Routing slots after neck shape cut

[RVA]

Mates,

I need practice making necks, and I had this quilt maple blank, so I had some fun in the shop today. In a classic case of pure planning, I later discovered that the stability of quilted maple would be greatly improved by a couple of carbon fiber rods. However, I am not sure how to slot the channels at this stage. Of course, I would like the rods to run parallel to the truss rod, on either side. Any suggestions are greatly appreciated,

 

 

 

[RVA]

Make that "poor planning", not pure planning! I missed my editing window.

[henrim]

Truss rod channel would be perfect guide but it depends on your router base and guide if you can use it.

Other possible way is to mount the neck to a square piece that you use as guide. Clamps, double sided tape, screws (on peg holes) etc. 

Probably easier with a table top router but shouldn’t be too bad with a handheld either.

[Bizman62]

That's not going to be as difficult as what one fellow builder did for an old acoustic a few winters ago. See, first he had to strip the fretboard off. Not a big deal as he was going to replace it anyway so the only thing to consider was not to tear the actual neck. Then he had to plane the neck level, still attached to the fragile acoustic body. And then he finally routed two channels for carbon fibre rods. And of course glued a new fretboard and hammered new frets in.

Agreed, the trapeze and floating bridge construction allows for a bit more slack with the neck break angle than a glued one not to mention the thick neck - I happen to have a similar one and the V neck is over an inch at the first fret. Still not too bad for a novice.

After this lengthy prologue, let's start with the good news. What makes this much easier than, say, a Gibson type neck is the lack of headstock angle. Even a carved neck of this construction will lay flush on the table by its headstock and heel. Double sided tape is all you need for attaching but if you want to you can even drill holes for screws. Pilot holes for tuners and neck pocket screws can be used for that.

The next step is to guide the router. There's two ways: You can either align a beam with the truss rod and lean your router against that. Or you can build a template to be used with a bearing bit. My choice would be #1, a length of 2x2 would be easy enough to attach to the table.

Oh, and I'm talking about a handheld router here.

For a table router I'd attach the neck to a square piece of board to bypass the headstock and compensate the wedge shape of the neck.

[Akula]

https://luthierylabs.com/laboratory/templates-jigs/truss-rod-channel-jig/

 

I use something very similar. It's three pieces of plywood screwed and glued together to form a U-shaped channel. Then I use four bolts to anchor the neck in the middle of this channel, and run my router on the top. I can do the truss rod channel (or CF channels) on a square neck blank, or a shaped neck, and since the router runs on the top face of the neck itself, I could even do it after carving the neck.

 

 - Jam

[RVA]

Thank you all for the very helpful suggestions. 

@Akula, cool jig. I may need to build one

Edited December 10, 2023 by RVA

[RVA]

Side question please: Should I be concerned about the decreased surface area for gluing the fretboard to the neck with routes for the truss rod and two 380mm L x 3mm W rods?

Thanks for any guidance.

[Bizman62]

3 hours ago, RVA said:

Should I be concerned about the decreased surface area for gluing the fretboard to the neck with routes for the truss rod and two 380mm L x 3mm W rods?

Knowing that there's aluminium U channel truss rods that are 12 mm wide and commonly used by makers like Martin I wouldn't worry.

There seems to be a lot of discussion about that question and for what it's worth there was a dead link to StewMac where they allegedly had told that wood glue would work with carbon fibre rods in a guitar neck. Also it was mentioned in several occasions that sanding the carbon fibre rough improves the grip despite that there's no pores in the carbon. So in any case it seems that Titebond will stick to carbon fibre better than to plastic or metal. And as a final thought, there's wood that is not optimal for wood glues unless treated specially (sanded/planed or wiped with acetone) just before gluing.

And of course you can use epoxy if in doubt. Or replace the carbon fibre rods with hard hardwood rods.

[henrim]

Area as such is not decreased as the carbon fiber rods are glued in to the neck. Typically with epoxy. Granted PVA glue you typically use for gluing the fretboard doesn’t bond to CF quite like it bonds to wood. So essentially there is less bonding area. Some people cover the CF rods with a strip of wood. Others don’t care.

10 minutes ago, Bizman62 said:

So in any case it seems that Titebond will stick to carbon fibre better than to plastic or metal.

While carbon fiber itself is not plastic, the rods are carbon fiber reinforced plastic. Typically epoxy.

[ADFinlayson]

You can make/buy truss rod slot routing jigs which you use with a bushing on the router, no reason why you can't use the same template to route a carbon fibre channel too. 

Important to note that carbon fibre will stiffen the neck but it won't stop it twisting if it really wants to so I suggest you leave it a couple of weeks once you've got your fretboard on - wood glue will introduce water into the quilt so you may see a bit of movement. If that happens then you can skim any twist off the back of the beck with a hand plane before doing your fretboard radius and the scoop down to the headstock which should make everything flat and parallel again.

 

 

[RVA]

More useful advice than I asked for or could have hoped for. Thank you gentlemen!

[RVA]

18 hours ago, henrim said:

Area as such is not decreased as the carbon fiber rods are glued in to the neck. Typically with epoxy. 

So put epoxy in the base of the channels for the rods?

[henrim]

4 hours ago, RVA said:

So put epoxy in the base of the channels for the rods?

I guess there are many ways to do it. Hard to say what is the best procedure, but I would consider at least:

- Clean and degrease the surfaces before applying glue.
- If you have to scrape or sand carbon fibre, use respiratory protection and eye protection. It's nasty stuff and the fine dust apparently stays in lungs forever.
- It would be good to have glue on the bottom and the sides. Epoxy has good filling properties so in that sense I think a little loose channel is not a necessarily a bad thing.  
- Epoxy is high viscosity stuff so the rods want to raise when pressed in. Clamp them good to get any air and excess glue out.
- Try to clean any squeeze out before the glue cures. Messy business though.
- Wood glue or super glue may be easier or less messy alternatives. They don't hold as well, but should keep the rods from rattling. With them I'd have a rather tight fitting channel.

[Asdrael]

I did the same with the same configuration. I found the best way to do this is building a jig for a router. that you can offset. I talk a bit about it in my initial build topic here:https://www.projectguitar.com/forums/topic/55104-first-build-birthmark/?do=findComment&comment=633813

You'd be better off looking at the video from the guy I stole it from, better explained, better done.

https://www.youtube.com/watch?v=36n_8JH9FKM

Once the jig is done, it's just a matter of aligning it to you lines. He uses it for the truss rod but if you make the channels to clamp it down long enough, you can offset the jig enough to do carbon rods alongside the truss rod. You can even (and that's the beauty of this jig) use it on non square wood, or to make angled routes if that's your thing. I would however recommend around 4mm distance between the channels once they are routed, and as thin as possible carbon rods but as deep as the neck shape will allow for. You can get a much larger choice of sizes in a RC modelling shop than in a luthier shop by the way.

[RVA]

On 12/14/2023 at 9:26 AM, Asdrael said:

I did the same with the same configuration. I found the best way to do this is building a jig for a router. that you can offset. I talk a bit about it in my initial build topic here:https://www.projectguitar.com/forums/topic/55104-first-build-birthmark/?do=findComment&comment=633813

You'd be better off looking at the video from the guy I stole it from, better explained, better done.

https://www.youtube.com/watch?v=36n_8JH9FKM

Once the jig is done, it's just a matter of aligning it to you lines. He uses it for the truss rod but if you make the channels to clamp it down long enough, you can offset the jig enough to do carbon rods alongside the truss rod. You can even (and that's the beauty of this jig) use it on non square wood, or to make angled routes if that's your thing. I would however recommend around 4mm distance between the channels once they are routed, and as thin as possible carbon rods but as deep as the neck shape will allow for. You can get a much larger choice of sizes in a RC modelling shop than in a luthier shop by the way.

Thank you!

The funny thing is that I made that jig and used it for the truss rod channel. Then I cut the neck to shape. I didn't think about sticking the shaped neck to a rectangular board and using it again until it was suggested here!

I hope to give it a shot tomorrow. I spent today making cutting boards for Christmas gifts

 

 

[RVA]

I got the carbon fiber rods in, and thanks to this forum, I also knew to wear a breather while sanding them flush.

Thanks mates!

 

[Asdrael]

Looking good and tight. Just remember they are there when shaping the neck so you don't sand through For next time, you can live as little as 4 or 5mm between channels and still be golden.

[Bizman62]

30 minutes ago, Asdrael said:

Just remember they are there when shaping the neck so you don't sand through

That's a good reminder! The height of the rods has never been mentioned in this thread unless that piece of information slipped my eye.

Back in the day I compiled this piece of math for calculating how much thickness you'd need for a flat inlay piece so it won't be sanded through when radiusing the fretboard. It might help estimating how much wood there is to cover the rods. If the rods are properly seated to the bottom of the slots you'd only need a single mm to hide the rods. Strength wise they could even peek through but making that look good might be challenging.

The actual numbers depend on the neck shape, but for a half round neck R would be about 22mm at the first fret.  Y is what you'd want to know, in this case in two locations. And just for clarity the drawing is "upside down" for this purpose, the fingerboard would be at the tip of the triangle.

 

[RVA]

4 hours ago, Asdrael said:

Looking good and tight. Just remember they are there when shaping the neck so you don't sand through For next time, you can live as little as 4 or 5mm between channels and still be golden.

Good advice and info. Thank you!

[RVA]

4 hours ago, Bizman62 said:

That's a good reminder! The height of the rods has never been mentioned in this thread unless that piece of information slipped my eye.

Back in the day I compiled this piece of math for calculating how much thickness you'd need for a flat inlay piece so it won't be sanded through when radiusing the fretboard. It might help estimating how much wood there is to cover the rods. If the rods are properly seated to the bottom of the slots you'd only need a single mm to hide the rods. Strength wise they could even peek through but making that look good might be challenging.

The actual numbers depend on the neck shape, but for a half round neck R would be about 22mm at the first fret.  Y is what you'd want to know, in this case in two locations. And just for clarity the drawing is "upside down" for this purpose, the fingerboard would be at the tip of the triangle.

 

Thank you.  Your calculations are impressive. That side of the brain never worked well for me!

[Bizman62]

2 hours ago, RVA said:

Your calculations are impressive. That side of the brain never worked well for me!

My wife helped me.

[Asdrael]

What you can also do is make the neck profile in a CAD software and see where everything ends up being. It's honestly not too hard. I use LibreCAD and you can get a decent overview.

 

[RVA]

5 minutes ago, Asdrael said:

What you can also do is make the neck profile in a CAD software and see where everything ends up being. It's honestly not too hard. I use LibreCAD and you can get a decent overview.

 

Thank you. I finally have a reason to try out CAD software!

[Bizman62]

13 minutes ago, RVA said:

I finally have a reason to try out CAD software!

Or if you're lazy can use a pencil and a ruler you simply guesstimate use a contour cauge to sketch the cross sections at 2nd and 12th fret of your preferred neck profile and draw a picture looking like the CAD produced one.

[Asdrael]

That too I could write a short tutorial if there is interest on how to do neck profiles with the facetting method in a CAD software. It's honestly fast and very convenient, and in the end you can laser cut quite a few templates to check what you have on your guitars, what you like, and your progress once you make your own.