Making an Archtop Ukulele- Take Two

Loar had Gibson switch to the F holes in the early twenties. Orville Gibson’s instruments had oval or round sound holes. The early A model mandolins from the late teens through the early twenties were killer instruments. I have worked on and played a lot of them. The big issue with them was the single transverse brace just below the sound hole was not enough to keep the top from collapsing under the string tension.
Brad
 
The standard procedure with f holes is to cut them smaller than needed, and gradually enlarge them when doing the final tuning of the body. That is more difficult to do with round or oval sound holes and maintain symmetry. In this case, I made the oval purposely small and added a side sound port that was gradually enlarged during the final tuning of the body.
Brad
 
This is interesting, Brad. With the falcate braces, how did you get them to conform to the curve of the top? I'm having trouble figuring it out by looking at your image. Were the braces pre-curved before gluing?
 
Each braces consists of three pieces of spruce, 3/4” x 9” x .080” thick. These pieces are bent to shape on the hot pipe and laminated together. The bottom contour that fits against the top is done by; shaving down the first couple of inches of both ends of the braces to get a very rough fit against the top. You use the washer- short piece of pencil trick to draw the bottom contour of the brace. The brace is held in position, the pencil inserted into the hole of the washer, holding the pencil/washer against the side of brace, roll the washer along the length of the brace and marking the contour with the pencil. A washer with a diameter of 3/4”-1” with a small center hole is ideal for this. The bottom of the brace is cut or sanded to shape. I then draw in the position of each brace on the top and cover the drawing with short pieces of self stick sandpaper. The brace is then rub fitted to the top, with the final fitting done using a chalk and scraper. Fitting braces to an archtop is tedious work, but must be done accurately for best results.
Brad
 
Ken Parker related that the original workers at Gibson were European craftsman who could easily fit the braces to the L-5s, although it was time consuming. To cut costs during the depression, they went to kerfed braces, that were forced and clamped to fit, and then capped with a thin strip of wood on top. This did not work well, and the quality of the instruments went down.
Brad
 
Archtop instruments need a binding jig to cut the binding channels, unless you are going to cut them by hand. The pics show my setup. The router tower is from LMI, and the sled I made. If you wish to do a sunburst and are going to apply the stain directly to the wood, take a wet cloth and dampen the entire outside of the instrument with water. When dry, sand smooth. As I am pleased enough with the results so far, but the instrument is likely going to be a prototype, I am doing some decorative work. But I am not striving for perfection, it will have a certain wabi sabi so to speak.

https://photos.app.goo.gl/tWxGj6k6efDsDFsM8

Brad
 
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Very nice looking instrument!
 
Gorgeous, Brad.

But I know I don't need another ukulele.

How much for the prototype?

-Kurt​

(Not that I afford it, anyway...)
 
Not that I am looking to take on another project right now, but how would such an instrument respond if the back wasn't carved, but just built on a 15 foot curved building form, and with the top carved. Would one notice any difference in tone?
 
Not that I am looking to take on another project right now, but how would such an instrument respond if the back wasn't carved, but just built on a 15 foot curved building form, and with the top carved. Would one notice any difference in tone?

You can build a 15 foot arch which is active or non-active. They both sound different (when not pressed up to the body.
 
To answer the questions;
The prototype will not be for sale, at least not soon. I need to build some more archtops to make sure I can repeat if not improve upon it. There are a number of things that can be done to tweak the instruments after they are finished. Modifying the bridge and tailpiece can yield surprising results. However If this works out, the price will be in the $2K range.

As far as putting an arched flat back on a carved top instrument, it depends on what you are trying to do. If your goal
is to replicate some of the great archtop instruments, not a good idea. Martin did it years ago trying to get some of the archtop market from Gibson. That did not work out well. I also tried it on my first archtop guitar, with results similar to Martin. That said, many of the modern archtop makers are searching for a sound much different from the classic ones. To that end, they are adding flat backs, carving the bass side in a different profile than the treble side and playing with different sound hole style and placement. There is a lot of potential to be discovered in my opinion.
Brad
 
I need to build some more archtops to make sure I can repeat if not improve upon it. There are a number of things that can be done to tweak the instruments after they are finished.

Hi Brad, it's looking good!

I am interested in hearing details of the top and back but having read your comments above, it looks like I should wait until you are certain your design is successful and can be reliably repeated. When I made my archtop, I had never seen one and had no real idea of how much of an arch was required, how thick it should be and whether top and back should be the same profile..etc. Hopefully after making a few more instruments, you will be able to answer all my questions and then I will have another attempt at an archtop.
 
Brad, I spent some time watching some of your earlier YT videos from 10 years or so ago where you led a fun archtop build on UU that featured an archtop uke that was sort of trapezoidal, with slightly curved sides that didn't require bending. Do you recall if that particular archtop uke had any features you'd change, or would that be suitable still for a first archtop uke project?
 
Thanks to those that have taken the time to go back over my original thread on building archtop ukuleles. The particular ukulele in question was part of a set I made for gallery in Cannon Beach that consisted of the ukulele and a Native American style flute, both decorated in a NW coast Indian art style. The shape of the ukulele was picked to resemble a coast Indian bentwood box. I think that a pineapple or boat paddle shape would actually be a better shape for an archtop. Those shapes lend themselves to carving a continuous recurve area around the perimeter, it is difficult to do with sharp corners.

I appreciate all those that are patiently following along as I plod around. It is my hope that in the end I will be able to supply some concrete information on nylon string archtop construction. And in doing so, motivate some others to contribute to the knowledge base with their efforts..
Brad
 
Brad, thanks for sharing this with us. An archtop build is in my future but I have to get orders finished first. I really like the idea of the pineapple shape to start with so that's probably where I'll go.
th
 
Brad,

MS 20 Series Top CNC Cut Layout.jpg2021-05-26_19-27-50.jpgMS 20 Series Mando.jpgHave you looked at the Martin Series 20 Mandolin? Always liked the looks and went to the trouble of drawing the instrument but never built it. ( We were able to Laser scan an Early 1920' F-5 Loar and used many of the contours from this scan as a guide for this design... and yes, we did build a number of F-5's along with several arched top ukulele's )

What you have done looks great.
 
Thanks very much for that information Kevin. I do not have any real experience with Martin mandolins, but I will look at the 15 and 20 series to see what I can learn.
Brad
 
After I strung it up unfinished, it was apparent that it sounded very nice as is, and did not need extensive modifications and thus could use some beautification. So I have been working towards that end, here’s what I have so far.

https://photos.app.goo.gl/apwnyRf6K9x18h1DA

I will be adding the fretboard markers next.
Brad
 
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