Feb 10, 2013

Banjo Boys, Chapter 9...

Aligning the neck to the rim (We think!)
Once again, God must have wanted the Banjo Boys to congregate and make progress.  As the Northeast is digging out of 2 feet of snow, we basked in sunny, cloudless, 62-degree weather.  Monty arrived at around 9:30 AM and Clint wasn't far behind.  I had already moved Winston out of the shop and shifted the table saw and 6" belt sander to their outdoor locale.  We were ready to pursue the perfect Dynaflow banjo!
The dowel rod in a vintage Vega banjo

Monty needed to start on his "dowel rod," a piece of wood that is fastened to the heel of the neck, extends through a hole in the rim and is attached firmly to the opposite side of the rim.  We had originally talked about using the scrap of wood remaining from where we cut out the underside of the neck.  In fact, I had already marked mine with the outline of a square-cross-sectioned dowel rod.  I intended to turn one end on the lathe to produce a 5/8" round dowel that will be anchored into a hole at the base of the neck.

Monty turning his dowel rod

Monty, however, had decided that he wanted to use a round, rather than a square, dowel rod.  I looked around the shop and came up with a section of 1" diameter dowel.  We chucked it up on the lathe (an old Shopsmith that was a gift) and Monty created the reduced-diameter portion that was needed.

As this was going on, Clint was focused on making the piece that will form a black veneer for the underside of his peghead and completing the installation of the remaining frets that he had started last weekend.  He had brought Zoe, Sarah's Tibetan Terrier, so he and Zoe were upstairs working together.

Next, Monty and I started creating the jig that is needed to hold all the components together to align and double check how the pieces fit.  It turns out that the geometry of the banjo is far from simple.  And there are widely varying opinions of what is "right" with regard to the specifics.  Google "banjo neck angle" some time.  You'll be amazed at how many "right" ways there are to align the neck with the rim.  The angle between the two segments should be 1.4°, 3°, 3.5°, 4°, or 4.5°, depending on which web site you believe.  Regardless of which design you choose, it is important to get everything properly aligned before you start drilling the holes that define how and where the pieces are fastened together.

The alignment jig in operation

After a few minutes of "creative cogitating," Monty and I came up with a very simple system.  We cut a 15" x 40" piece of 3/4" plywood as the base for our jig.  We then built a "platform" onto which we can rigidly mount the rim.  We even thought to put a center line and concentric circle to position the rim.  The only variables remaining are the elevation and angle (slope?) of the neck.  We adjust both using combinations of shims placed beneath the heel and peghead areas.  It seems to work.

We set up my neck in the jig.  One alignment method says to use a straightedge placed on the fret surface and extend that line out to the position of the bridge, where it should be 3/8" above the head.  Using that system, it was obvious that my heel angle was pretty far off.  So we got out the jig we built earlier for cutting the neck angle at the heel and we re-cut my neck.  Fortunately, it appears to have come out perfectly.

This enabled me to start shaping the back of my neck.  I used the belt sander and various wood rasps to get the rough shape.  Then I began sanding, using automotive block sanders that Monty loaned us.  He used these on his neck, and they really work well at removing wood and avoiding high and low spots.  I still have quite a way to go on my neck.

Clint and Monty enjoy the weather and the Barbeque
So our status is as follows: Monty is about ready to start assembly after we check out/re-cut his heel; Clint will probably be ready to cut out his peghead shape and back profile; and I will continue shaping my neck and begin fabricating my dowel rod.

Banjo Boy lunch today was at Whitt's Barbeque in Fayetteville.  It was a "three thumbs up" lunch.  Whitt's may become the official Banjo Boy lunch hangout.

'Til next time...

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