Zephyr259
Landlord.
I've done this several times now, 3 were split so I got a small batch of belgian ale in addition to the main batch, last one was meant to compare a lager yeast to a scottish ale yeast but the Scottish one got contaminated with belgian yeast...Another idea for a double brew day is splitting a full volume mash and boil into two half batches for fermentation I.e. 23 litres split into two 11 litres batches. So single mash , single boil with or without hops and then add hop tea or dry hop each smaller batch. Same yeast or different, additions like mango or grapefruit added a few days into fermentation. Of course you'll need two FV's.