OK, so based on the recipe I should let the extract guide me as far as shorter & longer boil or adding DME? Any charts to help guide this?
As others have said before, I think this is a BIG test batch until I get it dialed in...
If you want to boil down to a gravity, you need a way to measure how much liquid in is your kettle. One way is to take a piece of wood, plastic, or metal and mark off fractions of a gallon by incrementally adding fractions of a gallon of water to your kettle. Another way is to compute the amount of liquid in a kettle using a metal ruler. A kettle can be treated as a cylinder. The volume of a cylinder in square inches is computed using the following formula:
kettle_volume = radius x radius x 3.14 x height_of_the_fluid_column
For example, one of my smaller kettles has a diameter of 12 inches. If I measure 8 inches of wort in this kettle, then kettle_volume = 6 x 6 x 3.14 x 8 = 904.32 cubic inches.
There are 231 cubic inches in a gallon; therefore, the kettle contains 904.32 / 231 = 3.91 gallons of wort.
With that said, if you collect 6.5 gallons of 1.038 wort and you want to hit 1.060, then your final volume should be 38 / 60 x 6.5 = 4.12 gallons. In this case, you will probably want to add DME.
Dividing your collected volume by your desired volume and multiplying the collected volume S.G. by that value gives you the S.G. at the desired volume if you do not nothing other than reduce the amount of water in the batch of wort.
6.5 / 5 x 0.038 + 1.0 = 1.0494
Subtracting the S.G. at the desired volume in points from the desired S.G. in points and multiplying by the desired volume gives one the number of points of extract that need to be added to make up for the shortfall from the mash.
60 - 49.4 x 5 = 53 points
Using 46 as the number of gravity points available from a pound of DME yields:
53 / 46 = 1.152 pounds, or roughly 18.5 dry ounces of DME.