Since I've garnered so much knowledge from HBT I'd like to try and give back a bit. After several variations of BIAB I have finally dialed in what I think is a great process, and wanted to share it with those of you looking to get started in all grain. My equipment is:
40 qt aluminum pot
2 heatsticks, based on the design here: http://www.3d0g.net/brewing/heatstick
home made brewing bag made out of voile
The simplicity and lack of bulky equipment makes this great for apartment or low budget brewers (of which i'm both).
This is a pretty straightforward no-sparge take on BIAB, and the process goes like this:
1. Heat strike water to pre-determined temperature. (still dialing in the difference, but it looks to be between 8 and 10* above what my mash temp should be). This is less than most mash-tun based systems (12* seems to be popular number on HBT) because of the larger thermal mass of 7 gallons vs. 3 or 4 in a mash tun. Since this is a no-sparge method you'll want to heat all the water you'll end up boiling. For most of my 5.5 gallon batches I dough in with about 7 gallons, assuming for around 0.5 gallons of loss due to absorption and about a gallon of boil off during the boil.
2. Drop the bag into your pot and dough in the grains. Last 2 batches I've stirred with my huge whisk for about 5 minutes, or until your arm gets tired.
3. Put top on your pot and layer 2 large towels over the pot. Heat is off on the stove, so no need to worry about anything catching fire. I do not stir at all for the duration of my mash...i've gotten 70+ % extract efficiency both of my last 2 batches, and feel this is due to a constant temp during mash and a really good stirring first. In my mind at least, the larger amount of water leads to a better dissolved grain bill. I've had less than 2* temp loss over the 60 minute duration as well.
4. After your mash duration, grab the bag and dunk it a few times before slipping the large colander onto the top of the pot and plopping the bag of grains in the colander. This will allow the grain bag to drip directly into the pot as well as provide a spot to "squeeze" the bag from. With your hands or brew spoon I get as much liquid out of the bag, and over the course of 10 minutes I've gotten most all of the liquid out.
5. Boil, etc. just like normal.
As for capacity concerns, my Oktoberfest grain bill today was 12 lbs (courtesy of EdWort), and had about 1 inch of "head space" in the brew pot with the grains/bag in there. I figure I could do up to a 14lb or so grain bill with this method.
In my brew session today I was finished brewing, including cleanup in 4 hours. Have to admit that i've gone to a quazi no-chill system where I get the wort to about 100* and then pour into the carboy and get the carboy in its swamp bucket w/ ice to cool down the rest of the way before aerating and pitching yeast.
Previously, I messed around with adding in a sparge or mash-out phase of this method, but now have gotten good-enough efficiencies without, so I figure why complicate matters.