Calculating Water Volumes

[farmskis]

Ok so I want to better understand the whole brew process and I like to calculate things out by hand to know what all the brew software is doing.... I have read books and researched around and I am wondering if I am doing this right:
First I will calculate the absorption the grain will absorb based on the grain bill. Call it (A). Then I will add my Mash tun loss that is not able to be drained (B). Calculate the cooling factor (C). Also the Loss to trub in the boil kettle (D). Boil off is calculated (E). Now to get my Mash volume I use usually use 1.25qt/lb. I will add all of my losses (the shrinkage comes out as a percent and is calculated out) to get a total number for the loss. I will add this loss to the total I want to go into the fermenter. So if my loss number comes up to 2 gal and I want 4 in the fermenter I would start with 6 gal of water. And with that 6 gal I would use some to mash with and the rest I would fly sparge with. I usually add a little extra for the sparge to make sure I have enough to get to my estimated boil voume.

This seems right to me but the last time I brewed I was under. Either I lost more than I thought or I calculated wrong. Brewsmith seems to always be a little lower on the volume of water compared to what I calculate. Is my method correct for calculating the water volume?

 

[raysmithtx]

After several brews, Beersmith is dead on for me. Took a while to get the actual numbers to use though. The only problem I had understanding is that the heating expansion/cooling factor (4%) is not used for the entire volume and is used for measuring liquids not at room temp.

I don't know if this is the right way to do it but this is how I figure volumes:
Amount into fermentor * 1.04 (5.5 * 1.04=5.72 gallons)
Add the boil off amount (1.3 gallons)
Add the trub loss (.3 gallons)
Add the grain absorption (1.09 gallons)
Total all of the above to get my total water needed (8.42 gallons)

These numbers are from a recent brew where I hit every number perfectly.

So Beersmith figures I will be measuring my 'post boil' volume immediately after the boil and the liquid will be 4% higher than what will actually go into the fermentor.

Once I figured out to only multiply the 'into fermenter' amount by 1.04 and not all the other volumes, the numbers were perfect.

 

[MaxStout]

Boiloff rate seemed to be the biggest variable for me until I got a good handle on things. If you use the same kettle, same length of boil and keep the boil rate consistent, you should have the same boiloff loss. But a big, rolling boil will accelerate the evaporation. Having a wide-bodied kettle bumps up the rate as well.