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Guitar construction basics

The guitar construction follows traditional Spanish assembly techniques although Mr. Beltran uses modern technology where such technology yields results that are superior to traditional methods.   

One example of modern technology is the use of vacuum gluing to glue the soundboard bracing and the bridge to the face of the guitar.  The even clamping pressure and low humidity at the glue line as a result of the high vacuum make this method superior to the traditional mechanical clamps. 

The woods used by Mr. Beltran in the construction of his classical guitars are the finest available.  The wood is stored in a controlled environment, as is each guitar during its construction. 

Top woods include Englemann Spruce, Redwood, and Western Red Cedar.  All brace wood is selected from billets and then hand split. 

Wood for the back and sides are generally Brazilian Rosewood, or dalbergia nigra as it is called (that is over 60 years old), but due to cost, Mr. Beltran also builds  guitars in select East Indian Rosewood (dalbergia latifolia) and Cocobolo (dalbergia retusa), which is a Brazilian Rosewood, and has a sound that is quite similar to dalbergia nigra.   The base guitar prices are based upon the use of Indian Rosewood. 

Mr. Beltran considers the finish to be as important as the other considerations in guitar construction.  The back, sides and neck, where durability is a primary consideration, are finished with nitrocellulose lacquer.  The top is finished with french polish to maximize its flexibility and minimize damping.  The entire finishing process takes approximately six weeks.  The guitar can be completely finished in french polish or nitrocellulose lacquer by special order.

Guitar rosette design process
 


Slicing the rosette into 1.5 mm pieces
 

Guitar construction


There are small wooden blocks that hold the guitar top to the sides.  This picture shows those blocks being glued in.  Maestro Schneider called them “twinos.”  Most luthiers call them “tentelones.”


“Binding”   The purflings and bindings, which is the wood that goes around the perimeter of the guitar, are glued to the guitar using rope.  There is a function in that they seal the end-grain of the top or back, slowing the transfer of moisture, and also, the bindings guard against splitting of the top or back, if the guitar is banged against something. 


The braces are carved after gluing them onto the top plate.  There is a process of tuning the guitar top, which involves selective thinning of the top and carving of the braces, while tapping and listening to the guitar top and feeling the resistance of stiffness of the top.

 

 
 

The making of a Thomas Beltran classical guitar

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The guitar rosette design is made from wood, and then inlayed into the guitar.  A new pattern begins with a large drawing of the design as shown in photo A.  Initially,  brown was going to be used for one of the colors. Later, it was decided it would blend in too much with the color of the top.  Instead,  red was substituted for brown.  Once the design is laid out, then thin strips of wood are glued up to form the “log” as shown in photos B and C.  Each of the flat panels is made up of about 9 strips, representing each column of the rosette.  Those panels are then glued-up into the square.  The ends initially look like the photo E.  Once the rough end is sliced off, the mosaic pattern emerges, as shown in photo F. 

 

 

 

 

 

 

 

 

 

 

Once the slot for the rosette is made in the top, pieces, about 1.5  mm thick will be cut from this log like slicing up salami (see photograph at left).

 

 

 

 

 

 

 

Photographs G, H and I show the construction of a guitar top.  This top was a replacement.  The guitar, waiting to receive the top is shown in the background of photograph H.

 

 

 

 

 

 

 

 

Photographs J, K, L, M and O show how guitar sides are made.

 The sides are bent on the side bender shown in photograph J, which originally was made to bend cello sides.  The side bender is heated up to about 200 degrees, and the sides are bent.  You can see the pitch that has come out of the wood during bending.  Once the sides are bent,  the rosewood sides are laminated with Spanish Cypress.  Once the sides are assembled,  beech linings are glued to the sides.  They serve to increase the side thickness to give a gluing surface for the back of the guitar.