Follow along. Concert Uke Build

Yeah nice series Allen. One thing I've always wondered is if a builder shellacs the back and sides before gluing how one masks off the little bit that gets glued to the sides? That part. I don't shellac my insides but I want to but I'm never sure how to go about it. Just sticking the nozzle of a sprayer in the sound hole does not cut it.
 
Yeah nice series Allen. One thing I've always wondered is if a builder shellacs the back and sides before gluing how one masks off the little bit that gets glued to the sides? That part. I don't shellac my insides but I want to but I'm never sure how to go about it. Just sticking the nozzle of a sprayer in the sound hole does not cut it.[/QUOTE

Back and sides glued on? Shellac. Or top and sides glued on? Shellac. Last piece shellac to within an ants foreskin of the join and voila.
 
Putting some shellac on the inside is easier than you think. I apply it to the sides with a pad before the top or back is glued on. For the top and back I will usually apply to the entire surface and after it's dry I use a razor blade to scrape it back where glue needs to go. I only apply a very thin coat, so what needs to be scraped off is whisper thin. Takes only a few seconds.

Alternately, you can glue the back on first and apply to those surfaces you see and don't worry about the soundboard.
 
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As I mentioned earlier, I have designed as many things as reasonable into my instruments in order to assure that the neck will align and bolt to the body with minimal fuss. So this is how the neck and fret board work together.

I build my necks with a scarf joint for the head stock and glue ears to each side. Afterwards the head stock gets a head plate veneer and a back strap veneer. It makes for an incredibly strong head stock. They also get a Carbon Fiber truss rod down the center of them. That's what the machined slot is for.

Neck Blank1.jpg

I machine my fret boards on my CNC router. This slot alignes the center of the fret board blank to my jig plate and afterwards will by used to locate the fret board to the neck as the CF will also extend up into the fret board.

CF Slot1.jpg

The CNC does the rest while I work on other jobs. The entire machining process for a compound radius, fret slots and fret markers is about 20 minutes.

Fret slots you will notice stop 2mm from the edge of the board. It makes the fret board a great deal stiffer than through slots. Plus you don't get the fret tangs poking through the edge of the fret board should it shrink in drier conditions.

The slots need to have some relief / bevel to the tops in order for the fret wire to be installed. Especially in very hard timbers like this Gidgee. I use a home made awl that has 4 sides that are very sharp. Just one scrape with the point down the fret slot and it does the job. You can see that the first few frets still need the treatment.

This is also the finish off the CNC. Only need a light sand with fine paper afterwards.

Fret Slots1.jpg

Fret markers are installed with CA glue and allowed to dry. Leveled with the fret board, and then it's time for the frets.

If you are installing frets on a radiused fret board, then you need to put a curve to the wire so it will conform to the fret board.

Fret Bender1.jpg

And because the fret slots don't extend right through, the tang has to be nipped off each end.

Fretting1.jpg
 
I make all my own bindings so that I can size them appropriately for ukuleles and choose timbers that compliment the color pallet I have in mind for each instrument. I worked out a simple method to attach the purfling strip to the binding so they will be bent together. These are made from some Australian Blackwood sap wood with black / maple / black purflings to match the rosette and back inlay.

For this job I use a PVA glue over HHG because it'e easier to dispence as a thin bead on the edge of the binding.

Making Purflings1.jpg

Here you can see the parts sitting on a couple of granit slabs. I will use one as the back fence in order to clamp the pieces together. Pushing everything down flush to the base and letting dry for about 10 - 15 minutes before pulling them out and repeating with the next piece.

Making Purflings2.jpg

I have two more laminate trimmers set up with their own dedicated bits. One to cut the binding rebate, the other to cut the purflings.

Install Bindings1.jpg

Here I'm fitting the purfling to the back. This is one of those jobs you have to get right. Any small gaps will draw your eye and spoil the job. I will get all of them in place and then wick thin CA onto the edge where the back and soundboard contact the purfling. I have used HHG and even PVA previously, but have found that the CA is the best option here after spending the time to fit them.

Install Bindings2.jpg

After an overnight dry I take them to the drum sander for their final thickness, then tape them together and bend them all at the same time. This especially helps with fragile and easy to break highly figured timbers.

Install Bindings3.jpg

Now it's just a matter of fitting them very carefully to the instrument. Trimming to length and cutting the mitres on the purflings to meet up with the end graft I installed previously. I use HHG for this job. The heat and moisture really helps in getting them to settle into place.
 
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I built a tenoning jig sized for ukes based around several ideas from the guitar models you can see posted around the internet.

The idea is that an adjustable arm is attacthed to a hinged jig plate where the neck blank will be anchored and machined.

All of my perspex bracing templates have the bridge position marked out on them, so I hold them in place and adjust the lenght of the arm to coincide with that scale length. Then the body of the instrument is placed in position and the adjustments made to the tilt of the jig so I get the desired relief at the bridge position.

Bit out of focus but you should get the idea.

Fitting the Neck1.jpg

As I have been rienforcing the idea of designing and building with an intent, you will notice the aluminim dowels in this photo. They fit the truss rod slot that is machined into the neck and assure that all the machining I'm going to do will use that reference.

Fitting the Neck2.jpg

The other knobs you can see are for clamping cauls to hold the neck in place, along with the adjustors for the arm and the pitch of the jig.

Fitting the Neck3.jpg

After I've machined the tenon, I use a small template to pencil in the shape of the heel, then remove exess on the bandsaw and clean up with a rasp. From here I need to relieve the area between the penciled in lines and the tenon. This is so when I floss the cheeks of the neck I'm only removing a small bit of material to achieve the fit.

Fitting the Neck4.jpg
 
The last part of the neck fitting system is this aparatus. You will recall I used one station to drill the neck block. A hole precisely placed in relation to what I will also into the neck.

Again there is the truss rod alignment for the neck. A 10mm hole is drilled with the aid of the drill guide. It will acommodate a 10mm Aluminium dowel that extends from fret board surface of neck though the heel.

Fitting the Neck5.jpg

After the dowel is installed I then drill a 5mm hole through to accomodate the M6 thread I will tap and use to bolt the neck to the body.

Fitting the Neck6.jpg

I loosely attach the neck to the body and then use 100 grit emery paper to floss the cheeks of the neck to get a proper fit to the body. Adjutments to the pitch, yaw and set of the neck can be made this way but with all the careful planning so far all that was required was 5 smooth passes on each side with the emery paper to floss the joint for a perfect fit.

I slip a thin masking tape between the neck and body so that I can glue the heel cap in place without the danger of glue squeezing out onto the body. After it's dry I will remove the neck from the body and glue the fret board to it.

Fitting the Neck7.jpg
 
The fret board and Carbon Fibre truss rod are glued to the neck with Epoxy. Allowed to dry overnight and then it's on to shaping the neck. I use a coarse and fine rasp for the bulk of material removal. Then refine shape with a combination of a card scraper and sand paper.

The way I try to explain it to students is that you remove wedges of material from the neck, then split that wedge by taking another wedge on either side of it untill you are left a relatively smooth shape that doens't take much to refine into the finished product.

Neck Shaping1.jpg

It takes me 15 - 20 minutes from start to finish.

Neck Shaping2.jpg
 
After the body and neck have had a thourogh sanding and inspection for any flaws I'm ready to move onto the finishing process.

I pore fill all my instruments. I use a clear epoxy resin for this. On open pore timbers like this Australian Blackwood it will take 3 applications to achieve a perfectly smooth surface.

 
After each application of epoxy is allowed to cure it's sanded out with P220 sandpaper and another application just like the last. After the 3rd round I give it a clean up and thourogh inspection. Attach the neck for a final sanity check before dissasembly and masking off the sound hole and fret board in preperation for the application of a sanding sealer.

Ready for finish1.jpgReady for finish2.jpg
 
What radius do you use on the fretboard? In the picture the frets seem very curved, but maybe it is just a trick of the light.

It's a compound radius that is 12" at the nut end and 16" at the soundhole end.
 
A catalysed polyurethan sanding sealer has been applied after the epoxy pore filler sessions are complete and the instrument has bee finish sanded up to P220. The beauty of this sanding sealer is that once its cured (2-3 hours) that's it. No shrink back that you will have for solvent based products.

This is a high build product, so it's important to only apply one coat.

Levelling sanding sealer1.jpg

It's time to level sand the finish. This is done in 3 stages with P220 grit paper. The first is at 45 degrees to the grain direction.

Levelling sanding sealer2.jpg

It's ok to have a few shiny (low) spots after this first step. Hard to see in this image but there are some in the upper bout and around the edge near the bindings.

Levelling sanding sealer3.jpg

Now sand in the opposite direction.

Levelling sanding sealer4.jpg

And finally with the grain.

Levelling sanding sealer5.jpg

At the end there shouldn't be any low (shiny spots) and ideally you will not have cut through to timber. Now onto applying the clear finish coats.
 
The top coats are applied in the same manner as the sanding sealer. One coat with an overnight cure and level sand with P400, and then another coat of clear. Same deal with overnight cure and another coat of clear. Now the instrument has a nice full gloss coat and I start out with P800 to give a quick level sand. Not much is required now because of all the careful work that has gone in up to this point.

I then move onto using my 75mm (3 inch) random orbit sander with 3M Trizac wet sanding paper. Moving from P1000 through to P3000.

Wet Sanding1.jpg

The process goes very fast and leaves a lovely satin gloss finish that's silky to the touch. The client has requested the satin finish, but if it were to be gloss, then this is the point that I would move to the buffer.



Now I can attach the neck. I do some fret work prior to attaching the neck. With some touch up once it's glued in place.

Fret Dressing1.jpg
 
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Time to make the bridge. I machine up dozens of blanks of various timbers every few months so I can just pull one out and add the decorative veneer to the string platform. This one is curly Gidgee with a straw colored curly Blackwood veneer.

Bridge1.jpg

Bit of glue and clamp up for a few hours.

Bridge2.jpg

Then it off to the CNC to machine the saddle slot and drill the string holes. And finally a thourogh sanding and polish.

I use a template to help locate the bridge. And it's always a good practice to use a string to do a sanity check to make sure that the string path is going to be running from nut to saddle where it's expected to be. A little off on way or the other is very dissapointing when it comes time to install the strings.

Bridge3.jpg

Carefully scrape the finish away to raw timber where the bridge will sit. Get clamps in position and even do a dry run to determine if you have everything correct. Then apply glue and clamp. Set aside overnight.

Bridge4.jpg
 
The top coats are applied in the same manner as the sanding sealer. ...

I've been watching your finishing technique with interest. I'm always interested in how others do it. I'm with you on stopping at about 3,000. Sure it doesn't give a glass like lustre that 90,000 does (90,000???), but it is good enough. I know a luthier that does his final polish with paper towels. His philosophy is that the too shiny a finish is off putting and intimidating to the player and I think he might be right. It is more about the player and less about the luthier and their egos in the end. Wise words.
 
Satin finishes in a spray on product are rather hit or miss.

You either use one that has a flattening compound in it and hope that when you spray it, there are no flaws or dust specs whatsoever. As any work you do to remove them will mean that you have to do the same to the entire instrument. So a far more consistent approach is to just plan on level sanding what ever finish you are spraying on and pick a final sanding grit that will give you the desired amount of sheen.

One easy way for the novice is to use 0000 (super fine) steel wool and some paste wax.

However all satin finishes will start to develop a shine to them wherever the player has contact with the instrument. Such as the neck and where the arm crosses the lower bout. Effectively polishing up these areas. I like to see this, as it means that the instrument is being used as it's meant to be. Not hung on the wall like some piece of art.
 
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There is a fair number of steps involved in the set up of an instrument. And this isn't meant to be a comprehensive "How To" on the subject. But I'll give a couple of pointers that should get you through with acceptable results. In fact, a lot better than many factory instruments that I'm asked to work on.

When making a nut, you need to determine the height of the frets so you have a reference in shaping it. Use a pencil that has been flattened on one side to ride on top of the frets to mark this on the nut.

Set Up1.jpg

Once you have removed all the material that isn't required and sanded and polished it up you then need to determine where the strings will be. I use a straight edge to determine this.

Set Up2.jpg

After making with a very sharp pencil the two outside string positions and scoring those lines with a fine saw you then you grab your string spacing tool made by Ken Timms.....OK, it's not absolutely necessary, but it works a treat and really cool.

Score those lines with your fine saw and then deepen all 4 slots with your sting files. Not too deep. Just enough to keep the strings in place. We'll adjust depth later.

Set Up3.jpg

Determining the action at the 12th fret is also easy to work out with something as simple as a drill bit and a straight edge. Grab a 1/8" drill bit and place it at the 13th fret. Lay your straight edge on top of the first fret and the drill bit. Measure the distance from the bottom of the saddle slot to the bottom of the sttraight edge and it tells you how tall your saddle needs to be for the correct action at the 12th. Here I've already made the saddle and just checking to confirm the measurements.

Set Up4.jpg

And finally once the strings are on, you adjust the action at the nut. This is done by fretting the string at the 3rd fret and observing the distance between the bottom of the string and the top of the fret. It should be apporoximately the thickness of us old timers would refer to as a rolling paper. Perhaps a couple of them for the thicker C or low G strings.

You sneek up on this adjustment. As when you get close it can be the difference between one or two strokes of the file as to being spot on or too low.

Set Up6.jpg

You may need to adjust the action at the 12 fret again once the strings have had tension on them for a few days. It's common and desirable for the top to pull up and the bridge to rotate a bit and could mean adjustments are required.
 
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