IBUs for a Fat Tire clone?

[Jesse17]

I just finished brewing my Fat Tire extract clone from AHB, and it went nice and smooth. Then, while recording my process, I decided to calculate the IBUs. I came up with only 12.46 total IBUs. Does this seem right, or did I goof the math somewhere? Does anyone know what a Fat Tire should be?

Here's the recipe:
Extract: 7 lbs. Extra Pale LME
Grains: 3 oz. Biscuit Malt
1/2 lb. Crystal 90L
1/3 lb. Victory Malt
6 oz. Munich Malt
Hops: 60 Min. - 3/4 oz. Northern Brewer (4.95 AAU, 9.88 IBU)
15 Min. - 1/2 oz. Hersbrucker (1.65 AAU, 1.63 IBU)
05 Min. - 1/4 oz. Willamette (0.95 AAU, 0.38 IBU)
Yeast: Wyeast Fat Tire Yeast

 

[malkore]

that sounds low. i'm not big on fat tire because its a little on the bitter side for my tastes.

 

[bradsul]

4.95AAU of the Northern Brewer in my DB (9%) gives me 23IBU. What is the AA% of your NB?

 

[SuperiorBrew]

I just brewed this and it had an IBU of 20 I plan to keg it this weekend but so far the hydrometer samples have seemed pretty close from what I can remember to the original. I would say your a little light on the IBU's

BeerSmith Recipe Printout - www.beersmith.com
Recipe: Fat Tire Clone
TYPE: All Grain

Recipe Specifications
--------------------------
Batch Size: 11.00 gal
Boil Size: 13.13 gal
Estimated OG: 1.047 SG
Estimated Color: 11.5 SRM
Estimated IBU: 20.0 IBU
Brewhouse Efficiency: 75.00 %
Boil Time: 60 Minutes

Ingredients:
------------
Amount Item Type % or IBU
8 lbs Munich Malt (9.0 SRM) Grain 42.11 %
8 lbs Pale Malt (2 Row) US (2.0 SRM) Grain 42.11 %
1 lbs Biscuit Malt (23.0 SRM) Grain 5.26 %
1 lbs Caramel/Crystal Malt - 80L (80.0 SRM) Grain 5.26 %
1 lbs Victory Malt (25.0 SRM) Grain 5.26 %
1.00 oz Northern Brewer [8.50 %] (60 min) Hops 12.9 IBU
2.00 oz Hallertauer Hersbrucker [4.00 %] (14 min)Hops 6.3 IBU
1.00 oz Williamette [5.50 %] (2 min) Hops 0.8 IBU
1 Pkgs Wyeast 1792 Fat Tire Ale Yeast Yeast-Ale


Mash Schedule: Single Infusion, Medium Body, Batch Sparge
Total Grain Weight: 19.00 lb
----------------------------
Single Infusion, Medium Body, Batch Sparge
Step Time Name Description Step Temp
60 min Mash In Add 5.94 gal of water at 169.8 F 154.0 F


Notes:
------
4L Starter

 

[Jesse17]

4.95AAU of the Northern Brewer in my DB (9%) gives me 23IBU. What is the AA% of your NB?

The package says 6.6 % Alpha Acid on the Northern Brewer, 3.3 % on the Hersbrucker, and 3.8 % on the Willamette.

 

[Scimmia]

Your calcs may be right, sounds like this is a partial boil? That's not a lot of hops, and they're pretty weak, too.

FWIW, I've seen a FT clone on the green board that everyone was raving about, it calced out to 37 IBU.

 

[SuperiorBrew]

Draft Magazine has the New Belgium Fat Tire listed at 18.5 IBU's

 

[Jesse17]

So now I'm wondering, is this enough bitter to balance with the Extra Light Malt Extrac? Or, did AHB send me the wrong hops? Or, what? I'm going to assume that it's a decent clone, because it got great reviews on the AHB website. I'm just wondering why there's such a discrepency in the IBUs?

 

[SuperiorBrew]

I guess you willl know in about 6 weeks
I bet it will be fine, but you could always dry hop it for a little more kick

 

[bradsul]

I just plunked the recipe into promash (I assumed a full boil with a 19L (5G) batch size). If you did a partial boil you may be off a bit but I get 27IBU. I got an OG of 1.056 with the numbers for generic light LME so that gives you a BU:GU of 0.48 wish I'd say is pretty good for that beer.

 

[Yuri_Rage]

I bet it will be fine, but you could always dry hop it for a little more kick

Dry hopping won't impact the bitterness at all, just the aroma and flavor. To kick up the bitterness in an already fermented beer, you need to boil hops in some water and add the resulting "hop tea" to your beer.

 

[HumuloneRed]

I plugged it into promash using the Rager formula and it came up 26.1 IBU which is within the range of other clones I have seen.
I should turn out fine.
Cheers,

 

[Jesse17]

Ok, I understand that it will probably come out fine, but I'm really wondering why everyone gets such a high IBU compared to mine, when they plug the recipe in their programs.

Here's my math (just for the Northern Brewer hops (since it's the main contributer to the IBUs)

According to Palmer, the formula(s) are as follows:

AAU = Weight (oz) x % Alpha Acids (whole number)
4.95 = .75 x 6.6

IBU = AAU x U x 75 / Vrecipe
9.88 = 4.95 x .133 x 75 / 5

This is using a gravity of 1.112 (for the 2.5 gal. boil) which is what palmer lists as typical DME, I'm not sure what Extra Light LME is, but I read 1.054 after I toped up to 5 gal. so half the volume would make it 1.108 which should be close enough.

 

[Spyk'd]

Here's a cool calculator if you don't have any brewing software. Just make sure to change the AA of the defaults to the actual AA of the hops you're using.

Calculator

I've checked it against ProMash and it's VERY close. Who's to say who's wrong...



Easier than doing all that math, anyway!

 

[Jesse17]

Here's a cool calculator if you don't have any brewing software. Just make sure to change the AA of the defaults to the actual AA of the hops you're using.

Calculator

I've checked it against ProMash and it's VERY close. Who's to say who's wrong...



Easier than doing all that math, anyway!

Well, I tried the calculator you linked to, and it also came out with 28 IBUs. So I'm sure the beer will be fine. I'd just like to figure out what the problem is with my math.

Does anyone else actually use the Palmer's formulas? Are they wronge, or am I just missing something in the math?

 

[bradsul]

I programmed Palmers formula (the generic IBU formula) into my brewing software and I get 24.7 IBU for a full boil. My guess is the other calculators are just having problems with the partial boil.

 

[StallionMang]

I agree with the previous post. Some brewing software packages aren't designed to consider partial boil. Go with your Palmer calculations. They have worked for me thus far.

Going forward, if you notice that your boil volume of 2.5 g ends up making it very difficult to attain the IBU level that you desire, either of the following two things should help:

1.) Obviously you can experiment with increasing the hop additions and re-calculating. But don't make the mistake of increasing all of your hop additions. Remember, the low boil volume is only crippling the ability of the hops to bitter the beer. It is not affecting the flavoring or the aroma. Therefore, if you increase the hops, only increase the bittering hops; otherwise, you may end up with way too strong of a flavor/aroma.

2.) A more elegant solution that will allow you to save money by not purchasing additional hops is to do late DME addition. Start off your boil with only a small amount of the DME, say 3 lbs, for example. Then, near the end of the boil, add the rest. This has the effect of lowering your boil gravity, thus compensating for the low boil volume. If you redo the Palmer calculations with 3 lbs DME instead of the full 7+ lbs, you will definitely see the difference.

Thanks!