Preparing the Western Red Cedar top

The Master grade Western Red Cedar top is extremely stiff with very tight annular rings so I plan to bring the center thickness to 130 thousandths of an inch (130/1000″).  I am using accurate calipers to measure the starting thickness. I will create a gradient from the center to the perimeter of the top, bringing the perimeter to 100/1000″.

Measuring the starting thickness of the Cedar top.

Measuring the starting thickness of the Cedar top.

Using my Performax drum sander, I carefully remove thin layers from the top. It takes over 100 trips through the sander to arrive at 140/1000″. I will use a random orbital sander, a scraper, and sanding blocks to achieve the final thickness but this will happen after joining.

Thicknessing using the drum sander.

Thicknessing using the drum sander.

The bookmatched top pieces need to be joined using a butt joint. This is an extremely important join as the top radiates as a whole and the join should never fail with the continual stress exerted by the movements of the top. In order to ensure the stability of the join, I prepare each Cedar half using a trim router and 1/4″ straight bit. I run the router several times along the edge of each piece. To test the evenness, I hold the two pieces together in front of a bright light source to see if there is any “candeling” (any light showing through). Fortunately, the first candeling test is successful.

Using the trim router and routing jig to prepare for the top join.

Using the trim router and routing jig to prepare for the top join.

Using rope to join the top pieces together.

Using rope to join the top pieces together.

To join the top pieces, I use a method developed by Spanish luthiers over 200 years ago. I built a jig that uses rope to pull together two thin pieces of wood while keeping them flat. I apply a thin line of glue on each side, place it in the jig, and wrap several runs of rope in four positions along the width of the top. I then insert Mahogany wedges under the rope to pull the tops together by tightening the rope.

Inserting Mahogany wedges under the ropes to tighten.

Inserting Mahogany wedges under the ropes to tighten.

The Cedar top glued and drying in the joining jig.

The Cedar top glued and drying in the joining jig.

MDR-

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