My 2nd all grain efficiency, need help..

[wolkphoto]

Today I brewed my 2nd all grain, it was a golden ale. Things don't make sense...here's the grain bill (5.5 gallon batch in brew pal app):

8lb 2 row
.75lb carapils
.5lb crystal 10L
.5lb Vienna

@ 75% efficiency i should get 1.040, but i got 54.8% w/ my 1.030 pre boil gravity reading. It was a 60 min boil and 6.5 gallons from my mash went into the boil kettle. Just racked into my fermentation carboy, and I'm hovering right around 4'ish gallons of wort. However, my expected post boil gravity of 1.049 was reached. What gives? I have a small batch, and planned for 5.5 gallons. There is maybe a half gallon or so in the brew kettle hanging out w/ the trub that I didn't bring over. Anyone have any thoughts on what went down?

 

[TipsyDragon]

first you have a dead spot on your mash tun which is why you got 55% efficiency. as you boiled from 6.5 to about 4.5 your gravity went up because the water in the wort went down. obviously you had more boil off than you expected. next time adjust your water additions and grain bill accordingly.

 

[ajf]

I think I understand what you mean.
You were expecting to collect 6.5g from the sparge with a gravity of 1.040, but you collected 6.5g with an apparent gravity of 1.030 which comes out at ~55% efficiency.
Then after the boil, you ended up with ~4g at 1.049 (which is the gravity you would have expected assuming 75% efficiency).
If this is not close to what you meant, then stop reading. I can't help you. If it is close, then there are a few things that can explain it.
First, there is no reason why you should achieve 75% efficiency. If you are like most people, your efficiency will start out lower than that, but increase as you get more familiar with the process.
Next, your volumes are estimates. Small errors in the volumes can accumulate when calculating efficiency, so your true efficiency could be greater (or less) than you think.
How did you measure the pre-boil gravity? If you used an hydrometer at temperatures over about 100F and applied temperature correction, then the temperature corrected gravity could be very different from the real gravity. (Temperature correction does not work very well at temperatures > 100F).
Did you stir the wort really well before taking the pre-boil gravity? If not, the wort at the bottom of the kettle (first runnings) will have a much higher gravity than that at the top (final runnings). If your volume calculations are accurate, you ended up with 4g in the fermenter and 0.5g left in the kettle at a gravity of 1.049. This would mean that the 6.5g pre boil gravity would really be about 1.034.
If you ended up with 4g at 1.049, it looks like you got an end-to-end efficiency of about 63%.
If you want to improve on this, I would suggest that you increase the pre-boil volume by at least 0.5g, and try to reduce the amount left in the kettle, when racking to the fermenter (a good whirl-pooling technique can help here).

-a.