Acoustic Guitar Construction

I am nearly finished with my first flamenco guitar. The flamenco is a long time coming as this spanish cyprus set was my third guitar set I bought many years back. I have suspended most of my knowledge on how to build a guitar and have been following Paco Chorobo of Chorobo Guitars online class. The class does cost but it is 22 hours long and includes the plans for the guitar, solera and templates. The course is nicely detailed and while viewing, besides learning how to build this guitar I picked up some woodworking techniques I did not have. Sometimes watching how they're using tools is just as valuable as what is being taught in the section.

I have taken pictures of the build but I have been slow starting this blog. I will break it up into a few posts as there are a lot of pictures. I will mostly focus on new stuff and changes to my build style but I will include a bunch of pictures of all of the steps.

I had the plans printed out. Luckily it is close to exactly the same size as the LMI classical template I have and used to build my solera and bending molds and build molds. So lucky me I am a step ahead! I joined up a spruce top I had; in the flamenco tradition it is a cheap "flawed" spruce top. Acoustically it is very nice but I got it cheap.







I have a stash of Spanish cedar scarfed joined neck blanks I picked up so I joined one with a Spanish cedar block for the heal.



I used a plane to thickness the head stock from the face side, new for me I always thicknessed from the back. Once thicknessed I went back and thinned the fretboard face of the neck to move the nut location above the end of the scarf joint.







I also profiled the heel using a template from the plans, but I forgot to take pictures.

From the plans I cut out the headstock template, taped it to some plastic and made a permanent template. I taped the template to a bit of Brazilian Rosewood and cutout the head stock veneer.






I made a jig to cut slots in the neck heal. Pretty simple jig, I screwed a guide in a bit of 3/4" sign plywood cut to size on the table saw and then I installed a fence perpendicular to the cut to hold the neck. It is easy to use: Set the blade at 3° toward the nut, set the height, line up the slot cut line with the end of the jig, cut one side. Flip the neck to the other side of the fence and repeat leaving the blade angle and height.









I made my slots wide, I will use a wedge once I am ready to glue in the rims. I have cracked sides taking them in and out of the slots.



I finished roughing the neck by establishing the shape of the heel. I just used a chisel

I ended up following Paco's rosette design. It just happened that I had all of the parts including a big enough bit of zipflex. I just bunched a bunch of red and black purling lines together to form the rings. I used my bishop coheran plunge router base to cut the slots. I had the right size end mill for the zipflex, and my purfling pattern was also the same size as the zipflex.












I also joined the back with a rosewood strip





The plan had a side template for a .6 meter radius. I traced it on a piece of mylar to make a template.



I cleaned up one side for the top with a plane and used my template to mark the sides, I profiled them on the bandsaw, checked which way I wanted to bend and marked them for the top and waist. At this point I had my kit and was ready to build.













The next morning I bent the sides in my side bender.





While waiting for the second side to cool I made an end block including a preinstalled end graft. The preinstalled end graft is working out as it make it easy to glue on the sides square.





I mark the center line on each side, measured in half of the end graft width and cut to size; cleaning up on my belt sander.







With the end graft preinstalled the sides can be glued one at a time and still be centered a square.



In a like way I cut the neck side of the rims to fit.



The end of another day. I am starting to see a guitar in the parts.

Before bracing the top, I needed to install a sound hole donut and finish off the sound hole. Using my router I cut a circle of WRC. In its crossgrain orientation I marked the location where the transverse braves cross the donut, marked and used a scalpel to cut to size.





I used a right triangle to orient the soon to be ring and glue it down





While that glue was drying I glued down the back's center strip.



I used my router to cut out the sound hole



Here is a tip on how to trim of the sound hole without need to cut it exact.
I first fit an extra wide fiber strip into the sound



Still holding it do size I pull it out and cut both strips at a diagonal





Now I have a strip scarfed on each side.



when installing the ring you can slide the scarfs against each other until the ring fits perfectly. As the ring is wider than necessary there is room for adjustment making the ring smaller or bigger to fit. Glue it on and trim with a scraper, chisel or plane.







On a flat board I glued on the transverse braces to the top and moved on to the back.



Using the template in the plans I made a .6 m radius bar and used it to radius and glue the back braces to the back. I only had one radius bar so I glued the braces on one at a time. Not shown is cutting out the slots in the center strip to fit the braces.







The fan braces are not radiused rather they are pressed in a dished solera. My solera has a 2 mm dish in the lower bout. This was for my tradition classical guitars, but is perfect for this guitar as well.



I braced the top in my gobar deck and profiled the braces on the back







With the rims in place in the solera, I marked the size of the top's transverse braces and trimmed them to size with a razor saw and a chisel.

Making progress

Paco's method is to glue the top to the neck, I normally glue the rims to neck first. Paco's way is very traditional. I normally use linings ot kerfed linings on the top in classical guitars as I want the rims really well supported as to not bleed energy into the sides. So normally I completely build the rims and neck assembly before gluing the top and back. Flamenco wants to be a little looser, so instead of linings tentallones are used; will be pictures later.

Before I can glue on the neck I need to route away the portion of the heel that the top sits on. The top is flush with the face of the neck so a recess need to be cleared for it. I use the top to set the depth of the router. When I route I will keep a portion of the base on the neck face to cut out the correct sized rebate. Sorry no picture of the routing just setting the bit height.



Even though the neck will ultimately be tilted the neck needs to be glued flat to the top. When the back is glued on in the solera the neck will be tilted slightly setting the neck angle the top happily bends to accommodate. I could not use my solera as it has a tilt for the neck. See below



So I just drew a straight line on a board and used it in the alignment and glue up of the top to the neck.



I spent a bunch of time making sure the neck was on straight using the center line on the top and line drawn on the work board.





Just like downtown.



Making a gluing down the tentallones was a pain in the ... Not hard but mind numbingly boring. The keen eye will note that the ones in the lower bout were a little farther apart. That was to make that interface a bit looser.









But another milestone

I fit the back to the guitar and cut out rebates for the backs braces (sorry no pictures) but look at one of my other builds as I have documented it a bunch. But here I am ready to glue the back on. I spent some time cleaning up the inside with sandpaper and removed any glue with chisels and scrapers.





The back fit with little play, but I still spent time making sure that the neck and tail were lined up correctly. The center strip in the back really shows off any misd alignments.

A few clamps were used to glue it onto the solera. I have one clamp holding the neck down on the solera to force the neck angle. The neck angle of a spanish heel guitar is set when the back is glued on.



Before routing the binding channels I leveled the rims. The bind jig indexes off of the sides so any irregularities can show up in the route. Also you do not want to be sanding the rims level after the binings are in as you will thin the bindings. I mark up the rims with a pencil and sand it off looking for low areas.





I routed the channels leaving the area close to and under the neck unrouted. It is tedious hand work to finish off the channel. It is probably the one required step that makes a spanish heel harder than a bolt on. A router is a wonderful tool. I do not have pictures of the hand work on the back but I do have a few for the top.

I use a fancy binding tool to cut the bottom of the channel in the rims. It is index to the top so it can be set and do a pretty straight cut.




I then use the top template to help mark out and cut the inside of the channel with a scalpel. I only cut through the top with the scalpel. WIth clean lines on the show edges of the channel it is not to hard to chisel out the rest of the channel.



Not pictured but worth noting this guitar has a purfling ledge as well. So I had to move the template and cut that channel as well. I would mark through the top with the scalpel and use a chisel to clear the rest. In any case I got it all installed.








A classical guitar has its neck pitched about 2 mm forward to achieve a string height at the saddle of around 11 mm from the top. This flamenco guitar is going to have a string height of 7 - 8 mm. If I was to use the neck angled to lower the height 3 mm I would have to pitch the neck forward another few inches. That is too much so the course teaches to tile the fretboard Removing 2 mm at the saddle side of the fretboard relative to the nut gives about 3 mm reduction of string height. So that is what I tried. Also the bass side is 1 mm thinner than the treble side to help keep the string height above the top more even with the difference in action.

My first attempt I shimmed up end of the fretboard a bit more than 2 mm and placed smaller shims to help support the fretboard and ran it though the drum sander.







You can see the sanding marks moving toward the high corner with multiple passes through the sander (treble nut side)



It sort of worked but there were two issues. The first is the unsupported wood flexed a bit so the back of the fret board was not level. Also as the work board exited the sander and extended past the belt it put a bit of extra pressure on the trailing edge of the fret board, oversanding it. I did not do a good job supporting the work board as it exited the sander.


So I glued a thin bit of ebony on the oversanded edge. I placed the fretboard on a 3/4" plywood and then shimmed the plywood. I also made sure to support it as it exited the sander. This method worked great I got a level fretboard with the correct slopes.





Here I am at 2 mm. Add 6 mm to get a 3 mm action and we are at 8 mm string height. Life is good.



So I glued on the fretboard, and looked to start craving the neck.



I used rasps, knifes, chisels and for the first time a gouge to carve the neck transition and the heel. I mostly use a spoke shave to carve the neck. Sorry I get into a neck carving zen and did not take many in progress pictures. This spanish cedar was a pain. It carved like butter in one direction and hardly at all in the other direction. I worked around it but it is a pain using and edge tool going up hill in a curve instead of down.







Here is where I got to.

Very inspiring John!
I don't want to horn in on your thread, but your talk of a purfling ledge brought to mind a guitar maker in Czechoslovakia name Jan Tulacek, who I corresponded with a number of years back.
To my surprise, many of the European makers do not even use binding! As in one picture, you can see that the back has a very thin purfling with no binding; the top has a wide purfling arrangement but no bindings. This is purposeful on their part and traditional. He uses a chisel to cut that purfling ledge, unbelievable.
Thought it might be of interest.

Very nice work and log John.