Fly sparge efficiency

Hey guys some what experience Brewer here. Looking for some help regarding fly sparging on my new set up. I understand sparging will somewhat lower your gravity from what you measured pre sparge. My pre sparge OG was 1.083 (closer to my estimated then preboil). After fly sparge my preboil gravity was 1.053. I inputted my whole set up into beersmith with all the measurements and effiencey and I am still coming up way short as far as gravity goes. Any help would be much apprefiatedm. Thanks!

Also here’s the grain bill
15 lbs pale ale malt
2 lbs oat malt
1 lbs flaked oats
.5 lbs carapils
.75lbs honey malt

Mashed at 148 with 7.5 gal
Fly sparge with 4.25 gal at 168
Collected 8 gal at 1.051
Pre sparge was 1.083

Is your total volume completely mixed?

This plus you mashed about 2/3 total volume and sparge  1/3.  I split more like 50/50,but still see significant drop in gravity from mash to end of sparge and total volume collected.  What was your target preboil Gravity? 11lbs base malt will yield me about 1.054-55, so would expect yours to be much higher with 15lbs pale malt.

According to beersmith my estimated preboil was 1.064. This is for a 6.5 gal batch size. I need 8 gal total boil volume because of all my losses. Just finished the boil and am at 1.059 which is 20 points off the 1.079 I was shooting for

No at least it’s no supposed to be. I shoot for 8 gal total boil volume for 6.5 gal into fermenter.

Are you just accepting the efficiency Beersmith is using, or have you adjusted it to your system’s efficiency?

I’ve entered mine of 65.13 on this new system