cad The Lancaster

[Prostheta]

Hi all - this is the beginning of what should be a long-term project going through many stages. The guitar will be a fairly standard two-humbucker superstrat, however the point of the design is to document the process from beginning to end.

Part of this will hash in with the CAD series of articles I'm penning whilst other bits will be the basis for various how-to articles. A productive design despite being more or less a standard. Essentially, a guitar that anybody can build. Depending on the availability of time, I will try and make this using the most basic of tools and equipment. A simple everyman's build.

The name "The Lancaster" comes from the planes that a family ancestor in the RAF flew in his final operations of WWII. I figured that a more vintage "slow looking" design seems to mate with the bomber theme. It's a tenuous link, but a good starting point nonetheless.

[Prostheta]

The first step I take in any new design are the very basic specifications that define the instrument from the outset.

• Bolt-on with vintage square heel
• 25,5" scale
• Original Floyd Rose bridge
• 12" nut radius with 1,6875"/42,85mm width
• Non-tiltback headstock

The less important specifications which don't necessarily drive the design process

• Dunlop 6105 fretwire or "narrow, perhaps taller"
• Rear-loaded electronics
• Side-mounted jack
• 6-in-line headstock
• Radiused top/back
• Arm and belly cuts
• Ferrule-fitted hex bolts and threaded insert mounting

I'm open to opinions about the truss rod. In a perfect world, I'd like to use a Stewmac spoke wheel nut to adjust from either the heel end or in a slot between upper frets to get the best acting motion out of it. Alternatively, it might be a good opportunity to demonstrate a single-acting rod in a curved and filleted channel? I'm quite fond of U-channel rods myself, however I need to remember that as an "everyman's design" these aren't always easily available.

[Prostheta]

Okay, starting a new file from scratch in TurboCAD. I set my space units as mm with a precision of 1, or tenths of a mm. I can still manually place items to tighter tolerances. I also set a default grid of 10mm purely as a visual sense of reference. This is totally unimportant once we get working.

Using Imperial matters here nor there since we're working in decimal rather than fractional. I'll do the necessary conversions either way so Imperial users can follow.

[Prostheta]

I usually have all of my "standard" layers set up in a template, however I'm taking this from the top. My most important layer is one I call "guides" which I set up with a contrasting default colour. Anything that helps differentiate it from the rest of the drawing. The "0" to the right is that layer's Z order. Later on I might change the stacking order of layers for a bit of visibility.

[Prostheta]

Next, I'll draw the first two important parts of our reference geometry; the centreline and absolute bridge placement which is perpendicular to the centreline. Both go through the XY origin (0mm, 0mm). This was done by selecting the GUIDES layer, turning on Grid in the snap palette and using the Line tool.

 

Et voilà. (I forgot....turn the layer colouration to "By Layer"! That means anything you draw uses the layer's set default)

[Prostheta]

Okay, we have the basics from which everything else is built. The next step is to create a guides layer for our fretwork. Again a new layer is created and given a default colour:

 

 

[Prostheta]

We're going to cheat a little here. Cheat is a bit of a strong word because using geometry to your advantage isn't a shortcut in the negative sense! Grab your fret placement sheet, FretFind2D or alternatively use our basic fret calculator:

 

Inputting 25.5 calculates an even-tempered 12th-root-of-2 set of scale measurements. Here, we are interested in the values of the fourth column, "Distance from nut - Metric". Incidentally, TurboCAD happily accepts and converts values different to the current measurement system through manual input of 2in, 2", 2mm, 0.002m, etc.

[Prostheta]

By "cheating", I meant "using the measurement system to your advantage".

Firstly, activate the Select tool. Second, right-click in the workspace and activate "Make Copy":

[Prostheta]

The process from here might seem a little confusing in how we're doing it, but it saves us a bit of calculation and simplifies things. We're going to repeatedly copy existing guides to create a separate set of fret guides.

Firstly, select the vertical guide placed at x=0mm;

 

The object will change colour and transformation nodes and the centrepoint will appear. Next, in the Inspector Bar change Size Y from "600mm" (or whatever height your vertical guide is) to something slightly wider than the neck will be. I chose 100mm. Without pressing Enter, click into Pos X and input the first fret location. Now press Enter.

[Prostheta]

This duplicates the selected object with an exact copy, including the parent layer and appearance values. We made two changes ("transforms") simultaneously; the Y extent (from 600mm to 100mm) and X centre (0mm to 36,35mm). Doing these transforms individually (pressing Enter in between) would have created two objects with each individual transform.

We want to place this new object onto the Fret Guides layer. Simply double-click "Fret Guides" in the Design Director. The green tick will change to signify which layer that object exists on.

You might have noticed that the Inspector Bar says "36,3mm" rather than the value we inputted. TurboCAD internally located the object at 36,35mm but displays the measurement according to the chosen tolerance. It's all good.

[Prostheta]

The process from here is more or less identical to copying the initial guide. Ensure that you are using the Select tool and that the new fret guide is currently selected. One by one, type in the fret location values in the spreadsheet column, pressing Enter after each one. I went up to 24 frets even though I have not decided how many frets the finished design will have.

You should end up with an array like this:

[Prostheta]

I find it logical to work on guitar designs as I would look at them from the front. What we've done here is to place fret locations using absolute placement. It's better than relative placement ("distance from last fret") since any rounding is no issue, avoiding compound tolerance errors (±1% + ±1% + ±1% + ±1% + ±1% +....) which can play havoc with intonation!

The shortcut is that I temporarily used the X coordinate as a way of placing the frets. The fret locations are the wrong way around (left to right) and in the wrong place! We'll place one more guide and then flip the lot left to right. That will put things right.

Firstly, use the Select tool. Right click in the workspace and check that "Make Copy" is still active. Now, select the vertical green guide. In Pos X, input either 25.5in or 25.5" (the scale length) and press Enter. We are using the original Imperial measurement since that was the original value and the spreadsheet doesn't convert that value anyway. We'll now have this:

[Prostheta]

We want to flip that lot end to end. Right click in the workspace and deactivate Make Copy.

[Prostheta]

Zoom out a little if you need to. Click and drag a selection box around the vertical guides only, not the horizontal guide:

You can do multiple selections with Shift and Ctrl if you need to add or remove anything from the selection.

 

Next, input "-1" into the Scale X transform box in the Inspector Bar:

 

Press Enter:

[Prostheta]

And there we have it. Everything that we need to build the rest of the geometry from! I think at this stage I'll save my work....

In reality, I have this basic scale template already saved for use in different designs. By using it as a group including the bridge point at nut point I have an object which I can shrink or stretch to specific widths corresponding to a scale length. Since each fret is at a point correlating to a specific percentage between the nut and the bridge, the scale calculation holds true.

Let's make a couple of tweaks. These are simply visual aids to highlight important places later on.

Select the 12th fret (count them along and check the Pos X value in the Inspector Bar against the spreadsheet). Adjust it's Size Y to 150mm. Do the same for the 24th fret.

[Prostheta]

The next step that I like to take is to figure out the neck taper and string locations. The width of the neck affects how the body's heel is dimensioned, so we need to do this first.

We're planning for an Original Floyd Rose here, so referring to the specs sheets we find that we have a string spacing at the bridge of 10,7mm between strings. That said, there seems to be some variance....anywhere from 53mm total spread, 10,8mm and other values! A tenth of a mm isn't going to cause problems so we'll stick with that consistently.

Change to the Line tool and change the active layer to GUIDES. Change Snap Mode to grid only:

[Prostheta]

Zoom in fairly closely to the bridge area:

 

You'll find that as you move the cursor around the drawing area it is followed by a magenta diamond showing the snap point. Currently mine is snapping to every 10mm. If yours isn't, right click on the grid button in the Snap To selector:

...change it to 10mm

 

 

Edited September 18, 2015 by Prostheta

[Prostheta]

Next, draw a horizontal line 20mm wide:

 

Repeat this exact same line one above the other, equally-spaced until you have six:

[Prostheta]

Change from the Line tool to the Select tool and drag a box around all six of these lines.

 

We're wanting to space these out equally according to how the strings are spaced over the OFR. Since we're looking at 10,7mm over six strings; 10,7 x 5 = 53,5mm. In the inspector bar, input that size into the Size Y box and press Enter. The selected objects are then stretched to that height, automatically spacing them 10,7mm each.

[Prostheta]

We're now wanting to locate these guides at the bridge point. These will serve to tell us exactly where the saddles should be located at their furthest-forward mark.

Firstly, in the Snap To palette select Intersection and deselect Grid:

 

Click the yellow dot in the centre of the six selected lines (if they are deselected, drag a box and reselect them) to pick the objects up and hover the cursor over the point where the vertical guide meets the horizontal guide. The cursor should snap and a magenta diamond showing the snap appear. Click to drop the objects.

Alternatively, you can simply select all six lines and change the Pos X and Pos Y values in the Inspector Bar to 0mm.

[Prostheta]

State of play:

 

The next job is to do almost the exact same thing at the headstock end. Firstly, select the six lines and Edit > Copy them. Zoom out and zoom back into the headstock end before Edit > Paste:

[Prostheta]

Referring to the specs for the type 3 OFR locking nut, the E-E string spacing is 35,95mm. Change the size of the six line object group to this, and place over the nut-centreline intersection as previous:

 

Finally we want to place guides showing the absolute width of the nut unit. Firstly, left click anywhere away from an object in the workspace to deselect everything. Next, click the top line of the set of six. Then - holding down shift - click the bottom-most. Right-click in the workspace and select "Make Copy".

 

The nut specification say that the unit measures 42,85mm wide. Enter that into the Size Y value and press Enter. Deselect "Make Copy" in the right-click menu and left click in empty space to deselect all objects.

 

So this is what we now have (zoom out):

[Prostheta]

Before I knock off for the day, we'll add in the strings provisionally. Create a new layer called "Strings" and assign it a colour such as a mid-grey. Change the Z-order from 0 to 10. As we work, layers will be re-ordered and strings tend to be on top.

 

Change to the Line tool and ensure that Intersection is the only active tool in the Snap To palette. Select Strings as the active drawing layer:

[Prostheta]

Carefully click at each bridge location point to start a line, before moving the cursor over to the headstock to finish it at the appropriate end point. Use the mouse wheel to zoom in/out as you work:

[Prostheta]

All six strings placed: