IBU calculation help

[sully20331]

Hi everyone, I am trying to remake a Long Trail Pale Ale. I plugged my recipe into Hopville, and got everything spot on with some tinkering(using the same recipe they use) and can't seem to get the IBU's to 35, like Long Trail does.


malt & fermentables
% LB OZ MALT OR FERMENTABLE
52% 4 6 Briess CBW Golden Light LME- added at 15min
24% 2 0 Briess CBW Golden Light LME
12% 1 0 Briess DME Golden Light
6% 0 8 Cara 8 (Cara-Pils)
6% 0 8 Crystal 40L
Batch size: 5.0 gallons
Original Gravity
1.058 / 14.3° Plato
(1.052 to 1.061)
Final Gravity
1.015 / 3.8° Plato
(1.013 to 1.016)
Color
8° SRM / 15° EBC
(Gold to Copper)
Mash Efficiency
75%
hops
USE TIME OZ VARIETY FORM AA
boil 60 mins 0.5 Centennial pellet 10.0
boil 10 mins 1.0 Cascade pellet 5.5
boil 5 mins 1.0 Cascade pellet 5.5
Boil: 7.0 avg gallons for 60 minutes
Bitterness
40.5 IBU / 5 HBU
NOTE: IBU results higher due to late boil additions
BU:GU
0.70
yeast
Wyeast American Ale II (1272)
ale yeast in liquid form with high flocculation and 74% attenuation
Alcohol
5.7% ABV / 4% ABW
Calories
191 per 12 oz.
misc
USE TIME AMOUNT INGREDIENT
boil 10 min 1 tsp Super Moss HB

Can anyone offer any insight? Or, can you tell me if 5.5 IBU difference will be that substantial?

 

[slarkin712]

First, I doubt that you will notice the 5.5 IBU difference. Second, your average boil volume of 7.0 gallons seems high to me if you batch size is 5 gallons. Considering that you are doing an extract recipe I would think that your average boil size would be very close to your batch size. When I used to do extract I think I would start with a little more than 4 gallons of water for steeping the grains. Then adding the LME and DME brought my volume up higher. And over the course of a 60 minute boil I might lose 1 gallon. So I have to top it off with a little water. My average boil volume was probably around 5 gallons. I'd adjust your boil volume and then see what the IBUs are. This should reduce them, as your hop utilization will go down.

 

[sully20331]

First, I doubt that you will notice the 5.5 IBU difference. Second, your average boil volume of 7.0 gallons seems high to me if you batch size is 5 gallons. Considering that you are doing an extract recipe I would think that your average boil size would be very close to your batch size. When I used to do extract I think I would start with a little more than 4 gallons of water for steeping the grains. Then adding the LME and DME brought my volume up higher. And over the course of a 60 minute boil I might lose 1 gallon. So I have to top it off with a little water. My average boil volume was probably around 5 gallons. I'd adjust your boil volume and then see what the IBUs are. This should reduce them, as your hop utilization will go down.

Thank you. I did that and it adjust down 2+ IBU. I'll take it!