The Cat Can Dobro is a type of slide guitar. I made my plans for this instrument for the Boy Scouts to help them complete the Music Merit Badge.
One of the requirements of the badge can be fulfilled by making a musical instrument. While there are some simpler instruments that can be made, I find that the kids really like making this one. Then they have an interesting instrument that can be played and that they can be proud of. At a merit badge fair I had 9 kids signed up for the morning class, and none for the afternoon. At lunch, many saw what we were doing with the dobro, and my afternoon class had 23 kids! Help! Now I bring two helpers with me which makes a big difference.
The original Dobro looks like a guitar with a big metal disk (resonator) in the center of the body of the instrument. This amplifies the sound, and gives it a unique tone. The strings are raised above the fret board, and the instrument is played horizontally with finger picks or fingernails for the right hand, and a steel bar to slide with the left hand. The Cat Can Dobro uses (you guessed it) a cat food can for the resonator. It sounds surprisingly like a real Dobro. You can play it with a steel bar like a Dobro, or use a narrow glass bottle neck, like a beer or hot sauce bottle. (If you put an electric pickup on the strings, you won’t believe the cool sound it has.) The materials for this instrument cost less than a dollar, not including strings.
For tuning pegs it uses bolts (2 ¼” long by ¼” diameter, fine thread) that have a hole drilled for the string to attach. At the other end of the strings is a 1 ½” nail, which is pounded in at an angle, and then the head is cut off and filed smooth. The nut and bridge are made of acrylic (like Plexiglas or Lucite), sanded smooth on the edges and then notches are filed to hold the string spacing. They are held in place by the string pressure on them. The scale is a little shorter than a guitar, so that it can use used guitar strings: you just cut off the messed up tuning peg end and there will be plenty of string left to fit nicely. If you have a lot of instruments to make, you might convince your local music store to donate some strings. The gauge is not critical.
I made my scale from a steel guitar, where the second fret had the correct distance to the bridge for the nut of the dobro. I copied the distances, and my pdf version should print out correctly. Make sure when you print it that it is set for 100%. Some kids drew the scale directly on their dobro, but some also had difficulty with the accuracy of the lines, and didn’t understand the need for a little accuracy. If the frets are too far off, it will be difficult to make decent sounding music. For many kids, a project like this is the first time ever that they will use a hammer and nail, a square, sandpaper, or a wrench.
Of course you can use a tuna fish can, but the name “Tuna Can Dobro” just doesn’t sound as good. Also, they are usually made of steel, and steel cans sound terrible. They just can't give the tone of aluminum. Around me, I have not been able to find any appropriately sized aluminum can with anything but cat food in it. Pop-top cans require larger slots in the body than can-opener tops.
I cut the blanks for the body on a table saw out of 2” x 3” lumber, cutting the taper and the 3 slots. When possible, I assist the kids in drilling the tuning peg holes in the wood body with a drill press. Sometimes I have them drilled ahead of time when I am teaching it away from a drill press. The holes can be drilled by hand, too (not recommended for kids under 12 without close adult supervision to get the angle close enough). I drilled the string holes in the metal tuning bolts with a drill press. The kids sand the body, bridge and nut, pound the nails for the strings, screw in the tuning pegs, glue on the fret board, gently tap the can into place and then string it. When stringing, turn the peg clockwise to tighten the string, with about 2-3 wraps of string on the peg when it is tight. Very thin strings require more wraps to keep them from slipping. Then I teach them to play “Mary Had A Little Lamb” on it. They can be real awkward at first, and after a time you can sometimes see the light go on in their head!
Three times I have had a kid come up to me at a later date, and say he put a pickup on it and plays it in a band on occasion.
Drawing of plans for the Cat Can Dobro
Drawing of the fretboard, to print a guide for the string spacing.