Low ABV at the end of Fermentation

[jfwayBrews]

I’ve been all grain brewing for about 8 batches now. The last few I’ve noticed had a low ABV. I didn’t take Hydrometer readings, but can tell you after 6 tall glasses, you feel nothing.
So anyway, I’ve been doing the hydrometer readings on my last few and up to now, getting what I expected.
This batch is an oatmeal stout. Recipe reads Specific gravity between 1.035-1.060.
After the boil when I pitched my yeast I was at 1.050. I used WL labs liquid yeast and did not use a starter (never have).
My readings at day 7 and day 9 are both at 1.024 which to me indicates the fermentation is done and that would give me an ABV of 3.5%. The guy at the brew store told me this batch would be up around 6% (22lbs of grain for 10 gallon batch).
So my question is should I do anything?
I have (2) 5 gallon buckets.
For each bucket, should I boil 1 quart of water and add ~1lbs of Corn or Cane sugar and add another vial of yeast?
Do I let it sit for another few days?
To get to 6%, or close to that, the SG would have to drop to 1.005, and I just don’t think that’s going to happen.

 

[pabloj13]

Well if the yeast did in fact crap out, you certainly don't want to add a bunch more sugar. Going forward, making starters is probably a good practice to get into as is taking hydrometer readings consistently. What temp are the buckets at? Maybe gently swirl and warm a few degrees?

 

[Copperpots_Brewing]

Definitely either start making starters, or go to a dry yeast. I've used US-05 several times, and that yeast can plow through just about anything! If you insist on using liquid yeast, make a starter or pitch 2 vials. Do you know what the estimated OG or FG was supposed to be? It could be an efficiency issue, but it seems more like a yeast issue. They are probably overwhelmed with the amount of sugars and just quit.

 

[kh54s10]

Did you pitch one pack/vial of liquid yeast in a 10 gallon batch?

If so I would think that the yeast may need a month or more to finish the beer.

1 pack/vial is generally considered minimal for a 5 gallon batch.

If you are stalled at 1.024, I would raise temperature a little, if it is now below 70 degrees and swirl the beer some to rouse the yeast.

If this does not make the fermentation finish I would pitch some more US-05 yeast. I would not add any sugars or anything else.

The OG between 1.035 and 1.060 it extremely vague. Where did this recipe come from?

To get to 1.005 is unlikely with almost any brew.

If you post the grainbill someone could calculate what the expectations should have been.

 

[Calder]

22 lbs in 10 gallons. Your LHBS probably expected you to have an OG of 1.060. With 75% attenuation -you would end up at 1.015 and be at 6% abv. I think that is a reasonable assumption.

If you only got 1.050, then your mash efficiency was pretty low. What mash temp did you use? A high mash temp will result in a high FG.

1 vial of yeast for 10 gallons is way too little. Having too little yeast can stress the yeast, and cause it to stall before it finishes. That's another possibility.

First, check temp. If it is too low for the yeast it will stall out.

 

[jfwayBrews]

Thanks for the feedback from all.
I’ll try to answer all with this. First, this was my grain list (in lbs)
Amount Name
15.25 Pale malt (2-row)
1.75 Roasted Barley
3.3 Flaked Oats
0.67 Chocolate Malt
1 Dark Crystal
Mash was 165 deg starting temp. At the end of the hour, I measure the mash temp and am around 150-155 deg. Sparge with 165 deg. Takes about 45 min to fully empty.
Boil 60 minutes in keg/pot. End up with ~10 gallons.
Bring the temp down to ~70-75 deg. Measure SG and got 1.050.
Transfer to (2) 6.5 gallon buckets.
Pitch 1 vial of WL Labs yeast per bucket.
Move buckets to my boiler room which is a steady 70 deg.

Recipe came from the brew shop and the guy recommended I use liquid yeast for this batch. He always asks me what I prefer (Dry/liquid) and I say you tell me. My last batch was Belgium and this Stout he recommended the Liquid.
As for the OG, the recipe printout says OG between 1.035 and 1.060, I agree, kind of vague.

I can’t check my temp now, because my friend is too cheap to buy his own thermometer and took mine, but the temp of the room is 66 deg. Surprised, because the buckets are about 4 feet from the boiler and this has to be the warmest room in the house. I guess I can add a space heater next to them to make sure I get the temp up around 70-75 deg.

So for now, sounds like maybe I should buy 2 packets of US-05 yeast and add 1 to each bucket. See if that will restart.
In the future, should I increase my Mash Temp (start 175) or keep that same temp, but mash for 90 minutes, instead of 60 min?
I guess, what’s the optimum starting Mash temp and mash time?