Secondary fermentation question?

Ideally, zero. I'm a proponent of not moving out of primary at all (except for lagers or large beers which need extended aging), but I understand the need to open up a primary for fermentation space. Even so, you want to stay in primary as long as possible. Having said that, it's tough to put a number on your question. Yeast will eat available ferment able sugars. How much is left when you rack will be the determining factor as to how many points you drop. The smaller cell counts won't stop them, it'll just slow them down, unless you manage to shock them somehow.

So, long story short, there's no way to tell. It simply depends on how much is left when you rack.

 

like jokelahoma said, probably zero, but could be a very small drop. there is no rule of thumb except that once you reach FG, it's effectively done until you provide more fermentable, like bottle conditioning.

remember that the yeast cake is yeast that has floculated and stopped fermentation. it's resting, waiting for the next job. if things are going right, the small remaining yeast suspended within the beer are doing very little except consuming the last bit of fermentable, and possibly consuming some odd compounds. getting the beer off of the yeast cake shouldn't have any effect on fermentation if you have already reached your FG.
Cheers.

 

I wouldn't worry about the trub so much - most of it gets in my carboys, and I leave beer in primary for up to 4 weeks without any off flavors. YMMV, but probably not.

 

I would word it a bit more strongly than Longstaff: I wouldn't worry about the trub at all.

I always leave my beer on the trub for weeks (maximum of 4-5 weeks) and I have never experienced off flavors (fusel alcohols, etc.) from this process.

Cheers!

 

just remember, airlocks leak. and yeast sometimes stalls. you really do want to check your gravity before you bottle. sometimes yeast craps out before all of the fermentables have been consumed. if you prime and bottle, that's going to result in a night of painting ceilings.

don't sweat the trub. really, just let it settle in your primary. used to be a concern in older homebrew texts, but it is not an issue for 95% of homebrewers. if you let beer sit for 4 months in a primary, then maybe.

if you are bottling directly from the primary or will transfer, it will help if you tilt the bucket/carboy on a phone book and let it sit for a few hours, overnight, with the spigot on the high side. or, place the racking cane on the high end. then when you siphon or turn the spigot, dump the first 10 ounces or whatever. after that it should be fairly clear beer. you can decant from trub, hops, yeast easily.
Cheers.

 

Airlock bubbles can be a sign of changing pressure as well. Like, for example, if your fermenter is surrounded by air, but then by water, the outside pressure applied on the fermenter will result in airlock activity until it stabilizes. Believe it or not, the simple act of opening and closing the garage door will produce airlock activity on my saison which has been fermenting for nearly three weeks now. All that to say: don't trust your airlock.

Depending on how quickly you transfer to secondary, how much fermentables are left over in the wort, and how much active yeast makes its way to the secondary, you can have anywhere from no additional activity to a reasonable amount of activity (then of course, there's the matter of alcohol tolerance and this, that, and the other). Stirring up the wort in the form of transferring it to the secondary may give your yeast a second wind, albeit a short one.

But as others stated, typically you want a minimal amount of yeast activity at this point 'cause you're going for clarity, and yeast activity is just gonna make that process take a little longer.