How to Build a
Conical Fermentor Cheap

By Scott Northuis

**1.
****Decide
on size of vessel needed and size components.**

For
my set up, I wanted a 15-gallon model.
I needed to figure the size of the two components, the cone and the
cylinder, to get my desired volume. I
tried to make the unit look symmetrical in that the height of the cylinder
equals the height of the cone. The
formulas needed to figure the volume and heights of the conical is as follows:

·
Volume of
Cylinder = Pi x radius squared x height

·
Volume of
Cone = 1/3 x Pi x radius squared x height

·
Height of
Cone = Square Root [Diameter squared (Diameter/2) squared]

·
Circumference
of a Circle = 2 x Pi x radius

·
1 cubic foot
= 1728 cubic inches

·
1 cubic foot
holds 7.38 gallons of water

To
start, I guessed at a diameter of 16 inches.
This gave a height of cone around 13.86 and a volume of 3.97
gallons. I then sized a cylinder
section with a 16 diameter to get around 11 gallons. This worked out to be a height of about 13. Since my heights were fairly close, I
decided to run with this.

**2.****Figure sheet material needed. (also size of ball valves and
fittings)**

Now
I was ready to figure out the size of pieces that I needed to build the
fermentor. The cylinder section is easy
to figure out. I know the height from
above, so now I need to figure the circumference of a 16 diameter circle. The Circumference was approximately
50.27. So I needed a sheet of copper
13 x 50.27 for the cylinder.

For
the cone, I only need to know the diameter to figure the sheet size. To make a cone shape, I need to draw a
semi-circle with a radius equal to the diameter of the cone, 16. In terms of a flat sheet of copper, I will
need a sheet 32 long x 16 to make the cone.
For the top I needed a 16 diameter circle plus another circle for the
cover. So the top needs a 16 x 16
piece of copper. Ill assume that my
cover will be slightly smaller than the top, so Ill make that about 13 in
diameter, which gives a 13 x 13 sheet of copper.

Totals:
13 x 50.27 sheet, 16 x 32 sheet, 16x16 sheet, and a 13 x 13 sheet. Luckily my local scrap guy had some sheets
lying around that fit the bill without too much waste. I used approximately a 1/32 thickness
sheet. I do not know the gauge, but
this is fairly thin stuff. It was easy
to work with and seems to be pretty strong when brazed. If you have access to better tools for
cutting, then try going a little heavier gauge.

The
fittings I used for the bottom drain and side port was a 7/8 coupling and a
1/2 coupling respectively. This is
because I had a 7/8 (or Ύ) ball valve and a ½ ball valve lying around.

**3.
****Sketch
and cut shapes (grind parts)**

Now it is time to cut out my shapes. For the top, I just drew a 16 diameter
circle and cut it out. I also cut a 14
diameter circle for a cover (to fit over the top after a hole has been cut in
it). The cylinder section is easy, just
sketch a 13x50.27 rectangle and cut it with tin snips. Try to be as accurate as possible so that
fitting the parts together will go smoothly.
Take a compass and sketch the 16 diameter and 13 diameter circles and
cut with tin snips. Now the hard part,
rig up a string or straight edge so that you can sketch a 32 diameter
half-circle on the 16x32 piece of copper.
Make sure you take your time and get this accurate. Also sketch a small 7/8 radius half circle
with the same center mark as the large half circle. This is the hole for you bottom port. Cut with tin snips and grind/file all edges smooth on all
pieces.

A picture of the cone sketch is shown below.

**4.
****Form
parts and braze**

Okay,
now its time to form the cone and cylinder sections, then braze them
together. The cylinder section is
fairly easy. Just roll it until the
edge meet. I rolled it so that it was
slightly smaller than the actual diameter at first, so I could hold the
shape. Once the shape is formed, I took
a green scotchbrite pad and cleaned the edges.
I then used vice grips and clamped the meeting edges together. I did not overlap the edges. Once clamped, I fluxed the joining parts and
then spot brazed a few spots with a propane torch and standard household solder
to hold it together. Take your time,
because if you get it too hot, it will buckle.
When I felt comfortable that it would hold shape, I finished brazing the
entire outside meeting edge (you can do the inside, but it was easier to work
on the outside). You should only have
to do one side because the solder should seep through. Check your brazing to make sure it settled
smooth. If it doesnt, you will need to
grind and polish later or touch it up with the torch.

For
the cone section, I took a piece of 7/8 copper tubing to help bend the bottom
tightly. The top (or larger portion) of
the cone will follow. Try to get the
bottom as tight as possible because this will help hold its shape. Take your time on this, its not a race.
After I formed the cone, I cleaned the edges with a scotchbrite pad and clamped
the edges together (do not overlap). I
then spot brazed a few spots to hold it together. It might help to have a friend hold the cone and push towards the
middle of the cone so you can get the seam to stay butted. Once it was held together, I finished
brazing the outside of the cone. Remember
to take your time so that you dont have to grind the solder later. The last bit of brazing involves the 16
circle cut for the top. I set this
inside the cylinder, approximately 1/8 down from the top all the way
around. This gives plenty of room to
solder it in place. Once I got it to
fit, I soldered all the way around.

**5.
****Build
cover**

Once everything is soldered, I cut out a 12 diameter hole in the cover and
ground the edges smooth. The picture
below shows what it looked like at this point.

Now what I did from here can be changed or modified, but this is what I did on
this prototype:

I brazed two pieces of ½ copper to the sides of the fermentor. I then put together a bracket that is brazed to the top of the 14 lid. I drilled a hole in each piece of ½ copper so that I can put a cotter pin through it and the bracket to hold it down on the fermentor. I also added a ring of food grade silicone under the lid to seal it to the fermentor (let it dry before attaching it to the fermentor!)

**6.
****Fermentor
Stand**

I built the fermentor stand out of 1x1 box and 1 x 3/16 flat stock. I took the flat stock and formed it into a 15 diameter circle and welded it end to end. I then drew up a template on cad to build it with 3 legs at a 120 degree angle from each other, with a base piece to hold it together. I made the legs about 30 tall. I would recommend checking the size of your kegs first, before cutting the legs. Here is a drawing with some dimensions:

**7.
****Ferment
away**

Thats really all there is to it. If you dont want to build one for yourself, send me an email and we might be able to work something out.

Email Address: snorthuis at hotmail dot com