I want to replace an acoustic guitar that I lost in a house fire. I like to build things so I have decided to build a guitar. I have built electric guitars but this will be my first acoustic. To educate myself in the art of acoustic string instrument construction, I built a tenor ukulele from a Stewart MacDonald kit. The ukulele build was humbling but quite instructive and it served its purpose. As I neared the end of that project I was ready to order a solid wood guitar kit from Martin Guitar. I am not a loud strummer, I am a fan of finger-picking folk rock like early Bob Dylan and Paul Simon and I want a guitar that will record well. For these reasons, I picked the Martin 000-28 model. It has a medium sized body, short scale and slightly wider neck than the more common dreadnought. I have two books on guitar making to help me: Guitarmaking: Tradition and Technology by by Jonathan Natelson and William Cumpiano and Build Your Own Acoustic Guitar: Complete Instructions and Full-Size Plans by Jonathan Kinkead. The Kinkead book came with plans for an Orchestra Model guitar which has the same body size as a 000 so I will be able to use part of those plans in the construction of the Martin. Blues Creek Guitars has dozens of exceptional instructional videos on YouTube featuring John Hall. I am a rank amateur luthier and if I have the patience, I will watch all of these videos as I build the guitar.
Friday, February 7, 2014
I ordered the Martin kit from Blues Creek Guitars. I can't say I wasn't excited when it came. I videoed the unboxing:
The parts all look great to me. There is some natural grain variation. The book matched back:
A close up of the tight grain and rosette on the top:
The fret board is Richlite. Should this bother me? Don't I want an ebony fret board? Look at this:
Smooth, hard, jet black. I'll use it.
Kinkead says make a mold. I contemplated mold design. Since the sides are already bent and profiled - thicker at the tail end, thinner at the neck end - I decided I didn't need a deep mold. Based on a Martin mold, I used three thicknesses of 3/4" plywood. I cut these from a 21" wide by 8' long scrap of plywood from the attic:
I traced the outline from the Kinkead OM plan:
I stacked three pieces and screwed them together:
I made radial cuts like the one shown above to allow me to move around with the big resaw blade on the big band saw. I went back and shaved as much wood off as I could without going over the line:
I repeated these steps with the other side. I cleaned up the saw cuts with a drum sander on the drill press. Here are the two halves with the plan underneath:
February 9. I gave myself a little room to mess up by scribing the center line slightly inside the mold as seen in this photo. The arrow points to the center line:
I trimmed the mold to the center line on all four faces where the two halves meet and clamped them together. Then I drew straight lines on the outside of the mold on the neck and tail ends and trimmed the outside of the mold so the edges were flush at the meeting faces:
I screwed a wood strap on the tail end and screwed an old hinge to the neck end. Here are the rosewood sides in the mold for a test fit:
February 10. I replaced the wood strap with a clasp to make the mold easier to open.
February 11. I trimmed the outside of the mold, sanded the top, back and sides. This will look nice on the wall:
This picture shows that the sides overlap in the center. I will have to trim them:
I lay the sides into the mold:
I marked a line on each end of each side to know how much to cut off:
I put a square against the straight top edge and drew a line all the way across. I have to square against the top edge since it is straight while the back edge is slightly curved:
I clamped the side to the work table under a straight piece of oak to serve as a fence and I cut the end with a fret saw:
I did the same with the other ends and fit the sides in the mold. Now they fit without overlapping:
The neck and tail blocks are both higher than the sides as seen in this picture:
Helpful Hints from Martin say the blocks should be flush with the top so I'll do that, but cut the blocks so they sit a little proud of the back edges, to be sanded flush with the lining later. Marking the tail block:
I cut the blocks on my big band saw:
I dry fitted the blocks in the mold with little Harbor Freight clamps. I put blue masking tape over the seams on the outside to prevent glue from squeezing out and to hold the sides together:
You can see the center marks I made on the blocks to help me line them up on the center of the mold. I spread glue on the blocks, set the clamps again making sure the blocks and sides were tight against the table. Then I opened the mold, flipped the rim over and clamped the blocks on the other side. The tail block:
The neck block:
I wiped the squeezed out glue off with a damp paper towel, let it dry over night:
Here is the kerfed lining or kerfing. Very flexible. Smells like fresh cut cedar:
I'll start with the top edge so if I make any big mistakes, I can fix them and any repairs won't show. I mounted the rim in the mold and stood it up so I could work without glue running down the sides. I played with one piece of kerfing, flexed it and it snapped in a couple of places. No big deal as far as the function of the kerfing. Just inconvenient. So I sprayed a second piece with a fine mist of water and massaged it to soften the kerfing. I was then able to bend it and clamp it for a test fit:
Gluing the kerfing. On the first try with the first strip, practically no glue squeezed out from the inner edge so I pulled it off and put more glue on. I would rather have too much glue than not enough. Perhaps by the last strip I will have figured it out:
I made a spreader to hold the sides in shape while I put on the kerfing:
I made it from a turnbuckle and some scraps of plywood:
First side done as seen from the other side and a better view of the spreader:
Working on the other side, this is what water does to the kerfing:
There should be enough glue, not too much, not too little:
All clamped up on both halves:
For each line of kerfing, I let the glue dry for about 30 minutes, removed the clothespins, then scraped the excess glue off with a little scraper before it got too hard
. Kerfing done:
What's that pipe flange doing in the center of the table?
I have to level the sides, the kerfing and the blocks. I will do whatever works. Whatever the method, planing, scraping, sanding, I have to secure the guitar body in place. I drilled the mold in two places, drilled identical holes in the table so I can use pins to hold the mold in place:
A close up of the tail block shows that it's a little high and it has ridges left by the band saw:
The plane quickly took care of the lines:
I built a go bar deck between February 13 and March 1. It first had oak sides and 3/4" plywood top and bottom. In the picture below, I am testing a home made go bar, ripped from a scrap piece of flooring
I made a dozen on the band saw to test clamp something big:
The force, according to the bathroom scale, can be anywhere from 8 to 25 pounds. Many luthiers say 8 to 10 pounds is good, using 3/16" diameter 2' long fiberglass rods. The top is bowed from the force of the go bars. I got some 3/8 threaded rod, nuts, bolts, washers:
I redrilled the top and bottom pieces with 3/8" holes and bolted it together:
I reinforced the top of the deck by screwing on another piece of 3/4" plywood.
That should do. I ordered 3/16" diameter fiberglass rods and vinyl caps from Goodwinds to make durable go bars that should deliver uniform force.
March 1. Leveling the rims continues.
While waiting for go bars, I continue with other tasks. The big MDF disk seen in pictures above becomes a flat sanding disk with a sheet of 60 grit sandpaper glued to it:
I'm ready to sand the back rim in the picture above. This set up makes sanding sure and easy. The heavy sanding disk rotates on the pipe assuring a flat plane. No dust flying either. To be sure I sand enough but not too much, I drew a chalk line on the rosewood edge:
The neck end:
After sanding, checking the chalk line. It's easy to see where I have sanded enough and not enough:
I finished the back rim, flipped the body over and repeated the exercise on the top rim. I had to be more careful on the top rim because the sides are cut so that the top slopes slightly towards the neck end. I pushed on the left side of the sanding disk so it would follow this slope. Here is the sanded top rim:
Both the top and back will be slightly arched so I am not done sanding the rims yet.
The spruce top and the rosewood back will each have a slight arch. The radius of the top arch should be 28' and the radius of the back arch should be 15'. The rims need to be sanded at a slight angle to match these curves. First I thought of making curved dishes with a router. After more exploring, I decided to make two sanding blocks. I made them by cutting curves into 2" wide pieces of 3/4" plywood. I determined the "sag" of the curve by using this online calculator. I drew the curves using the shape of a deflected metal ruler between nails:
I cut the curve on the band saw and used the first piece as a template to cut three more pieces with the same curve. Here are the two blocks assembled with 5 2" drywall screws. 80 grit sandpaper is being glued to the block in the back:
Finished sanding blocks:
March 5 and 6
Fiberglass rods and vinyl caps arrive. I lined them up and marked them at 20". This should be the correct length for clamping the top or back on.
In the garage, I cut through the rods easily with an angle cutter with a metal cutting disk. Back inside I washed them off and put vinyl caps on the ends:
30 go bars. I test three of them here:
The bathroom scale says about 10 pounds of force.
When the two back halves are held together in front of a light, it is clear that two edges are not perfectly straight:
I need a flat sanding surface. The MDF disk should do:
Sanding on this disk yields inconsistent results. So I tried the ultra flat band saw table as a sanding base. Still not consistent.
I set up a shooting board:
Better, but still not good enough. I need a well-honed plane iron, perhaps a longer plane. There is a slight arch in the edge that I can't flatten with this short plane.
I took the pieces to the shop teacher who generously offered the use of his joiner. This yielded the best results though even a power joiner did not give perfectly straight edges. Here are the back pieces after the joiner:
I will go with it. The back pieces will have an internal brace along the seam to give more strength to the joint. Move on.
I made a nail and baton press recommended by Kinkead. I nailed five nails on each side of the back pieces.
A 1/4" thick baton arches the back as seen in this dry fit:
I put a finger-smoothed bead of Titebond glue on each edge, then inserted the herringbone inlay. After glue up, I removed the baton and pressed the pieces down. I wiped off the squeezed out glue and clamped the pieces down with go bars on clamping boards to assure uniform pressure:
This was the first time I used the go bar deck. Very fast and easy :-D Here is a close up of the joint the next morning:
It looks and feels very tight and strong all along the seam.
After a very long break, I found the time and space to continue building the guitar.
July 6. During the building hiatus, I lost two back braces so I had to replace them some how. After too much pondering, I fashioned two back braces from African mahogany. I used my handy bench sander to give the brace a curved bottom. I used an existing back brace to trace the proper curve.
Here are the four back braces. The farthest and nearest are the homemade mahogany braces:
July 9. I glued on rim supports, cut from scrap pine or spruce (window casing):
I cut back strip brace into five pieces to fit between back braces:
Clamped with 5 go bars:
I made a long thin sanding block to sand the strip after the glue dried:
July 10-12. I scraped, routed, scraped again, to prepare for end trim:
Slot prepared, trim pieces on the left, scrap wood the right will serve as a gluing caul:
Glue and clamp:
All sources say to build at about 50% relative humidity. I live in South Jersey. 'Nuff said? I got a 50 pint dehumidifier before continuing with guitar assembly. I weighed the back, top, braces and rim every day after I turned on the dehumidifier and watched the weight decrease daily for a week. Then I continued.
July 19. X-braces glued in the morning:
The top sits on curved blocks cut with a 28' radius to match the curve of the top braces. Good squeeze out indicates good glue coverage.
Top plate and top bar in the afternoon:
July 20. Glue bridge plate and tone bars in the early morning:
I trimmed and roughly shaped the side bars, glued them on at 11 AM:
Back braces glued mid afternoon:
July 21. Glue sound hole braces using weights.
Gluing Top and Back
July 30. I sanded, chiseled, sanded again, chiseled again, both the top and the back braces until I could dry fit them with confidence. For each, I clamped them dry on the go bar deck to make sure the surfaces met correctly. Here is the top showing all the braces:
Glue the top:
After gluing the top, I had to add 6 pieces of kerfing, cheap insurance to keep the braces from popping up when the guitar is banged around. My mistake, cutting the X-braces and the top bar too short. This is my fix:
Glue the back:
Purfling and Binding
August 1. I used the laminate trimmer with edge guide to trim the top and back, generated lots of select tonewood dust
Close up of the first pass on the back:
Top and back, first pass:
After second and third passes with the trimmer:
The right tool to clean up the flush cuts, drum sander on the old drill press: