Koa\Bearclaw Sitka Spruce 00 Steel String Guitar blog:
Apr 05 2020
While locked up in social distancing I have been working on a commision. This will be a Martin (xbrace) style 00, 12 fret short scale guitar. It has been awhile since I have built an X-braced guitar but for the playing style and what this client is looking giving him a Martin sounding guitar is the right choice. Going back and forth a bit I assembled a kit from which to build.
With some really figured and flamed Hawaiian Koa. I felt really guilty about the Koa as it was an auction item in the Seattle Lutherie Group auction that went way below cost.
Unfortunately the sides were a bit too wild and their was a flaw in a dark figure line on a side that seperated when bending. Amazingly not on the venetian cutaway side but in the wide curve on the non cutaway side.
I did have a lot of Koa so I grabbed another set of sides that were a good color match. Still figured but not as much flame. Same back as the previous picture just different lighting.
So the second set of sides I thinned to just under .080" and I scraped the inside of the cut away to .070" from just past the waist through the cutaway bends to the end.
I sprayed them both with supersoft II, wrapped them and let them set under some weight (a big piece of ebony) overnight.
No problem with these bends in my fox style bender. While bending the cutaway I heat the bottom side of the cutaway area with a heat gun. I really took my time screwing in that last tight bend. I also used my stainless spring steel slats as my soft steel ones seem to ebonise koa. I learned that on my set of broken sides. It can be sanded out but I could also avoid it using stainless. I really need to take care removing the cutaway side as the spring steel can blow it up. (happened to a friend of mine once).
To get the heel block just right I put poster board under the guitar sides in the mold (not shown) and I traced out the pattern for the heel block. I glued that to chunk of mahogany and cut it out on the bandsaw.
I used to try and glue in the heel block in one go. Now I glue first to the non cutaway side and then glue the cutaway side to the block. To assure alignment I set a couple of clamps while the sides are in the mold to hold it in position. I then remove the clamped block and side from the mold to make sure I can really clamp it.
I also glued on the tail block, a cut and slight shaped piece of mahogany.
I radiused the back to 15' and the lower bout of the top to 30'. First the back. My side templates are really close to the correct shape for both sides. They are close enough that I cut the sides pretty close, leaving just enough extra to safely put the radius on the heel block without making the guitar too thin.
You can see in the first picture before doing any sanding the rims fit tightly on the radius dish
I do a combination of sanding and planing. I mark the top of the rims and the blocks with pencil. I sand for a bit, turn the sides over and plane where the pencil mark was sanded off. I repeat this unto the heel block is completely sanded\ planed to the correct radius.
When the back was radiused I turned it over and put tape on the blocks. The tape is to stop me from sanding the back on the top's radius dish. This was a procedure I had to learn multiple times.
I leave the dish back side down in the 15' radius dish and radius the top firstI radius the lower bout to just past the middle of the waist with a 30' and then use a flat disk to clean up the upper bout.
I went ahead and installed some kerfed linings on the back side. Pretty straight forward. I do remove a bit from each of the kerfed blocks around the cutaway so that they do not run into each other on the tight bends.
I took it back to the 15' dish and cleaned the kerfed linings up. I will do the top linings after I have a top and I can make sure the rims are profiled for the correct neck angle.
On to the top and back tomorrow.
Apr 15 2020
Moving on ... I leveled the back kerfed linings in the 15' radius dish and spent a bit of time getting the tops profile correct with a combination of a 32' radius dish and a flat dish. I use the radius dish mostly on the lower bout and the flat dish mostly on the upper bout. I want the body to have close to the correct neck angle before gluing on the linings. Not shown ... I clamp on the unbraced top and use a straight edge laid on the fret board extension area and projecting over the saddle position. I want to see 2-3 mm of height over the top at the saddle location at this point. That way I know I am close. I will fine tune the top rim profile before closing the box.
I started to glue on the kerfed linings
While waiting on the linings I cut a scarf joint, cleaned the faces with a plane and glued the headstock to the neck.
While the neck glue was curing I install a bunch of side supports into the rims
I cleaned up the neck joint and neck face with a plane, laid out the nut and the 12 fret and made a stacked heel out of the remaining neck wood. It was really close, I almost had to use another block of Mahogany for the heel, but I did not have any that was as light as this piece.
Before I forgot I end stalled my slight more fancy end graph treatment. The center strip is ebony with a black and peach wood purfling. I used a scraper as a straight edge and a scalpel and chisel to cut and clear the channels
Now I am ready to start the braces
Apr 23 2020
To brace the top I made a bunch of 5/16" brace stock. I wanted it all to start at 5/8" tall so I pulled out my new band saw guide and ripped a 1 mm strip off the brace wood. I cleaned up the brace wood in my belt sander until it was just 5/8" tall.
I stacked some guides to get my 5/16" width and ripped the board.
I cut the x brace legs to size and marked out a 30' radius on the bottom
Planed them close and (not shown) finish sanded the bottom on my radius stick.
I transferred the angle of the X from my plans to the braces and made the first cut with a razor saw. I use the saw like a mirror to make sure I am straight up and down. I set the brace in the vise so that cutting down to the vise is the correct depth. I cut both braces at the same time. one is cut bottom side up the other topside up.
Using the first cut and a bit of brace stock as a guide I mark out the second cut with a scalpel, cut to depth with the razor saw and clear with a chisel.
I must have cut the angle close!
I cleaned up the radius of the X brace on my radius dish.
Marked out the brace pattern on the top using my template.
I glued it down in the radius dish in my go bar deck.
I did a rough scalloping of the x braces. I place peaks 3" from the edges I start the scallop right at the bridge patch.
I double and triple check that the bridge patch is correctly located.
Using a template I cut out a bridge patch out of some sort of rosewood. I think Panama Rosewood. I make double and triple check that the bridge patch is correctly located.
The cats were even there to check
Sure that it was correctly located I glued it to the top. I could have used a caul, but I have a lot of go bar sticks.
Using a bandsaw I preshaped the rest of the braces. Probably the last time. I find them just as easy to carve once glued to the top, like I did with the X brace.
I radiused the braces and glued them top the top on a radius dish.
I only radius the ends of the transverse brace leaving 4 inch in the center flat. This helps keep the top flat under the fretboard and avoids over arching the top. I have a special caul with the opposite shape when I glue it to the top.
The arch of the top is perfect. The drill bit at the saddle location is 2.5 mm the exact height I was looking for with the straight edge flat on the neck extension area.
A bit more rough carving and gluing on the popsicle brace gives me a top ready to mate with the rims.