Gourd Banjo III

Skewering the Gourd

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Now that the neck has been carved to its basic shape, it is time to put the neck and the gourd together. This is done my skewering the gourd with the dowel piece of the neck. To do that, I cut two holes in the gourd for the dowel and then gradually enlarge them until the neck fits all the way through the gourd with a tight friction fit.

I want to put a small angle on the neck to allow the action of the strings to be low, and that is done by cutting the hole at the rear of the gourd a bit higher than the hole at the front of the gourd. Here is a drawing of the basic idea.


I calculated the diameter of the gourd where the dowel stick goes through it. The dowel stick goes through the gourd in the middle of the stick, and the top of the finger board should be even with the top of the gourd. Since the neck is layered from 3 boards that are each 3/4" thick plus the 1/4" finger board, the bottom of the dowel stick should be 2 1/2" from the top of the neck. If I subtract half of the thickness of the dowel, or 3/8" to center the hole on the dowel, then the location where I should measure the diameter of the gourd is about 2 1/8" from the top of the gourd.

Just for grins I thought that I would measure the distance as well. Here is my new toy, a digital caliper.


Since I have a frailing scoop, I had to cantilever a board out over the heel of the neck to measure it.


Then I measured the thickness of the board so that I can subtract that out.


From the readouts, the depth of the neck at the heel is 2.7765" - 0.2755" = 2.501". That number looks familiar. Pretty cool, hunh?

The diameter measurement was somewhat tricky because I don't have a caliper that large. First, I measured around the circumference of the gourd using a tape measure. OK. I admit that I estimated the location where I measured the circumference. So sue me.


The measurement came out to 45 7/8". Divide by π to get the diameter and I get

45.875 / π = 14.60246602868139706


We will assume that the diameter is 14.6" for the next calculations.

I decided that I want to make the neck angle 1° since I made the angle 1° on my previous banjo and it worked out well.

n = length of the tailpiece section = 14.6" inside the gourd.
a = angle of the neck
d = deflection upward of the rear hole

tan(a) = d / n = d / 14.6

I want to figure out what d is to provide a neck angle of 1 degree. We can go ahead and solve the equation to get.

tan(1°) = d / 14.6


d = tan(1°) * 14.6 = 0.2548"

That is just over a 1/4 inch. So the rear hole needs to be cut 1/4" above the front hole. Good enough! HA. So, here is my procedure for figuring out where to put the hole:

I didn't do any real work on the gourd or the neck today because it is pouring rain and miserable outside. So I only spent about an hour today planning this out. Log 1 hour today.

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Original post date June 21, 2009

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Last updated July 8, 2009