Sunday, January 3, 2016

Making a Ukulele mold

So, I built two tenor ukulele molds over the past few days, and they turned out great! Naturally, I didn't document a thing, so I documented my next build of two soprano ukulele molds. Again, naturally, since I was documenting my work, they didn't turn out as well, and I made some errors in my process.

So why post then? Well, there really isn't much information about how to make these things, other than "make a mold that matches the shape of the body you want to build". Thanks a lot for that terrific advice.

Thing is, I did make decent molds that are probably serviceable, but they have a couple of major flaws that ensure that they won't be useful for a very long time. I'll talk about it when it is time.

This is one of the tenor molds. The top and bottom have bolts that are tightened by wingnuts. These are made of three layers of 3/4" MDF from the hardware store. 

So, I had some more pieces that were 12" by 18", which I thought would make good soprano molds. I knew that there would need to only be two layers for these, since sopranos aren't as deep as tenors. 

I spent some time tracing my favorite uke body as a model for the mold. This was then sliced in half to make a template. 

I glued the paper to a piece of 1/4 plywood that would serve as a template. I then went to the band saw to cut away the body shape. 

Lots of relief cuts first, so that the blade doesn't get stuck. 

After being rough cut, I took the template to the spindle sander. 

Not bad! 

I then made a template for the other side. This may seem silly, but what it did was allow me to evaluate the template when I put the two pieces together. I found a major mistake in the bottom of the template, where the thing actually curved inwards, which wouldn't be noticeable until you put the two together. I refined this more on the spindle sander until I was happy. 

I countersunk three screws into the template and the first layer of MDF, 

Again off to the band saw. 

Making relief cuts. 

And cutting the bulk of the material out. 

I did not go all the way to the template. 

Now, using a template following router bit, I finished off the rest of the cut. I'm making two molds, by the way. 

Here is major boo boo number one. I really should have taken the time to align these. Instead, I ended up losing a fair amount of wood at the ends of the molds. Not good, these pieces were a tight fit as it was. 
This is the template following bit. The bearing is on the bottom, and will follow the template, cutting the MDF to match the pattern. I'm not sure why I didn't get a shot of the actual routing, other than the fact that I am using two hands and trying not to slice my fingers off. 

The screws left little dimples in the wood. This would be a problem for gluing. 

Release the chisel!

Nice slice, man. 
Plenty of glue, and spread it around. 

This part I did well. Here are the keys: 1) Make sure that you keep the piece in this orientation while it dries, so that the glue doesn't run up on the sides and mess up your attempts at routing the second piece of MDF. 2) let the front edges stick out a bit on your new piece, you can level them with the router bit when it is time. It is almost impossible to get it right otherwise, so don't bother. 

When it is dry, time for more relief cuts. 

Four pieces, ready to go. I put a bit with the bearing on top in the router table, and did the routing operation again. I then sliced off that extra protruding wood from the top and bottom of the template. 

This looks just lovely, but the top and bottom are too thin to allow drilling for a bolt. This is a problem. I chose to go with clasps instead. 

Predrill the holes, and treat with CA glue. 

Not good enough, but it will have to do. The MDF doesn't handle screws well, and the clasps were too wide for this to really work. It was a bummer of a way to end the project. These will work, but they might not be long-lasting. 

After the clasps are attached, I went to the spindle sander again to carefully refine the shape and remove the lumps around the sides. This also makes sure that the pieces truly meet well on the top and bottom. 

The finished molds. They look nice, but I really can't hope for them to last very long. 

The next step will be to finish the insides of the molds with polyurethane so that ukulele bodies don't stick inside. (I am really proud of the fact that I can type "polyurethane" without spelling mistakes. Twice.)

The good news is that I have templates ready to make more molds when and if I need to. This is important - these kinds of templates and tools need to be kept around for re-use. They don't take up much space, and should work the next time I need to do this. Hopefully I'll read this blog entry before going ahead.

Wednesday, December 23, 2015

After the Master's degree

Part of the reason I have had difficulty keeping this blog updated is the fact that I have been working on my Master's Degree for the last year and a half. Finally, I have graduated, and I now have time for the things that I love.

My first priority after I graduated was to tidy up my garage to make it usable during the winter. I've never kept a clean workbench, and it was time to find places for things that I typically leave on the floor. I also received a set of shelves from some neighbors that I mounted over the workbench, so I have better storage.

Today, I did some minor work on the Martin and the Cromwell.

First, the Martin.
I'm not sure if I have mentioned this guitar much. This is a 1929 Martin Tenor guitar. It is in terrible shape, having been disassembled about 30 years ago and left in an attic with the parts wrapped in a newspaper. It sustained a bad hit to the bottom bass bout, and the front and back were very damaged as a result. I cut the damaged portion out today. It's scary to have to replace wood, but the damaged portion was pretty bad. I need to clean up the cuts. 

Cleaning up the cuts on the Martin will require some small sanding blocks. I'm making them today, with contact cement, wood blocks, and 100 grit sandpaper. It's really cold, so I know that it will take a while for these to be ready to use - perhaps a couple days of drying time will be necessary. 

9 mil thick gloves to keep the glue off my hands. 

The blocks are drying. Those are some short mismatched chunks of kingwood on the left - I figured that I won't be using it for anything else. Fancy!

A little weight to move things along.  
The Cromwell bridge is going to be a problematic reglue. The top is very bowed, and so it the bridge. There is no way to flatten it back out, so I have to create curved cauls for the reglue, so that I can back up the bridge properly. There is another issue though - the bridge plate is not behind all of the bridge, so there is a gap that also has to be supported. 

A bit of sander work creates a curved board that I can work with. I'll glue cork to this. 

I put a contour gauge in the guitar to see where the parts are. This guitar is ladder braced, which means that the braces go straight across the top, instead of in the x-pattern that other guitars use. 

I traced this on paper, and then used a magnet to locate the tall brace close to the bridge. This shows how much space I need to work with. 

I started gluing up the first layer, and realized that it will also take a day or two to dry, so I won't be able to add the thin strip that is needed for the part of the top where there is no brace or bridge support. 

Tuesday, June 23, 2015

More work on making the Kamaka flat again

I've had just a little time over the last couple of days to work on that Kamaka.

To review, the end block is too long for this instrument, and has pushed both the top and bottom off from the sides. I've already fixed the bottom, and now to work on the top. 

That crack is actually useful, it relieves the stress when I work in the sanding card. 

This is a sanding card. I glued 60 grit sandpaper to a gift card, and cut it down in width. It is flexible, thin, and stiff. 

I work the sanding card in and out, bending it up so that it doesn't also sand the sides. I put some pressure on the top in places as I work the end block down.  

After about 20 minutes, it is getting closer. 

Another 15, and I'm really close. The sides of the block are still too high, so I work these with more pressure.  

Once I was happy with the end block, I then got to work with a tiny sanding block for the bridge area. The bridge was never glued down flat, and there was some pretty thick residue to be scraped away. 

I also used a knife for some of the work. I always forget that I can sharpen these things. 

Well, here is something funny. I was trying to plan for regluing the bridge, and discovered that the bridge brace, called a popsicle brace in the case, is only under the bottom half of the bridge. I put a craft stick in the place where it is attached. Weird! This also complicates gluing the bridge, as I want a nice flat caul underneath the bridge. I'll cut up a craft stick and attach it to the caul, which should balance things out pretty well. I won't do it today, though, I'll just glue the end block. 

Hide glue and some acrylic plates to keep everything flat. I glued the crack too, might as well. 

I also did some gluing on a stenciled Silvertone that I am putting back together. Easy stuff. 
The Kamaka is really coming along, I just need to reglue the bridge, and possibly do a little intonation work with it, and then it will be done. The Silvertone has a few more tight cracks to deal with, but nothing awful. I hope to get back to the Guild and Cromwell later this week.

Monday, June 8, 2015

Opening the top on a Kamaka uke

Today was a hot day, 104 degrees in the forecast. This is great if I need to use heat on an instrument, but not great for me.
The instrument in question is a late 50's, early 60's Kamaka uke, with the most beautiful top I've seen on one of these. The problem is that the uke shrank when it left the moist Hawaiian climate and came to the dry mainland. One part did not shrink, the tailblock, which may have been too long to start with. (These were hastily made instruments. They are wonderful, but let's not pretend that these are master-built instrument.)
I already fixed the back, by running a credit card with sandpaper on it through the rack, reducing the tailblock to the correct size. Now for the front, which is better attached, has a big crack in the top, and nothing is moving.

That little gap at the top is what I'm working on. 

I really don't want to lose that little splinter of wood, if I can help it. 

And here is the crack, which follows the grain of the top. The bridge is all tilted and not down very well. 

I heated up a palette knife with my alcohol lamp. I also used a pipette to drip in a little water from time to time.  

After a bit of water and jsut a little prying, the bridge popped off. Notice how little of it actually made contact with the top. I'll have to clean off this glue and make sure that the contact is much better.  If you look carefully, there is a spot of white haze under the right side of the bridge on the top of the uke. This was the result of a bit of steam coming off the palette knife when I put it into the water. I wiped that with alcohol and it went away. 
Sure enough, that splinter cam loose. Now what? 

I grabbed a sticky note, and stuck the splinter to it. 

Fold it up, and stick it in the case. I can put it back when it is time to glue things back together.

After about a half-hour of careful prying and heating, I was able to loosen the top. I decided to stop and let things dry out before I went on.