davewhite
Luthier / Guitar Maker
Luthier
Aemulor et ambitiosior
Posts: 3,548
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Post by davewhite on Jun 20, 2016 11:53:34 GMT
Rob - what I like about your guitar making is the way you resist the temptation to overthink things  |
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R the F
Luthier / Guitar Maker
Posts: 1,135 
My main instrument is: bandsaw
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Post by R the F on Jun 20, 2016 14:51:02 GMT
I find it so much easier than building guitars, though, Dave.
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R the F
Luthier / Guitar Maker
Posts: 1,135
My main instrument is: bandsaw
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Post by R the F on Jun 20, 2016 17:18:12 GMT
As you may know by now, I tend to make mistakes the first time round (and sometimes the second time, too) and have to re-do things. Well, I'm afraid this seems to apply no less to my "envelope of string vibration" calculations. Thanks to all for keeping quiet about it so as not to embarrass me. I'm attempting to rectify the error but it may take some time....
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Post by andyhowell on Jun 20, 2016 17:57:27 GMT
I don't know what you're all on about... don't you just glue some spare wood together, stick some nails at one end and wind strings around them? Precisely! |
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R the F
Luthier / Guitar Maker
Posts: 1,135
My main instrument is: bandsaw
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Post by R the F on Jun 20, 2016 22:06:24 GMT
I don't know what you're all on about... don't you just glue some spare wood together, stick some nails at one end and wind strings around them? Like this Guaneri viola neck attachment, you mean? |
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R the F
Luthier / Guitar Maker
Posts: 1,135
My main instrument is: bandsaw
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Post by R the F on Jun 21, 2016 16:50:36 GMT
I am aware that I may not be exactly intriguing everybody with this particular aspect of the build but here, for what it's worth, is the corrected version of the string vibration envelope upon first being plucked - but this time I've remembered to fret it at each stage:  Bearing in mind what's been said, I've reduced the vertical amplitude of the vibration to 1.5mm each side of centre and (as in the previous diagrams) the vertical scale is 10 times the horizontal scale in order to show what's happening a little more clearly. The end of the fretboard is 6.4mm high - don't ask why - and the frets are 1.19mm high because that's the height of the frets I use. I've only provided minimal clearance above the frets in this diagram but I don't think that affects what it shows. Even though it's taken many hours to produce this diagram - and even involved registering on a Solid Edge 2D help forum so that I could learn to draw it more efficiently - you may notice that what it suggests is pretty well exactly what the previous one suggested: that you need a very slight relief (it's about 0.5mm here) centred around frets 5 to 6 and the rest is straight lines. (The fretboard here is, in fact, dead straight from the left end to fret 6, then levels off and is dead straght again from 4/5 to 0.) Still awake? Well done! It's back to wood, glue and routers next... |
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francis
C.O.G. 
Posts: 2,483
My main instrument is: Whatever I'm building...
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Post by francis on Jun 21, 2016 16:54:25 GMT
Is that true for bass and treble sides? And what about neck relief along its length - very slight up-bow?
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R the F
Luthier / Guitar Maker
Posts: 1,135
My main instrument is: bandsaw
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Post by R the F on Jun 21, 2016 17:12:50 GMT
Thanks for feigning interest, Francis! This is neck relief along the length of the fretboard and you could describe it as a very slight up-bow from about fret 5/6 to zero. Earth-shattering, eh? (The treble side would follow the same pattern but less so).
(Action, out of interest, is about 2.5mm at the 12th fret and about 0.4mm at the 1st.)
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R the F
Luthier / Guitar Maker
Posts: 1,135
My main instrument is: bandsaw
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Post by R the F on Jun 21, 2016 21:35:00 GMT
Used my slightly hit-and-miss but simple binding-channel jig to router out the rear corners of the box ready to receive some (thankfully) simple bindings. This'll give you a flavour of how things stand:  Of course, you can't get right into the corners as you'd like to with any kind of jig so there was quite a lot of finishing things off with my little purfling-cutter (see front bindings for pictures) and with good old chisels and files. I wasn't quite sure what to do with the body/neck join at the back since the last one was okay... but only okay. Here it is:  This time I decided to carry the full binding right across the base of the heel, which left me with a thought or two about what to do with the heel. My first thought, of course, was to avoid doing the obvious; I always try to do that. "The obvious" in this case would be a heel cap with a nice line or two but then I had a vision of one of francis 's heels - what you might call a "bull-nosed" heel (if you remember the Morris) - indeed, a heel-like heel - so that's what I'm planning to do, Francis willing. So far it looks like this:  Messy, eh? but it'll come up nice. I probably didn't sound too enamoured of my router jig at the beginning of this post and that's mainly because it can allow over-enthusiasm from the router on occasion. Here's a little mess I'll have to sort out before I finish:  I'll have to see what can be done about that, too! Now, about those string vibration envelopes.... |
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Post by andyhowell on Jun 21, 2016 22:29:43 GMT
You might as well be speaking Klingon ;-)
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davewhite
Luthier / Guitar Maker
Luthier
Aemulor et ambitiosior
Posts: 3,548
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Post by davewhite on Jun 22, 2016 7:44:45 GMT
Rob, Cutting binding channels with routers is a tricky business - you need sharp router bits and the ability to stop the router from tilting either by hand or with a jig. Good progress though.  To add a few grains of sand to your well oiled string vibration analysis - what happens when you start using a capo on the guitar and your 5/6 fret "relief" position creeps its way up the neck as the capo moves up and what does this mean for the perfect fretboard design? Also does your analysis allow for the neck/fingerboard itself vibrating and interacting with the string? Internet "guitar headbuilders" need to know |
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R the F
Luthier / Guitar Maker
Posts: 1,135
My main instrument is: bandsaw
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Post by R the F on Jun 22, 2016 9:00:51 GMT
I'm glad you asked me that, Dave. I just happen to have a perfected diagram up my sleeve which I thought the clientele couldn't stomach but, since you ask, they'll know who to blame...  That's it with the angle-back of the neck to (10 times) scale and with the string fretted (or capoed) at all possible points to fret 19. I advise you shake your monitor if you want to see the neck vibration factor added in. As for the router, the problem is that holding the body against the jig is a bit precarious and it can suddenly whip the whole thing sideways if you're not thoroughly braced against it, which is what happened. I'll have to build one like yours some time soon. |
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davewhite
Luthier / Guitar Maker
Luthier
Aemulor et ambitiosior
Posts: 3,548
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Post by davewhite on Jun 22, 2016 9:14:03 GMT
I'm glad you asked me that, Dave. I just happen to have a perfected diagram up my sleeve which I thought the clientele couldn't stomach but, since you ask, they'll know who to blame... That's it with the angle-back of the neck to (10 times) scale and with the string fretted (or capoed) at all possible points to fret 19. I advise you shake your monitor if you want to see the neck vibration factor added in. And your conclusion for the perfect fretboard profile is . . . ? |
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francis
C.O.G.
Posts: 2,483
My main instrument is: Whatever I'm building...
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Post by francis on Jun 22, 2016 9:29:33 GMT
Surely your saddle height now will increase the rotational loading at the bridge!
Can you not get the same by rotating the neck profile 'up' slightly so the saddle height decreases?
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R the F
Luthier / Guitar Maker
Posts: 1,135
My main instrument is: bandsaw
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Post by R the F on Jun 22, 2016 9:38:33 GMT
(In answer to davewhite): Much the same as it was before I started! But, to be serious for a moment, I think I would have been aiming for more of a scoop around frets 6 to 11 previously and I now see that that could start causing buzzing up around 13 to 14. With my extended knowledge (!) I would shift the lowest point to somewhere near fret 6 since, as the drawing shows, this is where you get the main effect of the "linear" wave from the string at its longest. Incidentally, the scoop only measures about 0.5mm from the straight line at its deepest on this diagram, though this does depend on how much vertical vibration you build into the drawing; I've allowed 1.5mm either way from centre (at point of pluck), which I think is reasonable. I apologise to all who find this a bit "US luthiery forum" (which this forum happily seems to avoid) but promise I won't be measuring anything from now on. I just come out of it with the knowledge that the important area to deal with when preparing a fretboard is around fret 6 - and happily forget how I got there. |
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Jo whoever he is.
