Having a hard time with intonation

aviezero

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I've only recently gotten into uke building. I have had a much easier time than I expected with one exception. I can't seem to get any of my ukes to play the right notes. It seems no matter what I do all my frets are flat or sharp or a random combination of both. I've used precut fretboards from kits and from mainland. I have my bridge to 12th length the same as my nut to 12th. From the instructions in my kit it seems I'm having problems that I shouldn't be having. I hate to ask but I can't find any research or guides on this. Any help would be appreciated.
 
Are you familiar with saddle compensation? Most of us add a couple of mm to the scale length to make up for the string stretch (which will vary depending upon how the action is set.)
Hopefully your precut fret boards are from a reliable source. What's troublesome to me is the "random" part of your question. Stay tuned. You'll get your answer here.
 
Could it be string quality?
 
I've tried different strings.

I'll clarify what I meant by random.
After the strings stop stretching I tune after each note just to make sure. On the plus side Am7 sounds great.
G string - 1st fret, +40 cents / 5th, +20 cents / 12th, +40 cents
C string - 1st, +30 cents / 5th, +5 cents / 12th, -10 cents
E string - 1st, +8 cents / 5th, +5 cents / 12th, perfect
A string - 1st, +36 cents / 5th, +9 cents / 12th, +9 cents
 
A couple of things you could start with to help your intonation. You need to add compensation so that your open string and twelfth fret are the same. If the twelfth fret note is sharp you need to move the saddle contact point farther from the nut, i.e. lengthen the string. Hopefully you can do this by beveling the top of the saddle. Before I would start that I would check the string height at the nut and the twelfth fret. The higher it is the more it will tend to sharpen fretted notes. A second factor is how hard you push down when you fret notes. The harder you push the more it tends to sharpen notes. This is especially true near the nut and up high where the frets are close together. This might account for some of your random readings. If you play hard you may have to slightly flatten open strings to get a workable intonation everywhere else. Anyway, how high is your action? And what is the scale length?
 
I chopped off a bit of the fretboard making the 1st fret shorter by about 1.5 millimeters. This made a huge difference but, I'm still off in some places by 20 cents. I'm thinking my fretboard has bad fret placement. I did the same thing to my mainland fretboard and it's nearly perfect now. Thanks for the help. Time to make my own or order another mainland.
 
I chopped off a bit of the fretboard making the 1st fret shorter by about 1.5 millimeters. This made a huge difference but, I'm still off in some places by 20 cents. I'm thinking my fretboard has bad fret placement. I did the same thing to my mainland fretboard and it's nearly perfect now. Thanks for the help. Time to make my own or order another mainland.


Sorry I couldn't get this to you sooner.

1) Check the fretboard. Is it measured out and slotted correctly? Use a caliper to measure from the breaking point of the nut to the crown of the fret and compare your measured values with the nominal values for the given scale length.

2) Check the action. How high is it at the 1st fret, the 5th fret and the 12th fret? Measure from the crown of the fret up to the bottom of the open string and compare your values with a ukulele (of the same scale length) that you like and sounds good to you. One easy check for nut action problems is to put a capo on the 1st fret or second fret and strum away. If you're having problems (sharpness) in the first few frets, the capo will bring the nut action down as far as it can go and you can see what it sounds like with that low nut action.

3) If you're also sharp around the 12th fret (which it looks like from your description), you may also want to look at bringing the saddle down some and maybe also compensate the 12th to saddle measurement some. Like Chuck said, you add a little bit at the saddle end - take it slow and check carefully. You may be talking about 0.5, 1, 1.5 maybe even 2 mm. Take a look at the stewmac fret calculator - it gives you standard saddle compensation values for a selected scale length.

4) Nut compensation can be a good thing, but it may set things off elsewhere - best to measure the nut to 1st, 2nd, 3rd (from the breaking edge of the nut to the crown of the fret) very closely and compare with the nominal values. But remember, getting the action right comes first. We did have a soprano last summer where we actually did the same as you and compensated the nut by about 1.5 mm - but when I think back I wonder if we should have taken a closer, even closer, much closer look at the fret measurements and the action before doing the quick nut fix.
 
Stewmac fret calculator. That is an amazing tool. Thank you. I've been using measurements from my store bought ukes and comparing.
 
Hi aviezero, I use a vernier caliper to check fret spacings. I measure from nut to the inside edge of the fret and then add half the fret thickness if this makes sense. You need to fret the strings very lightly if you're checking intonation with a tuner, you can sharpen a string by 5 cents easily just with finger pressure. It's taken me a good while to get to grips with intonation especially on a soprano, after playing guitar for a long time my ears pick up dodgy tuning; certain chords on the uke sound strange and yet against a tuner are virtually perfect. The octaves across the G and A strings can sound a mile out when they're not. I reckon if you can figure this stuff out you're halfway to being a decent builder. I add 2.5 mm for saddle placement, so a soprano with a scale length of 350mm would have the leading edge of the saddle 352.5mm from the nut and that suits the strings that I'm using, the climate and so on. I'm on my 8th hand build and I've got one that I'm really pleased with sound and intonation wise and I have to say totally worth it.
 
I bought an expensive digital caliper and measured everything thoroughly. Everything is coming together now. It's amazing how much and how fast you can learn something with a little help. Thank you all.
 
I bought an expensive digital caliper and measured everything thoroughly. Everything is coming together now. It's amazing how much and how fast you can learn something with a little help. Thank you all.



you guys all just spoke jibberish to me.. wow im scared to try to build one now lol
 
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