I got hit by the (ridiculously) low attenuation bug using MJ Newcastle Dark Ale yeast. The same bug that bit beersk a few posts back. I brewed a 1.038 mild that finished at 1.016, and that was using 7 oz invert sugar and a small percentage of dark malts. Calculation: ~57% attenuation
The beer itself tastes fine if not a little thin. It does not taste under attenuated or sweet; in fact it tastes very NOT sweet, surprisingly. The yeast flocculates very well - too well. Good brewing practices were followed throughout: aerated with O2, rehydrated yeast, lag time was short - under 12 hours, fermentation chamber at 64F allowed to rise to 68F, brought to 71F room temp when temp dropped to 67F and allowed to remain at 70s for 7 more days, crash cooled.
I had mashed high at 156F since I was looking to have some body to the beer and didn't want it to finish sub-10. Turns out, MJNDA can't eat sugar with any complexity to it whatsoever. BTW, I've mashes at 156F a few times before without this kind of reaction from the yeast. I suspect a 150F mash would have ended maybe 4 points lower.
Moral of the story: When using this yeast, set BeerSmith yeast properties to 64-70 attenuation, mash very low, consider a sugar addition, be prepared for your beer to finish a bit higher than expected.
Aside from the attenuation issue (which is hard for me to look past), the yeast itself worked very quickly and the beer tastes very nice. There is a fair amount of non-sweet maltiness remaining in the beer especially when you consider it's a full 5 gallon batch with 6 lbs of grain
. Since I've only had a sample it's hard to really tell the yeast character, but I do feel like I sense some dark fruit characteristics but they are subtle and work with the beer flavors. As a comparison, Burton Union gives pronounced yeast character to it's beers. The final ABV in right around 2.9% so you can even let your kids try without feeling terrible