[Will's Swill]

On a Brewstrong session, Jamil made note of the fact that fermenting 5 gal of beer in a 15 gal conical will tend to produce more esters than it would had you been fermenting 1o gallons of beer due to an increased amount of pressure on the yeast. Palmer agreed as well. Although, I'm uncertain as to how they confirmed this information.

I have a 14.5 gal conical fermenter that I've used to ferment 5 gal of beer and I have noticed and increase in esters from an aroma and flavor standpoint but this was based from batch to batch and not a side by side comparison. I really need to do duplicate back to back batches (5 and 10 gal) then do a blind tasting.

Not following you (no surprise, I haven't had a homebrew this evening).  If increased pressure causes more esters, then 10 gallons of beer should have more esters than 5, you seem to be saying your experience is the opposite. 

How did they account for changes caused by the increased headspace?  There will be a lot more O2 left that can diffuse into the wort with the fermenter 1/3 full than when it is 2/3 full, especially if they are using straight O2.  It's just not as straightforward as doing two batches like that.

Hey!  What happened to the magical CO2 blanket?   

[tschmidlin]

How did they account for changes caused by the increased headspace?  There will be a lot more O2 left that can diffuse into the wort with the fermenter 1/3 full than when it is 2/3 full, especially if they are using straight O2.  It's just not as straightforward as doing two batches like that.

Hey!  What happened to the magical CO2 blanket?   

The O2 in solution will be taken up really quickly by the yeast, allowing the O2 in the headspace to diffuse into the wort/beer before CO2 saturates the solution.

[Will's Swill]

You got an answer for everything.   

[gmac]

You got an answer for everything.   

He hasn't told me how big to make my fermenter yet. 

[bluesman]

On a Brewstrong session, Jamil made note of the fact that fermenting 5 gal of beer in a 15 gal conical will tend to produce more esters than it would had you been fermenting 1o gallons of beer due to an increased amount of pressure on the yeast. Palmer agreed as well. Although, I'm uncertain as to how they confirmed this information.

I have a 14.5 gal conical fermenter that I've used to ferment 5 gal of beer and I have noticed and increase in esters from an aroma and flavor standpoint but this was based from batch to batch and not a side by side comparison. I really need to do duplicate back to back batches (5 and 10 gal) then do a blind tasting.

Not following you (no surprise, I haven't had a homebrew this evening).  If increased pressure causes more esters, then 10 gallons of beer should have more esters than 5, you seem to be saying your experience is the opposite. 

From my experience, when using my 14.6 gal Blichmann conical fermenter to ferment 5 gal vs. 10 gal of beer, there is an increased level of ester production due to a lesser amount of pressure applied to the yeast. Conversely, when fermenting 10 gal there is an increased level of pressure on the yeast, therefore suppressing (slowing) the ester production.

[tschmidlin]

You got an answer for everything.   

He hasn't told me how big to make my fermenter yet. 

I think you should make it as big as you like.

You've got the 60 degree angle for the cone, which I think is a good idea.  You've got to figure out the height and width constraints and use that as your guide.  But if you're looking for a number, I wouldn't go less than 18" wide just for the stability.  I would probably do 20".

If you have a cone that is 18" at the top, it will hold 5.7 gallons.  The cylinder on top, 18" across and 12" high would hold another 13.2 gallons.  So if my math is right you've got 18.9 gallons, which is in your 15-20 gallon range.  I think there's enough space on a 4'x8' sheet to lay that out, but I could be wrong.  Figuring out the geometry of a cone laid flat is more geometry than I want to do right now.

[tschmidlin]

Not following you (no surprise, I haven't had a homebrew this evening).  If increased pressure causes more esters, then 10 gallons of beer should have more esters than 5, you seem to be saying your experience is the opposite. 

The confusion is in the wording.  When Ron said this:

fermenting 5 gal of beer in a 15 gal conical will tend to produce more esters than it would had you been fermenting 1o gallons of beer due to an increased amount of pressure on the yeast.

he meant that the increased pressure on the yeast in the 10 gallon fermenter reduces the esters.  It took me a second to get what he meant too.

I'm still skeptical that it is the pressure and not the O2.

[Will's Swill]

Ah, right.  I read it wrong.  I'm tracking now.

[bluesman]

Ah, right.  I read it wrong.  I'm tracking now.

Sorry for the confusion...I was only on my second cup of coffee that afternoon. 

[gmac]

I think you should make it as big as you like.

You've got the 60 degree angle for the cone, which I think is a good idea.  You've got to figure out the height and width constraints and use that as your guide.  But if you're looking for a number, I wouldn't go less than 18" wide just for the stability.  I would probably do 20".

If you have a cone that is 18" at the top, it will hold 5.7 gallons.  The cylinder on top, 18" across and 12" high would hold another 13.2 gallons.  So if my math is right you've got 18.9 gallons, which is in your 15-20 gallon range.  I think there's enough space on a 4'x8' sheet to lay that out, but I could be wrong.  Figuring out the geometry of a cone laid flat is more geometry than I want to do right now.

You make a good point about it being at least 18" wide for stability.  I was going 14.5 just because that was basically the diameter from a 4 foot circle.  But, we can probably lay it out another way and minimize the waste.  I've also decided to keep my old fridge and use it as a fermentation chamber (gotta buy a temp controller).  Just bought a 17.5 cu ft freezer yesterday to hold kegs so the fridge will now be free.  Need to make sure that what I build will fit inside the cabinet of the fridge. 

[tschmidlin]

I think you should make it as big as you like.

You've got the 60 degree angle for the cone, which I think is a good idea.  You've got to figure out the height and width constraints and use that as your guide.  But if you're looking for a number, I wouldn't go less than 18" wide just for the stability.  I would probably do 20".

If you have a cone that is 18" at the top, it will hold 5.7 gallons.  The cylinder on top, 18" across and 12" high would hold another 13.2 gallons.  So if my math is right you've got 18.9 gallons, which is in your 15-20 gallon range.  I think there's enough space on a 4'x8' sheet to lay that out, but I could be wrong.  Figuring out the geometry of a cone laid flat is more geometry than I want to do right now.

You make a good point about it being at least 18" wide for stability.  I was going 14.5 just because that was basically the diameter from a 4 foot circle.  But, we can probably lay it out another way and minimize the waste.  I've also decided to keep my old fridge and use it as a fermentation chamber (gotta buy a temp controller).  Just bought a 17.5 cu ft freezer yesterday to hold kegs so the fridge will now be free.  Need to make sure that what I build will fit inside the cabinet of the fridge. 

That sounds great.  Now that I'm a bit more awake . . . lay the cylinder out long ways along the long edge, and you still have 36" by 96" to play with (plus part of that is still 48" wide).  If the cone is 12" radius at the top, then laid flat the max you need is a 32" circle.  If I've laid it out right in my head, I think you might actually have enough there to make two of them that size, and maybe one lid.

[gmac]

I hate leaving posts without closure so here's what happened.
My friend's machine shop got very busy, very quickly and I now own the worlds flattest fermenter.  Basically, I have a 4X8 sheet of stainless and that's it.  Guess this will have to wait until things slow down.   

[dcbc]

At that batch size, I don't think it makes much of a difference. I have been fermenting in a tall, narrow 15 gallon Cornelius keg for the last couple of years without any noticeable effect on flavor from my smaller batches in carboys and buckets. The issues with hydrostatic pressure don't tend to really impact flavor until the vessels are much larger.