Follow along. Concert Uke Build

BR Ukuleles

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I was requested to document the build of a concert uke by the client, and thought that I might as well post it here too.

It's going to be a fairly standard instrument for me. Using some very curly Australian Blackwood and will have a 16" scale length in order to get 14 frets to body.

I started off with a couple of long flitches in order to get the bookmatch of back and soundboard.

Brenda's Blackwood Concert1.jpgBrenda's Blackwood Concert2.jpgBrenda's Blackwood Concert3.jpg

After triming them out we get to joining the pieces together.

 
Great Allen. Very much looking forward to the development of this thread.
 
Got a bit more done this afternoon.

The side material is cut slightly over lenght and a template is used to mark out the cut line for the body taper. There is also a mark on the templat that designates the waist.

Side Template1.jpg

After triming the taper the sides are fed through the drum sander. Sending them through on an angle helps the sandpaper cut the material, and makes it last much longer. They are run through with the grain on the last few passes very lightly to minimize the scratches.

Sanding Sides1.jpg

After they have been brought down to 1.7mm thick I give them a pass over with the card scraper to clean up most of the remaining sanding scratches.

Scraping Sides1.jpg

They get a quick shape on the bending iron. It's pretty close, but I will "Set" the shape using a solid form and a silicone heat blanket. You can see it in the background.

Side Bender1.jpg

The temperature is regulated with a control and temp. sensor that is in contact with the wood. You do not walk away from this set up as the potential for fire is something you don't take for granted.

Side Bender2.jpg
 
Hey thanks Allen. Great series. I do my back and tops joins with tape too which works great and is so simple. Differences: I don't use a shooting board (not needed) and I don't use hide glue (tightbond). The one thing I noticed is that you seem to speak with an American accent. Are you an ex-pat American or just a Queenslander with a different accent? Just wondering.
 
Hey thanks Allen. Great series. I do my back and tops joins with tape too which works great and is so simple. Differences: I don't use a shooting board (not needed) and I don't use hide glue (tightbond). The one thing I noticed is that you seem to speak with an American accent. Are you an ex-pat American or just a Queenslander with a different accent? Just wondering.

A Canuck from a very small town on the West Coast of BC. Been in Australia for 15 years.
 
Today I managed to get some inlay done. Both back and soundboard were run through the drum sander to clean them up and then cut to shape on my laser.

The back was first. Sap wood from the same Australian Blackwood. Stuff with that much curl doesn't get tossed in the bin.

A note about glue. As everything is hard wood, and I wanted to make some progress today, I used CA glue for most of the inlay work. With the Maple in the purflings they will have a tendency to show a black line at the mitre join if you were to just use CA. So to help stop this it's best to coat the ends of those cuts with PVA glue. In this case the 4 short bits of purfling where glued in place with PVA so it coated the miters on the longer pieces as well.

Back Strip Inlay2.jpg

For nice clean results with purflings I like to inlay the material and afterwards come back and route the purfling channel. Spliting the line between the inlay and background material.

Back Strip Inlay3.jpg

Purflings can vary in thickness slightly, and there is very little chance you can push a 1.05mm piece into a 1.0mm channel. So to make sure that they are all a uniform thickness and just every so slightly thnner I run them through a jewelry roller press.

Sizing Purflings1.jpg

And to cut the mitres you need an extremely sharp chisel. Also take the time to make sure the back of your chisels are flat and polished. It makes judgine the angle of the miter cut childs play.

Back Strip Inlay4.jpg

And the result with a spit coat of shellac wiped on.

Back Strip Inlay6.jpg
 
The soundboard was treated in exactly the same way as the back inlay.

Rosette Install1.jpgRosette Install2.jpgRosette Install3.jpgRosette Install4.jpgRosette Install5.jpg

Afterwards it was run through the drum sander on the back side to get to the desired thickness. Combination of calipers, flexing and tapping for me to decide where I'll settle.
 
And to cut the mitres you need an extremely sharp chisel. Also take the time to make sure the back of your chisels are flat and polished. It makes judgine the angle of the miter cut childs play.

Good tip. Obvious perhaps, but I've been using a razor and my eye and results are sometimes less than perfect... You probably know this Allen, but a coat of 1lb shellac on wood before getting anywhere near it with CA will prevent the dreaded black line or worse... Works with purfling too.... Lovely wood. Just lovely. Unfortunately not available to me. At reasonable prices that is. Someday maybe....
 
Lot's of ways to attach necks to bodies, and this is the method that makes the most sense to me.

I want to design in the alignment and attachment from the start. So it starts with the neck block. I hope that the following will make sense when you see it in context.

I machine up long lenghts of material with a 20mm rebate that will end up being the mortise for the tenon that will be on the neck. I cut one end square and then trim the other end at 2 degrees. This will be towards the back and coincides with the taper of my sides from butt to neck. I mark both top and back on the block. The angles are subtle and easy to get things mixed up.

Neck Block2.jpg

All my measurements are based off of the soundboard, so the block goes into a jig that I designed for several operations. Here I will drill a cross hole in the block for the bolt that will hold the neck in place.

Neck Block1.jpg

The neck block needs some shape on the glueing surfaces to conform to the sloped shoulders of my body. I use a 12" radius sanding beam to achieve this. Witness lines are penciled in to show progress. It only takes about 10 swipes to get the correct profile.

Neck Block4.jpg

I glue it in place, and afterwards the tail block goes in. Masking tape to pull the joint together helps stop things from slipping about when the clamps are going on. And a great tip if you are going for a really tight joint that doesn't require an end graft.

The arrows penciled on the sides are also a reminder to me for which side the soundboard is.

Rims1.jpg

After the blocks are dry, the rims are installed into the body mold and taken to the raduis dish. I have this one set up on an old potters wheel. Because I took the time to trim the sides to my template profile, as well as cut that 2 degree angle on the neck block, there is very little material to remove. It only takes about 5 seconds to fair up the profile and ready to glue on the linnnings.

And now is the first time that you can see that my body mold has a machined out area at the neck block that I slip in a 20mm wide hardwood block that also aligns with the instruments neck block. The fit on both parts is very snug. This assures me that the neck block geometry is setting me up for an easy fit to my neck later in the build.

Radius Dish1.jpg
 
I shape and laser engrave the back reinforcement strip prior to glueing it in place.

When you do this for a living it's really important to work efficiently. Brace stock is something I go through a fair bit of. So it makes sense to prepare heaps of it in the few different dimensions I use so I just have to pull out the amount I require on the day.

So after the back reinforcement it's allowed to dry I prepare and fit the back braces. I use the 15' radius dish to put the shape on the bottom of the braces first.

Another big time saver is to do all the shaping that is practical to braces prior to glueing them to the back or soundboard.

For the back I set up a fence and stop on my bobbin sander to make sure that the scallop on all my braces are the same lenght and depth. Putting the scallop on these takes less than 30 seconds.

Then I go to my large belt sander and put a gentle radius onto the top profile. This again is less than a 30 second job.

The rebates are cut to fit the braces and I'm all set.

Back Braces1.jpg

Then it's off to the Go-Bar deck. I use a form that has my back radius machiened into it. Since the top of the braces now have a rounded over top, I use a flat bit of spurce to support the end of the Go-Bars.

Back Braces2.jpg

After these dry there will be next to nothing needed to do prior to attaching the back to the sides.
 
The sides have had the back profile defined in the radius dish. The soundboard edge of the sides are pushed flat to my reference table and then both neck and tail block are clamped in place. Again keeping the body geometry aligned.

Now I fit the linings to the back and glue in place with hot hide glue (HHG).

Unlike PVA glues, HHG dries extremely hard and makes a very noticible difference in the tone of instruments built using it. Many builders may charge a premium for using it.

Linnings1.jpg

When using HHG you want to see some squeeze out. You can either let it cool for a few minutes and pull the exess off. It will be like a rubber band. But in my tropical environment it's rarely cool enough for this to happen unless its the dead of winter, so its easier to just wipe away with a damp cloth.

Linnings2.jpg
 
After the back linnings have dried (overnight in this case) I take the rims back to the radius dish and flush them to the sides. If you are careful about the glue up all that needs to be removed is less than a millimetre, so takes just 5-10 seconds.

This is the first time you've got to see the tail block. I use plywood for this, as it's far more suited to the job it's required to do. However I add an off cut of the side material to dress it up a bit just because it's easy to do, and why not?

The mating surface of the tail block to sides also has to have a shape to it for my instruments rounded bottom. It can be shaped in a similar method as used on the neck block, but in my case I machine up long lengths of stock on my CNC router and just cut off a length as I need it.

Another thing to point out is that the tail block has been relieved at a slight angle back to a point to the width of the linnings. This is important so that the the contact area for both back and especially soundboard is even all the way around the body. If you don't do this, then it's pretty well certain that the foot print of the tail block will telegraph through.

More LInnings1.jpg

Now it's on to installing the linings to the soundboard edge of the sides. It's done in exactly the same way as those on the back. Cleaned up and set aside to dry.

More LInnings2.jpg
 
Thanks for taking the time to do this.
 
Allen, its great to see how you work, making everything look so simple and straight forward! It's interesting to see how you do your neck blocks now that you've adopted the bolt on neck.

You mentioned that HHG dries hard and makes a difference to the tone when used to attach the linings. Some guitar/uke makers use reversed kerfing or solid linings to make a stiff boundary between sides and top to ensure its the top thats driven and not the sides ( so also done for acoustic response improvement). Since you have decided that HHG is important, what are your thoughts on the kerfing/lining type?
 
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In a larger body instrument like a guitar that has deep sides and requires braces / stiffeners on them, I can see that they will make a difference. But the ukulele's body is so much smaller and shallower that I believe it's already stiff enough.

Concerning reverse linings, it's very easy to break the web on them when installing on the small uke body. You can also see faceting on them in a uke in the tight bends. While it won't make a difference in function, aesthetically it's totally unacceptable to me. They are much more suited to guitars

It was and to some extent still is reasonably common to see single layer solid linnings that are cut from exrta sides on instruments that didn't have bindings and purflings. But if you installed bindings them something wider was required. Now you are talking a 3 or 4 layer lamination.

To use solid linnings you either have to go to laminated sides that are made in a mold so they are perfectly shaped, and then another mold that takes into account those sides thickness to laminate up the solid linings so that you are assured of a good fit.

Or use single layer solid sides as I do, and then use them to glue up the solid linings, using them as the form. As any small variation in shape means that they won't fit.

As you can imagine, this is a very labour intensive process, an at he end of the day will reflect considerably in the base price of the instrument.
 
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The linnings to the soundboard are flush sanded flat. Again as i'm carefull with glueing them in place this takes less than 30 seconds.

Leveling Linnings1.jpg

Now it's time to fit the back to the rims. Careful marking out where the braces will be inlet into the linnings, triming to length and checking the fit prior to applying HHG and the clamps.

Fitting Back2.jpg
 
This is the first time you've got to see the tail block. I use plywood for this, as it's far more suited to the job it's required to do. However I add an off cut of the side material to dress it up a bit just because it's easy to do, and why not?

Ya know, nobody ever talks much about tail blocks. They get no respect. I think your use of plywood in this area is perfectly fine. It really doesn't make a difference to the sound or stability. However since I seem to have a lot of mahogany scrap from one piece necks, I make my tail blocks from mahogany scraps and that works just fine. Plus maybe nobody else will ever know what is in there, but I do and that seems important to me for some weird reason. Only the luthier knows.... By the way, I use an unknown radius on my tail blocks but it is close to 16 inches as far as I can tell. It just is what it is. Seems to work.
 
Allen,
Thank you for your generous thread. It is a gift to a beginner such as myself to have access to different techniques -- and your ukes are so lovely.
 
Now onto soundboard.

I install the braces in 2 stages. First is the upper and lower transverse braces as well as the bridge patch. Again, like the braces for the back these are scalloped and rounded over prior to glueing in place.

Soundboard1.jpg

After they have dried then the fan braces are also glued in place. These are shaped close to the final dimensions and after dry will get the scallops into them for the final voicing of the top. A good clean up sanding and a spit coat of shellac keeping the edge that will be glued up clean.

Soundboard2.jpg

Again the brace locations are marked out and rebates cut into the linnings to fit them in. Transverse braces are trimmed to length and the fit is checked several times to be certain it will go together as planned once the HHG is applied.

Inside the Box.jpg

When using HHG, you have to move quickly keeping in mind that if it cools before you bring the parts together your joint will be poor. Once you get proficient at it, large glue ups like this are easy. I use a clamping caul and M6 screws to apply even pressure.

Closing the Box.jpg

After everything has dried, the body is removed from the mold and the top and back are flush trimmed to the sides and get a clean up sanding.

Flush Trim.jpg
 
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