I've seen some friends who have converted a barrel to stand vertically with the top off and act as a primary fermentation vessel. Most recognized would be Casey Brewing and Ale Apothecary. My goal here is to take that concept and use it for the secondary fruiting process.
Here is the parts list for the bottom drain:
1.5" Male NPT to 1.5" TC
1.5" TC 90° Elbow
Place your barrel on end. The head facing up at this time will be the head that will be the bottom in the end. Pick the head that is flat and uniform.
Place your parts on the barrel head and dry fit them to find the location of your drain. Mark it with a pen. Make sure you find a wide stave so your hole is entirely in one stave and not in-between two.
Drill the hole with a 1 3/4" hole saw. This is your drain. I did consider putting the drain in the center of the head and adding a 12" TC extension. I decided against it because it's an extra seal and gasket that can leak. In water testing this, the edge location is best for getting that last 1% to drain out by simply tipping the barrel.
Insert your tap. This is the hardest part. 1 3/4" hole is probably 1/16" too small, so that piece goes in hard. I found by cutting a 45° on the top 1/8" edge of the hole, that the threads were able to rest partially inside. No matter what, it's a beast. But that's good, it won't leak!
Next, flip the barrel over. Your drain is at the bottom now and you need to remove the top head. You may want to mark the head's orientation by putting an arrow on it where the bung lines up. With the top 3 hoops removed, you'll be able to pull the head out. Drive the hoops back into place.
This is what the inside of my barrel looked like. Innerstaves. I removed all the innerstaves and the wires holding them in place. Spray out the inside of the barrel and scrub/scrap away all the bulk organic material from previous fermentations.
Tip the barrel up and install the elbow and shut off valve. Continue cleaning the inside of the barrel and draining. I'd recommend filling the barrel completely with water to make sure your staves are in line and hoops are tight.
And voila! There it is. I took one of the innerstaves and made a little handle for the lid. On the bottom side of the lid I screwed another innerstave across all the head staves to keep them in place and one solid piece.
This is what others have done for primary fermentation vessels. For me to use it as a secondary fruiting vessel, I want to go one more step.
I worked with my welder to fabricate this last piece. It's a fruit sieve made out of stainless steel screen material. This piece will rest at the bottom of the barrel during fruiting. When I go to drain the barrel, this will keep the fruit from clogging the drain line. It's 20" in diameter, which fits perfectly inside a wine barrel. The side is made out of the same perforated material as the top and is 2" tall.
My plan is to do a small batch of raspberry beer in here first, which is typically a 3 month fruiting process for us. During the initial high fermentation stage that the introduction of raspberries creates, I'll be resting the lid on top of the barrel to prevent bugs/debris from falling in. The large opening will allow me to punch down the fruit periodically. After the initial sugars are consumed and CO2 production tapers off, my plan is to lay a sheet of plastic over the top of the barrel and use an extra hoop to seal the plastic around the side.