I double batch always with Grainfather , same time but get 2 cubes.
I start with 23 ltrs, at strike temp then leave on mash low heat setting while stirring in,then slowly mash in my 8.5 to 9 kgs max of grains, slow and steady stir and stab with paddle up and down like mixing up concrete.
Usually once I've stirred in about 7 kgs of grain, I swing the top pipe over the top of the grain bed, start pump, and pump approx 2 -3 ltrs of water ontop.
This then makes it much easier to mash the final 2 kgs in.
I usually then mash for 75 mins and do 20 min mash out at 78. This helps with sparging.
Then, I just keep sparging till I see it dripped upto the 30 ltr mark.
I then place the malt pipe into an old esky and sparge it with another 6 ltrs of water and just let the last goodness run out into esky while I boil. You can take top plate of, give the grain a stir and sparge with final water, I find I get the last sugars totally out. Then Usually about 7 to 8 ltrs trickles out into esky which works out perfect for top ups and keeps efficiency up. Sit the malt pipe ontop of a Tupperware container etc to keep it off the floor of esky or bucket to catch second sparge runnings.
I then use this final runnings to top up the boil while doing my additions,
Just top up slowly so the boil is not killed, or I have an immersion heater from my previous brewing days which is use to ramp up the temps in between strike and boils to save time.
When my boil is done, I top right to top , about 10mm from lip with runnings or boiled water .
I then wait for the temp to drop to about 90-92 degrees, then pump straight into 2 x 15 ltr cubes that I saved from fresh wort kits, or you can buy 15 ltr containers.
The full double batch Grainfather fills 2 of these perfectly to the top.
Seal, and leave, I also add my hop additions I would normally use at sub 15 mark into little hop socks straight into the cubes.
What I have now is an over gravity for style 15 ltr cube, actually more like 16 lts.
When time to ferment, I dump into fermenter and top up to 21 ltrs.
I usually get OG of 1.046 to 1.048 which is plenty for me, and I get 2 x 19 ltr kegs from one cook up.
Last sat, while doing yard work etc, I got 2 double batches , so 4 cubes of a nice pilsener and pale ale , and allowing for my immersion heater to save time and everything took about 7 hrs.start to cleaned and packed up. Also managed to mow yard and take kids to shops in between mash times to keep SWMBO happy. Lol
Espescially using no chill, saves heaps of water and about 30 mins per Cook up. It's a no brainer.
Unless doing a high grav brew, double batch all the way.
I've done about 25-30 double batches now, and works a treat.
Hope this helps.
