Query: Double Batch, Single BIAB.

[McFeast]

So, if the subject isnt clear enough, I am considering doubling the grain bill so I can have the equivalent of two 23 litre wort batches ready to be "watered down" and pitched.
Has anyone done this? I am sure plenty of you have and do.

I would think I would only need to double the grain amounts, which equates to 10-11kg. I would still try to use the same amount of water for a single batch, which i usually do at 35l (i've got the 40l crown concealed urn). In thinking about this I will no doubt have to reduce the amount of water into the urn so I can fit the entire grain bill in there, right? Is there any efficiency issues in doubling the grain bill for two batches?

What other tips can you blokes tell me about doing this sucessfully? Or at least, acceptably.


Thanks everyone.

Edit: Poor grammar, not clear enough. Probably still not helping anyone

 

[ben_sa]

maxiBIAB? http://www.biabrewer.info/viewtopic.php?f=89&t=352

 

[Bribie G]

You would need to do a good batch sparge in a side-vessel otherwise you will end up with woeful efficiency.

For example if you wanted to do a batch to water down to give you 6 fermenters with 23L batches you would end up with an urn full of concrete.

Ridiculous example but your plan sits on about 3 on that 1 to 10 scale if you see what I mean.

Why not grab your camping esky, some voile and try this. I do it regularly with great results.

 

[chrisso81]

My last (BIAB in a crown urn) brew I managed to get 26 litres of 1.064 wort into the fermenter from a 6.1 kg grain bill with a 78C mash out and a good dunk sparge. Brewmate calculated this at something like 88% efficiency. In my experience, if you really want to get the most from a BIAB urn system there's a lot to be gained from some thorough side sparging.

 

[philmud]

My last (BIAB in a crown urn) brew I managed to get 26 litres of 1.064 wort into the fermenter from a 6.1 kg grain bill with a 78C mash out and a good dunk sparge.

How do you calculate the amount of water you use to dunk sparge? Do you just leave a pre-determined volume out of your original amount?