Help with 2nd AG brew

Hey guys,
I've brewed one AG batch so far, and it turned out pretty well. I've learned some things since and want to make sure this batch turns out far better! I'm making a Belgian Quad tomorrow. Here's my grain bill:
8oz Cara Vienne Malt
4oz Chocolate Malt
2.5lb Munich Malt
13lb Belgian Pale Ale Malt
8oz Special B Malt

(I also have 1lb Dark Candi Sugar to add in the boil.)

With 16.75lb of grains, I expect to use 21qts of mash water. Assuming absorption of 0.2gal/lb and the fact that I lose about 1.5qts in the bottom of my mash tun, I should get 6qts out in my initial mash.

The recommendations I've seen on here are to not worry about having to boil off extra water and to go ahead and sparge with 2qts/lb, which is another 33.5qts. Assuming I do a double batch sparge, I should end up collecting an extra 30qts of wort, which comes out to a grand total of 9gal of wort! Still, I expect to boil off a little over 1gal/hr, so I can just boil it for 2 hours before my first hop addition.

Is all that reasonable so far?

In regards to my sparge process, is it generally recommended to add some of the sparge water at near boiling temperature to the mash to perform a mash-out (and presumably this is added prior to draining the mash water)? Can some one point me to the equations used to calculate how much boiling water to add? Also, when I drain my mash water, do I need to leave some in the bottom of the MLT, or is that unnecessary when I'm batch sparging?

Thanks,
JB

just use a brewersfriend.com why you wana boil for 2 hours for? you know how much gas or power you gona waste for doing 2 hour boil!!!!!?

I'm less worried about having to boil an extra long time and more concerned about getting everything I can out of my grains. The one AG batch I've done so far I had an efficiency of around 60%, and I'd rather use the extra propane to end up with a better beer! The target OG for this recipe is 1.098.

Boiling longer to fix efficiency is a band-aid. You need to fix the source of the problem. 60% isn't horrible though. You probably just need to make a lot more beer to dial in your process. As you do, you'll figure out the water volumes you need for your system, and the crush that works for you, etc. Just keep going and have fun with it.

yes, i agree with masonsjax! boiling longer is only a temperary expensive solution to this problem. plus you need more grain to compensate for a low eficiency. you can boil for 1 hour but with more grain!

Thanks guys. I'll keep all that in mind for next time. It seems that I managed to do a lot wrong on this batch. First, the recipe (Belgian Quad style with 1.098 target OG):
8oz Cara Vienne Malt
2.5lb Munich Malt
8oz Special B Malt
4oz Chocolate Malt
13lb Belgian Pale Ale Malt

1lb Dark Candi sugar added at the beginning of the boil.
1oz Nugget hops at 60min and 1oz Styrian Golding at 15min.

My mash didn't go so well. I got 22qts (ratio of 1.3 qt/lb) up to 170deg. I missed my target by about 10deg talking to a friend, so I ended up adding some ice and got a temp of 168deg in the cooler/MLT. I added the grains and waited ~5min. The temperature was 156deg, which was a bit high, but it was cold out and I figured it would drop some. I checked again 15min later and it was at 160deg instead. I added some ice and waited 5 minutes, and ended up with a temperature of 148deg instead. Unfortunately I didn't have any boiling water handy, so about 10 minutes later I finally got the 3qts of boiling water added and got the mash temperature back up to 152deg (now about 30min into the mash). It remained stable at 152 for the duration of the mash (I let it go 65 minutes total).

With all the ice and water additions I ended up collecting nearly 4gal of first runnings. I hadn't read the replies in here at the time, so I ended up sparging with 7gal total. 3.5gal in the first batch sparge at just over 180deg. I collected 3gal from there. 3.5gal more for another 15min batch sparge. I collected 2 more gallons for a total of 9gal of wort. An iodine test indicated conversion, but the gravity of the 9gal was 1.044 (after cooling the sample in the freezer). I boiled it down to 7gal in 1.5hrs and added the Candi sugar and started my hops additions. I also went ahead and threw in 1lb DME to try to bring the gravity back up a bit. I ended up collecting just shy of 5gallons of wort with a gravity of 1.081. I'll probably lose more of that than I'd like because my bazooka-T screen fell off in the pot, so I've got a heck of a lot of sediment in my fermenter. The recipe said that the OG target was 1.098, and I fell pretty far short of it, even with the DME addition. Still, at the end of the day, I made beer and I know about 10 things to do differently next time!

You have learned your lesson! Try to correct your mistakes next time.