Still chipping away. I started a new model and it's much more organized. Still having a hard time with the transitions, but I feel I'm on the right track. I'll work on it more sometime this week.
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Custom Aluminum Neck but NOT a Luthier!
- Thread starter WilbursaurusRex
- Start date
I'm not quite sure, but I think so. Mind you, I'm far from an expert on the matter. The tricky part is that Fusion want to have a plane or surface for the profile, so no matter what the shape need to be "deconstructed" to a flat drawing first. Of course, with enough planes and sketches anything is possible, if a bit tedious.
Makes sense. "Feel" of a neck is very difficult to imagine from a drawing or model. This method doesn't make much sense for a one-off, though. That's why I ended up doing the 3D bits by hand.
The I'm referring to are shapes you create in your model that are used to add or subtract from your model. For example if you want to create a thousand star-shaped holes in a sheet. You then draw one of the holes as a body, then you use this body as a tool to cut holes using the boolean function (Or in this case the pattern function).
In your case if you want to for example make the transition from the neck to the headstock you can create something that looks a bit like a bell or funnel cut in two and use that as a cutting tool. The sketch profile can be as simple as a square with a corner cut off using a bezier curve. Create a sketch with the profile you want and use the revolve or sweep function to cut away the parts of the model you don't want. If you use your neck profile as the rail for the sweep you can in theory make the transition perfect towards the neck. This is a bit tricky to explain in text. I'll see if i can whip up an example in Fusion when I get home from work.
Another thing: Don't underestimate the fillet-function when doing stuff like this. It is very nice for blending profiles that almost have a smooth transition. A large diameter fillet can hide many sins.
You can use guide curves and 3D sketches. I was trying that yesterday and didn't have much luck.
A fillet is a good idea which I've tried, but didnt work, but now revisiting it, it's probably bc the contact point was still 2 separate solids and had not been joined yet. I may retry that tonight
So I made a quick model to illustrate. "Please excuse the crudity of this model. I didn't have time to build it to scale or paint it." 
So this is the starting point. One extrude for the neck and one for the headstock. Both are joined to one body.
To make things easier I projected the important features to a new sketch and drew a basic shape. This will be the cutting tool.
Then sweep the shape along the profile you want to blend the shape to.
This is the end result. The tool had the wrong shape, but the idea still works. You can shape the tool further.
This is just an example on how a filet can be used to blend transitions.
A slightly different way of doing the sweep is a "Path + Guide Rail" sweep. In this example I have used three sketches: 1 for the sweep (Neck profile, in this case), one for the cutting profile and one for the other part of the profile to follow on an offset plane. This method can be useful if you want to cut along two different different profiles. Keep in mind that the profiles for the cutting profile and the rail MUST intersect perfectly. Use project or intersect in the sketch to make sure. This will also make things easier when you want to change the profiles later. I have used the corners as references here, but you could build the cutting profile further as well.
For more complex shapes it can be useful to make a tool body. In this example I just chose "New body" from the sweep operation from the previous example. the idea here is that you can build out this tool further by adding other shapes to it. When the tool is made you use the "Combine" function and choose a cutting operation. Target is the neck, tool is the newly made shape.
First of all: Be aware where and what your references are. If bodies have to intersect it's preferable that they are based of the same plane/sketch/point. The "Project" and "Intersect" functions in sketches are your friends here.So this is the starting point. One extrude for the neck and one for the headstock. Both are joined to one body.
To make things easier I projected the important features to a new sketch and drew a basic shape. This will be the cutting tool.
Then sweep the shape along the profile you want to blend the shape to.
This is the end result. The tool had the wrong shape, but the idea still works. You can shape the tool further.
This is just an example on how a filet can be used to blend transitions.
A slightly different way of doing the sweep is a "Path + Guide Rail" sweep. In this example I have used three sketches: 1 for the sweep (Neck profile, in this case), one for the cutting profile and one for the other part of the profile to follow on an offset plane. This method can be useful if you want to cut along two different different profiles. Keep in mind that the profiles for the cutting profile and the rail MUST intersect perfectly. Use project or intersect in the sketch to make sure. This will also make things easier when you want to change the profiles later. I have used the corners as references here, but you could build the cutting profile further as well.
For more complex shapes it can be useful to make a tool body. In this example I just chose "New body" from the sweep operation from the previous example. the idea here is that you can build out this tool further by adding other shapes to it. When the tool is made you use the "Combine" function and choose a cutting operation. Target is the neck, tool is the newly made shape.
Since I've worked in Creo Parametric for the last 25 years or so, and don't know Fusion, this might not be possible, but here goes.
Rather than removing material from a initial extrusion, does Fusion allow you to build a body from surfaces? When I tried to accurately model a neck profile, I used a boundary blend feature.
You need guide curves for this, as others have mentioned. External guide curves are a good idea anyway, because no matter how you f*ck up a feature, you'll always have the guide curves which you do not need to re-do.
So, a profile at the first fret (or nut), and one at the last fret outside of the body transition, and then two lines connecting the beginning and ends of the two profiles, make sure you draw the profiles from the same direction (not sure how easy it is to change the startpoint of a curve in Fusion).
And then for the body and headstock transition you can use the same method to create separate surfaces, which can then be tied together (in Creo that is, hopefully Fusion can also fo surface modeling, otherwise Rhino might also be an option).
Rather than removing material from a initial extrusion, does Fusion allow you to build a body from surfaces? When I tried to accurately model a neck profile, I used a boundary blend feature.
You need guide curves for this, as others have mentioned. External guide curves are a good idea anyway, because no matter how you f*ck up a feature, you'll always have the guide curves which you do not need to re-do.
So, a profile at the first fret (or nut), and one at the last fret outside of the body transition, and then two lines connecting the beginning and ends of the two profiles, make sure you draw the profiles from the same direction (not sure how easy it is to change the startpoint of a curve in Fusion).
And then for the body and headstock transition you can use the same method to create separate surfaces, which can then be tied together (in Creo that is, hopefully Fusion can also fo surface modeling, otherwise Rhino might also be an option).
Ah! Yes, I understand now. I have used that before but not thought to try it here. Thanks for the suggestion and taking the time to model it out!
Hmm. Fusion can do surfaces, but I've never messed with them, or really knew when to use them
If Fusion works similar to Creo, you can use surfaces to subtract something from a solid or add to it, but then the surfaces will need to be an enclosed volume. You can also create a solid from surfaces, but then they also need to form a fully enclosed volume, in Creo, you can tie them together with a surface merge. The trick is that every surface should align perfectly with another (advice is to use guide curves).
For the transition from body to neck and neck to headstock, you might also have a look at rounds/fillets with a variable radius, this way you can start with a small radius at the headstock, going to a larger radius at the neck. But then, the neck profile should be circular, and it is probably more shaped as an ellipse, or maybe symmetric b-spline, not sure how well that works. I think I'd go for a boundary blend or n-sided surface. I would use a new guide curve which is one half of the neck profile guide curve.
Surface modeling is fun!
But it sure is a rabbit hole in itself.
For the transition from body to neck and neck to headstock, you might also have a look at rounds/fillets with a variable radius, this way you can start with a small radius at the headstock, going to a larger radius at the neck. But then, the neck profile should be circular, and it is probably more shaped as an ellipse, or maybe symmetric b-spline, not sure how well that works. I think I'd go for a boundary blend or n-sided surface. I would use a new guide curve which is one half of the neck profile guide curve.
Surface modeling is fun!
But it sure is a rabbit hole in itself.
This is still getting worked on little by little but I keep jumping around to different aspects.
I actually had a question about neck relief come up. Why is it that we shoot for the maximum amount of relief between frets 7-9? Being that the ellipse of the string vibrating would be greatest at its midpoint, wouldn't that be the 12th fret between the nut and the bridge? Since scale length is nut to 12th fret x2. Or is it just that the force of the strings pull on the neck enough to require relief be added in that area of the neck (since it isn't perfectly flat with the force of the strings acting on it?)
I actually had a question about neck relief come up. Why is it that we shoot for the maximum amount of relief between frets 7-9? Being that the ellipse of the string vibrating would be greatest at its midpoint, wouldn't that be the 12th fret between the nut and the bridge? Since scale length is nut to 12th fret x2. Or is it just that the force of the strings pull on the neck enough to require relief be added in that area of the neck (since it isn't perfectly flat with the force of the strings acting on it?)
Hello Wilbur;
It's good to hear that you are still working away at it.
A quick answer: Relief is generally measured by putting a straightedge (or pressing a tight string) on the length of the fingerboard; touching the nut and the last fret. Not from the nut to the bridge saddle. So the Action is not part of the measurement. It's only the curvature along the length of the fingerboard, with the straightedge touching at both ends. That's how the relief is normally measured and specified.
Measuring like that, the ideal relief curve is a gradual curve from the nut to around the 7th fret. That curve is one quarter of a shallow ellipse, with the radius increasing to almost flat around the 9th. Then it stays flat from the 9th to the 20th or whatever. It does not curve back up from the 9th to the 20th; it's a straight line. That's important. The simple explanation of why is to allow for clearance of the oscillating string when you are fretting up in the 7th to 12th zone.
That's the geometry you should be designing for.
Thanks for the reply Bruce! I must confess, I still dont entirely get it. I understand most of what you're saying and I've measured relief and set up all my own instruments.
a string vibrating between 2 fixed points (nut and bridge) would have its largest deviation at the mid point (12th fret), and I would think that would only shift toward the bridge as you begin to fret notes. I know I'm missing something so thank you for your patience.
a string vibrating between 2 fixed points (nut and bridge) would have its largest deviation at the mid point (12th fret), and I would think that would only shift toward the bridge as you begin to fret notes. I know I'm missing something so thank you for your patience.
Here's what I mean:
The deepest point shifts because the straightedge is shorter length and tilts down to touch the end of the fingerboard. That's the way we measure relief.
Still chipping away at this. Actually got some good deals on aluminum drops about 5 months back. Looking at doing a 2pc sandwich body and using binding around the perimeter of the body to hide the seam. Luthiers, do you find binding material usually runs true to size and consistent?
Also, I've considered a truss rod, but haven't really found a good way to integrate one and still be able to do the weight relief I was hoping for. It's still an option, but I'm also considering carbon rods. I'm thinking that would allow material removal while keeping things stiff and help restrict the movement of aluminum during temperature variations
Also, I've considered a truss rod, but haven't really found a good way to integrate one and still be able to do the weight relief I was hoping for. It's still an option, but I'm also considering carbon rods. I'm thinking that would allow material removal while keeping things stiff and help restrict the movement of aluminum during temperature variations
Narrowing in on design aspects. 32" scale bolt on. 1" thick body with .125 thick pickguard to help give clearance for electronics
Despite the thin body, weight is still an issue. After initial chambering and weight relief I was still looking at an 8.3lb body
Despite the thin body, weight is still an issue. After initial chambering and weight relief I was still looking at an 8.3lb body
Yep. Aluminum is still 3.8 times the weight of maple. You'll need to mill away 74% of the aluminum to get it down to the same weight as a wooden bass.
