Super weak beer!

[Philmac]

I brewed AG Gamma Ray (see recipe) last week. I appear to have made an error in putting in too much water to start with- the OG was lower than it was meant to be. I added 500g of dry malt extract and got it up to 1.040. It is now at 1.020.
This is very weak-would i get more activity if i added more yeast?

I have certainly learnt a valuable lesson about getting your volumes right...

 

[dad_of_jon]

I'd add another bag of dme the recipe has been knocked off a bit anyways. Its still got lower to go but the mash may have given you more unfermentables. It could also be stuck but adding a different yeast that will munch up more sugars will take you further away from the recipe. So if you put another 500g in you can work out then new OG then find the new FG. add those together to the original OG-FG to get you're true abv. IF it is measuring higher than 1.020 (because the DME will have increase the OG) then the yeast has given up the ghost.

 

[Dutto]

Why worry so much?

The recipe gives you a Target of 1.051 so it isn't the end of the world if you miss it.

There's nothing wrong with "brewing light". Out of 11 brews this year, only three of mine were at an OG of 1.050 or above and seven of the remaining eight had an OG of 1.041 or below.

The more you add or subtract from a given recipe the further away you will move from what you wished to achieve ...

... so my advice is to sit back, relax and let the yeast do its stuff.