Tips for using SketchUp for drawing instruments

[Charlie Schultz]

I see a few folks (e.g. Steve Sawyer, http://www.mimf.com/phpbb/viewtopic.php ... 467#p53387) posting drawings that they've done using the free version of Trimble's SketchUp (a 3d modeling program).

You can run it off the web (I have not tried this and have heard it still has "issues") or download it here: https://www.sketchup.com/download/all (you'll need to create an account or use a google account).

Some comments from Steve:

I love Sketchup - I haven't done ANY kind of project, whether it be furniture, guitars, outside structures or even a complete remodel of my shop without starting with a sketchup drawing. Even things that I have full-size plans get re-rendered into a Sketchup drawing so I can make modifications or understand construction details that can't be easily visualized from a 2D drawing.

As to tricks or techniques, yeah, perhaps a few, but it's always a matter of being concerned about trying to teach your grandmother to suck eggs - you never know what other folks know, and risk insulting them with some stupid thing that they already know about, or something they've discovered how to do but with half the effort that my technique uses.

That said, I would say the most important tip is to find and install the Bezier Curve plugin. Can't do musical instruments with only arcs and circles. The other thing is to model complex curved surfaces by using Bezier curves as a guide, then simulating the surface as a series of triangles (all curves in Sketchup are actually a series of short line segments, each of which has end points and mid-points to which you snap the lines). Depending on one's patience for it, you can either get a complex curved surface somewhere in the ballpark, or damned close to exact, but it's a very tedious process. You can see an example of an "in the ballpark rendering" in the heel of the pic I just posted. I have another drawing of just the neck where I attempted to model a volute. Much more difficult, but I at least got some reference lines to work from when carving.

I've taught Sketchup classes to guys in my woodworking club, and would love to pass along whatever may be of value to others, subject of course to the concerns I mention above, so if anyone has any questions I'd be happy to answer them. I'm assuming that many others in this community also use Sketchup.

Anyone else have some tips or tricks?

[Steve Sawyer]

Here is a link to the Bezier curve tool I mentioned to Charlie:

https://extensions.sketchup.com/content ... curve-tool#

Here is a link to how to manually install the .rbz file:

https://help.sketchup.com/en/article/30 ... all-manual

Note the instructions for the tool on the download page. I find that it helps to have objects to snap to to define the curve. Also, each curve is defined by four points - the two ends, and the two "attractors" that pull the line into a curve. Normally you want all four in the same plane. If you don't, you get some really interesting 3-dimensional curves. This would come in handy when drawing something with a belly or pick-hand relief, but to control the placement of the four points, it can help to use guidelines, guide points or even temporary lines as points to which to snap. If drawing a flat curve, having a surface (defined as a group or component) to which the points will snap.

I should also mention that I will often (both with a vector drawing program like InkScape or with Sketchup) import an image (a JPG or PNG file) then use the drawing tools in that program to literally trace the image. I placed the drawing on the floor in my shop, sat on a bench and took a picture of the drawing with my phone, then imported it into Sketchup.

In the case of a dimensioned drawing, I used guidelines to define the critical dimensions, e.g. the widest points of the upper and lower bouts, the widths and length of the neck, the centerline, the length of the body etc. This makes drawing the various curves section-by-section using the Bezier tool much easier. In the case of symetrical elements such as the lower bout or the headstock, I copied then flipped the image once I had half of the shape done.

Hope this helps someone...

[Steve Sawyer]

Something else to mention, for those who haven't used Sketchup...

I know this is completely useless for the experienced builders, but for noobs like me, it can really be helpful to see the finished part in relation to the wood blanks from which they're cut or carved. Even when building furniture, I will use these techniques (particularly the x-ray view) to look at how complex joinery interacts with the various components, thus detecting when I'm going to cut into a dowel or tenon, or when two tenons are going to collide inside a joint.

Here is an example of a neck that shows the neck resting within the blanks that will be used to make it:

Here is the same set of components, pulled apart:

Here is an x-ray view of both the blanks and the neck. Note the rough layout of the volute, and that the blank hasn't yet been modified to provide some "meat" from which to carve it:

[James Meloan]

I tried to learn to use sketch up a couple of years ago but didn't stick with it long enough to gain any proficiency. I know there's tons of video tutorials out there, are there any you know of that are particularly useful for instrument makers?

[Steve Sawyer]

James - don't know of any off-hand that are specific to instrument building, but the techniques are the same no matter what you're designing. Robert Lange has a video series available that is specific to woodworking that is very good. Don't recall the price.

I've taught a number of people to use Sketchup. It seems there is a "hump" to get over at first, ironically more so for those who have experience with CAD programs. It's a whole different animal. Once you get over that hump, it's pretty much smooth sailing and you'll pick it up very quickly.

I have a short-scale bass in the build queue in my head. That one I see as being a swoopy carved body from some exotic figured wood, and am looking forward to modeling that with Sketchup. Should be interesting!!