1. Are you sure the rum was 21% ABV? That's awfully low; more like 40% is typical, but we'll go with it.so i made one of kahuna's recipe's. his pirate ale. so i got an abv of 5.74%
then i added a half of a handle of 21% abv rum to the beer. and ideas on how to figure out the new abv
Assuming a standard handle of liquor is 1.75 l:Here's the equation i believe:
Beer Alcohol Volume (5g) x 5.74% = .287 G (you have .287 Gallons of alcohol in the beer)
Rum Alcohol Volume (.132G=500ml) x21% = .022772 G
Yep, same as mine except you converted everything to G instead of ml.Here's what I get. (May or May not be correct)
5 Gallons @ 5.74% = .287 Gallons of Alc.
.875 L ( .231151 Gallons) @ 21% = .18375 L of Alc (or .0485416 Gallons)
5 Gallons + .231151 Gallons (Rum Volume) = 5.231151 Gallons total Volume
.287 Gallons + .0485416 Gallons = .335416 Total gallons of Alcohol
.3355416 G / 5.231151 G = 6.41%
Which is pretty close to your estimate, so they both make sense to me.
You may want to get a 2nd opinion, however.
It's an okay estimate, but:does this math make any sense?
if you figure that a handle of rum is 1/2 gallon. then half would be 1/4.
would it work this way. there are 20 quarter gallons in 5 gallons.
so if you divide 21(the % abv of the rum) by 20(to dilute it into 5 gallons)
you get .0105. so am i basically adding 1% abv to my brew going from 5.74% to 6.74%