Acoustic Guitar Construction

I put in the rosette this morning. For the outer rings I jammed two of the BWB purfling into each of the slots I routed making bwbbwb. I then routed a rebate for a claro walnut ring framed with black fiber strips. With the rings I wanted to suggest a martin rosette, but using a wood ring rosette more in my style.

I ordered some tops from Mario at Sprucetonewood and he sent along a split piece of Lutz sapwood bracewood. I sliced it up into braces (he would of had me spilt them for no run out) and they feel pretty good so I am going to use them on this guitar.





I inlayed the zipper strip, nothing exciting here.







Back strips
I saw a post with a picture from the martin factory where they were cutting up a reject top to make a back reinforcement strip and I thought I have a top I goofed up. So now I have a good supply of master grade back strips!

I glued the strips on close to the correct thickness and then sand them down with a sanding block I made with a 4 inch radius (or whatever the drum is on my drum sander) curve.











I bought a bunch of poster boards so that I could make protective covers for the top. $1.50 each. I have the top sanded to 120 and it is very close to the final thickness. Before taping on the poster board, I checked to make sure I have the top rim has the correct angle. I clamp the top to the rims and then I use a straight edge and roll a 2.5 mm drill bit right to the saddle location. That is the height I want to start with.





I drew the bracing patterns on the back and the top. You can see in the first picture I taped off the sound hole to keep bits of wood from being trapped and pressed into the top. I really want to make a top with no dings this time. We will see.

I put a 28' radius on the bottom of the braces I wanted to use for the X-brace and have them just a touch more than my final height at the joint. I copied the desired angle onto my protractor like tool and then to my braces. Make sure one brace is up and one is down if you are cutting them out at the same time like I do. I can not tell you how many times I forgot this. Even today, luckily I caught the error before I cut.

The joint is really tight and at the correct angle. I sanded the xbrace a bit more in the radius dish to make sure the assembled brace fit nicely in the dish. As I write I am waiting for the gluing up of the brace using my go bar deck to cure.

This is just fascinating. Eventually we might see how well the math describes the reality of wood. Thanks for posting the results.

Whoops this is a fairly long post as I have not been keeping up with the blog. Since the last post I have completed the bracing of both the top and the back and have fitted the braces to the rim. For those that want to follow I will lay out the pictures of the procedures I followed.

Those viewing my previous posts might have noticed I put in the x-braces before I put in the bridge plate. I normally do it in the reverse order and glue the bridge plate down on a flat surface. No big deal but when I did glue down the bridge plate I used my massive fiberglass slats to force the un radiused gluing caul down in the radius dish. Normally I used the much safer and friendlier fiberglass rods. Also in the pictures I sort of went back and forth between glued rough shaped braces and just radiused braces.







Sort of mixed into working on the top I also worked on the back bracing. Based on advise for the wood I am using and the purpose and size of the guitar I am building a non-live back guitar and have used four full height braces shaped with a plane to a near triangular shape. Trying to up my game on this back I took much care to get everything square and to have clean and square cuts into the back strip for the braces.

I first put 15' radius on all of the back braces. I use a combination of a plane to rough shape the radius and the sanding dish to finish it off. In the past I used the back strip as my guide for back braces. This guitar I made sure I had a straight edge to work with as you can see in the pictures. I used the straight edge and the square for all of the cuts I made with a scalpel and a new blade. The scalpel is so sharp there is no need for a saw as it cleanly and accurately cuts the slots. It worked out well as the braces pushed into the slots ended up square.











I went after the top and back braces with my chisels and block planes until I got the shape I wanted. Again trying to clean up my normal style I took more care to protect the plates while working on the braces. In the past I always ended up with some scratches deep scratches from the chisels. I ended relatively (to my past efforts) clean. Once I had the top braces to plan. I did tap tune them a bit mostly taking wood off of the finger and diagonal braces to the top felt alive. After the guitar is finished with the bridge on I may do some tuning from the sound hole based on the tops performance. I am happy where it is now it has some nice tap tones.














I fit the top and back to the rims. Here as well I have been trying to assure a tight fit from the beginning making sure to clearly center and carefully mark where the braces intersect the rims. Part of carfully marking the braces is I make sure that I can see and that I have access to mark them. While all of the tails of the braces are close in height I still individually set the my die grinder for each brace before I route the rebate into the kerfed linings on the rims. All in all the procedure went well for the top and the back.













With the top properly fitted, I rechecked that the angle on the top was right where I want it. The idea is a fret board extension flush to the top will be at the correct angle to give me the planned string height off the top at the saddle location. A 2.5 mm drill bit rolled up tight right at the saddle location.



Time for a shot of Everclear! (I only really use it for shellac).

Looking good John, you are leaving me in the dust!
Been sick with flu and haven't worked in the shop in a week.

Kevin

Kevin in California wrote:Looking good John, you are leaving me in the dust!
Been sick with flu and haven't worked in the shop in a week.

Kevin

Kevin,

I sure hope you feel better soon. The flu has been hitting pretty hard.

I used a bit of figured maple to make the end wedge. It is a relatively simple wedge without a black prufling strip. I went back and forth and finally decided if I could cut a clean channel a simple maple wedge would be fine. I think the only thing I started doing to achieve an accurate cut is to use a scalpel with a new blade instead of a razor saw. It takes a few passes with the scalpel but once the initial line is made it is easy to follow the cut. I had a couple of time on previous instruments where I slipped or managed to widen the cut while using a saw. Not shown is that I chiseled the waste out before I glued in the wedge. Being a wedge I probably could have gotten by with out clamps, but I clamped it down. ultimately it came our alright.














I used the fox style bending machine to bend both the bindings and the herringbone purfling. No problems bending the curly maple or the herringbone.









At this point I am nearly ready to close the box. I did add one step to my process, I use a 28' radius dish to profile the top rims including the heel block. To complement the flattened upper transverse brace, I took a couple of passes on the heel block with a plane to give a flat spot to glue the fret board.

flattened the heel block


I glued the back on first. This gave me a chance to make the back look nice as it is the one people see through the sound hole. I used a flush cut bit to cut off the waste.





glued on the top.





The next shot is me keeping a promise. I completely leveled the sides before gluing on the bindings. I promised in my last build that I was not going to be stressed out about thin bindings when I still needed to sand the sides. I used a hand held drum sander with an inflatable bed.



Sorry no pictures but I cut out the binding channel and the purfling channel. I am not sure how I did it but I cut part of the channel on one side for the herringbone too deep. (.5 mm or so) I caught myself before I went to far. Luckily I bent 2 extra binding strips. I glued one in to the channel I cut too deep, leveled it and I re-routed the channel at the correct depth. It is all inside so nobody will see. It is structurally sound.





I also promised myself no more gaps in the binding. I glued up binding and herringbone and wrapped the bindings tight with my new rubber strip. It worked! More tomorrow.