An acoustic for my nephew.

[Dave Higham]

About 10 years ago my nephew Dan asked if I’d make him an acoustic guitar. He knew what he wanted; an OM with a cutaway. I was frankly less than enthusiastic.

 Why? Well, I made electric bass guitars, I made them for fun and I made them for me. That way, if the customer wasn’t satisfied… I really didn’t want to make something to order, so to speak, that either he or I might be disappointed with. After all, the dreadnaught I made in 1971 was not really a success. It looked OK but it sounded crap … and it didn’t have a cutaway. I had made an acoustic bass guitar which looked nice… but that didn’t have a cutaway either. And anyway I had started making my next bass.

But after I’d made that bass, a year or so later, I didn’t really have room for any more. And anyway, I fancied a change so I decided to have a go. But I also decided not to tell Dan, so if it turned out to be a clunker he wouldn’t know, so he wouldn’t be disappointed.

So this is how it went. It’s quite a long story. I decided I’d try to include almost all the bells and whistles I could think of. So it would have a cut-away, a wedge shaped body for comfort, shallower on the bass side than the treble, an adjustable bolt-on neck, an access panel to be able to get at the adjustments without taking the strings off, and an arm bevel, also for comfort.

Claro walnut back and sides.Lutz spruce top.Honduras mahogany neck.Ebony fingerboard.

Starting with the tail block which consists of a bit of mahogany (off-cut from a bass) and a bit of old-growth birch plywood (I call it ‘old-growth’ because it’s very nice all-birch ply that I retrieved when we took it out of a shop we refit for my old boss about 40 years ago).

Glued them together, stuck a print of the drawing to them and trimmed them to size. (I draw up plans in 2D CAD for the instruments I make before I start. They also seem to get modified quite a lot along the way).

I roughly cut out a hole in the tail block with a jigsaw, but it really needs to be as smooth and circular as I can get it. So this stack of bits consists of1. The tail block

1. The tail block

2. A spacer with a larger hole in it

3. A carrier with a 5mm hole in the middle

4. A base with a 5mm hole in the middle.

The tail block is dowelled to the spacer and the carrier, and the carrier rotates on a dowel through its central hole and the base. The base is clamped to the drill table and the hole sanded by turning the tail block. Sanding increments are increased by delicately hitting the base with a hammer .

By the way, this isn’t a ‘How to do it’ thread. This is ‘How I did it’ and, as you’ll discover, it’s sometimes ‘How I made a cock-up of it’, so if anyone has any suggestions for ‘How I should have done it’, please feel free!

 

 

Edited November 30, 2021 by Dave Higham

[mistermikev]

ok, I'mma go out on a limb here... I get the feeling there is something there I don't understand.  Have no exp w acoustics, but have made my share of holes, lol!  Can't help but wonder why not use the ole 'router on a stick' trick to cut the hole?

[Dave Higham]

1 hour ago, mistermikev said:

Can't help but wonder why not use the ole 'router on a stick' trick to cut the hole?

Not sure what you mean by the 'router on a stick' trick, but I'd like to know. When I did this I was thinking the hole needed to be a precise diameter and perfectly circular (not quite the same thing) and this is the method I came up with using the means at hand. I later realised that it didn't need to be so perfect but that's often how one learns - from experience. I'm actually getting ready to do this again so, as I said, if there's a better way I'd like to know.

[mistermikev]

29 minutes ago, Dave Higham said:

Not sure what you mean by the 'router on a stick' trick, but I'd like to know. When I did this I was thinking the hole needed to be a precise diameter and perfectly circular (not quite the same thing) and this is the method I came up with using the means at hand. I later realised that it didn't need to be so perfect but that's often how one learns - from experience. I'm actually getting ready to do this again so, as I said, if there's a better way I'd like to know.

well you just mount the router to a board, then have a screw x distance away from the router bits edge... that is the pivot point.  drill a central hole... then cut a channel by dragging in the circle... then use jig saw to rough cut out, then follow with a straight bearing bit.

no idea what you mean by experience?  learning?  I just keep banging into things until it hurts enough that I stop lol!

 

[Dave Higham]

17 minutes ago, mistermikev said:

well you just mount the router to a board, then have a screw x distance away from the router bits edge...

Mmm. . . I'll have to think about that. The big router's too big. The Dremel would bounce off 1/2" birch ply. The palm router might work but adjusting the diameter would be the problem . . .

[ScottR]

4 hours ago, Dave Higham said:

Sanding increments are increased by delicately hitting the base with a hammer .

Whilst playing "the Delicate Sound of Thunder"?

SR

[mistermikev]

1 hour ago, Dave Higham said:

Mmm. . . I'll have to think about that. The big router's too big. The Dremel would bounce off 1/2" birch ply. The palm router might work but adjusting the diameter would be the problem . . .

well for such a small circle you'd likely need to use a dowel rather than a screw and you'd just have the dowel long enough to poke out of the material into the base of your router.  could always use half inch plexi for the base of the router but typical base is 1/4" should work fine. (I typically have used this to do anything from an 4"R to 32"R circle).  adjustable on the fly - no... but adjustable in the sense that you can drill multiple holes multiple distances from the outter edge of your bit and get any radius you want.  essentially the sm principle of this:

just done in diy fashion.  using a full size plunge router or carefully drilling a hole and using just a reg router.

EDIT: keeping in mind... is this the BEST way?  i have no idea... it's a pretty easy method to get a perfect circle and easy is usually what I like to call best lol.

[Bizman62]

57 minutes ago, Dave Higham said:

The palm router might work but adjusting the diameter would be the problem . . .

Would this solve that?

 

[Dave Higham]

1 hour ago, Bizman62 said:

Would this solve that?

It well might. I'll look into it.

[Dave Higham]

This is another piece of birch ply being sanded (on a slightly simpler jig) to fit nicely into the hole in the tail block. This will be the access panel. I realised, much later, that it doesn’t need to be a good fit and is even better with space between it and the tail block. But that was much later.

Here, the mahogany side of the tail block is being sanded to the profile of the lower bout. The plywood disc is taped into position just to fill the hole because, without it, the sanding dust shot out through the hole and straight into my face.

.

So here’s what it looked like at this point.

[Andyjr1515]

 Intrigued! 

Not so much  by how the hole was/could be formed as much as where this is going to be used in an acoustic build  

 

[Dave Higham]

It's the tail block, and the hole's for an access panel. Lets me get inside to adjust the neck (if necessary) without taking the strings off.

[Dave Higham]

On 11/30/2021 at 4:05 PM, Bizman62 said:

Would this solve that?

Made one! Not tried it out yet, but will soon.

[Bizman62]

And you've just saved some $40 - at least that's the price for a Rockler branded one. Plus yours has that big knob for the bolt!

StewMac make a similar one for Dremels, called the Soundhole and Rosette Routing Jig, to be attached to their Precision Router base. Together they're about $200 so if you fancy saving even more bucks, that would be the next build...

Just a reminder: don't cut through with the router! Make a groove and cut the rest either with a saw, knife or trim router with the bearing running against the freshly routed groove. If you cut through, the center piece will go all over the place which will ruin your work and be dangerous for yourself!

[Nicco]

1 hour ago, Bizman62 said:

Just a reminder: don't cut through with the router! Make a groove and cut the rest either with a saw, knife or trim router with the bearing running against the freshly routed groove. If you cut through, the center piece will go all over the place which will ruin your work and be dangerous for yourself!

Top tip there, Biz! Something easy to gloss over if you're not thinking about it. 

[Dave Higham]

1 hour ago, Bizman62 said:

And you've just saved some $40 - at least that's the price for a Rockler branded one. Plus yours has that big knob for the bolt!

StewMac make a similar one for Dremels, called the Soundhole and Rosette Routing Jig, to be attached to their Precision Router base. Together they're about $200 so if you fancy saving even more bucks, that would be the next build...

Just a reminder: don't cut through with the router! Make a groove and cut the rest either with a saw, knife or trim router with the bearing running against the freshly routed groove. If you cut through, the center piece will go all over the place which will ruin your work and be dangerous for yourself!

I do have the Stewmac set-up and you're right, it's expensive but I've found it good for delicate stuff like rosette rings. A solution for cutting through is to use a backing board. The pin goes through the  workpiece and into the backing board.

[Dave Higham]

To make the tail block as good a fit as possible when gluing to the sides, I stick some abrasive cloth to the mould with double sided tape and, with a couple of guides clamped in place, rub the block on the abrasive. A few pencil or chalk lines on the block show when I have contact all over.

I’ll leave the tail block there and start on the neck block. This is a bit complicated because of the adjustable bolt-on neck. It starts with a bit more plywood, a bit more mahogany and a bit of maple.

Mahogany cut and trimmed into two pieces and the plywood glued to one of them and trimmed to size.

The two central holes are for the bolts and the two larger ones are for threaded inserts.

Threaded inserts being installed.

[Bizman62]

6 hours ago, Dave Higham said:

A solution for cutting through is to use a backing board. The pin goes through the  workpiece and into the backing board.

That's a valid option but you'd have to attach the piece firmly to the backing board while leaving a thin layer untouched only requires securing the piece from rotating.

[Dave Higham]

Machining the block for the neck tenon, etc.

The other piece of mahogany glued on to form a sort of Spanish foot.

The foot is hollowed out. It’s not to make it lighter but to reduce the area to be sanded to fit it to the concave surface of the back.

 

[ScottR]

Man, you do clean work. No matter how inconsequential or monumental the piece, they have the squarest corners  and sharpest edges and cleanest holes.....damn.

SR

[Dave Higham]

Milling holes for carbon fibre struts. Why carbon fibre struts? Traditionally, steel strung acoustic guitars have a neck block to which the sides, back and front are glued (not necessarily in that order). The neck was most commonly attached to the block by a glued dovetail joint.

Under the constant tension of the strings this assembly can deform. The area of the soundboard between the neck block and the soundhole can become slightly concave and the neck leans forwards, the neck block effectively rotating forwards.

The carbon fibre tubular struts are fitted between the front of the neck block and the sides near the waist to prevent this happening. The first person I came across doing this was Rick Turner, co-founder of Alembic.

The struts were let into the neck block at different compound angles because it’s going to be a wedge shaped body; deeper on the treble side than the bass. These are the little jigs used to form the compound angles. I think now that I could have made them both at the same angle and it would probably have worked just as well, but, as the French say,”why make it simple when you can make it complicated?”

One of the two retaining bolts will also be used to adjust the neck angle (through the heel from the outside) and the little maple block will house the barrel nut on the inside. The mahogany block is reinforcement. It sounds complicated (and it is a bit) but all should become clear.

Here they are all shaped and glued together.

By the way, I didn’t invent anything here. Stauffer (to whom C.F.Martin was apprenticed) made guitars with adjustable necks in the 1840’s. In fact, all the features I’ve included on this guitar have already been done by someone else in one form or another. Rick Turner said “there’s nothing new in luthery”. As soon as you think of a ‘new’ idea, you discover that it’s already been done. Ralph Novak managed to patent the ‘Fanned Fret’ idea but shouldn’t really have been allowed to. Multi-scale fretted instruments have been around since the 1600’s.

[Dave Higham]

I need to sand a curve into one side for the cutaway.

So that’s the neck block finished.

[Dave Higham]

I started on the sides by drawing profiles. Profiling the sides before bending means there’s a lot less to carve off to fit the back and  front. It also means the off-cuts can be used for bindings.

The mould is placed on the radius radius dish with spacers of different thicknesses to allow for the difference in depth of the body at neck block and tail block, I also had to use different spacers at each side because of the 20mm difference in the wedge.

A piece of thick paper or thin card is taped to the mould and a line is then traced using a piece of pencil lead stuck into a small wooden block. This is done for both sides because of the wedge.

The resultant profiles looked like this. Linings are obviously going to be fun, not to mention the bindings, but I might even be able to get profiled bindings out of the off-cuts.

 

[Andyjr1515]

This is what I call an engineered build!   Love the attention to detail and precision of that neck block...

[Gogzs]

Yeah, the precision and attention to detail is inspiring. Keeping an eye on this.