Guitar Neck Volute Issues

I have been trying to model for a guitar neck I will be making. I have nearly everything ready but the volute (Where the headstock meets the round of the neck).

Image of what a volute should look like

I am looking to achieve a smooth transition like the picture above, but have not been able to get good results. I have tried to Loft, Sweep2, and NetworkSrf, but none of them have had satisfactory results.

Does anyone know what I should be doing here?

Joe Mark 1 Neck Model.3dm (256.9 KB)


Here are a couple of ways I would do it. First the over build method is relatively easy and produces perfectly smooth results but is less accurate relative to some of the design curves. It will also require some point editing of the volute surface to dial in the shape. Second the patch method (it does not use the surface patch command) requires complicated steps with lots of rebuilding and matching of surfaces. The results are more accurate but tend to be less smooth. In this case Rhino was unable to fillet the edge. Which required additional steps to trim out sliver surfaces and then blend everything together.

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I’m a pretty new at all this. I just started Rhino a couple months ago. I don’t entirely know what is going on in the above processes. Could you elaborate a little?

Here’s the overbuild file for you to play around with. I think it’s the better method especially for new users. Turn on the cv’s on the volute surface to manipulate into the shape you desire. Then use surface trim.

It would be too difficult for me to explain the steps in the patch method. I would need to make a vid tutorial for it.arm test.3dm (677.5 KB)

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Thank you very much. I am working with that trying to adapt it to my model. If it isn’t too much trouble, could you send me the patch file (second picture) just so I can have something to compare it to? I’m looking at similar patching tutorials right now.

Once again, thank you so much for your assistance.

Here is an image of an approach that is more like the patch but based more on simple curve geometry. I spent some time recently with another guitar maker helping with their cad skills. I see a lot of the same mistakes and over complication of geometry in your model. Rhino has great tools for deriving simple and flexible geometry. The main lesson is that the fewer control points and curves you can get away with the better for CNC output.

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Hey, thanks so much for the image. Could you go into more detail about how your approach works? What do you mean by similar to patch but with simple curve geometry? I’m sort of struggling to find a reliable method of executing this.

The best approach I can recommended to beginners is “build it bigger, then trim it back.” Most beginners will try to create their design to the exact size of their desired form. That’s too hard and not good practice; just make it bigger and trim it back.

Here’s a free video clip with all of my favorite modelling strategies in one place, from my Rhino 5 lynda course. If you’re not a member, here’s one more link for 10-days free.

The example by @Stratosfear was excellent, so I recommend you study his generously provided file very carefully.


would there be any way to use the overbuilt style while still retaining the same specific shapes for the volute edges I am looking for?
I am interested in that method, and was able to replicate roughly the same design that he did, but was not able to while retaining my specific curves, which are important to the finished model.

The volute transition was done in 3 segments using Sweep2Rails. The rail curves were derived from your existing geometry + intersecting an extrusion of an offset with the neck surface for the lower curve on the mid section. The rails were rebuilt to match points and degree with minimum count for each. The profile curves were all rebuilt to have the same point count and degree. Your original geometry had many segments and high point count which definitely complicates the output. If I were actually prepping this model for CNC I would probably start over with each element - heel, neck, & head to clean up and simplify the bits and pieces.

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I have just one question, and I’m sorry if this is getting troublesome, I’m not terribly experienced with these things yet. The only part I’m unable to grasp from your model is how exactly you made the lower curve on the mid section. I didn’t understand what you meant by "intersecting an extrusion of an offset with the neck surface for the lower curve on the mid section."
Other than that, I think this will likely be the simplest method for me to achieve. Thank you very much.

Curve → Curves From Object → Intersection

I took the upper curve - flattened and rebuilt it then offset it and extruded. I then created an intersection curve for the lower rail. Make sure the upper and lower rail curves have the same number of points and degree. I recreated your neck surface so it was longer and could thus be properly trimmed.

Thank you so much, I’m definitely getting there. I tried to do your method, but seem to have messed up somewhere . I used the OffsetCrvOnSrf command to achieve the curve I used.

Joe Mark 1 Neck Model.3dm (409.3 KB)

EDIT: slightly better results, but still odd seams:

Joe Mark 1 Neck Model.3dm (362.2 KB)

The essence of the problem is that your basic geometry is very complex. Your neck has 2 surfaces that don’t run the full length and you have somehow extended that with additional surfaces to get to the intersection. The sweep 2 rails gives a nasty seam because of the complexity of the underlying model. Your flattened curve has 23 control points in 3 different segments. Here is the model I was working with ->

  • Default. = your original model
  • Geometry = rebuilt & simplified geometry derived from your original
  • Full Neck = new neck head & heel model joined together (new transition at heel also)
    This model is not watertight as I didn’t rebuild all of your original geometry. Again - the more simple the input geometry the better the model.Joe Mark 1-rev1_RCM.3dm (528.6 KB)
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I designed a guitar (and built) myself.

it doesn’t help you, but maybe you find it interesting!

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