hops / beersmith question

[bigdug]

I have been reading a thread from last year about partial vs full boils and I think I understand that If you are doing a partial boil (2.5 gals) that you will only net Approx 1/2 the Ibu's from your hops. I have been working on my first recipe using beersmith and i noticed you can change the size of you brew pot and this will affect the ibus (in my example a 3 gal brewpot will show a max 2.44 gal boil). Is this the proper way to calculate the amount of hops needed to acheive a given ibu rating for a partial boil or will I end up over hoping.

Thanks

Doug G

 

[JMSetzler]

BeerSmith accounts for boil volume and total volume when figuring IBU and hops utilization. You won't over hop if you follow those numbers...

 

[Pharmguy]

Yeah,like you said... as you adjust your boil volume the IBU's change. The closer you get to full boil, the more utilization. So in beersmith you can pick the brew pot size or just manually put it your batch size and your boil volume. In your example, you are not very likely to have 2.44 gal boiling so you would have to adjust that. The ibu's will also change if you do a late extract addition.

 

[Schnitzengiggle]

Yeah,like you said... as you adjust your boil volume the IBU's change. The closer you get to full boil, the more utilization. So in beersmith you can pick the brew pot size or just manually put it your batch size and your boil volume. In your example, you are not very likely to have 2.44 gal boiling so you would have to adjust that. The ibu's will also change if you do a late extract addition.

+1 for the late addition, if you are using a 3 gallon pot, I would suggest boiling 2 gallons with about .75 lb of your DME/LME with your bittering hop addition, it will increase your hop utilization, hence, you can use less hops and achieve the desired IBU's.

On a side note, and this is purely my personal opinion, Beersmith's default IBU calculations are done in Tinseth, I think Rager is a bit more accurate, simply due to the fact that when I have my settings set to Tinseth it seems to give me much higher IBU's using the same amount of hops, and my first few brews had less perceivable bitterness to them than I hoped. Since switching it to Rager, I think the IBU rating is more accurate. YMMV.

 

[bigdug]

Thanks for the replies guys.