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Missing BeerSmith's estimate OG numbers

 
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g8tors




Joined: 05 Oct 2011
Posts: 211



PostLink    Posted: Sat Jan 04, 2014 1:31 pm    Post subject: Missing BeerSmith's estimate OG numbers Reply with quote


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I am consistently coming up 2 to 3 points lower then BeerSmith's calculated OG. I'm using the formula:
(pre-boil vol)(pre-boil GU) = (post boil vol)(post boil GU)
My last recipe showed an estimated pre-boil gravity of 9.29 gal and an estimated pre-boil gravity of 1.042. Under the vols tab it shows 7.49 gal for post boil vol and under the fermentation tab it shows estimated original gravity as 1.054. Now if I plug those numbers into the equation to find estimated post boil OG I get:
(9.29 gal)(42) = (7.49 gal)(post boil GU) = 390.18/7.49 = 52 which is what I actually ended up getting.

If I consider the 4% cooling shrinkage then I can get the same number as BeerSmith
(9.29 gal)(42) = (7.49 gal)(.96 cooling shrinkage)(post boil GU) = 390.18/7.1904 = 54

If this is how estimated OG is being calculated then I'm not sure I understand why. It seems like the estimated pre-boil volume includes the 4% cooling shrinkage so if we take it out on the right side of the equation we would need to take it out on the left side as well correct?

I'm trying to figure out why my actual OG numbers are usually 2 points lower the BeerSmith's calculated OG and after spending a few hours thinking about this and looking at past recipes this is what I came up with. What am I doing wrong?

My equipment profile is setup for 1.8 gal / hr boil off, 4% cooling shrinkage, 1.2 gal loss to trub and chiller, and lauter tun deadspace is set to 1.04 gal.
My procedure is I collect my mash run-offs into my boil kettle and collect the pre-boil volume that BeerSmith says to collect. I check my gravity and if I'm off from BeerSmith's number I adjust my tot efficiency number under the design tab until BeerSmith's estimated pre-boil gravity matches my actual pre-boil gravity. I then boil for the set time and then run through a counter flow wort chiller into the fermenter. I then take my OG reading, then aerate, and then add yeast.

Any help would be greatly appreciated.

I posted this on BeerSmith's forum as well.

Thanks,

Scott
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Fejj




Joined: 10 Jun 2013
Posts: 213
Location: North Shore, MA


PostLink    Posted: Sat Jan 04, 2014 1:45 pm    Post subject: Reply with quote

Post your grain bill. It could be an efficiency issues.
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g8tors




Joined: 05 Oct 2011
Posts: 211



PostLink    Posted: Sat Jan 04, 2014 2:28 pm    Post subject: Reply with quote

Gain bill:
10.3 lbs American 2-row
2.35 lbs Vienna
.5 lbs Crystal 40
6 gal batch size. Its the electric pale ale

In trying to figure out why my numbers are so inconsistent from batch to batch and I figured out I have at least two problems

1 mash efficiency. I think I figured this one out. After brewing the electric pale ale this last time and getting an efficiency of 82%. I went back through everything and checked the calibration. I checked the scale I used to measure the grains and that was fine. I checked the volumes and that was fine. I then checked the gap on by barley crusher and there I found that the gap had gone from .045" that I originally had it set at to .060". I don't know how often the gap should be checked but I'm going to start checking every brew day.

2 My OG numbers are almost always 2 lower then what BeerSmith calculates and this is what I really don't have an idea of what is going on. And this is after I change my mash efficiency to get my pre-boil numbers to match up with BeerSmith's pre boil numbers. I've checked my boil off volume and that was dead on. My batch size was 6 gal and that is the same as BeerSmith.

Scott
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silverspoons




Joined: 21 Dec 2010
Posts: 555
Location: Webster NY


PostLink    Posted: Sat Jan 04, 2014 5:41 pm    Post subject: Reply with quote

"And this is after I change my mash efficiency to get my pre-boil numbers to match up with BeerSmith's pre boil numbers."



I don't understand what you're doing here.. are you changing the % of your mash efficiency?

Silverspoons
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g8tors




Joined: 05 Oct 2011
Posts: 211



PostLink    Posted: Sat Jan 04, 2014 9:10 pm    Post subject: Reply with quote

silverspoons wrote:
"And this is after I change my mash efficiency to get my pre-boil numbers to match up with BeerSmith's pre boil numbers."



I don't understand what you're doing here.. are you changing the % of your mash efficiency?

Silverspoons


Short answer:

When I measure my actual pre-boil gravity and find out what my mash efficiency was, I go back to the design tab in BeerSmith and change the total efficiency number until the estimated mash efficiency number matches the efficiency I actually got. There is an Excel file that will calculate this for you. If you know what the mash efficiency number is you can plug that number in and it will tell you what the total efficiency is.

Long answer:

Let me try to explain by using the last brew day as an example. I brewed the electric pale ale and under the design tab I used 73.33% as my Total efficiency and this gave me 88% for the estimated mash efficiency. 88% mash efficiency is what I got the last time I brewed this recipe. So I put in the grain bill and it shows Est Original Gravity to be 1.058. I do the mash and 15 minutes into it I check the pH which is 5.5 at room temperature and do an iodine test. I have never done an iodine test before and I wanted to see what the result looked like when iodine reacted with the starch. It slowly turned black. After an hour I did the iodine test again and this time the iodine did not turn black but slowly started to disappear. I mashed out at 168 and then started to sparge. My first runnings had a gravity of 1.063. I did a mash thickness of 1.3qt / lb but when I add in the extra water to account for the lauter tun dead space and the hoses and the HERMS coil it comes out to about 1.66qt / lb. According to the chart found here:
http://braukaiser.com/wiki/index.php?title=Understanding_Efficiency
I was expecting a gravity of about 1.074. Under the vols tab, Beersmith had it calculated that I needed to collect 9.29 gal for the pre-boil volume which I did. I then boiled for 10 minutes to dissolve the sugars and completely mix the wort. I stopped the boil, took a sample, cooled the sample, and took a hydrometer reading which was 1.042. BeerSmith was estimating my pre-boil gravity to be 1.045. at 1.042 my measured mash efficiency was 81.9%. I then went back to the design tab and changed my total efficiency to 68.33% which changed the estimated mash efficiency to 82% and now my estimated OG was showing 1.054. I then look at the new IBUs and estimated ABV to see if that is acceptable or if I want to make changes like adding DME or boiling longer and making less beer. On this one I decided not to change anything. I boiled for another 50 minutes, cooled and transferred to the fermentor. My OG reading in the fermentor at 60F was 1.052. This is two lower then what Beersmith was estimating me to get. When I went back and looked at my other recipes I have brewed I am almost always off my 2. The times I am off by more is when my volumes don't look right and I can't remember what I was doing or thinking.

Thanks for taking the time to read through this and decipher what I'm trying to say.

Scott
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Fejj




Joined: 10 Jun 2013
Posts: 213
Location: North Shore, MA


PostLink    Posted: Sat Jan 04, 2014 9:24 pm    Post subject: Reply with quote

when was the last time you calibrated your hydrometer? also is your hydrometer calibrated at 60f or 68f? your process looks right. It is well known that software predictions for OG are just that, predictions. the 2row you are brewing with may have less/more extract then that default 2row in beersmith.

How do you sparge? Are you fly sparging or batch? if you fly sparge are you trickling the wort out of the MLT at the same rate the sparge water is added?

Im sure a more seasoned brewer may have a better answer, these are just my thoughts:)
Cheers,
Jeff
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