Geoff St. Germaine

Today I got the endpin jack hole drilled and the back glued on and sanded flush to the sides. Here's the back and sides with all of my homemade spool clamps. I got the back glued on. The spool clamps needed very little pressure to get a nice tight fit. Here's the back and sides, now as one piece. The inside of the body. Here's the endpin jack. I had to bore a 3/4" hole about 1/2" deep into the tailblock in order to get the endpin jack to sit at the correct depth. The other concentric hole connecting to the outside is 15/32", which matches the LR Baggs or Fishman endpin jacks (I have some of each). I'll have to get the inside of the body and backside of the top sealed before I glue that up. That probably won't be for a few days.

This evening I got the braces cut out and the f hole binding finished up. I cut the braces from quartersawn red cedar. The blanks were 5/16" x 7/8" x 22". I marked out where they needed to be placed as parallel braces from the Benedetto book and then transferred the top plate's curve to each of the brace blanks. To transfer it over I could have used a compass, but a piece of scrap dowel and scrap wood that got the pencil lead up to the bottom of the brace in the deepest part of the carve worked just fine. I traced the curve on and then cut them out with the band saw before cleaning them up with my spindle sander. Tracing the curve onto the braces: After that it was the tedious job of fitting the braces. The braces need to sit perfectly flush with the top plate so that the top plate is not pulled into a different shape when glued to the brace. The brace is much stiffer that the top so a misshaped brace would deform the top plate. Apparently instruments in the cello family are intentionally built with braces with more curvature than the top to tension the top, but over time this tension drops with a noticeable change in the voice of the instrument requiring the bass bar to occassionally be replaced. Since we don't want to open up the guitar when the tone changes, having the brace exactly match the top curve is essential. Since the fit was so tight clamps were only necessary to get glue squeeze out and with the top plate being quite delicate, little pressure was used. Once the glue was dried, the braces were planed and trimmed. The height of the brace at either end by the end of the planing is 3/16" and the height in the middle is 1/2". The top plate is very noticeably stiffer along the longitudinal axis. Here's how the completed braces look. You can see that 5/16" difference in height between the ends and center of the braces is still more than made up by the curvature of the top such that the braces have a concave profile. Here's how the inside of the top and back now look with the sides: I've heard it said before, but it's a shame that most of the inside work will be completely invisible. While completely done for utility, I think the inside of the box has a very attractive "organic engineering" look to it. Oh well, the point at the end is to make nice music. Next up will be getting the top and back plates glued to the sides. I'll be sealing the inside with a couple of coats of sealer to prevent or at least very greatly slow any moisture absorption by the inside of the body. After that it may be on to the neck, or I may build up the other two bodies. I'm not totally sure. The only thing new about the necks are the fretboard extension and dovetail joints... all of the other work I've done before. I guess we'll see what mood I'm in when I get the body finished up with binding.

I really like the maple/purpleheart necks. Looks like some good quality work happening there!

I got to my favorite part of the build - neck carving. With all of my other builds, basses included, I've always gone for a shallow C profile. With this one, I'm trying about a modified V profile, as per the Martin D-18CW. I have to say that after getting it done, it is a very comfortable profile. Despite all the meat in the center of the neck, the V with the thinner neck at the sides feels like it should be quite fast. I had neck profiles to work from, so I made the profile correct at the three locations I had diagrams for and then simply connected the spots and blended the heel into it. I matched things up with my contour gauge. I started with the profile at the 1st fret. I carved the three locations with a rasp. Next up was the heel. There's a lot to remove here. This was mostly done with a straight gouge and a chisel to knock off some of the bigger spots. Once that was done I sanded it with 120 and it should be ready for gluing. I later found two spots near the heel that are slightly raised, so I'll have to touch those up. You can see them highlighted with pencil. I had to hold it into the pocket so see how it would look with the body.

Yeah, that might be the issue. The heat and moisture would surely speed up any chemical reaction that might otherwise take weeks or months to show up. The objective with the sanding stick was to drop the neckblock, tailblock, linings and braces to the sides while keeping them planar to the top surface. The sides were already at the correct height. The rim is very stiff and the sides were locked into the body mould with about 1/2" sticking up above the mould, so any flex should be negligible.

I think as a personal space instrument the idea works. I've been toying around with building something to travel with. I deploy on navy ships as an aviator and space is limited. I've been thinking of either a small acoustic or a bass with a built in headphone amp. I think in the end the headphone amp idea is going to win that one. Here's the progress I've made. I got the sides braces and linings installed. It's a bit of a tedious job. I cut the linings too thick. Benedetto's book suggested 3/32" thick spruce. Well I read 3/16" and as I was using cedar I bumped it to 1/4". In the end it won't be a big deal. It saves me having to add bits of kerfed mahogany to the braces. I'll just carve them a bit in the center to remove a bit of material. I used mahogany reverse kerfing. The claim is that reverse kerfing makes for stiffer sides. I'm not sure if that's true or not. For other two I'll be building I'm going to use regular spruce kerfing. I laid out the braces roughly as per Benedetto's book. I used about 4" spacing around the lower bout and 6" spacing around the waist. The upper bout was again 4" spacing and the cutaway has no bracing as it is so much stiffer anyway. Here's getting the linings and braces installed: The final bit around the cutaway... a bit of a pain to install. I used a flat piece of scrap plywood with a piece of an old sanding belt glued on (80 grit) to level the linings and braces to the sides. It worked like a charm. Here it is levelled. All that is left is to carve the braces a little. I've always thought that a bent body rim with installed braces and linings looks fantastic. This is the first one I've done and it looks even better in person. I also used to think that it took a master builder to get a body rim like that... apparently not. An interesting thing that I'd read about was colour changes in the sides due to the bending. Apparently this is caused by having the wood against the heated metal in a humid environment. I'd read of koa turning green and apparently walnut does the same. It's a little hard to tell, but there's a green-grey hue to the sides. I spot testing sanding it and it appears to be a very thin layer of wood on the surface that has changed colour. I'll try to avoid that next time and from what I've read, wrapping the sides in craft paper while bending will prevent at least most of the colour change. Next it will be getting the f holes finished up and the top braces installed. I expect both of those jobs to be fairly tedious.

I can see the bracing and tuning of a flat top acoustic being more difficult on a one off or limited production of instruments. All flat top acoustic basses I've played have suffered from the same low volume and lack of bass compared to what you would want or expect it to have compared to an acoustic guitar. I think the archtop may be more forgiving as you can adjust the response of the body via the recurve after string the instrument but before finishing if you wanted. I imagine a large part of the difference is going to come down to body size. Look at the size of a double bass... unfortunately that would make it too large to play they way we play bass, so perhaps the loss of volume and bass is the compromise we accept from an acoustic type bass. I spent a great deal of time making sure the bending machine would work properly. Bending the sides is the task that I am most uncomfortable with, especially when I'll be working with the master grade flamed maple I have for the next two. I won't say I can't afford to screw those up, but I really don't want to have to replace any of the sides as they are quite expensive.

Looks great! Any reason you went with the lip extending into the two horns that connects to the neck joint? Looks cool.

Next up was fitting the neckblock and tailblock. I made both from vertical grain cedar. Vertical grain spruce is recommended by Benedetto, but cedar made sense as it is what the top is made of and I had plenty on hand without dipping into the spruce I have for the other two I'll be building after this guitar. The dimensions of the neck block were as discussed in Benedetto's book. I really love that man's guitars and his book is excellent. It's a great resource, especially for the work on the body. Here are the sides with the tailblock and neckblock clamped in and drying. That catches things up to where they are now, so I imagine it will be a little more slower going on the updates.

So I moved on to the sides so I could get them in the mould and get some concurrent activity going between the top and the sides. I planed the walnut down to about 0.120", which was as thin as I could get them with my planer. I then set up my oscillating spindle sander to thickness sand them further. After doing a fair amount of reading, it seemed that 0.090-0.100" seems common, so I took them down to, as best I could measure, 0.095". I further thinned the cutaway section of the side to about 0.088". Then I went ahead with bending them. My process was soaking the sides in hot water for about 1/2 hour before attempting to bend them. I had read about using a thermometer or also that water sprayed on the forms to just start to sizzle and pop when they're hot enough. I went with the qualitative measurement and went about bending. Here's the machine, heated up and ready to go. I clamped the waist into the mould first, as this seems to be a pretty common procedure and logically made the most sense. It only took about a minute to get it clamped all the way to the mould. I listened closely for any cracking, but I didn't hear any. Next I clamped down the tail end before moving on to the neck end. Overall things went very well. There's not a lot of tight curving as this is a 17" body. I hoped this would be easy, as the cutaway would undoubtedly be more challenging. Fortunately it was. I got the non cutaway side clamped into the mould. It was time to do the cutaway... a more daunting task. Machine heated up: Side clamped in: Overall the cutaway took more time and I was very patient pressing it in place. I used my hands to get it to start conforming to the mould before I used the cutaway shaped caul to pull it in tight to the machine. For both sides I let them cool after the initial bending before heating them back up and cooking them for about 10 minutes. I had read that this helps "set" the bend. Whether this works or not, I had very little spring back and the sides went into the body mould easily.

I think polished aluminum with the carbon top would look fantastic! Great looking build!

Thanks Anthony! Fortunately, I have healthy kidneys.

Today we got all of the frets installed. We used the fret nipper to trim the fret tang from the ends of the frets and the thing worked extremely well. The neck pocket is complete. Next up is carving the neck and then it will be time to glue it in.

Next it was on to the inside carving. I used a 5/8" forstner bit with the point ground off to rough out the inside. I had done it like this before on a carved maple top for an electric hollowbody with very good results, so it seemed like a timesaver in this application. I set the drill to leave 5/16" all around to allow for carving the back down to a uniform 1/4" and the top to a graduation from about 7/32" to 5/32". Once this was done it was cleaned up, mostly with an Ibex palm plane that had a convex sole. I used my home made caliper to measure the top, made from the plan in Benedetto's book. Here's the walnut back starting to be roughed out with the forstner bit. The inside of the top. You can make out where the lamination went on with the ring around the rim. By the end of sanding this was quite a narrow line, extending only very slightly beyond the flat gluing surface around the rim. The completed back, clamping to the carving cradle. Since I'd punched through the top very near the rim the traditional f holes I was planning wouldn't work. Off to google images and I found a nice solution from Bill Moll's work that looks somewhat traditional but had the holes near enough to the edge to encompass the error. Here they are cut out and roughly cleaned up. Now all that is left for the plates is to clean up the f holes, bind them and install the parallel braces. I've starting bending the sides, and I'll try to get that updated soon.

Hey guys, thanks! Prostheta, yeah, it seems like lots of guys are doing archtop builds here right now. It is great. I'm a bass player, so I'm watching your thread closely. Here's where things went with the carving. I drilled a number of holes to establish the depth of carving for the top and back. Unfortunately, my drill press depth stop gave out and I punched through the top near the end of the drilling. On top of that, the depth stop had been slowly allowing some slippage before it broke completely. The result was that when the top was carved it was too thin at the edges. This required adding some material to the edges. Fortunately I had enough of the quartersawn red cedar left to fix it, but still it's far from ideal. Here are some photos of how things went. The top and back drilled: My carving cradle. The back is a mirror of the front. Carving away. A lot of work and a lot of shavings. Seriously, between the inner and outer carves of the two plates I filled an entire garbage can. Curled shavings take up a lot of space. The top is getting close here. I used a combination of chisels, gouges, a palm plane and a spoke shave to get this done. You can see around the rim on the last picture that the entire way around the drill starting going too deep. A poor craftsman blames his tools, but it is what it is. I blended it down and had to add 1/8" of material to the back as I was down to 1/8" on the sides, which is too thin, especially for cedar rather than spruce. Based on some reading I'd done on cedar vs spruce soundboard wrt stiffness, the red cedar top is 25% thicker than recommended in Benedetto's book, which is based on a spruce soundboard.

As following with Benedetto's book, I need some moulds and jigs and fixtures to get this done. Bending wood is completely new to me, so I've been doing a lot of reading. It seems that a side bending machine type of setup gets consistent and easy results. The downside to this compared to bending over an iron seems to be mostly the difficulty in setting up for many different shapes. As I haven't planned out making a bunch of different body shapes, I think the bending machine type setup will work well and will probably give me better results in less time. I built up a set of side moulds using 3 layers of 3/4" MDF. I sealed the inside with polyurethane. I made a template of the body, which was mostly to use to set up other jigs and fixtures, such as the body mould, the inside mould for the bending machine and some inside mould turnbuckle clamps. The bending machine I've built is based around some designs I've found on the internet. It uses three 200 W bulbs wired through a 600W dimmer switch. The body inside moulds are built to be set on top of the base so that the base can be reused and if I did decide to make some different body shapes then it just needs a different set of moulds. The other option to me was to use silicon heating blankets. I still may invest in them, but at $200+ for a setup, I figure I'll try this manner first, which seems to have worked for a number of people. Here's what I came up with, shown with the non-cutaway side mould. The mould is 3/4" MDF sides with zinc plated flashing mounted on it. The idea as this is a sandwich of the body side wood and another layer of flashing to support the backside of the side during the bend, which is supposed to reduce the chance of cracking or a faceted look to the bend. The eyelet bolts on the base of the bender take turnbuckles that connect to 3 clamps, a curved one matching the waist and two flat ones for the tail and neck ends. I'll try to update some more later today. Thanks for looking!

I've started a prototype archtop guitar build. There's nothing revolutionary about it, it's simply a prototype because I've never built an archtop guitar before and there are a number of new skills that I'll need to develop. Therefore, I'll be developing them on a prototype and then moving on to more expensive woods. If anyone's looked into purchasing the traditional type of "tonewood" for an archtop guitar, then you'll see that it is at a considerable premium for price. The aim with this guitar is to use suitable but inexpensive woods so that if something unfortunate were to happen then the cost of redoing something like a top or side would be low. I selected red cedar for the soundboard. Spruce is the most commonly used wood for archtop guitars, but in searching through the woodpiles at my local hardwoods shop, I was only able to find good quality quartersawn red cedar. I also looked at their sitka spruce and douglas fir, but I couldn't find anything decently quartersawn or without a lot of grain runout. The total cost for the board was about $15, far better than the $100-$300 I've seen for AA through master grade sitka spruce from specialty tonewood suppliers. For the back and sides it was a bit of a toss up. The guitars I'll make after will be flamed maple, so plain maple would be one obvious choice, but I find it too boring. Walnut seemed to be a more aesthetically pleasing choice and I was able to get the wood for the back, sides and neck for about $40. With that material collected I've started on this adventure. I'm following Benedetto's book pretty much exactly. Here are the specs for the guitar: 17" x 3" cutaway body Red cedar top Black walnut back, sides and neck Ebony fretboard 25" scale 22 frets White MOP block inlays Ebony headstock overlay White binding Ebony bridge, tailpiece, pickguard Kent Armstrong suspended pickup Chrome Gotoh open back tuners

I got this one finished. It'll be going to it's owner in a couple of weeks. I'm quite happy with how it turned out. The main area for improvement for this is finishing. It turned out well in the end, but it was a lot more work than it should have been.

Great work! Very inspiring!

I'll be following this one as well. I'm just starting 3 archtop builds and I've been following your archtop build as well. I'm sure this one will be every bit as good. Thanks for sharing!

Gorgeous!

The booze (and cigar) was post carving relaxing. The colour is going to be a burst. I'm not entirely sure what colour, maybe a yellow-amber or yellow-orange/brown. My other six string bass is turning out well, so the burst will probably be along these lines without the colour going all the way out to black.

Thanks a lot Bob!

I've been away for most of the past 2 and a half months. The only progress I've made is some work on the neck pocket. The only thing left on it is to get it all the way down to the right depth. After that I'll fret and carve the neck and then glue it in.

Today we started binding the headstock and getting the neck ready to glue on the fretboard. Unfortunately on the LMI order we'd thought there were 5 pieces of white binding in the order, but what came on the shipping invoice was only one, so we're stuck here until the next order comes in with the rest of the binding and parts for 2 other guitars.