Acoustic Guitar Construction

R. E. Bruné donated a Brazilian Rosewood guitar kit to the Guild of American Luthier conference for their auction. It included the rosewood set pictured a top set, a finished neck and wood for a fretboard and bridge. The kit was not going for as much as I thought it should so I bought it. The neck was 660 mm (not 650) so I put it aside and I had a sonically graded Pacific Rim Tonewoods Lutz top (also bought at the GAL) that I wanted to use.



First steps for me is to test the wood to determine a target thickness. I have 2 methods. The first method uses tap frequencies to determine the Young's modulus (stiffness). This method works great but it requires that plate tested is rectangular and uniform thickness. The top plates I had allowed me to do this test. It is easier to show rather than tell so here is a video of me testing the top plate.



The back plates were more trapezoidal so I determined the long and cross grain Young's modules using rectangular pieces from the area outside the profile of the guitar by performing a deflection test.

Dang John, That is a very nice set of BRW. Over here such a set cost around 1500 euro. It is available, but I think the price is out of proportion.
Herman

Herman wrote: ↑Thu Aug 24, 2023 8:44 am Dang John, That is a very nice set of BRW. Over here such a set cost around 1500 euro. It is available, but I think the price is out of proportion.
Herman

I got it for less than half that with a finished neck and top plate. I trying to bid it up a bit bit the auction but there were not enough buyers.

Then you did well. Very nice set. You are now obliged to make it into a perfect guitar.
Herman

Oh boy John
That will be a beauty for sure.
Will you keep it or sell it?

I am not sure if I will keep it or sell. I may keep it.

I jointed both plates the same way. I shoot the edges on a shooting board with a No. 62 Low Angle Jack Plane. Often I use a Bench plane for the the backs to avoid tear out but BRW planes like butter. I use an LMI jig to clamp the plates together.










I made a cheater rosette by installing a traditional classical rosette, routing the end grain tiles and installing a BRW ring with a couple red of purfling strips.









Just to finish with the top as the neck will be a long post ...

I thicknessed the top in my drum sander to 2.1 mm. I profiled the top so I could use the offcut to make a sound hole patch. (note I have not cut out the sound hole). I planed the edges of the offcut and used stretched tape to glue them together. Once glued I cut the patch to a template I have for my classical guitars and glued it to the back of the top indexing on the router index pin.













Now I can cut out the sound hole through both the top and the sound hole patch.

Very nice!