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This koa Maui ukulele has a pretty significant top crack, and cracked back brace.
First I’m going to glue up this crack, before it gets any worse.
We make pretty much all the clamping cauls from scratch here at Gryphon- there’s a huge variation of repair jobs, we often make the caul as part of the job. The caul keep things all on the same plane, and enables the clamps to be good and tight without denting the wood or finish. It has a cutout for small uke bridges and fits most small body contours. I then add a block to focus the tension in this isolated area.
Next up is reinforcing that top crack. I made a faceted diamond cleat out of Koa seen here. It’s a little thick at the moment, but I will sand it a bit once it’s in place to clean it up and make it look a little more at home.
I missed the shots of installing the cleat, but here it is in place.
Now I can start working inside. I have a homemade magnetized flashlight ideal for this type of thing. It frees up a hand, and that’s especially useful when dealing with a small instrument with a small soundhole.
Now we’ll take a look inside and see what’s going on.
Apart from the messy glue residue from manufacturing, there’s a pretty nasty broken brace. (It’s not too bad, but the limited access is what makes it tough). We usually use the StewMac scissor jack for this type of thing on guitars, but with something this small it limits your options.
I’m going to have to make something to wedge between the brace and the top, and then clamp from the outside to close it up. Before I start, I take my bendy piece of brass that I notched with 1/8″ increments.. just for a reference point. Then, when I measure the side of the uke approximately where I’m working, I can subtract the height of the brace for a rough idea of how long my wedge needs to be.
Here I’m cutting some bamboo from Frank’s garden. This is strong and bendy and our favorite for this type of job. With a long curved hemostat, I’m able to work it into the sound hole and crank it into place (after a few length adjustments).
Here it is in place.
Now that I feel good about the clamping setup, I want to get some glue in there and then put the bamboo back in. Here’s a couple of thin palette knives trying to work some glue into the crack.
Now with the bamboo in place, there’s a good “squeeze-out” as we call it, which indicates a good firm closed joint.
I want to add a clamp on the outside right over the bamboo to make sure it’s as tight as I can get it.
Now I need to clean off the excess glue. Through a small access this is harder than it sounds. This is a trick I learned from Alex Glasser of Iron Horse Instruments. A bendable tube with half a Q-tip in it gets down right where you need it to go.
Here it is in the case, all ready to go.
Thanks for reading!