Small mash v full batch mash

[Aussiekraut]

Beersmith is telling me that I need to do a 36l mash for a pre-boil volume of 29l and a batch size of 21l. The problem is that if I fill 36l of water in my 40l Guten, put in the mash tube and add 4.5kg of grain, I end up with a mess. Now technically, the mash tube is a stainless steel grain bag, so it's a BIAB setup for all intents and purposes. Considering I don't want to make a mess, I used to mash 30l but then ended up with only about 18l wort.

The last batch, I decided to mash with 25l water and then sparged with 7l of 77C water and ended up with pretty much spot on 21l in the cube. I know the sparge isn't necessary but I may as well run the water through the grain bed and pick up a few more goodies. 

The question is, does it make a difference if I do it that way, as opposed to the full mash? Well, besides the mess fo course  Should I consider an even smaller mash and sparge with more water?

@MitchBastard, you use a Guten and are doing small mashes IIRC. What are your thoughts on this?  Also, what's your boiloff rate? My 5l/h is a little high I think.

[MitchBastard]

Hey mate, 

hmmm I’m far from an expert so I’m not sure I’m the best to go for advice haha. 
 

id rekon your boil off rate is high. My rate is about 3ltrs per hour. 
 

secondly, your quantities are a bit different to mine also. I generally use 5.5kg of grain per bill, mashing with 20.75L and then sparging with 16.  I know plenty don’t do it but I’ve found sparging has helped me get what I want in the kettle for some reason. That gets me 23ltr in my cube and lately my efficiency has been about 75-78%.  
 

Would you  remove the malt pipe and gett a BIAB mesh bag and give that a go? There’s dead space between the kettle edge and the basket plus underneath as you would know. That would certainly help with more malt....

i like the process of mashing and sparging so I’ll advocate for that but I’m actually going to give a full volume mash in the next few batches to see how it goes.

dunno if I’ve helped at all sorry mate. 

[PaddyBrew2]

Beersmith will only tell you going from the metrics in your equipment profile. Whatever you’ve put in here , BS will adjust accordingly using or looking up these metrics.  I have the brewzilla but all these gutens and grain fathers etc are the same. 
i use about 6kgs grain. I fill 22 litres of water. Mash in.  Then I sparge until i hit the 29 litre mark. After my boil off and dead space, I have 21 litres in me cube 

[Hairy]

Just do a smaller mash and add a sparge.