Several problems with OG calculations

Hi,
  I think it looks pretty good - if you enter the "actual" Pre-boil vol/gravity into the Mash Details you can get your "measured mash efficiency", and also if you go to the fermentation tab and enter your measured FG and measured volumes you will get to see the "measured efficiency" based on those values.

  Therefore after you brew a batch - enter these measured values and you will get a very good idea what your total brewhouse and mash efficiency numbers are - use the measured total brewhouse efficiency as the basis for formulating your next recipe.

Brad

Thank you for the look Brad, that's helps ease my worries. I think the high gravity of the beer led to a lower mash efficiency than I got last time.

Is there a general rule of thumb for adjusting Est. mash efficiency when increasing the size of the beer? (Or in this cash, brewhouse efficiency -- but I find it simpler to think in terms of est. mash efficiency.)

Secondly, can anyone tell me what Rosenjm's issue was and how it was resolved? From his argument near the beginning of the thread it looked like he really did find a problem with how Beersmith calculates expected OG.

Hi,
  If you are brewing higher than normal gravity beers your efficiency is going to be lower because you are running a lot less total water per pound of grain through the mash.
  http://www.beersmith.com/blog/2010/05/09/how-to-brew-big-making-high-gravity-beers/ - Article on it

  The issue (Rosenjm's) with boil time not changing the numbers was resolved in an early patch - you can now specify in the equipment profile a "rate" of boil off.  His other issue is really related to the difference between batch and mash efficiency - which is why I pointed him to the article.  Since the program uses overall batch efficiency you can easily arrange your volume losses do not align with what a mash efficiency calculation would tell you.

Brad

Wow, I noticed in your article that big beers can reduce efficiency from (say) 72% to 60%.  That's a big drop.  I only lost around 4%, so I guess that's pretty good.

So, I guess there's no way to estimate the loss in efficiency?  It would be nice to have a rule of thumb. Say, 1% efficiency drop for every pound over a typical 10lbs?

Anyway, thanks for the help. I feel more confident about what the problems were and I can't wait to try again!

Just my 2 cents about big batches and loss of efficency.
That is exactly why I have 2 different size coolers for mash tuns.
I always use 1.5 qts per pound and get great numbers, normally low 80's for Mash efficency.
Before I had my second larger cooler for my big beers my numbers were not near as good on them as soon as I got down to 1.25 or less to fit the smaller cooler.
I always try to keep the batch to cooler size such that it is nearly full to keep the heat in.
Thats what works well for me.
Doing this the software is normally real close on everything I brew.

Ed
Brewing Beer For A Better Tomorrow