Stir plate for primary?

Ignoring the physics of perching your 6.5 gal primary on top of a stir plate, would it aid our yeasty friends to plunk a stir bar in the primary and keep the mix moving while it ferments?

Discuss.

Oxygenation would be a problem. The main reason to use a stir plate is to encourage yeast multiplication (aided by the additional oxygen and prevention of flocculation). When you pitch sufficient quantities of yeast, and provide initial oxygen, no stirring is necessary, the yeast are there to eat more than multiply.

Totally agreed. A stirbar may be beneficial in the very early stages of fermentation, but oxygenation is actually a problem later on. As long as you are aerating the batch prior to fermentation, you should have absolutely no need to stir it later on. Would be pretty cool to try and make one of those though. I would imagine that a stir bar for 5-6 gallons would have to be quite big and the stirplate would also be massive.

I've actually wondered about that myself. Instead of aerating the wort with a pump or pure oxygen, just set the fermenter on a stir plate for a couple of hours.

Oxygenation is only a problem after the yeast have completed their adaptive phase, ~4 hours. Assuming the stir bar has enough surface area and torque to cause a small whirlpool, it should work.

And interesting experiment would be to:

1. Brew a medium gravity batch of hopped wort.
2. Split into two large flasks and pitch equal amounts of yeast.
3. Aerate one flask with an aquarium pump.
4. Place the other flask on the stir plate for ~2 hours.
5. Wait 5 days.
6. Measure final gravities and conduct a taste test.
7. Repeat, this time with a high gravity wort.

I think you'd be fine to do this anytime before high krausen. I know many of the stirplates on the market can mix this quantity of fluid. I don't see how the results would be any different from using a wine degasser (except sanitizing the drill and rod are always a bit annoying).