Whats Happening With My Volumes

[Mantis]

I have my 50L straight sided SS pot measured out at 20 to 40L in 5L intervals of 4cm with wee dints on the inside of the pot. Before anyone asks I know they are acurate or else the 50L pot isnt 50L, that I havent measured just taken for granted.
Anyway my 25L cube I filled with water and poured into the pot and it came up to the 27L mark.
Now the weirdness starts. I have calculated my biab efforts so that I end up with 29L in the pot post boil thinking that with 2L lost to trub I should fill the cube. It doesnt fill the cube but goes close and there is less than 2L left in the pot.
Thinking that I should have around 26L to put into the fermenter but no..... , into the fermenter I only get 23L after the wort has cooled.
What is happening to my shrinking wort. I start with 29L in the kettle and end with 23L in the fermenter
And its happening all the time , so what am I missing here

Beginning to think I have a wort fairy helping herself from my cubes :blink:

 

[peas_and_corn]

You lose volume when wort cools, not sure about the %.

 

[Pollux]

I personally lose 5% on cooling.....

Have you actually confirmed the 25L sizing of the cube?

 

[clean brewer]

I have my 50L straight sided SS pot measured out at 20 to 40L in 5L intervals of 4cm with wee dints on the inside of the pot. Before anyone asks I know they are acurate or else the 50L pot isnt 50L, that I havent measured just taken for granted.
Anyway my 25L cube I filled with water and poured into the pot and it came up to the 27L mark.
Now the weirdness starts. I have calculated my biab efforts so that I end up with 29L in the pot post boil thinking that with 2L lost to trub I should fill the cube. It doesnt fill the cube but goes close and there is less than 2L left in the pot.
Thinking that I should have around 26L to put into the fermenter but no..... , into the fermenter I only get 23L after the wort has cooled.
What is happening to my shrinking wort. I start with 29L in the kettle and end with 23L in the fermenter
And its happening all the time , so what am I missing here

Beginning to think I have a wort fairy helping herself from my cubes :blink:

Boil Loss????????

Check the Volume on the Fermenters, Coopers are out by 1 ltr and Brigalow ones are out aswell.. If there are markings on them, they could be wrong...

 

[Mantis]

No, not boil loss. Starting with 32-33L preboil to end with the 29L post boil
Checked the cube volume like I said by filling it with water and pouring into the kettle, 27L.
Another thing is that the one time I did manage to completely fill the cube with wort, it only came up to 24L into the fermenter.

5% loss on 27L is 1.35L so that is certainly some of the loss

I am not really bitching here as 23L into the fermenter is fine with me, and now I know my starting volume of water and weight of grain to get it with the OG I am after.

 

[Effect]

my cubes are 20L but they hold more like 23.

my coopers mixing spoon has markings on it for my kettle...when I have finished boiling it says I have 25 litres in the kettle. When I chill it, I only get 21 or 22 litres in the coopers fermenter. Reasoning, the wort has expanded whilst hot so it is really only about 22ish litres or more...and the coopers fermenter is roughly 1 litre out (i.e. reads 20 is really 21).

I feel that this is similar to your problem...

 

[seemax]

either the cube is out or the kettle is out, more likely to be the cube.

 

[samhighley]

The cubes always hold more than they state, and they'll also expand a bit when you pour boiling wort into them.

Next time you poor the wort from the cube to the fermenter, take a look at how much you end up with in the fermenter.