I calculate: 7.4 gallons pre-boil at 1.042. 7.4 gallons is the hot volume, so cold it would be 7.12 gallons. 7.12 x 42 points = 298.8. 7.12 - 1.06 boil off = 6.06 gallons.

298.8 points / 6.06 gallons = 49.3 points or 1.049 post boil.

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