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I'm using RHINO3D 4.0 to model guitars. I'm having some difficulty designing the carve top, and the body contour; what would be the 'proper' method? I'm trying to model something similar to a les paul's arch top.

For the carve top, does it sound right if I just made a million lines horizontally across the guitar body with the correct profiles of the curvature and then apply the MESH command? What other methods might be better?

I was thinking of just making a circular type solid and using the boolean difference tool to cut out the body contour found on the back of the guitar.

Thanks a bunch!
David

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David
Vancouver, BC

The best way would probably to use a graft of around 1/4” increments and determine the elevation for each point on the graft and do as you said with mesh. If you want to do this in solid model you will have to create the point cloud mesh for front and back then convert form mesh to solid.

the only problem with this is ther may be a dramatic surface change that happens between graft intersection and that change may not be reflected in your mesh. so the tighter the graft the better but that means more elivation points to enter.

There are specialized interface tools that use a index probe to gather point cloud info. And there are companies out there that have 3d laser scanning capabilities you can hire to scan a top for you..

Complex compound radial surfaces which a carved top is are the hardest surface to map form basic cad input. Each cad system has different way of dealing with them. The geometry issues are the same but the way you inter the data may vary.

Your graft plan is reasonable. Keep in mind the more points (graft line intersections/ cloud points) you have the more accurate the mesh you will create.

the problem you will have with the Boolean approach is that most carved top contours are not spherically symmetric.

Sweep Along Rails, Network Surface, and Loft are your friends when it comes to making decent surfaces. Learn to make good 2D curves and the 3D work is easy. If you're in a jam it's good to be familiar with the Edge Surface command as well.

For the actual contour of the body you'll probably want to have a rough sketch to work from (scan one in and set it as a background image) and then use Interpolate Curve (the tangency option is handy!!). Rebuild your curves on cosmetic things to make them both smoother and smaller (data-wise).

On some things it's better to make a larger surface and then use the Trim command to cut it to size than to try and make your surface 'to spec' from the start. A Les Paul top is a good example of this: the surface you build will be symmetrical at the start and then trimmed to size.

Using a boolean is certainly one of the options for doing the back cutout; if you model up a beer gut to use as your cutting object you can get a perfect fit!

Rhino's a truly superb piece of software and you can do some great work really quickly once you know your way around.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Well.....I tried attaching a 3dm file and a zip file, neither of which will attach. If you want to pm me your email address I will send you the 3dm file.

It is of a double cut LP that I did some time back and this is one of the early attempts at getting a surface. It is not good enough to use, but will get you some practice and will allow you to get to where you need to be. It only uses 10 curves and the patch command to get your surface.

Mike

Don't let these guys fool you, doing a good surface for a carved top is not easy no matter what software you are using!

If you haven't done so already, I would recommend trying to surface out a neck before attempting a carved top surface...I posted a neck surfacing tutorial awhile back.

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http://www.PeakeGuitars.com

Well.....the patch system works pretty easily.

Mike

It is defininitely gets you something pretty quick, but check out how the recurve shape at the edge of the top changes as you go around the body. Using the patch method, it generally does not flow around the body consistently. You can tie it down more by using more profiles, but you will most likely still have some "ups & downs". It may be sufficient in that it may be easy to sand or carve these inconsistencies out.

The other method which I think Bob was referring to was to use Sweeps or Network Surfaces. These allow you to form a surface that follows the contours of the body a little better, but it can be a bit more time consuming to build a surface like this. If you were to model a violin or an archtop surface, you almost have to use this type of technique in order to make an accurate surface.

Even using Sweeps and Network surfaces, you will still end up with some parts of the surface that you have to patch in there.

One thing to keep in mind with generating surfaces is that it is best to try to surface things out using 4 sided surfaces as these will give you the fullest range of adjustability. Surfaces that appear to be 3 sided are typically generated as a trimmed 4 sided surface.

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http://www.PeakeGuitars.com

How about a top view of that guitar?? That looks like a nice double cutaway shape!

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http://www.PeakeGuitars.com

Hi Parser,

I'll do better than that. Send me your email and I will send you the file. You have to remember two things. It is not finished, and it was my first serious attempt at anything Rhino.

Mike

It is hard to tell but appears to me that near the sides the mesh you generated seems to curve in below the top of the bound edge. not much but just a tad. I of course can not confirm this with out viewing and quarrying the grid points in relationship to the UCS. The only reason I say anything about this is because this is a typical issue with building complex compound radial meshes with as few grid increments or reference points as it appears you used as displayed in the image. Now it looks really good out side of that and this may actually be the way you want to do this. But you might want to confirm tht the contour never dips below the edge unless that was intentional.

This is not meant as a critique but rather just something I visually noticed.

I'm working on an archtop surface at the moment...I'll post some pics of this this evening as this shows the other method of top surface construction we are talking about

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http://www.PeakeGuitars.com

Wow! Thanks for all the advice!

Is it possible to keep offsetting the original shape of the guitar, raising each new curve on the Z axis, and then draping over it? I'm still in the process of searching for a good tutorial for a arch top but it is so elusive!

Thanks for all the input!

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David
Vancouver, BC

That looks really nice! I think I came across that file sometime earlier during my search. Thanks for the help! What did you do to obtain this surface? My last patch attempt had the edges end up a slight bit funky.

Thanks a bunch!

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David
Vancouver, BC

Here are some screen shots of the archtop surface I've been working on...it basically consists of a bunch of 2 rail sweeps surrounding a central patch surface with a few miscellaneous surfaces filling in a few holes and forming the recurve around the horn.

I have yet to make a surface that is "perfect" but this one looks like it is good enough to cut with. I would offset the surface down to get the inside carve surface and then manually thin it out while tap tuning the top. One day I'll cut one out..! Too much other stuff going on to actually make this thing right now though..

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http://www.PeakeGuitars.com

A couple more comments on how this is made:
*everything starts with a good clean contour. I traced a benedetto .jpg file in Rhino to get me started and then moved it around until I liked what I ended up with.

*As mentioned, I made pretty extensive use of 2 rail sweeps; you can see that there are 3 major sections of this type of sweep. There are 2 "rows" of sweeps as you progress from the outside of the guitar to the inside. I really could have (and maybe should have) combined both of these one big 2 rail sweep. The third major section of 2 rail sweeps is the cutaway bout. The body is symmetrical till you get to there, then I wanted to do something different because I wanted the recurve to follow the contour around the horn.

*In doing those sweeps, you sometimes have to have a profile every 45 degrees...but with rhino it seems like you can get away with every 90 degrees.

*the last thing I did was to cap everything off with that central patch surface.

*there are certainly some other intermediary steps that I have left out. There is a lot of wireframe work in something like this...it definitely requires that you are familiar with all the spline editting/creation tools. In addition I did use some surface editting tools as well.

The main idea behind using the 2 rail sweeps is that this allows you to create a surface that follows the contours of the body. If you attempt similar shapes using patch or network surface, you sometimes end up with something that is pinched at the end, or just doesn't follow the shape as well as you would prefer. This method is more intensive than using some of the quicker methods but I feel I get better results doing it this way. Please let me know if you have any questions or comments....and by all means let me know if you see something I can improve on!

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http://www.PeakeGuitars.com

Quips and parser, here is a link http://www.cnczone.com/forums/showthrea ... post250583

Go to post #192 and I have an iges file there that was saved from my Rhino file.

Parser, my apologies for not emailing this to you. My wife has been battling breast cancer since May and ask me yesterday morning if she could have all my day! I of course gave it to her, but forgot to email you the file in the mean time.

Quips if I get a little time, I will do you a couple of screen shots showing the curves I used with the patch command to get that top.

Mike

Please don't worry about emailing anything! I would be happy to help you out if & when I could.

We'll keep both you and your wife in our prayers.

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http://www.PeakeGuitars.com

I attempted a guitar body that I normally make by hand in RHINO. Here is what I did to get here so far:

1) I made a line in the X axis of the exact width of the guitar, and a line down the Y axis. I then took a picture of my guitar and used it as a background image.

2) I drew the outline of the guitar using the ellipse tool and interp. curve; I then joined all the various line segments together.

3) I made cycloids all the way up and down the entire body... about 60 of them.

4) I tried lofting them at first, but my computer kept running out of memory. So I decided to just patch it with a stiffness of 8.

5) Using the original outline of the guitar, I trimmed the patch to the right size. <-- after patching, it ended up slightly larger.

6) I then used the extrudesrf tool and pulled it about 600mm

7) I then trimmed the bottom chunk of the guitar with a plane and capped it.

8) I decided to just cut a big chunk off the top and then cap it... thats how it looks now!

9) I also used an ellipsoid to cut out a body contour on the back of the guitar.

Is there anything bad about this method? I hope it will be good enough to machine.

Thanks!

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David
Vancouver, BC

David can you post a couple of shots of the guitar you are trying to get into Rhino?

Attached are two screen shots. One just of the wire frame I used and the second with a patch surface on it. Notice the number of wires used to get the surface.

I selected the outside profile curve first, the the cross sections second with the lengthwise cross as the last selection.

Mike

there's no real right or wrong way to do it. If the stuff on the screen matches the stuff in your head, then you got it!

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http://www.PeakeGuitars.com

In general, I would recommend staying away from drape command as it seems hard to control.

The basic idea is to create a "topographical" layout, but most guitar shapes are not simple offsets as you move up or down in thickness. You usually have to draw these contours manually since they do not change consistently as you progress up or down the part.

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http://www.PeakeGuitars.com