OK, so I've noticed a few things. Someone help me out if I'm totally off base here.
1. I already brought this up in this thread: http://www.beersmith.com/forum/index.php/topic,5124.0.html but to sum it up...
I have about 1.25 gal of losses between my boil kettle and the fermentor. If I select a batch size of 10.5 gal into the fermentor, BeerSmith2 gives me a PRE-boil volume of 14.3 gallons and a POST-boil volume of 12.2 gal (which works, 2.1 gal in evaporation; 14.3 - 2.1 = 12.2).
For a recipe with a OG of 1.045 with 100% pale malt (36 GU/lb), BeerSmith2 calculates 17.5 lbs of malt. However, if you do the math 17.5 lbs of pale malt will yield an OG of 1.045 for a 10.5 gal POST-boil volume, not a 12.2 gal POST-boil volume.
Assume 75% efficiency:
45 GU * 10.5 gal = 472.5 total GU
472.5 /36/.75 = 17.5 lbs pale malt
45 GU * 12.2 gal = 549 total GU
549/36/.75 = 20.3 lbs pale malt
In order to hit an OG of 1.045 with a POST-Boil volume of 12.2 (in order to get a batch volume in the fermentor of 10.5 gal) I need 20.3 lbs of malt. BeerSmith2 is telling me I need 17.5 lbs.
2. Changing the boil time has no effect on OG. It will change the POST-boil volume, but regardless of the boil time, the OG remains the same. I'm not sure what boil time it is using to determine the OG. Perhaps the default boil time in my equipment profile?
1. I already brought this up in this thread: http://www.beersmith.com/forum/index.php/topic,5124.0.html but to sum it up...
I have about 1.25 gal of losses between my boil kettle and the fermentor. If I select a batch size of 10.5 gal into the fermentor, BeerSmith2 gives me a PRE-boil volume of 14.3 gallons and a POST-boil volume of 12.2 gal (which works, 2.1 gal in evaporation; 14.3 - 2.1 = 12.2).
For a recipe with a OG of 1.045 with 100% pale malt (36 GU/lb), BeerSmith2 calculates 17.5 lbs of malt. However, if you do the math 17.5 lbs of pale malt will yield an OG of 1.045 for a 10.5 gal POST-boil volume, not a 12.2 gal POST-boil volume.
Assume 75% efficiency:
45 GU * 10.5 gal = 472.5 total GU
472.5 /36/.75 = 17.5 lbs pale malt
45 GU * 12.2 gal = 549 total GU
549/36/.75 = 20.3 lbs pale malt
In order to hit an OG of 1.045 with a POST-Boil volume of 12.2 (in order to get a batch volume in the fermentor of 10.5 gal) I need 20.3 lbs of malt. BeerSmith2 is telling me I need 17.5 lbs.
2. Changing the boil time has no effect on OG. It will change the POST-boil volume, but regardless of the boil time, the OG remains the same. I'm not sure what boil time it is using to determine the OG. Perhaps the default boil time in my equipment profile?