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Old 01-11-2010, 07:58 PM   #1
phished880
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Default BeerSmith IBU Calculations

I must warn you, this will probably be confusing. So Here it goes.

I'm making a Fat Tire Clone and when putting in the BYO recipe
5 lbs. Laaglander plain extra-light DME
0.50 lb. crystal malt (20° Lovibond)
0.50 lb. crystal malt (40° Lovibond)
0.50 lb. carapils malt
0.50 lb. Munich malt
0.50 lb. biscuit malt
0.50 lb. chocolate malt
3 AAUs Willamette pellet hops (0.66 oz. at 4.5% alpha acid)
1.33 AAUs Fuggle pellet hops (0.33 oz. at 4% alpha acid)
2 AAUs Fuggle pellet hops (0.50 oz. at 4% alpha acid)
1 tsp. Irish moss
2/3 to 3/4 cup corn sugar to prime
Wyeast 1056 or BrewTek CL-10



With the AAU Calculations BeerSmith comes up with approx 9IBU as compared to the 16 suggested by the brewer.
So my question is.
Which is more accurate? The Beersmith formula or AAu's???

Thanks

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Old 01-11-2010, 08:10 PM   #2
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I don;t have BeerSmith handy and, I don't try to match AAU's but I think something is a foul on your approach. AAU's are meant to give way to calculate the quantity needed at a variable Alpha rating to match the IBU's intended.

I suggest you google Calculating AAU's and try it manually to see what gives.

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Old 01-11-2010, 08:24 PM   #3
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Ok, here are the numbers or approx. i came up with.

.75 oz Will @ 90
.35 oz Fug @ 30
.5 oz Fug @ 10

but this gives me an IBU calc of 10.3
I know the calculations are not exact, but this the best way i could.

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Old 01-11-2010, 08:26 PM   #4
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Its possible that the hops used in the original recipe, though they may be the same type, have a higher aa%

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Old 01-11-2010, 08:26 PM   #5
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Quote:
Originally Posted by phished880 View Post
Ok, here are the numbers or approx. i came up with.

.75 oz Will @ 90
.35 oz Fug @ 30
.5 oz Fug @ 10

but this gives me an IBU calc of 10.3
I know the calculations are not exact, but this the best way i could.
I would take those and adjust up equally until I hit the 16 IBU the recipe calls for.
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Old 01-11-2010, 09:13 PM   #6
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Check your boil size. The boil volume has a big effect on IBUs. If you're doing a 2 gallon boil, for example, and the recipe assumes a 4 gallon boil, the IBUs will be vastly different.

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Old 01-12-2010, 06:42 PM   #7
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Are you doing late extract additions?

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