efficiency curve

Wow. did I have a good idea. (Thank you, thank you.)
So, maybe someone has mentioned this already. The higher your OG, the lower your efficiency, generally, unless you boil proportionately longer.
How about as part of equipment setup, you could plug in two batches at different strengths, and then BeerSmith uses the data to calibrate your mash efficiency curve? I brew a 5g batch of 10# and get 1.052 OG. I brew a batch of 13# and get 1.065 OG. Then, instead of a standard mash efficiency, the program loks at your #/G ratio and tells you what your sysstems efficiency would be. That would be cool. And of course, the greaterrepeatability you have in your mashing, and the greater difference between the two parameters, the better it woudl work. Or maybe each time you make a brew you can add the real OG/extract potential to ever refine the calculation.
Good? Easy?
Cheers!

Yeasty,
 This might just work - I guess the only question I have is whether to interpolate it as a straight line or some kind of curve.  My guess is that the efficiency declines to a larger degree as the SG increases.  

 I think I will need to research - but it is an interesting idea.

Cheers!
Brad

Great,  
for my big beers I figure a lot more boil off (longer boil) for two reasons,  first I want the complex carmelization that ocours and second to concentrate the wort.  Here is a link to a study I did with batch sparging and efficiency.

http://beerdujour.com/SpargingDeMystified.htm

Check out the graph at the end.

Fred

Here is a chart (bottom of page) which I made while trouble shooting the clubs brewing system.  In the process I plotted a number of brews to see what effeciency was doing.  The chart has 3 outliers

the circled one at 80% (after the fix)
the other two are interestingly, wheat beers

http://beerdujour.com/pico-efficiency.html

This should give you an idea of what you face trying to graph it.

Fred

Fred,
 Thanks again as always.   It looks pretty close to linear.  I would have expected a slightly higher dropoff myself for high gravity ales, but this is very good data to use as a starting point.

 Interestingly the dominant effect in theory is the total boil size relative to the amount of grain.  The lauter becomes less efficient as you have a large amount of grain and proportionally smaller amount of water because you don't have enough water to fully extract the sugars from the grain.  Therefore I would expect a slightly exponential curve with a higher penalty on efficiency as the OG rises.

Cheers!
Brad

suprisingly it very closely follows what I calculated for batch sparges too.  

Thoughts,
maybe you don't want to automaticly interpolate, provide a drawing tool for the user to draw a line (eliminates the need to handle outliers.)

Perhaps plot all, or marked, sessions from the brew log.

later

Fred

So, this was a year ago. In that time I've tried to pay more attention to eff vs boil size, and it seems that there's no reaon you can't come up with a good effeciancy rating for the grain:boil ratio. I've done some BIG beers, but collected proportionately big worts, and the efficiency is surprisingly similar. I did a 1.105 barleywine that gave me 82% efficiency, but I collected about 11g and boiled for four hours. That works out to about the same as a 1.050 beer with a 6.5g preboil.
I'm thinking that all else being equal, there's nothing magic about getting the sugars out of a lot of wort, and you should be able to easily plot your efficiency (assuming you use standard procedures each time) based on how much wort you gather.
Of course, pH and grain bill will affect the extract, but AEBE, it seems to be jsut a matter of always making a 1.050 brew of a certain volume, then boiling it down to your batch size.
...to a point, I guess.