Megathread: Les Paul/Aria Pro II PE-esque singlecut

[Prostheta]

The next step involves identifying what I call the "bridge line"; the line of minimum intonation. This is not the same as the line on which bridge studs are located, as this varies from design to design....we'll get to how we locate the bridge a bit later! In some ways this line is less meaningful that it first appears since it doesn't actually correspond to anything in the final design....except it sort of does. I'll clarify.

In the side XZ plane, this line should describe a plane perpendicular to the angled string paths, which doesn't necessarily correspond to one specific line across the top of the body. The higher the bridge is adjusted, the further back this line is pushed. The discrepancy is very small (in the order of a mm, see circled intersections in diagram) so out of simplicity we can discount it. Let's assume that we wanted the neck to join the body at (say) the 15th fret. We can temporarily treat the design as though it's a simple non-angled top-down design like a Fender and place this reference line based on that. There is always the option to move the line forward by a mm or whatever if that make you feel better, however intonation will always be moving in the opposite direction, so that mm works in your favour anyway.

 

tldr: even though you can be more accurate to no useful end, locate the saddle line in 2D and get on with it.

 

Now Playing: Killing Joke, "Psyche"

[Prostheta]

Since the design of the PE doesn't have a straight neck to body join, it's not easy to ascertain any sort of specific placement. I eyeballed the top horn and frets from photos and placed my a 24,75" scale template so that this lays between the 16th and 17th frets. This really doesn't have to be brutally accurate.

That leaves us with this arrangement. The entire design is translated so that the XY origin corresponds to the centreline and minimum intonation point intersection.

[Prostheta]

At this point we need to discuss the differences in neck angle and placement between the LP and the PE so we can make a choice on how to configure this instrument's geometry.

The typical Les Paul has three main planes to the body; the flat top where the bridge is located, the pickup plane between the bridge and end of the fingerboard, and the neck plane itself. In combination, these (usually!) result in the lower edge of the fingerboard binding meeting the upper edge of the body binding. A Les Paul-y type of neck configuration can be calculated from these values and requirements and you arrive at a specific set of elevation angles for the neck and pickup planes. Pretty easy once you see it drawn out.

In the case of the PE however, the situation seems less clear from photos I've examined. It's even entirely likely that APII's construction has changed over the years, especially given that the '77-'86 Matsumoku period were the "true" APII years and everything after was farmed-out hands-off to various factories outside of Japan. Brand name value only for the most part until recently (maybe). Anyway. The LP style of plane configuration didn't appear to translate to the PE exactly. This can be seen very clearly in how the binding gets super weird either side of the neck.

 

I'm genuinely not sure why this is, and yeah, it doesn't look good. I think we can improve on this. Normally I would be bugged to shit and end up having to understand exactly what I'm looking at here, and why it is so. I'd still come up with the answer that it looks like ass, so let's skip the song and dance unless you guys want to rattle the problem around?

How the binding works on the body-to-neck area for a LP means we can use that method of divining our plane geometry. Pick the best of either world.

[Drak]

Its done to hide the joint where the body switches from Mahogany to Maple.

I'm just pulling figures out of my ass here for a moment for argument sake...

If your core wood was 1.5" and your top (maple) was .75" (sorry I don't do metric)

Then the binding is going to go down to that depth, where they meet.

If your core wood is even less, say 1.5", and your top is 1", then the binding will be even deeper.

Because it's hiding the transition, wherever that transition happens to be.

The top of the carve at the neck area 'is what it is', (all the way around, actually) and the binding is not concerned with that final height.

Its concerned with hiding the transition between the woods, with the top being whatever the carve says it is.

[Prostheta]

Okay, so let's add a few things into our drawing to work towards these bits of geometry.

Firstly, the body binding is drawn in at 6mm tall, 1mm down from the base of the Maple into the Mahogany. I copied the scale template and placed that 19mm above the Maple for the reasons as discussed earlier. Currently this has no angle, but will be rotated around this 19mm point. We need a few more items. A line offset 2,2mm (1,2mm crown height of 6105 wire plus a notional 1mm for string distance from the frets) from the centreline of the scale template establishes the distance from the string path (which that line handily represents) to the surface of the fingerboard. Finally from this line, a rectangle representing a fingerboard thickness of 6mm is added. The fingerboard binding is assumed to be solely covering the Rosewood/Ebony and not slightly down into the neck wood like the body binding. So we're ready to manipulate these objects and figure out our planes!

[Prostheta]

This is a bit of a geometry trick. We're rotating a bunch of objects around a point at the bridge, but snapping them to a point which is offset from that axis. Essentially, the bottom of the binding. To do this, we add a guide circle with a radius equal to that offset. That is, the action/fret height/binding height, or 1,0mm + 1,2mm + 6mm....8,2mm.

[Prostheta]

Does this make sense? I've copy rotated rather than just rotated to show what happens. The important point is that the bottom of the fingerboard/binding coincides perfectly with the top of the body binding at the guide line indicating the end of the body at the centre.

[Prostheta]

I'm going to sense check this a little tomorrow, as the neck angle is showing at 5,5deg which is huge compared to an LP's 4-5deg. Either the Maple top is too thick, displacing the bridge upwards or something along those lines.....good job that we can methodically tweak anything to achieve what we need! A quick fiddle with lowering the bridge height by 2mm shows a reduction in half a degree or so of the neck angle. Shaving 2mm off the top would also realise an additional reduction of half a degree.

[Prostheta]

There is a slight discrepancy with the binding in that the body binding either side of the neck is slightly higher and lower since neither of them align with the centre of the neck/body coincident point. In theory this might leave a gap between the lower cutaway's binding and the neck and for the upper horn's binding to overlap the fingerboard. Or is it the other way around?  There are a couple of fixes or cheats that I can think of, however the discrepancy is so tiny that it might never even be noticed if I neglected to mention it. Literally, finish thickness grade differences!

[Prostheta]

15 hours ago, Drak said:

Its done to hide the joint where the body switches from Mahogany to Maple.

I'm just pulling figures out of my ass here for a moment for argument sake...

If your core wood was 1.5" and your top (maple) was .75" (sorry I don't do metric)

Then the binding is going to go down to that depth, where they meet.

If your core wood is even less, say 1.5", and your top is 1", then the binding will be even deeper.

Because it's hiding the transition, wherever that transition happens to be.

The top of the carve at the neck area 'is what it is', (all the way around, actually) and the binding is not concerned with that final height.

Its concerned with hiding the transition between the woods, with the top being whatever the carve says it is.

 

I was writing a lot today and missed this. I examined a lot of historical LP repairs and production videos. Yep, it hides that transition by design. It just nips into the mahogany. I arbitrarily chose 1mm in because there are no design pressures to do otherwise. I certainly wouldn't want it to go deeper than that as any recurve might become hairy, plus it reduces the distance from the back of the neck to the back of the body. The deep access contouring around the heel would then perhaps become part of that equation.

[Prostheta]

I put a little thought into why the neck angle came out as large as it did, and figured it out. I'd never measured it on my previous design, however the same issue manifests itself there. The point at which the neck and body meet is very different between a Les Paul and a PE....to the tune of around 38mm/1,5"! That reduces the distance from the bridge to the neck/body transition "pivot", increasing the angle significantly.

Immediately, there are a couple of options that can be taken here.

The first would be to simply accept the numbers for what they are - a 5,5deg neck angle. This might produce some slightly odd ergonomics that aren't the easiest to adapt to. My other guitars with TOM bridges have far more slight neck angles. It alters certain aspects compared to the design with a LP, specifically string break angles over the bridge. I'm not seeing that many positives with this one, just a "by the numbers, because".

....or secondly we adjust things out here and there. As discussed with the choice of bridge hardware, raising up the Hipshot Tone-A-Matic to the same sort of height as a traditional Tune-O-Matic leaves about 4mm of depth adjustment before the studs deck on the bushings. Recessing the bushings provides an additional 2mm of adjustment. So in principle, we could recover 4mm of bridge height and leave ourselves with a comfortable 2mm of downwards range and a mile upwards. I'd rather not shave the Maple down, even for the sake of a half degree neck angle recovery.

Lowering the bridge does affect a few things. The pickup plane changes its angle, and the height distance from the strings to the pickup plane reduces significantly, requiring pickup rings and pickup heights to be dialled in appropriately. The best thing to do is to play these changes out in CAD and see where the happy medium lays.

If anything, this probably goes some way as to explaining the oddities of the PE's body plane placements and why the binding is so weird because of that.

[Prostheta]

Briefly, let's talk about the pickup plane and a little on why we even have a neck plane.

Many guitar designs that would benefit from a neck angles don't necessarily have a neck plane or even a specific pickup plane. Consider a flat-topped Les Paul Jr for example.

There's no good way to introduce a neck plane into a flat top. Instead, raising the point at which the neck meets the body achieves much the same end. That additional 3-4mm or so of meat under the fingerboard mostly eliminates the need for a neck angle. Gibson even did this to models such as the Flying V back in the 70s. Sacrilege!

 

What this allows is essentially a flat 2D design more in line with the Fender top-down XY idea. Less manufacturing requirements in terms of angles and getting things just-so. No neck angle however, changes the ergonomics of the instrument as it no longer "wraps around" your body slightly and alters the downpressure over the bridge from a reduces string break angle. And it looks like ass when you have to hoist it up for a lot of height. This isn't so say that raising the neck at the joint precludes a neck angle. Both can be combined; a more slight neck angle plus a vertical offset. On some designs, this compromise between the two is preferable so that the upper frets are placed in a more playable position. The upper positions on that V look terrible....

Introducing a neck plane to a carved-top instrument can also simplify the neck construction at the neck end. A set neck tenon in a flat body/angled neck instrument not using a full-width tenon requires a shim of material to be left (or added) under the fingerboard to provide support. Milling this out is not entirely the simplest job to do, since we're not talking straight 90 degree faces any more, with adding a thin shim the slightly easier option.

----

The neck plane in a carved top (usually) runs parallel to the plane of the neck/fingerboard glueing surfaces. That way, the body wood in the neck plane provides a glueing surface either directly to the fingerboard itself or to some neck wood left under it.

Beyond the neck joint, the neck plane is then of no use. It serves primarily to support the bits of the neck missing either side of the tenon. So between the neck joint and the bridge, we have a new plane for the pickups which is essentially a dot-to-dot way of tying the two.

[Prostheta]

Ugh, that JPG compression. Hopefully you can read this.

So, at the bridge point we have a red line showing the string path, plus a parallel line below that calculated from nominal action (1mm), fingerboard thickness (6mm) and fret crown height (1,2mm). The magenta line of the neck plane coincides with the top of the body binding line at the neck-body coincident point. The blue line represents the pickup plane which is a simple dot to dot from the end of the fingerboard to the bridge line. The numbers now look a bit more in line with expectations, having reduced the nominal D/G saddle coincident points to 15mm above the Maple cap.

[Prostheta]

This also helps to illustrate why angled pickup rings are so important for carved top instruments. The base of the pickup ring fits to the pickup plane, whereas the pickup itself needs to be parallel with the strings. 4,45deg minus 2,1deg lets us know that our angled pickup rings need be so at 2,35deg to achieve this. We'll look at this again further down the line....

[komodo]

Gah! I suffered through this last year with the Black Queen. It was made worse with the Trisonics, body mounted and no great way to adjust up or down.
Lots of measuring, checking, rechecking, measuring, at almost every stage. I'm not sure I was ever 100% confident until it was strung up and I was playing it.
It also has a pretty strong neck angle (can't remember how much), but isn't really an ergonomic issue. 

[Prostheta]

I didn't think that ergonomics would be a huge issue, however I wanted to try and avoid that unless the design absolutely demanded it. The string break angle over the bridge saddles would likely be more of an issue. Clearly this is why the PE had such a weirdly modified area either side of the neck. Best of both worlds is a good way forward.

I've grown very accustomed to drawing everything out and knowing exactly where measurements are critical, what and where to check them, etc. There's often a series of knock-on effects with errors compounding each other. My worst enemy is always myself though, choosing to take a shortcut here or there just to get some positive reinforcement for the day. I always mess something up when I break from the diligence.

[Prostheta]

I'm somewhat nervous about how and when I can make this guitar happen "in the wood", since I am certain my employer will be closing shop in the coming weeks. I'd like to say "months", but it's really not that....I may have continued work with a business running parallel to my current employer, but that's likely in a diminished capacity hours-wise, maybe not at all. The bottom line here is that I'd like to build this using CNC with a secondary discussion on how to achieve this with hand tools only....neither of which are really available outside of my workplace. So this could get to point where I can only pursue it as theory, which is a major bummer. There's always something, it seems....

That said, I aim to do a few threads that take a concept and run it through the processes of design with discussions on how to turn desktop work into a real thing, choosing tools and practices that are most appropriate.

So this project is currently looking at maybe €600-800 worth of materials and hardware if my guessing game is on point. The wood won't entirely be cheap since it'll be pre-milled and dried (but should come with more reliability in quality because of that), hardware is coming from disparate sources with many outside of the EU (yay, import duty and VAT); everything should be bought at the same time on the basis of having a solid path through the build rather than piecemeal. We'll see what the coming weeks offer, but regardless of whether I can personally make this one happen, I can still detail how to design a complex carved-top instrument at the desktop and describe methods of translating that to different working circumstance....just maybe not my own!

[Andyjr1515]

For playing, although there is always an adjustment period from what you are used to, I think generally more neck angle is easier than less.

Based on that many LPs and the like are often around 5 degrees, 5.5 should feel like putting on your favourite old slippers.

In cases like this, always ask someone with arthritis ;)

[Prostheta]

Hahaha. Am I needing to be asking, Andy?

Adding in the neck angle that the initial draft suggested is eminently do-able, however I think I'll pick this aspect from the LP and not what the PE's neck-body joint pushes into the geometry. An actual PE doesn't have anywhere near this sort of neck angle, so it feels a little bit pulled out of the air. Discarding that weird binding and neck plane thing going on with the PE and sticking to the JFW formula from the LP is the right thing to do.

Aria did some weird stuff to make things function!

[Prostheta]

Gah! I feel like such as ass for letting myself get distracted by other ideas that bloom into projects of themselves.

Well, this PE/LP build is going to be financially burdensome compared to simpler builds. That much is pretty par for the course with Les Paul, topped PRS' and similar high end builds. Acquiring good woods for the purpose should always take as long as it takes.

My distraction at the moment is my Invaders guitar. I'd like to hope that I can make my way through that one (and its own problems) and make headway with this PE/LP before the end of the year. I'll go through the rest of the design work in creating a carved top in Rhino, then discussing how to extract that out to various methods of implementation, whether those be freehand carving (this will be theory only, I'm crap at that), a contour set for routing and of course the full CNC rout(e).

Normal service will resume.