70qt extreme mash tun problems

[brewrench]

I'm sure this has been posted multiple time but I'm sorry I couldn't find what I was looking for. My problem is with my mash efficientcy. On the last batch I only got 61% which blows. It consisted of 11.2lbs of 2 row and 11.2lbs of wheat. I was hoping for atleast a 1.056 and only got 1.047. My mash tun has a 5 row copper manifold with slits every 1/2 in. facing the the bottom. I fly sparge with my hose from my hlt to the top of my mash tun into a tupperware container so not to disturb the grain bed. any help would be greatly appreciated.

[TheDarkSide]

This post may help:

viewtopic.php?f=&t=25081

How long did you mash and what was your water to grain ratio? Next time you may want to crush the wheat malt a little smaller and use rice hulls.

[Ozwald]

Tell us more about your mash. Temps, times & grist ratio would be a good place to start.

[spiderwrangler]

I fly sparge.

Well, there's your problem.

[snowcapt]

I fly sparge.

Well, there's your problem.

+1

[tlael]

There are too many un-addressed variables here to guess.

Could be the wheat - How long did you mash for?
Could be sparge speed - I've found I need to slow down while fly sparging (to a painfully slow rate)
Mash temp?
Grist ratio?
Mash pH?
Sparge temp?

[cornhole]

5 row copper manifold with slits every 1/2 in.

Equipment-wise I put a nylon mesh bag over the manifold, don't know if that would help your situation. I batch sparge.

[brewinhard]

Yes, you might need to slow down your sparge to make sure you collect enough of your sugars. I use a refractometer for this purpose to make sure I don't oversparge to the point of astringency. What was your expected efficiency?