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Discussion in 'Tele Home Depot' started by epizootics, Sep 24, 2019.
Just curious how much relief you have and what your action is.
I've got an unfinished 24" scale neck blank here, hardwood...
I'm tempted to make this one without a TR and put the frets straight into it .... a real one piecer..
would a 24" scale neck be less likely to bow without a TR?....
Cool beans! Any idea what the wood in question could be? As always, I'm lost when it comes to identifying Ozzie timber.
In my book, a 24" scale neck is less likely to misbehave under tension from the strings than a longer scale neck, with or without a truss rod, because (1) it takes less tension to tune your strings to a given pitch (which can however be nullified by using a heavier string gauge, like many people like to do with shorties) and (2) because the same bow would leave the nut closer to the plane defined by the top of the guitar on a shortie since the arc would be shorter. Also, for a given neck pocket length, the neck-pocket-to-overall-neck-length ratio increases if you make the neck shorter, and because the neck heel is usually thicker - and screwed down against the body - it is the part of the neck that is least likely to bend.
...at least that's my rationalization (and partly why I went for a short scale on this build), but I might be overlooking a bunch of factors
A true one piece neck is more likely to bend under string tension than one with a glued-on fretboard, but if your wood is well-seasoned (which seems to be the case here - it looks like reclaimed wood from interior construction?) and hard enough, and if you don't profile it too thin...I'd say you'll be fine!
By the way, the neck from this particular build still hasn't moved one bit in spite of the big changes in temperature and humidity our flat goes through in the winter & spring.
It's a piece of old building hardwood, probably a dressed stud... a Eucalyptus of some sort, spotted gum maybe?... nothing exotic...it seemed nice and straight, not too heavy...
I usually buy necks for builds... this will be my first carve when I put my mind to it.... I'll have to size it and radius the top and will need a jig of some sort to curve it... hard stuff this, it would be a hard sand to radius it....and cut fret slots..
here's the back...
..or go and get one of my old twisted necks and steam the board off... that might be another way to go..
I use a set of 6" long radiusing cauls a friend CNC'd for me a while back, but can be find for really cheap on eBay...No matter how hard the wood, if you start with good quality 60- or 80-grit sandpaper, you'll be done much quicker than you think. I like the shorter cauls because they give me the option of adding relief in the middle of the neck prior to fretting.
Necks are nowhere near as bad as they seem. However, you may want to go with a truss rod for your first one - it gives you more options down the line if something goes wrong. This being said, and looking at the Janka hardness for spotted gum, you'd probably be fine without a TR.
I'll need to remove 5mm off the top.... routing it off in a radius jig will help remove that material bit by bit to get the thickness right...
or flat plane it more and put a rw board on....
But look how spaced apart the growth rings are. I think it’s going to need help remaining straight.
I actually just evaluated the math behind this the other day for my brotherhood build.
My model, with 190lbs of string tension applied 0.5" from the centre of the geometry indicates there should be about 1/8" of movement of the nut.
Comparing it to a couple different shapes of steel/aluminum, it seems relatively reasonable.
Please note, this model assumes the neck is a rectangular prism, and that the elastic modulus is that of maple, approximately 1830 kpsi. Likely more deflection will take place.
Out of interest here. Are there tables that allow you to do the math assuming a semi-circle or arc, or can it only be done for a rectangle? My guess is not, or else you probably would have done it. And whereas I instinctively agree with you that there probably would be more deflection with a semicircular neck, I assume that it would not be a simple case of it being linear according to the reduction of material.
The figure you give does show (even for a rectangle) quite a lot of deflection. Then again, Leo did have to concede that the necks needed truss rods rather quickly into production.
Bently, I would love to see your model. I have have a couple of bridge shear and torque models (primarily for acoustics and archtops but they can be extended to electrics ) - I would love to see yours. Particularly where you think you will get 1/8 displacement of the nut.
You could definitely do the model for the arc, and without looking into it too much, you would probably just have to use calculus to determine the deflection of the arced back with a taper length wise. I'd probably just figure deflection of the arced neck of a wider size and of a smaller size and average it. The difference won't be substantial, as you aren't increasing the height, which has a cubic relationship to deflection, whereas width only has a linear relation.
The biggest point of concern for me is the elastic modulus of wood can vary a lot and my source was an old scholarly paper, i dont really trust it.
Sure, you can see some more info on my brotherhood build page, but I can go deeper in PM if you like. This is my FBD.