Showing posts with label Bracing. Show all posts
Showing posts with label Bracing. Show all posts

Saturday, December 14, 2013

Soundboard Braces

The soundboard braces have been shaped to a 25 foot radius and attached to the top, again using hot hide glue. I look forward now to profiling and carving them to their final dimensions, my goal being a light and lively soundboard. This is surely the most tactile and intuitive stage of the entire building process, when machinery and power tools lay temporarily silent, and finger planes, chisels and sandpaper take over.


A useful pointer to where I'm at on my quest to build a high quality instrument is that the soundboard bracing on each new guitar still seems to be lighter than that of the last. In many respects, I'm sure it's a good thing that my evolution as a guitar builder has been such a gradual process, with small incremental improvements marking what has been a long journey. Where soundboard bracing is concerned, I acknowledge that a bolder individual willing to take risks would equal my progress after far fewer guitars, but I'm happy nevertheless to plod along at my own cautious pace, learning as I go, improving my skills and gaining satisfaction from the improvements I see and hear after each guitar is completed.

With my weekends still dominated by household chores, my resolve to chip away at this guitar in spare moments through the week is certainly yielding results, as evidenced by my latest posts. Lurking in the background, however, is the need to construct bending forms and an outside mold to accommodate the modified body shape I've recently devised. Unfortunately, at some point soon, this necessity will act as a barrier to further progress and I'll be unable to avoid the task any longer! 

Cheers
Pete

Saturday, August 27, 2011

The Fingerstyle Guitar - Notching the Kerfed Linings

Once the kerfed linings are glued to the sides, the sandpaper-lined concave dishes I made use of when shaping and gluing the top and back braces serve their other purpose by helping me sand a drop-off onto the edges of the rim assembly to match the curvature of the back and top plates.

Sanding guitar rims


Kerfed guitar liningsI can then use a Dremel rotary tool to rout pockets into the linings to accommodate the brace ends. Using the more traditional kerfed linings whose saw kerfs face into the guitar body, there's always a danger that if one or both edges of a brace pocket happen to be in close proximity to the kerfs, a chunk of wood will be dislodged as the pocket is cut. With reverse-kerfed linings, however, the individual sections of wood between the kerfs are firmly glued to the sides and serious chipping of the exposed face of the lining on either side of the brace pocket is far less likely, provided some simple precautions are taken.

When routing the brace pockets, it's important that the Dremel is guided in such a way that the router bit's clockwise rotation doesn't contribute to tearing or chipping of the linings as the pocket is cut. This is particularly important to observe where the left-hand edge of the brace pocket is concerned (i.e., with the guitar side facing me). With that in mind, I make my first cut towards me in the direction of the guitar side along this left-hand margin, easing the router bit into the lining for the equivalent of around half the bit's diameter; a second shallow entry cut on the right-hand side of the pocket defines its width. Several light passes are made from left to right until a single recess is created between the two entry cuts. I repeat this process until the recess extends to the guitar's side and make final adjustments until the end of the brace fits snugly within the pocket. It's difficult to avoid chipping entirely, but by guiding the router in the manner I've described, it's of a minor nature and can be easily cleaned up with sandpaper.




I rout the pockets in pairs, beginning at the tail-block end of the body. If the first pair of pockets is accurately marked and cut, the centre-line of the back will be correctly aligned from that point on. If a minor adjustment to the back alignment is required, the pockets can be modified accordingly. The second, and subsequent pairs of pockets can then be more accurately positioned, with correct alignment of the back more firmly established as each pair is cut.

Some builders postulate that because reverse-kerfed linings stiffen the rim assembly once attached, there are resultant improvements in the sound of the instrument. Occasionally, it seems, views such as this are repeated often enough by individuals held in high regard within the luthier community that they become accepted as fact, whether or not they've been held up to close scrutiny. I acknowledge that I have a lot to learn and always try to have an open mind when reading of the experiences and opinions of other more experienced builders, but after looking at popular wisdom such as this from all angles, I'm left unconvinced. For what it's worth, my personal view is that while it's somewhat helpful having a stiffer rim to work with in the course of constructing the instrument, from the point at which the back and soundboard are attached to the rims, any contribution the linings may have made to the rims' stiffness is eclipsed by the strength of the top and back in compression. I suspect that in the finished instrument, the linings - reversed or otherwise - play little part beyond their primary purpose: to provide a gluing surface for the top and back plates.

Cheers
Pete

What's In a Name?

The back and sides of this guitar are of narra, which is an alternative name for a wood that's most often marketed here in Australia as ...