Thanks for all the advice guys but I still have problems with the notes being slightly sharp when I fret them. This is what I have tried:
I moved the bridge back a bit to compensate but this in turn changes the scale length and then the placement of the frets.
I tried increasing the break angle at the bridge and the nut.
I have increased/ decreased the hight of both nut and bridge.
I changed the thickness of both nut and bridge to make sure the cut off point at beginning and end of the scale is exactly where is should be to calculate the scale length.
I changed the action both at the nut and the 12th fret giving it a slight increase from nut to 12th fret and also I tried it having the action almost level all the way down the neck.
I tried using different size frets so that the pressure was different when fingered.
I've done it all and it still pulls sharp. Lowering the action has helped but I can't go much lower and anyway I have seen other guitars with fairly high actions and they sound perfect. I didn't think it would be this hard. I really want to move past this so I can put my energy into being creative with different styles, shapes, sizes but I just need to make a prototype that works.
I was thinking of buying some plans or buying a decent cbg and copying it but in the spirit of the cbg I wanted to spend as little cash as possible.
I have listened to a lot of cbg's on youtube and although most of them look great they don't always sound too good. Most of them sound like they are out of tune a little. Is it that hard to build a decent sounding cbg?
Maybe it's all of the above or maybe I'm starting to lose my mind?
If anyone could help please do otherwise it was good just to vent my frustration.
Thanks
Replies
You, sir, are not alone:
www.cigarboxnation.com/forum/topics/fret-spacing-and-sharpening
My CBGs played sharp when I used 'standard' scale calculators. As others have said, some sort of stretch compensation is needed if you wish to improve the accuracy of the intonation. For the last 2 I used the linked site that allows you to tick the 'stretch compensation' box and the results have been pretty good.
http://windworld.com/features/tools-resources/exmis-fret-placement-...
Nice one. I will check it out.
Typically mine pull sharp for one of several reasons and the fix I found.
Scale length is wrong - remeasure the distance from the nut to the 12th fret and double it. #1 problem I have with intonation. Didn't show up until I installed frets in one. I'd used the slide and my ear to compensate and estimated the intervals. Once the frets were installed, it was what it was, right or wrong.
The action is too high - set the action as low as you possibly can, regardless of whether you like it and see if it helps. If it does, then you know.
The frets are spaced wrong - make a new neck, only use a slide or sing off key.
The frets are too tall, leaving a big valley to bend into - use a vintage fret wire
Based on what you've said, I'm leaning towards the scale length being wrong. Did you measure out your fret locations or lay another guitar neck next to it and transfer the marks? If you measured, take the dial calipers and check to see where it's off. If you used another neck, if it was a Gibson, thinking it was 24 3/4", it's probably not. They vary from 24.58" to 24.75", so do other brands in the 24 3/4" scale length. Fender's 25.5 varies by .20", PRS is the only factory built I've seen that is always the same 25" scale on every guitar.
In the end, none of mine have set up perfectly. They all have their quirks and I work around them. Cigar box guitars are not concert instruments. Perfect pitch is not what they are for. They are for the back porch, everybody singing off key and having fun. Listen to Seasick Steve, Robert Johnson or Blind Willie and tell me their guitars are tweaked to perfection. Don't let OCD spoil your fun.
Good words of advice. I was thinking when is a cigar box guitar not a cigar box guitar. When it is no longer fun. I think I will just chill out a bit and try to enjoy the quirks like you say.
Cheers
All scale lengths require compensation for the bridge. If you look at Stewmac online, their fret position calculator, each scale length for each type of instrument (i.e. guitar, mandolin, ukulele, classical, dulcimer) have their own "additions" for compensating for intonation at the bridge. The "true" scale length is a starting point, and then adjustments must be made at the bridge to address things like string gauge/type.
You mentioned trying this, but worried that moving the bridge back towards tail would change position of frets. Actually, only the bridge becomes further from the nut. The distance between frets remains constant.
The video clip here shows how a luthier sets up his bridge on a banjo. Different instrument, but same principle. The host describes in simple terms how and why.
https://www.youtube.com/watch?v=o3GPARmX0C0
Hope this helps
This helps a lot. I think I'm starting to understand now. It's been a combination of all these things. I want to have a guitar with near perfect intonation. I didn't realize how many factors were at play. When I change one thing I have been pushing another thing out. On the plus side I am learning a lot and I think I have got it.
Thanks again. Everyone on this site is very helpful. I will post some pic's and some audio. See if it passes the cigar box nation test.
Can you post some pictures of the neck, with some closeups of the nut area and a close side shot of the string height at the nut and the 12th fret?
Thanks for the interest.I will take some photo's and post them.
Cheers
i,m above my head for this type of detail,but noting your frustration,i thought i,d throw an idea at you,have you considered changing string guages,maybe your current strings are preloaded too much and when you bend them to fret,it sharpens them too much.as i said,a bit above me ,but just an idea
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