Big Hollow Guitars

Planing the top edge of the sides flat. This is the edge that will eventually support the top. (slide 1)

I do the waist bend first because it is easier to judge where you are and where you will be after bending (slide 2). I have the side sillouhette marked on the bench. This is my reference I will bend the sides to.

The upper bout bend. You can see the device I am using to bend the material with (slide 3) . 

The lower bout bend. You can see I still have a little further to go to get the end to sit on the line (slide 4).

One more session of heat and compression and the side sits on the line (slide 5) . 

Then I clamp it in the mold to mark it for length (slide 6).

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Fitting the back braces into the backstrip can be quite frustrating especially when one requires the braces to fit snugly. The following process should help the user attain accurate results.

First, layout marks are made to position the braces properly. Then each brace location is marked with a knife. First it is drawn across the strip on one side of the brace, then the brace is shifted just over the cut and marked on the opposite side with a knife. This makes for a tighter fit (slide 1).

Next, cuts are made 1/16” inside the line with a sharp chisel (slides 2&3)

The isolated chunk is cleared out (slide 4)

Using the large chisel again, the gap is cut to the knife marks (slide 5)

A smaller chisel to clean it out (slide 6)

The cavity is scraped clean (slide 7) 

A test fit reveals the brace fits snugly in the gap (slide 8)

After the back plate is sanded to thickness, the first step is to install the backstrip, the narrow spruce reinforcement piece that will remain visible on the inside of the guitar. (slide 1) 

When it is dry, the strip is planed to thickness (slide 2) 

Next, a rough rounding is performed with a small plane, essentially chamfering the corners (slide 3) 

Then I cut some adhesive-backed sandpaper and put it in the cavity on my sanding block. The slight crown of the block sands the backsitrip into a smoothly domed contour. (slide 4) 

The last thing that touches the inside surface of the back is a very sharp scraper. This tool lets me remove all the sander marks with a few passes. (slide 5) 

Stay tuned for “how to install a brace in the backstrip”

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Shaping the top bracing starts when you remove the top from its clamps (Slide 1).

The braces are all still square-ish, and a little overtall. The following process of carving the top brings the size of each brace down to the proper mass and stiffness, as well as gives me a chance to feel and hear the top coming in to it’s own as a vibrating plate with many different modes/frequencies that ring well.

I set the height of the transverse brace with my bailey plane (slide 2).Then I plane down the corners until it has a parabolic cross section (slide 3). The rest of the process requires a very sharp chisel (slide 4). I use several water stones of various grits up to 8000. 

The ends of each brace must be trimmed down thin where they will be tucked into the kerfing (slides 5&6).

The sides of the finger braces are tapered (slide 7). This is done to all of the bracing in order to make it lighter while retaining stiffness.

The belly braces after final shaping. These braces can be shaped without curved surfaces, so I can cut their final facets with the chisel (slide 8).

The last step on the top is to sign and date it. I use a 4 digit numbering system, the first  2 digits reference the number of guitars I’ve made, the last two are the year (slide 9).

The finished, carved, and signed top. On to other parts! 

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So last post we left off at this picture. The kerfed linings are notched out and ready for the back to be glued on. You can see the hot glue pot in the foreground. The first area to be glued is the neckblock, arguably the point of highest stress along the perimeter (slide 2).

From there, glue is applied with a plastic spatula in short sections. Then 3 or 4 go-bars are placed on cauls so that they exert clamping pressure on the fresh hot glue before it gels. I proceed this way all the way around (slide 3).

After the joint dries (24 hrs), the mold is removed from the go-bar deck. Any excess glue showing on the inside is rewetted and scraped off, leaving a clean interior joint (slide 4).

Next the vertical reinforcements are fitted, three to a side. These parts help keep the sides from splitting if they experience stress. (slide 5)

The top surface being planed flat (slide 6)

After the kerfed linings are glued in, they must be sanded to form a flush surface with the sides. I remove most excess material with this Ibex hand plane, then I clamp the body in place to use my radius sanding dish (slide 2). Repeatedly rotating this dish while gently pressing it onto the guitar eventually does the trick (slide 3). 

The back of the guitar gets temporarily clamped onto the top, the center strip trimmed to fit snugly at both endblocks, and the centerline aligned. Next it is time to mark each brace  along its intersection with the sides, and the sides at their intersections with the edges of each brace (slide 4). 

Each brace is trimmed 1/8” inside the mark, so it extends into the kerfing pocket but stops just short of interfering with the side of the guitar. The X-acto razor saw is taped on either end to help avoid random saw cuts on visible wood (slide 5). The cut-off material is then removed (slide 6)

The marks on the outside of the guitar are transfered to the top surface, and form the edges of a pocket sized to just accommodate the brace (slide 7).

Once these steps are completed on each brace end, you have a back that fits onto its sides, and if your measurement and execution is correct, the back can only fit exactly where it is supposed to (slide 8).

Next Post: Gluing the back on the sides using hide glue

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Photo numbers:

1. This treasured instrument was in need of some major work when it arrived. Not only did it need a new bridge and two top cracks fixed, the back had a soundpost crack. Because the soundpost exerts pressure onto the back, a crack at it’s base can’t be repaired in the conventional way. A patch must be made to fit a cavity under the soundpost that almost extends to the front surface of the back.  I carved the cavity to an ellipse with scrapers, checking my depth by backlighting the cavity. As more and more light started to show through I could tell how close I was to poking through the back. I stopped short of that, and focused on smoothing the surface of my cavity to accept my patch.                                              
2. The original builder took care to put his info in places that aren’t visible from the outside. Markneukirchen has been the center of german violin making for hundreds of years. I have been to the German national instrument museum there, and briefly considered attending their musical instrument building technical school.                                                                                                                            
3. Albert Theod. Heberlein. The Heberlein family violin tradition is large and long.        
4.   At the time this was built, it was built for wholesale to international retailers such as Carl Fischer, who never bothered to fill in the date.                                                                                               
5. Many repaired cracks                                                                                                 
6. This point is the result of about 4 hours of fitting this patch into its cavity, then scraping off the chalk marks. repeat.                                                                        
7. Patch in cavity, receiving chalk marks on high spots                                                  
8. Fit has been confirmed, now it’s time to glue and clamp! The appropriate glue for this application, and for all violin family applications, is hide glue. Click for more on Big Hollow Hide Glue Custom Guitars                                         
9. The backing block has been popped off, and the patch scraped flush to the back. Care is taken to match the contours of the inside of the back.                                 
10. Top is going back on!

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The box from Allied Lutherie arrived today, which is exciting because now I can start building Goldie’s guitar. 

Shameless Plug:

As Part of the purchase price of your new custom Big Hollow Guitar, I can create regular blog posts that can keep you and your friends updated and involved in the process. How cool is that?

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