Sparging problem - help please?

[edit1now]

Things are going wrong today, and the normally smooth fly-sparging routine isn't. It's become a batch sparge by accident.

I would like about 23 litres of 1050 after the boil.

In the receiving vessel I have about 12 litres of wort at 16 °Brix, or 1065.

In the mash tun I have about 20 litres of wort at 5 °Brix, or 1020.

I think I need 30 litres of wort at 10 °Brix. or 1040, so I can wind up with 23 litres at 1050 after the boil.

Question please - how do I work out how much of the thin wort to add to the thicker wort to get my pre-boil gravity? If it's too thin, I could boil for longer, and if it's a bit thick I could let it down with more water.

[edit1now]

Thanks Chris! I'm feeling a bit stronger now (after restorative tea and toast) so I'll go and slosh in the garage.

[edit1now]

The 22 litres in the MT was of course including the grains

I've just put 12 litres of 5 °Brix into the 12 litres of 16 °Brix and got 10.8 °Brix, so I added two litres of sparge liquor and got 10 °Brix i.e. 1040. Probably a nadge over 30l, but I can't tell until I get it into the boiler with the sight tube.

I'll see what it's like after an hour boiling - probably about 8 pm at this rate

[edit1now]

Pre-boil: 31 litres at 10 °Brix

[mac]

You could work it out with these 2 calculations;

(db+ec)/(d+e)=a

Where;
A= target gravity
B= gravity in boiler
C = gravity of remaining (in mash tun)
D = volume in litres of remaining (in mash tun)

(12x1.065+11x1.020) / (12+11)
(12.78 + 11.22) / 23
24 / 23
= 1.043

And;

Beginning volume = End volume (in litres) x end gravity (in points) / beginning gravity (in points)

?? = 23 x (50/43)
= 23 x 1.162
= 26.7 litres

Bit late now though. Sorry

I use these in a little MS Excel programme I've written so it would be good to get some feedback because they could be completely rubbish

[edit1now]

Thanks mac. I'll have to have a go with those.

Wound up with 23 litres in the fermenter at 1054.9 (the point comes from the temperature correction). Absolutely in the right ballpark. My last several wheat beers have come out a bit on the strong side - 6.8% ABV for one of them - and strange things happen when I try to stand up after drinking a couple of halves.

[mac]

Thanks mac. I'll have to have a go with those.

Wound up with 23 litres in the fermenter at 1054.9 (the point comes from the temperature correction). Absolutely in the right ballpark. My last several wheat beers have come out a bit on the strong side - 6.8% ABV for one of them - and strange things happen when I try to stand up after drinking a couple of halves.

23 at 54.9 corrected. Close enough.

I've had that 'getting drunk from the feet up' problem and a 6.8 wheat beer would be a good way of doing it

[edit1now]

What I need to do next is cross-calibrate between my cheap refractometer and my hydrometer - probably make up some sugar solutions in different concentration. I can't be having with cooling hot wort to use the hydrometer during the mash and the boil.

When I was in Amsterdam last June the IJ Brewery had a very nice Wit beer which was 7% - all their beers except the Pils are quite strong, and they only serve in 250ml glasses - we had some trouble staggering back to the tram stop and hence to the campsite.

[edit1now]

Pitched a starter of Danstar Munich Wheat Beer yeast 10 pm Saturday 23rd. Aerated for 2 hours with HEPA filter and stainless airstone on Sunday morning.

Wednesday 27th May 3 pm: 1011.2 corrected for 15.6C hydrometer. 5.6% ABV using HMRC fudge factor of 0.13. Looks like I'll need to bottle this on Friday

Thanks for your help and support, guys!