AS the title suggests.
Brewed a WCIPA on the weekend and set eff to 80%. This gave me 1.066 SG with 11.6kg grain in 50L wort.
I undershot so was trying to adjust the efficiency to get the correct SG in the recipe. So I set it at 70%- 1.064, and thought that's too high.
So I set it at 60%-...