LorenFL
Well-known member
Glad I could provide some inspiration!
I ended up not doing this. I got to reading about compensation at the nut, which is something you don't hear about much on ukuleles. But, it's not uncommon on guitars.
I'll spare you the gory details, but I have a theory based on measurements of my uke and some research.
Ukes used to be built with the frets placed using "the rule of 18". The spacing of the next fret was exactly 1/18th of the remaining scale length. Modern ukes are built on more precise math. They use a number that's exactly 17.8-something for precise fret placement. And then they always have to add some "compensation" at the saddle to account for the string stretch when you fret a note.
The old method automatically incorporated that compensation at each fret by making each fret just a little longer!
So, my theory is that modern factory-built ukes are nearly perfect in dimension. I measured a lot of things on mine. 15" scale. Exactly 7.5" 12th fret. First and second frets EXACTLY where they should be according to the Stew-Mac fret calculator. It's built to mathematical perfection. BUT... that perfection doesn't take into account the string stretch!
So, on my uke, I first adjusted the action at the saddle and nut. Better, but still not perfect at the 12th fret, and even less perfect at the first and second fret. Not bad. Playable. But, more error than I was happy with.
Then I read about nut compensation, and even one anecdotal post that said some luthiers will place the first fret at the same span used for the second fret. On a concert scale uke, that's a difference of about 1.2mm. Interesting.
You can experiment with this with zero risk by just shimming a piece of wood under the strings right in front of the nut. I got out my trusty utility knife and sliced a sliver of pine from a board out in the garage (because I couldn't find a square toothpick or a matchstick). Whittled it down to about 1.5mm width and just taller than the height of my strings off of the fretboard. Wedged it in there, and retuned. WOW! Amazing improvement in low-fret intonation!
Then, I took a breath and yanked the old nut off. (came off easily, but it is a bit intimidating) Grabbed one of my new nuts, made some measurements and marks and filed a .75mm relief in the nut so that it can hang over the fretboard. I also filed a little bit off of the bottom of the nut so that I don't have to cut the slots so deep.
The result? Near perfect intonation without having do go dangerously low on the nut slots! I'm within +/- 2 cents at the 12th fret. Within +4/-2 at the first fret, and +/- 2 at the second fret except for the E string. It's off by as much as +8 on the first fret. That's checking with an app on my phone that gives me 1-cent accuracy. On my cheap tuner that only shows increments of 10, it looks perfect!
So, I could (and probably will) do a little more work with that nut compensation and add some custom compensation to just the E string. Then I'll put on my new strings and hope things don't change too much!
It's amazing how much you can improve a setup with just a little knowledge and experimentation!
Bought some super glue yesterday to fill my E slot. (it's currently got a piece of paper under the string) Trying to decide if I want to do that, or just start with a new nut blank. I guess I'll go the easy route first just so I can say I did.
I ended up not doing this. I got to reading about compensation at the nut, which is something you don't hear about much on ukuleles. But, it's not uncommon on guitars.
I'll spare you the gory details, but I have a theory based on measurements of my uke and some research.
Ukes used to be built with the frets placed using "the rule of 18". The spacing of the next fret was exactly 1/18th of the remaining scale length. Modern ukes are built on more precise math. They use a number that's exactly 17.8-something for precise fret placement. And then they always have to add some "compensation" at the saddle to account for the string stretch when you fret a note.
The old method automatically incorporated that compensation at each fret by making each fret just a little longer!
So, my theory is that modern factory-built ukes are nearly perfect in dimension. I measured a lot of things on mine. 15" scale. Exactly 7.5" 12th fret. First and second frets EXACTLY where they should be according to the Stew-Mac fret calculator. It's built to mathematical perfection. BUT... that perfection doesn't take into account the string stretch!
So, on my uke, I first adjusted the action at the saddle and nut. Better, but still not perfect at the 12th fret, and even less perfect at the first and second fret. Not bad. Playable. But, more error than I was happy with.
Then I read about nut compensation, and even one anecdotal post that said some luthiers will place the first fret at the same span used for the second fret. On a concert scale uke, that's a difference of about 1.2mm. Interesting.
You can experiment with this with zero risk by just shimming a piece of wood under the strings right in front of the nut. I got out my trusty utility knife and sliced a sliver of pine from a board out in the garage (because I couldn't find a square toothpick or a matchstick). Whittled it down to about 1.5mm width and just taller than the height of my strings off of the fretboard. Wedged it in there, and retuned. WOW! Amazing improvement in low-fret intonation!
Then, I took a breath and yanked the old nut off. (came off easily, but it is a bit intimidating) Grabbed one of my new nuts, made some measurements and marks and filed a .75mm relief in the nut so that it can hang over the fretboard. I also filed a little bit off of the bottom of the nut so that I don't have to cut the slots so deep.
The result? Near perfect intonation without having do go dangerously low on the nut slots! I'm within +/- 2 cents at the 12th fret. Within +4/-2 at the first fret, and +/- 2 at the second fret except for the E string. It's off by as much as +8 on the first fret. That's checking with an app on my phone that gives me 1-cent accuracy. On my cheap tuner that only shows increments of 10, it looks perfect!
So, I could (and probably will) do a little more work with that nut compensation and add some custom compensation to just the E string. Then I'll put on my new strings and hope things don't change too much!
It's amazing how much you can improve a setup with just a little knowledge and experimentation!