Calculating IBUs with late hop additions

[bhondorp]

Hey all, so I'm trying to dial in a hop schedule for my beer coming up this brewday. I've got a very noobish collection of hops (got a little carried away at the shop), but I am looking to get 7oz of hops into a brew with under 70 ibus (mid to low 60s is ideal). I put it into beersmith and noticed that the different formulas give wildly different calculations, particularly with late addition hops, which is what I am focusing on. At this point, I have fiddled enough to finally throw in the towel and get some help. I've currently narrowed the process down to a 30 minute boil (nessecary) and all of my hop additions are in that 30 minute window (with the exception of 1.25 oz dry hops)... i'm going for hop flavor and aroma but not huge bitterness. My questions are as follows:

1: most importantly, will this beer be a under or overshoot for bitterness?
2: unrelatedly, will the addition of corn sugar thin out the body too much?

Here is the recipe as it stands:

30 Minutes --- 3/4 oz warrior at 30 mins 29.4 IBU
20 Minutes --- 1/3 oz of each hallertauer, ahtanum, hersbrucker, glacier, and willamete (~1.66 oz hops total)
15 Minutes --- 6lbs LME, 2 lbs DME, 1 lb corn sugar, the same 1.66oz hop blend, whirlfloc
5 Minutes --- the remaining 1.66 oz hop blend, yeast nutrient
Flameout --- 1lb honey
Dry hopping --- 1oz chinook and .25 oz remaining warrior.

Yeast: 2 packets of Danstar Nottingham

Estimated OG 1.078

 

[Rivenin]

what is beer smith showing for this? i dont have it at work or else i'd fiddle around some more.

you dont need to do a 30 minute boil though, you could do a 60 minute boil, just add those in at 30.

why dont you knock down some of the hops to get it where you want it and save the rest for later?

and one other suggestion, for the late hops, why dont you start at 15-10-0, that way you'll get a tad more flavor with a touch less bitterness?