Archtop Jazz style Tenor

Hello everyone, I would like to post some progress pictures of the tenor Uke I'm working on. Its based on archtop guitar construction methods and will see some changes as it comes together. For now the specs are:
17'' scale
11.5 long body
9'' wide lower bout
6.75 '' wide upper bout
19 frets
machine tuners
pickup
Maple 3 ply neck
Doug Fir top
Walnut fingerboard, sides and back
Binding all around

I do my initial sketches in CorelDraw then export to the CNC for cutting.

Thanks for looking, Vince

Here's a pic of the 3 ply neck blank, the center strip is walnut. The neck block is a 2 piece stacked glue-up. Some fine tuning was needed with a file and scraper on the cheeks of the neck to get a snug fit. I will likely change to a sharp florentine style cutaway with the 2 side pieces joining at the pointy end. Because the tight bend of the one piece side I'm currently making, that side (lower) kept cracking while bending. -Vince

Looks great. I cant wait to see and hear the final product. I love archtops.

Thanks Booli, I can't wait to hear it too. Glad to get the bending mold covered in sheet steel, I happened to have a piece of 22ga in the garage. Next is to make a stand to raise it off the bench when bending sides. In the pic attached here is a full size mockup I made to get an idea of the final dimensions. Also on the short list of jigs to make is a male or female mold for assembling the body and lining up the neck. My thoughts is to make this on a single long board. I did cut a female mold board in MDF and what a time it gave the router, the board was scrap after that. I may cut the work board in walnut which routes nice little chips and not a lot of dust. Thanks for looking -Vince

After getting the bending form together I tried a couple of sides with the heat blanket. I had thinned the maple side down to about .075'' with a plane before placing it in the mold. I didn't have my thermometer on hand to check how hot the blanket was getting. I heat cycled it up to full hot 2 twice and left it clamped up overnight. When I removed it the next day there was a lot of springback, I touched it up on the hot pipe to get it closer to its final shape but I still wasn't happy with results. Also of note , this side was done dry with no pre-wetting. Next I tried a 3 layer laminate of Makore veneers I have here, each with an approx thickness is 1/42 of an inch. I stacked the three layers dry in the mold and bent them at the waist with the heat blanket, I followed the same routine of touching them up one by one on the hot pipe (very easy with 1/42 stock) I got the 3 layers uniform and applied titebond in between and placed them back in the mold., After being fully clamped over night the side popped out in great shape, no spring back and very firm for its thickness. My mold shape is made with some springback figured in, in the case of the glued up veneer side it kept the mold shape exactly, sort of over bent. I will try 4 layers on the next test with the outer most being a Maple Birdseye veneer. In the attached pic, the solid maple side is in the back and the 3 ply Makore is in the front. Any comments and tips are appreciated, Thanks Vince.

I've made slow progress since the last post. I went with the laminated sides and have them glued up to the neck and tail block. The rounded cutaway was too difficult to get right so I opted for the pointy style Florentine cutaway. I laid out the finger board along with the block inlays for the CNC. I left the extra waste material surrounding the board so it would be square when I ran it thought the fret slotting saw. The board tapers from 1.5'' to 1.375 at the nut. Its walnut and the final thickness should come in at .20'' inches. Also it will have .060'' white binding, this was figured into the dimensions when cutting the board. Thanks for looking, Vince

As for bending..... if you are bending with a form...... .055-.065 is probably a better bend for archtop ukulele sides. If you were going to do this again you can make the bending molds somewhat different.... attaching photo of guitar.... for ukulele I'd add one more center section..... but otherwise the same...... you will need two different bending molds if you plan on doing a cut-a-way..... one for the straight side the other for the cut-a-way..... and you will need some kind of ram to force the material into the curve of the cut-a-way..... would suggest veneer softner overnight before attempting this for a ukulele cut-a-way bend. (Although this might better be performed with a hand heat bender....but it can be done with a machine if one has a desire to do so.)



Think you will be better pleased with the feel of the neck/fret board if you go from say...... 1.98 to 1.375' - binding/wrap thickness.....

It appears that you have Aspire ....... it's possible to cut your top& back with this software if you have a desire to do so...... you will need to research and find out how to make the file for cutting/shaping ... but it can be done.... should take about 45-minutes to an hour for both top&top inside with the CNC. ( We use other software )

Sorry! no final pictures..... we gave this to one of our grandchildren.

Hope you enjoy and get more time to work on this.

Blessings,

Kevin

Hi Kevin, thank you for taking the time to post. You've been down this road and I appreciate your advice. I'm not using Aspire but another Vectric product called Cut3D. I'm working on a model of the carved top now, its a slow learning curve for me but I'm confident I'll get there. I went with the pointy Cutaway on this one and will re-visit the rounded cutaway down the road for sure. Best regards, Vince

Tonight I'm testing a neck jig I made over the weekend. It has a 15 degree ramp to work with the headstock angle. I used it to surface the top and back of the headstock down to .45 inch thickness. I milled the tuners holes by using the laser as a guide. I will cut the outline of the head shape on the bandsaw and use a sanding drum chucked in the drill press to get to the final shape. I hope to eventually cut the head shape on the CNC including the binding channel. The third picture is checking how the fingerboard lines up with the neck. The inlays are white swirly acrylic cut from a 1'' x 5'' block sold by pen-turning suppliers.That stuff sure stinks awful when you cut it. There will be no radius on the fingerboard and there will be a bone nut. The extra wood I left around the fingerboard will serve as extra surface when I flat sand it, so to prevent me from rolling off one side and ruining the board. Thanks for looking, Vince

Not shown in the third pic is the 3 boards that went to the scrap pile. It took that long to figure why my inlay pockets were off center. When changing from a 1/4" to a 1/8" mill I ever so slightly moved the router on its sliding gantry. So when beginning the finish pass it was slightly off. The solution was to leave the power turned on that feeds the stepper drive motors, this keeps them locked so the router won't move.

Amazing work, but too high tech for me!

Bob

Vince,

You will find all kinds of ways to do necks..... probably best to do peghead reverse of what you show and make it 90 degrees to bit. If you do it this way you can shape and cut it out and drill peg holes with cnc. Attaching some photo's of fixtures we have used..... the most elaborate one is by Chris Klumper of LuthierTools..... a close friend. The first fixture is to be used with a shaper or router.

Hope this gives you some more idea's, part of the fun for me is figuring out how to conquer the problems......

Blessings,

Kevin

Thanks Bob, I'm still learning while I use this machine. But I gotta admit its a lot of fun!.

Kevin, your suggestion is right on target, I intend to flip the neck for machining with a spoil board underneath. The jig you posted looks very well thought out. I also enjoy the challenge of figuring out ways to machine and hold down parts on the table. It's good exercise for this old noodle of mine.
Below are 2 pics of adding kerf lining to the sides. Thanks for looking .Vince

Thanks for sharing, Vince!

My Pleasure BigMamaJ40. Here' tonight's work on the top. I cut a test piece on the CNC to see where I'm at with my contours. My previous method would be to use a Wagner Safety Planer which scared the heck out of me at times. The top blank is .625'' (5/8'') thick overall. The first pic is my drawing of the contour layers which is imported into the CAM (computer Aided Machining) Program, 2nd pic is the CAM software rendering before anything is actually cut, pics 3 and 4 are the test piece which took 23 minutes to route. Thanks, Vince

I am very intrigued by cnc machining. I'm thinking of making some parts for resos in one if I can get it to work. For an arch top I would probably hack away with chisels and planes but that looks like great fun too.

JustVince said:

My Pleasure BigMamaJ40. Here' tonight's work on the top. I cut a test piece on the CNC to see where I'm at with my contours. My previous method would be to use a Wagner Safety Planer which scared the heck out of me at times. The top blank is .625'' (5/8'') thick overall. The first pic is my drawing of the contour layers which is imported into the CAM (computer Aided Machining) Program, 2nd pic is the CAM software rendering before anything is actually cut, pics 3 and 4 are the test piece which took 23 minutes to route. Thanks, Vince

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Thanks for sharing. Those pics look interesting. Can you tell the CAM software to render a 'negative' cut (180 degree flip, and then mirrored image), and reverse the wood (flip it over), insert it into the CNC and recess the wood down with the same gradations?

Thus you would get a rough arched top with symmetrical gradations on both sides....

How will you smooth out the gradations to a nice fluid slope? By sanding it?

I need a 3D PRINTER, a 3D-Scanner, Laser or Plasma Cutter, and a CNC machine !!! But I have no space for them now, nor funds for such a setup.

Alas, oh but to DREAM!

Sven said:

I am very intrigued by cnc machining. I'm thinking of making some parts for resos in one if I can get it to work. For an arch top I would probably hack away with chisels and planes but that looks like great fun too.

Click to expand...

I encourage you to consider building your own CNC machine, I did. The shapes you're making in your blog for the reso's would be ideal to machine. -Vince

Hey Booli, What you describe is basically true for carving the underside of a archtop. All the design elements like 'mirror, flip and rendering a negative from a male shape' are included in most CAD programs like the free SketchUp program, the trick is figuring out the sequence of those steps to get what you want in the end result. For me its trial and error but I enjoy the challenge. I was doing basic generic shapes only a year ago and can now create more complex surfaces. Google SketchUp, the free 3D Software is easy to learn and has great features for anyone looking to learn to model in 3D. The next step for this top will be to knock down the stair graduations with a sharp chisel and a finger plane, then sand and scrape. Then back onto the CNC to cut the 'f' holes. Thanks , Vince

Here's the result of tonight's work in the shop. It took about an hour total because I took breaks to let my fingers get back their feeling . I knocked down the stair edges with a chisel first, then used a finger plane to slowly work the shape using the bench light to better show the curves. Running my hand over the top also reveals any high spots that needed attention. Thanks for looking. -Vince

Early before worship and had a little time to play....

I'd suggest that you try using curves rather than graduations..... you will get a better top/back.......most of the 3D modeling packages that I'm aware of allow you to draw surfaces along curve lines and blend/merge/loft curves. When we are doing a new model we always first do a wire frame ( we almost always draw a 2D drawing one top view, and one side view ) and basically use cross sections through what we are doing to form our initial tops.... the more wire frames the more molded your top can be.

You will need to add re-curve to the outer edge of your existing top.

Attaching some photo's showing what I'm talking about. By the way brought a model into Aspire with no problem...... (We personally don't use Aspire for this kind of work ... we do have it.... it will work. It maybe that the software that you have want do 3D following but only level cutting... Sorry, don't remember... if this be the case you could use a third party programs to slice the model much like the 3D printer works and you would still get a more accurate top/back with much less hand work.... just some thoughts.....)

Blessings,

Kevin