This is how I made a cookie-tin banjo... learn from my mistakes!
Step 1: Step 1
Find some wood and other junk.
In my case, a dumpster appeared while campus was remodeling a building - goodies ahoy.
Look for some wood that's atleast 1.75" by 20" ... bigger would be better. Hard wood is best... i think my is pine
Step 2: Step 2
Tear that wood up and make it usable.
Cut it to the rough length you need for the neck - I made my neck 19", and I made the head from a second piece (I suggest against this, but it's your call). I also made the portion that attaches the neck to the body separate... again, I suggest making it one piece (mine kind of bows there).
Step 3: Step 3
Cut off anything that doesn't kinda look like a banjo.
A saw helps with this part. Power tools really help here... I didn't have much for power tools.
So, i penciled a vague banjo shape, and sliced off the parts that didn't look banjo-y to me. There was lot's of whittling with my pocket knife to get the final shape. Try using a bandsaw if you can.
Step 4: Step 4 (optional)
Slip with the coping saw, and cut you hand.
I highly advise against this step, but if you want to follow my example, more power to you.
It looked pretty bad until i washed the blood off.
Step 5: Step 5
Cut off anything that doesn't really look like a banjo.
This means more bandsaw/coping saw/pocket knife work.
Step 6: Step 6
Cut off anything that isn't a banjo.
Make the shape comfy - round off the corners, blend the different sections together, etc.
On mine, the Neck was 19" from the Nut (the top part by the tuners) to the cookie-tin, and the 5th string's last fret was 663 mm from the Nut (with the tuner peg a bit above that).
At the nut, mine was about 1 1/2" wide, and at the base, it was about 1 7/8" wide.
1/2" to 3/4" thick is plenty good... do what ever looks good to you.
Step 7: Step 7
Attach/shape the head.
I made the head on mine as a separate piece... don't do this unless you have to. It caused me a lot of problems.
I tried making the head tilt back at a nice 22.5* angle (that's what the miter box had). And then I horrifically messed up at attaching it and split it. I attached the next one at a 90* angle... It's not pretty, but it works - kinda.
Step 8: Step 8
Make a sticky part to go through the cookie-tin.
If you took my earlier advice/had a big enough piece of lumber, this will be just a matter of shaping.
In my case, i put a hole in the end of mine, and put a dowel (actually it was a broom stick... much cheaper) in it and then used a peg to keep it in place. I suggest making yours square-ish and finding a better way to attach it.
I didn't take a picture of this for some reason. Oops.
Step 9: Step 9
Add some hardware.
I made my tuners from 5 thumb bolts. You could use some eye-bolts for this... or be fancy and use actual guitar tuners. Be creative here.
I took the bolts, and drilled a hole through them to attach the strings. Again, your mileage may vary.
Step 10: Step 10
Attach the cookie-tin.
I cut some holes in it, shoved the dowel through, and then ran pegs through to hold it in place.
Be creative here, as well. Just don't let the bottom of the tin rest on the dowel, or you'll deaden the sound - it needs room to wiggle.
Step 11: Step 11
Make a bridge.
This is the part that the string rest on above the cookie-tin. The rule of thumb is: higher, lighter, and thinner the better - it transmits sounds better and louder this way. But keep it with in reason. I've whittled several now, so feel free to play around.
Step 12: Step 12
Add a nut.
If need be, add something to make a definite ending to the strings. Otherwise, you'll get a buzzing sound from the string length changing as it vibrates.
I used half a dowel... I've seen it done with a few nails up top too - just make sure the string bends there and it'll work (this is what I did for the 5th string).
Step 13: Step 13
Add some strings.
Find a spot to tie some strings to... some add a screw for each one... others tie them all to the end and call it good enough.
I've used several things, with different effect.
The first set was the inside of some parachute cord... it sounded good in a thumpy sort of way.
Then I added a guitar string (.013" i think) - it sounded a lot like a steel string banjo.
Also used some random nylon string i found (very bassy), and some upholstery thread (kinda quiet, but nice tone).
Seriously, if you can attach it, it'll probably work. A lot of people use fishing line (30-60 lb) and weedeater string. Give it a try.
Step 14: Step 14
Realize I don't know how to play a banjo.
So, there are two things to remember when playing a banjo:
1) there is no such thing as a wrong note.
2) there is no such thing as a wrong technique
If it makes noise, and you like it - then it's music :p