Beginnings of an ArchTop Uke

Kevin Waldron

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Someone mentioned and Arch Top Ukulele and little interest appeared.

We thought about it and then we decided that we would tackle it anyway. So for several weeks now we have been designing an instrument. We have finished all the drawings, and will this weekend attempt to cut the molds/plates.

I'm including several of the drawings for those interested. It is a tenor size, neck angle is 3.5 degree negative angle, bridge height will be right at 5/8" from top with neck angle. Top Plate is .71" rise from the ends and it does have re-curve in the top and back plates. Top/back thickness is approximate .15" preliminary. We will know more after we get the plates cut. We are also working on a cut-a-way but it is not as simple as simply slicing the outside perimeter and adding the curve if you want the re-curve and thickness to continue all around the edges.

Blessings,

Kevin
 

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Hi Kevin, I have made nine arch top ukuleles so far and before that had over one hundred carved top mandolins and guitars under my belt. I have plans available to anyone who wants them and can send them to you if you send me an email. If you want to do this right, I highly suggest you get ahold of and study Roger Siminoff's book on building a bluegrass mandolin and Bob Benedetto's book on building an arch top guitar. The tops and backs of arch top instruments are graduated in thickness just like violins. The thinnest area is the recurve and the thickest is in the center. Also, this graduation from thick to thin is not linear, it stays thicker in the middle of the top and back and then thins rapidly as you near the recurve area. My tenor sized ukuleles are .078" thick in the recurve area and .140" in the center. Nylon strings do not offer much tension or down pressure, so things must be carved delicately. The depth of the sides is another critical measurement as the top and the back must work together. The body size of a mandolin and a tenor ukulele are pretty close and I use 1 7/16" sides for both.

Brad
 
The side bent out of one piece, I like that.
Isn´t a little block at the lower end necessary, to bare the forces of the strings and maybe mounting a strap pin?
The other block looks very massive to me. And I think, it might be an advantage to reduce the glueing area, by carving out the upper and lower end of the block, leaving only a rim for glueing and to give way for excess glue into a hollow space.
Just my thoughts, I´m not a luthier, only an automotive engineer...
Will it be carved by hand or milled by a CNC machine?
 
Brad,

We would love to have some of your plans and knowledge.

I also think that I need to tell you this is not our first rodeo....... we also build mandolin, mandala, violin, double bass, and arch tops guitars, full instruments as well as kits.

We'd love to hear what your experiences has taught on the arch top ukulele with as many instruments as you have done. I'm sure you could save us some time...... when this was first posted in and earlier post......arch-top uke's there didn't appear to be much interest and we couldn't find any plans...... so what we have we derived from what we knew ( or thought we did ).......... the rims are 1.59" tall with out the plates. We also graduate our plates although it may not show up in the drawings...... granted they are not to final thickness...... look at our process that I include below. What kind of tone bars are you using for the top? cross.. parallel skew ? Have you ever tried a sound post?

Tube,

I'd agree the head block is somewhat large and probably can be trimmed some. Realizing that we use the cnc to get close and leave the rest to be done by hand carving and luthier skills, I'd agree the gluing area needs to be taken down around the head block, and yes we will add a tail block.


What we usually do is carve the pro-to type with the cnc first....... work out any bugs......hand carve and shape... etc..... then we have a laser scanner that we then go back and scan the actual instrument or plates that we now have and we then update our cnc files. Even after the top and back plates are machined with the cnc we usually leave material to still hand carve because of the nature of each piece of material.

We would love to have any and all information available for these instruments. Thanks you guys for your information and critique.

Blessings,

Kevin
 
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Kevin, I certainly did not mean to imply that you did not know what you are doing, my intent was to supply more information to those without any experience with arch top instruments. The two most common mistakes I see are incorrectly graduated tops and backs, and too high of side depths. Also I forgot to point out, the backs are usually 20% thinner than the tops as they do not have to support any string pressure. I use very light parallel braces and follow Bob Benedetto's reasoning that the bass bar is at the same angle as the treble bar and they both pass right under the feet of the bridge. I have not ever tried a sound post, but others have with poor results. On a violin, you are continually feeding energy into the instrument via the bow, fretted instruments are a different animal. But this brings up, why the rib depth is so important, the back must be close enough to the top to vibrate in sympathy with it. If you send me a PM with your email address I will gladly send you a copy of my plans. They are somewhat crude, but may supply some useful info.

Brad
 
Kevin, what did you model it in, and any chance of a copy of the file in .obj or similar format ?
 
Brad,

We've tried without success to send you several private messages but the forum seems to crash our email is kevin@waldroninstruments.com

Big Kahuna,

Let us get all the bugs worked out and we will see..... Rhinoceros is our program but we can probably translate to obj files.

Blessings,

Kevin
 
No worries. Rhino is an excellent piece of software for product visualisation, if I weren't already a Cinema 4D user, I'd dedicate some time to learning it. I guess you already know, but if you don't, Keyshot 3 can import Rhino files directly for rendering, and has a pretty good set of wood materials.
 
We've done all the preliminary work prior to cutting of the actual components for the Arch Top Cut-A-Way...... I personally like it the best. May have to make one of these to keep.

Blessings,

Kevin
 

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I am very anxious and interested in seeing this.
I built an archtop F-5 mandolin back in the early 80's using Roger's book and a copy of an old (1920's) Gibson F-5 mandolin.
 
Update:..... we finally today had time while waiting on other things to cut on the laser to mess with the Cut-A-Way top and back plates. I'm enclosing a cad file showing how the tool paths look in the program (all the blue lines are actually the tool following the program back and forth until it cuts the needed material away) , then several photo's of the actual plates while being cut, then the plates cut-out with alcohol on them. Both plates are from one piece of mahogany that was slightly less than one inch thick. The cnc took approximately 22 minutes per side to cut.... or about 45 minutes per plate ( final step over was 5% and feed speed was 500 inches per minute for those that are interested). Little finish work had to be done when they came off the machine..... but I'm sure they still will need to be tap tuned. Tomorrow "Lord willing" we will cut the body mold and the bending forms for the sides all on the cnc. It's our intent to update along the way.

Blessings,

KevinArch Top Uke Tool Path Top.jpgBNMWE87517.jpgBNMWE87503.jpgBNMWE87506.jpgBNMWE87509.jpg
 
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Nice work Kevin....I've been thinking of making a few archtop soprano's but with a diferent aproach..I'm useless at operating CAD and CAM..but my Son Mike is quite good at it..So i'm going to try and get him to to make me some male and female mold's out of 20mm Aluminium plate..so I can form the tops and backs using heat and a press..I've had some success bending arched backs on my sopranos with this method....so I'll see how it goes with a reverse curve ...I know some of the big Guitar companies use this method but they use laminates.
 
Ken,

Frank Finocchio does this with his arch top guitars and solid wood. Frank first uses a steam box to get the material pliable then molds them one half at a time over a reverse mold and then uses a jointer to joint them after they are formed and then glues them together. I can't see why what your wanting to do want work. If we decide to offer these as a kit we probably will attempt something like this ourselves it's very wasteful to cut good stock the old way. Maybe I need to make you some reverse molds for you to try? We need a guinea pig...... We could make them out of Extira...... (waterproof MDF if you guys don't have this product). Let me know if you have an interest in trying it.....

Blesssings,

Kevin
 
Brad, I am interested in your plans

Brad:

I have been looking for plans for a tenor archtop uke for several days. I have an uncle who has built a number of guitars, including archtops, and he has agreed to work with me so that I can build a good quality uke. For a number of reasons both acoustic and aesthetic, I would like to build an archtop. My email address is mikelyons8951@gmail.com. Is there any chance you could send me a copy of your plans. They would be very much appreciated, and I would be very happy to keep you and this forum informed on my progress.

I have never built an instrument before, my uncle has. He wants to pass on the knowledge and skill that he has. He also has all the tools needed, so I don't have to go out and spend money on that. He also has a good supply of excellent koa, mahogany, and spruce. We have plans for a flattop tenor (Martin style) but not an archtop. If you are so inclined, I would love to acquire a set of plans.

Thank you in advance for anything you may be able to do for me.

Mike Lyons (blueleo)
 
The rise of the arch on my mandolins from the bottom of the plate to the top of the arch is .625" after machining then I take anywhere from .010-.020 off in the sanding process. Where are you measuring from to get the .71" height? That seems like a pretty steep arch if its measured from the top of the plate edge. What is the neck angle?
 
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