Hop substitute math

[UnrulyGentleman]

I'm hopeless with most math, but here's the deal. Recipe calls for multiple additions of 5.5 AAU Centennial hops (or .5oz of 11% alpha). LHBS didn't have Centennial, so recommended substituting with a combo of cascade and Columbus. I have no idea how to convert my blended 13.9% Columbus and 6.5% Cascade to the recipe. I have 2 oz of the columbus and 1 oz of the cascade, but no idea how to blend them and then add them.

 

[lutherslagers]

when in the boil does your recipe call for hop additions? What type of beer are you making? What is the total number of IBUs the recipe calls for?

 

[UnrulyGentleman]

Style: IPA
Total IBU: 56
Hop additions from Recipe:
.5 oz of 11% Centennial at 60, 45, 30, 15
.33 oz of 11% Centennial at flameout and .33 oz dry hop

Again, I have 2 oz 13.9% Columbus and 1 oz 6.5% Cascade

 

[BigEd]

Maybe we need an algebra section at HBT as it seems it's no longer in the curriculum in the public school system. 2 oz of Columbus @ 13.9% added to 1 oz of Cascade @ 6.5% is (2 X 13.9) + (1 X 6.5) divided by 3.

2 X 13.9 = 27.8
1 X 6.5 = 6.5

27.8 + 6.5 = 34.3 / 3 = 11.4

At 11.4% for the blend you could just substitute it on an equal weight basis for the 14% Centennial in the original recipe.

 

[DeafSmith]

You could simply use .32 oz Columbus and 0.17 oz. Cascade for each boil addition (AAU of 5.55). For the flameout and dry hop additions, AAU doesn't really matter so much, but if you wanted to keep it the same, use .22 oz. Columbus and 0.11 oz Cascade.

AAU calc. for the boil additions is:
(0.32 oz.)(13.9 AAU/oz) + (0.17 oz.)(6.5 AAU/oz.) = 5.55 AAU

Total used:
Columbus = 4(0.32 oz.) + 2(0.22 oz.) = 1.72 oz.
Cascade = 4(0.17 oz.) + 2(0.11 oz.) = 0.90 oz.

EDIT:
BigEd's approach is probably the simplest - just blend and then substitute and you'll probably never know the difference.

 

[lutherslagers]

I use the Ray Daniels formulas for calculating IBUs. I'm assuming you'll have 5.5 gallons at the end of boil and also assuming you're desired OG is above 1.050. I also really like the flavor and smell of cascade, so I'm adding them late. Here is what I would do:

60 Min - 0.25 oz. Columbus
45 Min - 0.20 oz. Columbus
30 Min - 0.25 oz. Columbus
15 Min - 0.50 oz. Columbus
0 Min - 0.50 oz. Columbus
0 Min - 0.50 oz. Cascade
Dry hop - 0.50 oz. Cascade
Totals IBUs = 56.9

Now, since this is an IPA you could consider raising the IBUs. in which case I would use all your hops like this:

60 Min - 0.50 oz. Columbus
45 Min - 0.25 oz. Columbus
30 Min - 0.25 oz. Columbus
15 Min - 0.50 oz. Columbus
0 Min - 0.50 oz. Columbus
0 Min - 0.50 oz. Cascade
Dry hop - 0.50 oz. Cascade
Totals IBUs = 73.2

I would do the later.

 

[ajf]

I'd use 0.5 oz columbus at 60, 45, 30, and 15 minutes
and 0.5 oz cascade at flameout and dry hop
This would increase the IBU's a bit (but barely above the taste threshold), give you a bit more aroma, and use up all the hops.

-a.