Recipe Formulation Help

[Mr. Dripping]

Good morning, could anyone help me with or explain the following please.

I have a recipe for 23 litres of beer and it is given as:
Pale - 3850g
Invert sugar - 846g
Fuggles 3.3% AA - 114g 90 mins
Fuggles 3.3% AA - 22g 15 mins
OG 1045
Bittering units - 30

I've plugged the recipe in to BeerSmith so I can scale it up and adjust for my hop AA.
I entered as the ingredients above and I am getting an OG 1052 and bitterness 47.1 IBU (Tinseth)

I have converted my hop weights for the 4.9%AA fuggles that I have using the following formula - wt of original hop x AA of original hop / AA of substitute
This gives me a 90 minute addition of 76.8g and 14.8g at 15 minutes - Beersmith gives this as 46 IBU

The book which the recipe is from uses EBU's and in the forward to the recipes the author says that 80g of hops with AA of 4% will give 28 EBU, and lists another example of 80g of AA 8.7% giving 60 EBU's.
There is no further explanation and I cannot work out how the EBU figure is arrived at.
The book states that recipes are worked out on 75% mash efficiency - I have BeerSmith set at 75%

I don't understand why the OG is 7 points out.
I can scale this down no problem, but I would like to try and understand why there is a difference and if scaling it down will affect it in anyway.
My other concern is the bitterness level. My software is giving me IBU's that are about 50% higher than the recipe states (that's if my understanding that EBU and IBU are more or less interchangeable) and I am worried the beer will be far too bitter.

[mark4newman]

Hi

IBU could be caculated using rager?

OG is 7 points out, I wouldn't worry about. It might just be you have chosen a different maltster or Pale ale grain.

My two pence worth

[Mr. Dripping]

I've run the hop additions through an app I have on my ipod - BrewMath.
AA 4.9%, weight 76.8g, 90 mins, 40 litres of wort at 1045 gives 33 IBU Rager and 26.7 IBU Tinseth.
The 15 minute addition comes out at 2.4 IBU Tinseth and 1.6 IBU Rager.
I'm happier with these figures.......perhaps my hop utilisation factor is set too high in BeerSmith?? I will need to check that tomorrow.

On the gravity. I have decided to use the amount of pale malt described in the recipe and then add the invert bit by bit 15 mins from the end and check with the refractometer to bring my gravity up to 1045.

If anyone can offer up anything further on the bitterness calculations I would be grateful .......especially the recipe authors calculation of EBU. Thanks.