Building a Boot Dryer

Winter is coming and I need another boot dryer. I have one with heat but in use I've never needed to use it to dry my boots in a warm room. So I decided to pull some bits out of the junk draw and make a boot dryer using a PC case fan and a wall adapter. It worked as you can see my prototype above. I'm going to lead you through each step to build this dryer.

This design is reliant on having a box to disperse the airflow from the fan. In my prototype I used the following materials to build it:

• one 12" x 12" x 3/4" plywood
• one 12" x 12" x 1/4" plywood
• two 3.5" x 12" x 1" pine boards
• two 3.5" x 10.5" x 1" pine boards
• four 2" x 12" Sch40 PVC pipes
• Twenty Four 1 5/8" x 8 screws

You will also need the following tools:

• Drill
• Saw (I used a chop saw and a table saw)
• 2" hole saw
• 2 3/8" Hole saw
• 3/32" drill bit
• 3/8" drill bit
• Soldering iron
• Tape measure
• Square
• JIgsaw
• Flat screw driver
• Phillips screw driver

You will need some electrical components as well.

• 120mm fan (static pressure)
• 12 vdc wall adapter
• 5.5-2.1mm barrel jack
• Electrical tape

Let's get our wood cut to size.

We need to make a square box measuring 12" x 12". To do so we need to rip our boards down to a true 3.5" board. I started with a 8" board so my real measurement was 7.5". If you get a 4" pine board you are already there.

Once you have your board ripped we need to do some cross cutting. I used a chop saw but a simple miter box and hand saw would work. We just need the sides to be square. Cut two pieces 12" long and two pieces 10.5" long. The reason for these shorter sides is our boards are 3/4" thick. We need to add each side together and subtract it from 12" to make sure we fit inside our 12" x 12" footprint.

Boards can crack unexpectedly so let's predrill to reduce that chance. In my example I used 1 5/8" x 8 screws where 8 is the wire gauge of the screw. I used a 3/32 drill bit to predrill my 3.5" x 12" boards. To make sure we get them in the right place mark out a line 3/4" from the edge of the board. After that make a mark halfway between the line and the edge, this should be at 3/8" make sure you are around 3/4" from the top and bottom sides and drill them through. Do this to both 3.5" x 12" pieces.

Once drilled screw in the screws part way. This will help in the next step.

Time to do our first bit of assembly. Take a 3.5" x 10.5" board and line it up so the screws in a 3.5" x 12" board go into the endgrain as shown in the pictures. Line them up so there is a smooth corner and screw them in.

Do the same on the other side of the board so you get a U shape.

Finally close the box by adding the other 3.5" x 12" board. You might need to forcefully align the last corner depending on how accurately you cut the sides.

Now we need to mark out the top to do this we will need a tape measure, a square, and the case fan you will use.

Starting in each corner measure over 2.5" from each corner. This should give use two lines that cross which will be where we drill our outlet holes.

Measure 6" from each side and draw a line to find the middle. Extend these out so they go all the way across the box. Take your case fan and align each corner with one of these lines. Once aligned the fan will be directly over the center. Take a pencil and trace the inside of the fan housing between the fan blades. This will give us a line to cut out later with the jigsaw.

It's time to drill some holes. First step is to mount a waste board to your drilling surface. I used two pieces of 3/4" ply leftover from another project. The key point is to support the board you're cutting so if cuts clean on the backside and to prevent the pilot drill bit in the center of the saw from drilling into your drill press table or worktable.

As you can see I used a drill press since it has a depth control on it. Set the depth control so we have about 1/4" of an inch of material left in the plywood. This will form a shelf to hold the outlet pipes. On my drill press this control is on the quill extension. If you are drilling by hand take a sharpie or some tape and mark your hole saw so the mark will be even to the top surface of the board as a depth guide.

Make sure your drill in running around 350 rpm. Faster can be hard to control in a drill press. Drill the 4 corners.

Now change the 2 3/8" holesaw out and put in the 2" hole saw. Line up the pilot bit with the pilot bit made from the other hole saw and drill all the way through. After each hole you will need to remove the drilled out core from the holesaw using a screwdriver.

Drill a hole all the way through the center circle as well.

In each outlet hole you should have a small ring of material left, break it out with a screwdriver. This will leave a flat surface in which you can set a peice of 2" pvc pipe. At the end of this step your top should look like the first photo.

It's time to cur out the center inlet hole. To this use a jigsaw. Follow a curved path starting in the hole you drilled and spiral out until you are cutting just on or just inside the line. When you finish it should drop out.

Just like the sides we want to pre-drill the top with a 3/32" drill bit. This will help prevent the top from cracking and will make it easier to assemble. Just the like sides make your marks for the thickness of the board (3/4") and drill your marks halfway between the edge and the mark or at 3/8". Align your fan again and using a drill mark the spot where the screws will go that will secure the fan. Remove the fan then drill the holes.

It is important to know how your top will sit on the frame we made earlier as you don't want a screw from the top hitting a screw from the frame. Look at the first picture in this step to see the orientation of the screws in relation to the screws in the frame. You should secure the top with 8 screws. When screwing it down try to make sure each side is flush, it will make the next step easier.

Attach the bottom in the same manner. Since the bottom is 1/4" ply you won't get much benefit from pre-drilling. Just align it and go for it.

With everything secured it's time to sand it down. In my case I have access to a belt sander so I used that and a course belt to trim up a error. However a simple orbital sand will work, just a bit slower. Start with coarse grit paper and move up (80 grit to 120 grit to 180 grit to 220 grit) until you get a finish you're satisfied with.

Once you're ready make a quick sanding block and round off all the edges by holding it at a 45 degree angle and sanding down the edges. No one wants to cut a foot by kicking a sharp box and by rounding the edges you will reduce the likelihood of it denting or splintering on impact with something.

It's time to wire this up. First step is to cut a small notch in the side of the frame on the bottom. This will allow us to get power into our dryer. Take our 2.1mm jack and tie a small knot in the wire this will prevent it from being pulled out of the dryer.

To do the next step we need to identify the ground and positive wires on the fan. If we look at the fan header we will see three wires for a case fan (CPU fans have 4 wires). One of these wires is a speed control which in our case is not needed as we want full speed. The middle wire will be our positive wire. One of the wires on the side will be the ground. If can see a small 1 that wire will be the ground. If you hook it up wrong it just won't work. Sometimes the ground will be black however sometimes all the wires are black so we need to guess and check.

Now we need to cut off the connector and strip the wire back. Do this with a pair of wire strippers. Expose about a 1/2" of wire. Next we need to do the same to the 2.1mm jack wire.

Once they are stripped we will twist them together like shown in the photo. This will make a strong mechanical joint. After that we solder them to make a strong electrical connection. Lastly we wrap each wire individually with electrical tape to prevent shorting.

Once we have everything connected and tested we need to install the fan and fan guard.

To do this we can use our same 8 gauge screws and screw the fan to the top from the outside. I made a laser cut fan grill but you can use any commercial grill. I suggest one with a mesh pattern to keep the boot laces out of the fan.

I also recommend using a screwdriver to do this as the fan housing is plastic and will strip much easier than the plywood.

Once the fan is installed place the jack into the notch and re-attach the bottom. Test it out my plugging in the wall wart and see what kind of airflow you have.

I've found 11" or 12" long 2" pvc pipe works very well for this project. Let's cut 4 pieces for the outlets.

Once you have them ready it's time to drill a few holes in the pipe. To do this I recommend making a saddle that will hold the pipe as you drill it. Use the 3/8" drillbit and make a series of holes. These will allow the airflow to expand inside your shoe. I recommend not drilling holes and further down than you need too (around 2 - 3 inches from the top) if you are going to use this dryer with shoes as well as boots. Once you have them done lets install them. It should be a close fit.

Now is the time to apply a finish of your choice. You want something that is water resistant as it could get wet. I'm just using a polyurethane over a coat of SealCoat dewaxed shellac. The shellac dries much faster than the poly and gives me a quick base to build poly on (it saves me 8 hours of drying).

When the finish is dry it's time to finish it up. You could simply install your tubes press fit or epoxy them in for a more permanent solution. However you need to remember your really epoxying the PVC pipe to your finish so hopefully you took your time and made it strong. This will just prevent the tubes from lifting out of their sockets.

I hope this instructable was clear and provided enough detail for you to make a boot dryer of your own in your garage or workshop. Each step was written out in detail so my class could follow it.