Need help with recipe calculations (math involved)

[tal82k]

Hey all, I am in a brewing science class. We had an assignment to make a recipe for a tripel using the following parameters:

10 gallon batch
IBU 39
OG 1.081
pilsner 2-row malt
adjunct: 17% fermentable sugar
hops: tetnang, saaz, or golding
yeast: WLP530
Pitch the yeast at 64 degrees F, allow it to get to 68 for the first 5-6 days
Secondary fermentation at 46 degrees for 4 weeks

First, I tried calculating the hops in ounces. I decided randomly to use Saaz hops with a 3.5% AA rating.

I came up with .84 oz with a 60 minute boil:
((.35 decimal AA x ?oz x 7490)/10 gallons)*.176 AAU = 39

Next, I tried to calculate how much grain. I thought I would use 79 gravity points and get the rest by the adjunct. I did (lb/g)(36 extract potential)(.7 extract efficiency)(10 gallons)= 79 and got 3.13 lb/g. This would come to 31.3 lbs total malt.

I don't know how to deal with the 17% fermentable part for the sugar. Does this mean that I should use the Brix scale and convert it to Specific Gravity? If so, how? Prior to thinking about that part, I did this calculation:
(1.081 target - 1.079 current)/.005 x 10/5 x 14.2= 11.36 oz
This is based on table sugar. 14.2 oz raises 5 gallons .005 gravity points.

So what have I done wrong? What have I not though of? Anything is helpful.

 

[HairyDogBrewing]

I think that sugar is meant to be 17% of the fermentables.
So enough sugar to get 0.17*81 gravity points.
Then get 0.83*81 gravity points from the grain.

Hop AA utilization is something like 30 - 35% for a 1 hour boil.
You will need about 3 times as much hops for your target IBU.

 

[tal82k]

HairyDogBrewing, thanks for the post. That was really helpful.

 

[frankstoneline]

for IBU's here is a great rundown on how you do it.
http://www.howtobrew.com/section1/chapter5-5.html

 

[frankstoneline]

after a quick number crunch you can simplify the above equation to this for your hop choice and the gravity of your brew (roughly)
390/(3.5x.176x75)=oz's hops (added at 60 minutes)
so you would need ~8.442 oz's of the aforementioned saaz hops.

gravity calcs:
17% .081 = .0138 contribution from adjuncts
using a grain gravity chart candi sugar has a contribution of .036/lb/gallon and turbinado (raw sugar) has a contribution of .044/lb/gal
so, (.0138/.036)x10 gallons = 3.8lbs
and
(.0138/.044)x10=3.13 lbs turbinado.

someone else chime in on my math if it's wrong?

 

[dcp27]

dont forget the grain needs to be adjusted for the proper amount of sugar, so its really about 26lbs pils.

as for the hops, that should have been 0.035 AA not 0.35, which is where your error came from. also, your initial utilization of 17.6% is much closer than the 30-35%, but just curious on how you came up with it?

 

[frankstoneline]

dont forget the grain needs to be adjusted for the proper amount of sugar, so its really about 26lbs pils.

as for the hops, that should have been 0.035 AA not 0.35, which is where your error came from. also, your initial utilization of 17.6% is much closer than the 30-35%, but just curious on how you came up with it?

The link in my first post provides a utilization table based on gravity of wort vs boil time.
also, in the example used in the given link palmer doesnt convert AA's to a decimal, and leaves them as the listed whole number %, thus 3.5, not .035 (though I was a bit confused myself on that issue, which i believe he explains as being readily taken care of by the metric/american conversion factor of 75, but I could be wrong). When I checked my numbers they rounded out nicely, though I didnt bother to calculate the base malt weight.

 

[dcp27]

I was curious where the OP got it from since he's in a brewing science course and that old equation has since been proven incorrect. Besides, 17.6% is incorrect because that's based on post-boil. Depending on the pre-boil volume its actually closer to 20%

 

[frankstoneline]

I was curious where the OP got it from since he's in a brewing science course and that old equation has since been proven incorrect. Besides, 17.6% is incorrect because that's based on post-boil. Depending on the pre-boil volume its actually closer to 20%

I see my error now, thanks.

 

[dcp27]

No problem, its an easy mistake. It's all relative anyway so as long as you always do it the same way you can still gauge your results.

tal82k, where are you taking that course at? I didn't realize we had any out here

 

[frankstoneline]

out of curiosity what would be the proper numerical rundown for the hop utilization? would you sub ~12 for 10 in the volume and .035 for aa's?

 

[dcp27]

sorta. 10gallons would still be in the equation because the final IBUs is based on that volume. however, you need to use the utilization based on the OG of 12gallons worth (or whatever the pre-boil volume may be), although somewhere in between would probably be more accurate. there really should be a factor on the equation (found below the chart) that adjusts the gravity/volume throughout the course of the boil. either way its just an estimation, so as long as you stick to one way it really doesnt matter what you do.

 

[tal82k]

Thank you all for you posts. I got my hop AAU table from the class, but it does not say where it came from. I realized that I had put .35 instead of .035 before reading that post, which has been a problem haunting me since I first learned about percents... The table that I have is the same as the one that frankstoneline posted.

I think we are just going to use the bleached, processed plain boring white table sugar (we made a dubbel on the first day of class with it).

As for grain, I redid the calculation and came up with 23.46 lb of pils (I assumed two-row would contribute 1.036 per gallon. I could not find a list somewhere of what specialty grains may contribute...)

For sugar, after hearing the suggestion that he meant that 17% of the fermentables would be sugar, I did the following calculation:
.0138/.005 x 10/5 x 14.2
This was based on what I said earlier that 14.2 oz raises 5 gallons .005 gravity points. I got 6.62 lbs.

Finally, with regards to the class, I am a final semester student at Hampshire College. The dean of Natural Science is big into beer and homebrewing, and managed to get a grant to teach brewing as fermentation science. Most of the students are students at the college, but there are two who are from the community. Just saying he is open to it...

 

[dcp27]

As for grain, I redid the calculation and came up with 23.46 lb of pils (I assumed two-row would contribute 1.036 per gallon. I could not find a list somewhere of what specialty grains may contribute...)

I'm getting 26.68lbs. 81points*0.83%*10gallons/70%eff/36ppg

here's a list of ppg for most grains: https://www.homebrewtalk.com/wiki/index.php/Malts_Chart
and one for adjuncts: https://www.homebrewtalk.com/wiki/index.php/Fermentable_adjuncts

For sugar, after hearing the suggestion that he meant that 17% of the fermentables would be sugar, I did the following calculation:
.0138/.005 x 10/5 x 14.2
This was based on what I said earlier that 14.2 oz raises 5 gallons .005 gravity points. I got 6.62 lbs.

sucrose is 46ppg not 28ppg, so its more like 3lbs. (13.8*10/46) or use 0.008 instead of 0.005 in your equation. also you seem to have incorrectly converted oz to lbs (16oz = 1lb)

Finally, with regards to the class, I am a final semester student at Hampshire College. The dean of Natural Science is big into beer and homebrewing, and managed to get a grant to teach brewing as fermentation science. Most of the students are students at the college, but there are two who are from the community. Just saying he is open to it...

damn, thats way too far unless its a weekend class