Category Archives: X-Bracing

X-Bracing

Gluing the X-braces

Well I got a little more work done on the top plate. I left off last time with just the x-braces glued on after shaping them. I also pre-shaped the tone braces.

In the next step I glued up the rest of the braces and did some final shaping. On this guitar I am using scalloped braces as opposed to non-scalloped. Scalloped braces offer a little more vibration in the top plate given more overall volume. Non-scalloped give a more even, balanced range between the highs and lows. The scalloped style is more common with the vintage guitars. Finger picking guitarists tend to prefer the scalloped bracing for its range and volume.

Gluing on the six tone braces. Notice they are notched in under the x-braces for added structural strength.

The bracing around the sound hole. These are only 2mm thick.

I then drilled a hole in the brace for the upper bout for access to the truss rod and then glued it on flat. This brace is not arched. The top plate will transition from a dome to flat in the upper section. Some do this and other don’t. I am trying it this way to make the finger board, which extends down past the 14th fret easier to attach to the sound board. I also glued on the bridge patch, which protects the top plate from the guitar string ends digging in under tension. I used some 2mm quatersawn ebony.

Finally I took a scraper and rounded off the edges, did some hand sanding and added a half-lap top crown on the x-brace intersection.

When I do some tapping on the sound board it has a nice tone. I am not sure what to listen for as I have no experience here but I can say I hear the wood singing. That is to say there is a resonant tone.

This sound board is finished. Next I will move on to the back.

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Gluing the X-brace

Now before I glue the braces down on to the back of the top plate I have to shape them to the desired radius. As I mentioned in the last post I am using a 25′ radius.

The radius dish I made will be used for the glue-up but it will also be used for putting the radius onto the braces. I have seen some make a special jig just for putting a curve on the braces but I like the idea of using the radius dish. So in the next step I tack some 120 grit sandpaper down on to the inside of the dish where the brace will lay and start sanding by moving the brace back and forth.

Sanding the correct radius into the x-brace

Checking the fit. I will also do the same for the other braces excluding the braces in the upper bout.

Before I glue the x-braces down I need to notch them so the other 6 tonal braces can tuck in under them. The braces in the upper section stay flat.

I pre-shaped the tonal braces so I could find my position to mark and notch out on the x-braces. I also marked my end points and maximum depth for the scalloping on the braces. I used a French curve template and a thin strip of hard maple to trace curves on to the braces.

I pre-shaped the x-braces before gluing them down. You can see my end point and maximum depth pencil marks. It seems many luthiers shape the braces after gluing them down but many luthier supply shops sell pre-shaped brace kits so I decided to shaped them before gluing to avoid any nasty slips I am prone to making.

All the braces pre-shaped and ready to go.

A close up of the scalloped braces.

Gluing down the x-brace with my makeshift go-bar. The go-bar is a clamping system many luthiers use to get clamp pressure down on top of the piece. In my case I didn’t actually make one I just used 1.4 meter x 10mm dowels in between the braces and my workshop ceiling. I even put rubber booties on them cause I get rain leaking in when it pours.

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Laying out the X-Bracing

In this step I will begin to layout the X-bracing. X-bracing is the most common method of bracing for a steel string acoustic guitar. It was developed by C.F. Martin between 1840 and 1845.

In the first step I take my plans and make triangular cut outs at the end point of each brace with my Japanese kiridashi knife. I then lay the plans out on the back of the top plate and mark with a pencil each triangular section.

I then take a straight steel rule and join up all the points effectively laying out the brace positions.

With the positions marked I lay out the braces just to check things out. The braces are also quatersawn spruce with straight clear grain. Here I want to also mark my position for the half lap cut I will make at the intersection of the x.

Here you can see the x-brace joined with a half lap joint. It is a fairly snug joint. It is not yet ready for gluing up though.

Again I lay out the braces to check things out with the x-brace in position.

In the next step I will show you the method I used for making the radius dish shown in the above two pictures. This is what is used for putting an arch on the top and back plates.

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