Sunday, April 29, 2012

Building a Mountain Banjo: The Pot


      In an earlier post I wrote that the true essence of the banjo is taking what one has, and making music out of it.  That is what the earliest banjo players did with their instruments consisting of a gourd covered in skin, a stick for a neck and some strings.  In time the banjo evolved into the modern banjo, which is probably what most people think of when a banjo is mentioned.  However, the were many intermediate styles and designs that developed after the gourd banjo and before the modern banjo.  One that has always interested me is the "mountain banjo."  It is a unique banjo design that was intended to be easily constructed with limited tools.  Unlike some other designs, it does not require laminating ply to form a circular pot nor does it utilize a gourd or grain measure for the pot.  Instead, circular shops are cut our of solid wood stock.  It is probably not the strongest method, but it works.  I have wanted to build a banjo for some time and this type of banjo seems like one of the easiest to build.  In addition, I also like the old fashioned look and sound of this banjo style.  Today I had a little time off, so I just decided to start building one, but I have very limited experience building instruments.  I once built a cigar box guitar, but that is it.  I have documented what I have done below.  As I build more I'll be sure to post updates.  Anyway before I get any farther, I figured I should add a video so you can hear a "mountain banjo."


      So there it is, the "mountain banjo."  Now you can tell why I want to make one.  In this post, and others to follow, I will document my construction so you can learn from my ideas and especially my mistakes.  I have to admit, I'm not doing this on my own.  Randy Cordle's free plans and construction advice posted on Bluestem Strings are what I'm modeling my banjo after.  The following youtube video was also inspirational.  I hope to document my work in a little more detail than the video for those who are not familiar with woodworking (although I am no expert).   I have also heard that the Foxfire Book III hard plans for a banjo like this, but I don't know for sure.  Sadly, I don't own that book.


      Today, I wanted to gather some materials and at least get the pot started.  I wanted to use scrap and salvaged materials in order to keep the cost low and also because that is how these banjos were often made.  People used what they had.  I didn't have any 1/2" solid stock wood but I did find some scrap 7/16" birch ply in my garage.  It is not traditional in the sense that it is ply, but it is very traditional in the sense that I'm using what I have on hand.  Of course, I had to make some minor adjustments to account for the missing 1/16" but that wasn't too hard.  I'll also have to figure out how to seal the plywood on the side, but that is a challenge for another day.
      The first thing I noticed when looking at the plans was how many circular cuts must be made.  Instead of using a jigsaw, scroll saw or coping saw (which would all work) I decided to use a router so I could get a nice clean, almost perfect circular cut. To help me, I decided to create a simple jig.  It looked a little like this.
My jig is shown here.  The router is bolted to the top board.  The nail holds the jig to the board below but allows the jig and router to rotate above the board.  By rotating the router, I was able to cut nearly perfect circles.

This photo shows the underside of my jig.  I simply countersunk bolts into the jig and screwed them directly into the router.  To change the radius of my circular cuts I simply drilled multiple nail holes in the jig and moved the nail to the correct hole.  I measured the radius from the edge of the router bit towards the center of the jig.  The edge of the bit that you measure from changes depending on the cut you are making.  For cutting the outside of the circular hoops, measure from the edge of the bit closest to the nail hole.  For cutting the inside of the hoops measure from edge of the router bit that is farthest from the nail hole.

      The jig was nice because it allowed me to make nearly perfect cuts.  I can also save the jig to quickly create parts for a second banjo if I like how this one turns out.  The cuts come out nicer if you make multiple, shallow passes with the router instead of one or two really deep passes.  The exact depth will depend on your specific router and the wood you choose.  Just start shallow and experiment around a little.  It is also important to cut the outside circles first.  This way, when you need to make the inside cut, you can still attach the jig to the center of the circle.  Of course, if you don't have a router or you don't want to make a jig, you could always use a compass (or even a pencil and string) to draw a circle and then just cut it out with a jigsaw or coping saw.
      When you cut the top and bottom pieces of the pot, you can use the router and jig to cut the curved part of the outline, and a saw to cut the straight part.  Sometimes I offset my cuts by 1/16" or 1/32" and then sand the wood down to the final size.  It reduces the risk of accidentally cutting into your piece.  Of course, you could accidentally  sand too far into your piece too, but sanding is easier to control than cutting.

When you cut out the top and bottom pieces of the pot, do not cut a complete circle.  You need to leave a little material for the rectangular shaped part that the neck screws into (see plans).  I'll cut the inner part of the circle out later.
      The plans call for the middle part of the banjo pot to be 1" thick.  I could only find 3/4" thick scrap pine so I had to do a little extra work.  I decided to just cut 2 identical circles and glue them together which resulted in a 1 1/2" thick circle.  After the glue dries, I'll run it through a planer until it is 1" thick.  I am a little worried that the pine won't be strong enough, but I don't want to buy wood for this project so I used it anyway.  When I glued the two circles together, I arranged them so the grains ran perpendicular to each other, just like the alternating plys in plywood.  I think this will make it stronger, but I'm not sure.

Here are my two circles before I glued them together.
Here they are again, now arranged as one unit.  The router really helped to make them uniform, but I'll sand them down to an even closer match later.
Here they are again, glued, clamped and waiting to dry.  Note the wood scraps that I placed between the clamps and the circles.  They prevent the clamps from leaving impressions in the circles.
      That is where I left off today.  It got dark so I cleaned up.  So far I have invested $0 in materials (okay...I did technically pay for the material at one point but it is leftover from other projects so I'm not counting it as a cost) and about 5 hours in time.  I don't think I'm doing a bad job either.  Next time I will sand the parts down, plane the center circle down to 1" and maybe start shaping the neck.  I have some cherry from a friend that I might use fore the neck.  Over the next few weeks I will also be looking for old violin pegs (I might try to make some) and a rabbit, groundhog, cat or goat skin (for the head).  I'll post more when I get the chance to work on it again.

The three pieces that will later form the pot.

5 comments:

  1. I do own the Foxfire book with the banjo plans. I built one from the book years ago, and also used plywood, the reasoning behind this was that it was what was handy. The plans called for an animal skin for the head. Instead of an animal skin, I used some old aluminum flashing I had laying around. It is an interesting sound, but more metallic. Thanks you for the encouragement. I think I may have to build another one now!

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    1. Dan,

      I'm glad I was encouraging! Part of my goal with this blog is to help people realize that one can build, brew, play or learn almost anything as long as you are not afraid to give it a try. Aluminum flashing as a head material sounds interesting. Do you have any videos or sound clips?

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  2. how did you cut the center circle with that jig? Did you keep it nailed to the center?

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    1. I'm assuming you are referring to the fact that once the circle is cut, the wooden pieces will be detached and free and therefore the router might slip and mess up the cut. There are two ways I thought of to get around this. One is draw out the circles ahead of time and picture how the board will be cut up into individual pieces. Next, put at least two screws into each section that will later be cut out to form an individual piece, and screw them into a scrap piece of plywood underneath. This way, even when the cuts are made, the pieces and the jig (see photo) are still attached to the scrap wood so they won't slide around. An alternative is to use the jig to cut almost all the way through the board and then finish the cut by hand with a coping saw. Of course, this would require some sanding and might not look as "perfect" as using the router.

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    2. I just realized that I may not have interpreted your question correctly. The key to getting the center cut is to make sure to do the outside cut first. Then you discard the scrap and cut out the inside of the circle using the instructions in my reply above. I hope this helps. If you have any questions, please comment. Also, I have been trying to get the rest of the building posts up, but work and school keeps me pretty busy. The banjo is done, I just have to get some good photos of how to assemble it.

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