fretboard relief

Timbuck

Timbuck

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I don't bother with it on my sopranos, but if I did ..I would be interest to know how others do it when there is no truss rod to adjust.
Do you add the relief to the neck before fitting the fret board? or do it to the fretboard before it's fitted ? or dress the frets with relief...if so is it done by sanding ? scraping ? or planing ? or some other method ? and how much relief is enough?
 
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Put into the fretboard, scrape and then sand. I only dial in a tiny amount (0.1 mm) which really ensures no back buzz. Perfectly flat is probably fine. An adjustable truss rod would likely do nothing unless it was a 2 way, then you have all the control that you'll ever need. I just stay with a dense neck wood and dial in the minimum.
 
I think Pete on a recent Facebook video says he relieves the neck before he attaches the fretboard. If you're on FB Ken, check out the Pete Howlett Ukulele Owners Club page and look at his videos posted in the last week or so.
 
Relief is in the form of an arc..where is the apex of the arc what what fret position ....the vibration of an open plucked string makes many different waveforms depending on the tuning as many slo mo videos on YouTube show like sine waves ... to produce a single waveform the string will be a very low note..So as the string viberates from the bridge to the nut does that mean the centre of the arc (the deepest point of relief) needs to be at the 12th fret arcing upto nothing at the nut? or where ? It's confusing stuff.:confused: ..I'll stick to flat :)
 
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For ukes I put the small amount of relief in the neck before the fret board is glued on. I use a stationary 6" by 48" belt sander for this which I had built for me 20+ years ago.
 
I've sanded relief into the fret board before fretting and attaching to the neck. This is the hard way, at least for me. The easier way is to use a stiff card scraper to take a little material off the top of the neck before gluing the board on. It doesn't take long to get used to how much needs to be taken off.

This gauge is a big help:

30737741618_72e6576fc0.jpg


The contact points on either end can be slid along the track after loosening them, so that it accommodates different scale lengths. The unit is zeroed on a granite plate before each use.
 
saltytri said:
I've sanded relief into the fret board before fretting and attaching to the neck. This is the hard way, at least for me. The easier way is to use a stiff card scraper to take a little material off the top of the neck before gluing the board on. It doesn't take long to get used to how much needs to be taken off.

This gauge is a big help:

30737741618_72e6576fc0.jpg


The contact points on either end can be slid along the track after loosening them, so that it accommodates different scale lengths. The unit is zeroed on a granite plate before each use.
Click to expand...

Yes! thats a great idea to measure the relief..but I want to know.. where is the deepest part of the relief ? at what fret position? and why? and is there any mathamatical data to back up this theory.
 
I myself believe that this relief idea started when some well known player had a fretboard that was not perfectly flat and true, and trying to get a great low action (like his rival had) discovered that he could file away the buzzing fret in front of the note he was holding down (like you do..we've all done that)
This filing method works :) but! now the next fret buzzes :(so out comes the file again..this went on to the next fret and repeated until the neck was free of buzzing, as he aproached the higher end of the neck the problem becomes less and the buzzing decreases co's this is where the action was higher than the rest of the frets to start with..as a result he ended up with a buzz free concave neck with a great action at the top end and at the nut end... but! not so great in the middle :)..Then he thought ; I'll have to cover my tracks by explaining to the other players that this "relief idea " is the way to go .. and as he was a well known outstanding player, who would argue. :music:
 
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I agree Ken but sometimes you have to apply some snake oil to your work. It's like hide glue - wonderfully dismissed by famous luthier Goodall. Now I know there are those here who will swear by it but I cannot get on with it period. Does it make for a better instrument? Who knows... there simply isn't enough empirical data and any opinions just that. Anyway, neck relief or no, I now put it in and can sleep nights.

BTW, I think the same about tapered soundboards. IMHO it actually occurs when you scrape back the binding so must have been there all the time right and a anyway that membrane needs to be thinner at the edges and thicker in the middle... Do I smell buffalo droppings?
 
I recently completed a six-string guitar and put a truss rod in. So I could play with the relief.

What happened was that the string tension put a slight forward bow in the neck, as expected. Using the truss rod I could remove this entirely, but then I got fret buzz when the action was set at normal acoustic guitar levels (around 1.8mm for the high E at the 12th). Adjusting for a fraction of relief (about the thickness of a sheet of printer paper at the 7th) remove the buzz.

I suspect the relief issue really only arises with (a) low action and (b) long strings which (c) pull the neck forward. Because of (c), the gap at the 12th is fine, but at lower frets it may not be enough because of (b), i.e. the arc of the strings as they vibrate is taller than on a short scale instrument.

It might be relevant that on a classical guitar, which is low tension and thus doesn't pull the neck forward much if at all, the plane of the fretboard is set so the nut is higher than the plane (if the guitar is on its back) and usually there is no relief in the fretboard.

On soprano ukes the scale is so short that, at normal playing action, no relief is necessary. If it were, you'd need to set it up like a classical guitar, with the nut higher than the fretboard plane. Note that mandolins are the same (even though their action is much lower).
 
There's an old trick I haven't seen mentioned in many years. A crayon was used to color the fretboard between the 1st and second highest fret. Then the crayon was sanded off, avoiding the fret slots at either end. Then the board was colored between the 2nd fret slot and the 3rd highest slot and carefully sanded off. Then on to the 3rd slot and the 4th highest, and so on until the middle was reached. I've never tried it, but I've never intentionally built in any relief either.
 
Here's a slow motion video of a ukulele open string demo showing the vibrations of all the strings, and you can see why you dont need relief as ukulele open strings especially the "low G string" vibrating/ oscillating the most still dos'nt move enought to require it...any other higher notes played on the uke will just vibrate even less.
https://www.youtube.com/watch?v=wN4JA1LGS0o
 
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Commonly on classical guitars relief is put under the wound bass strings - 0.2 to 0.3 mm with the 'peak' around the 7 th fret, the plain strings have either no relief or the tiniest fraction - 0.1 mm.
I can't tell you if it gives any real world advantage. Even if it does I suspect it's a tiny amount.
 
Fender suggests the below relief on their guitars with a scale of 648mm. Different relief for differnt radiuses. Can you estrapilate that directly for a ukulele? I have no clue. I also wish I knew the exact shape of an ideal relief. The shape of the relief you get on a guitar is a pretty even bow with the low point arount the 7th or 8the fret. I made a board with what I imagine to be an ideal relief on a tenor ukulele, covered it with sandpaper and sand my relief into my necks before attaching the fingerboard.

I imagine the ideal relief to fall off rather quickly then a little more slowly till you reach the 8th fret or so then slowly come up to the end of the finger board. Kala puts a lot of relief in their tenors atleast the one measued. Close to 25 thousands !!!


Radius
7.25"
9.5"-12"
15"-17"


Relief
.012” (0.3 mm)
.010” (0.25 mm)
.008” (0.2 mm)
 
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Timbuck said:
Yes! thats a great idea to measure the relief..but I want to know.. where is the deepest part of the relief ? at what fret position? and why? and is there any mathamatical data to back up this theory.
Click to expand...

What Chuck said. :)
 
Just throwing in a last few words here. The scientist "in me" says that the relief on a stringed instrument ought to follow
cosh (cosinus hyperbolicus) if there should be any, i.e. relief. Possibly if a vibrating string can be approximated by a string exposed to only the gravity, i.e., hanging down? From there the relief could be estimated.
But it would also be a matter of playing technique, strings and the set-up varying in between different players. I guess.
 
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