Gravity ABV Question

[wbuffness]

So I brewed a barley wine last year and it ended at 1.095 OG. Then 3 weeks later the gravity was 1.028 and I added 7.5# frozen (thawed) cherries and 4# dark sweet cherries (canned in syrup and drained). I waited another month in the secondary and took a reading of 1.020 FG. What's the process of figuring my ABV? I assume you can't just use 1.095 and 1.020 because the cherries had to have added some of their own sugars which fermented out, right? Please explain.
Thanks!!

 

[kevinb]

Did you take a gravity reading after adding the fruit? I believe that you need to calculate the abv from two additions separately:

[(sg1 - fg1) + (sg2 -fg2)] x 131.25 = abv

In this case 1 is the initial fermentation and 2 is the second fermentation after the fruit.

 

[wbuffness]

No I didn't take a reading right after adding the fruit. Bummer. So I guess I will never know the actual ABV. That formula does make sense though. I will have to remember that the next time I make a late addition of fruit or other sugars.
Thanks for your response!
I was just reading online that adding fruit to beer can actually lower the ABV of higher gravity beers because the fruit is around 1.040. Can anyone confirm this? I read it here... http://www.themadfermentationist.com/2010/10/adding-fruit-to-beer-increases-alcohol.html

 

[Calder]

You are not going to like the answer. Adding the fruit probably lowered the effective gravity of the beer.

Yes, the fruit does have sugars, but for the volume of the fruit you added, the gravity would be lower than the gravity of the original wort (especially a BW).

Whenever I add fruit, I assume it is gravity neutral.

If you want to do the calculations yourself, fruit has approximately 10% of the sugar as plain table sugar by weight. That is, 10 lbs of fruit is equivalent to 1 lb of sugar.

 

[wbuffness]

Bummer! Thanks Calder. I will keep that in mind when adding fruit.