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April 15, 2018

Learning to Make a Bowlback Mandolin Pt. 3

Mandolin Pt. 1 >>
Mandolin Pt. 2 >>

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This is my third attempt at making the bowl and the mould or form that it is built upon. And this time, more than before, I was struck by the realization that one doesn't become proficient in making an instrument, but rather becomes proficient in making each part of the instrument.

Each part of the instrument requires a fair amount of attention and intensity and needs to be mastered before moving on and I suppose if I were working in a production shop I might spend a good deal of my career - if not ALL of my career - mastering one part of the instrument.

Making mistakes is necessary but perhaps not for the reasons you might think. I learn so much from experimenting and making mistakes along the way because I develop my eye and better understand the limits that I'm working within.

On my last attempt I found out that the problem with my mould was that it was rounded and so the ribs were high centering. This became more accute as the job progressed. The cure was to flatten and even concavenate the facets of the mould. That allows the ribs to join at the edges.

I tried a combination of sanding, scraping, and filing the form to make the concave shapes. And although I was able to do it I came to the conclusion that western red cedar really may not be the best wood for this type of mould.

My plans have a pattern for the keel or center rib. The rest of the ribs are similar but must be slightly altered to fit. By laying a batten along the rib pattern edge we can see that it is actually a straight line. These lines need to be marked while shaping the mould but you'll be rubbing out that line as you sand and scrape, so I decided to try cutting a fine line with a saw and then pencil along the cut and that way I never lose my lines. Positives and negatives of this approach? I don't know yet but time will tell.

Another idea I'm trying is to hollow out an area for the tail block. Hopefully this will allow me to more accurately shape it to fit the inside of the last two staves. Of course, those staves cannot be glued to the block while it's in the mould, since it then might be difficult to remove the bowl.

Part of making the bowl is making both the tail and neck blocks. The neck block connects to the body to the neck with a horizontal dovetail. I've laminated some spruce and made a rather large block of wood compared to the final block. This keeps my hands away from spinning blades while shaping.

After the large block goes through the router for the dovetail it gets screwed to a piece of scrap in order to slice off the piece for the actual block. Then it's attached to the mould with a couple of screws.

I'm using a draw knife, belt sander, and then I hand sand down to the final size, being careful to line up the facets that are on the mould. I think having a bigger and better band saw would make this a quicker job.

In the other mandolin videos I showed my home made thickness sander. I also have a video showing how it was made. When running the thin ribs through a planer they break up, so the sander was necessary. A large thickness sander is over a $1000, and I only need it for the ribs, so this is a good alternative.

My pipe bender is presently a piece of aluminum pipe with an electric charcoal starter as the heating element, which I found out can be bent in a vise to make it fit into the pipe without hurting it. I've been strapping the ribs to the mold and letting them cool overnight. Fitting the ribs is probably the most important and most difficult part of the process and there are a number of different ways of doing it. I'm trying different approaches and getting better as I go along, but I'm still trying to find and develop my way.

I'm using Titebond 3 for the glue. Different parts of the instrument will be assembled with different kinds of glue, and I'll be trying different glues to try and understand the difference between them. Push pins are used like small clamps. Recently I've also been trying carpet tacks. They are very sharp and have a somewhat flat side to push against the rib.

You can see that each time the bowl moves further along, as does my learning experience. The main thing I supposed I've learned is to not let the time and effort and work that I've done before stop me from throwing it all away and trying again. If you do this in your projects AND persevere, you probably won't regret it.

Unless you just want a mandolin. In which case, it's probably better to just go out and buy one.

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