An acoustic for my nephew.

[Dave Higham]

Thanks for your comments @Andyjr1515 and @Gogzs. I spent my working life in engineering so I suppose it shows.

[Dave Higham]

I’d decided to attempt a Florentine (pointy) cutaway so I started by making a simple bending former. Here it is in action. It’s in the cooling down stage here. I don’t muck about trying to take photos while it’s heating up.

Bending the rest of the treble side on the home-made Fox-type bender.

The rest of the side bending went more or less OK. There was some spring-back but the sides went into the mould fairly easily. I started assembling the sides by gluing this block into the pointy cutaway junction. I actually managed to get a good mitred joint of the two side pieces, but I can’t remember for the life of me how I did it L. Which is a pity, because I want to do another one.

Then I trimmed the sides so the rest of it fitted into the mould.

[Dave Higham]

After the sides were trimmed, the neck block was glued in place. This needed a few clamping cauls because of the complicated shape.

Here it is glued.

And the tail block getting glued.

Then a session of ‘driving the bus’ to sand the sides and end blocks to a 15 foot radius using the sanding dish at 2.34 p.m.. It doesn’t take long, thanks to the pre-profiled sides; even so, power steering would be nice!

This is the result.

Although I didn’t think to take a photo, I chalk all the surfaces to be sanded, so when there’s no chalk left, I’ve sanded enough.

[Dave Higham]

Many people think that the more rigid the sides are the better, and solid linings stiffen the sides up quite a lot. Some laminate the sides which makes them even stiffer. Some even laminate them with a kerfed core, which makes the sides so thick that thay don’t need linings. That’s a bit beyond my scope so I decided to make laminated spruce linings

The outer form of the jig is hinged in two places. It makes it slightly easier to get it together when the laminations are trying to slide all over the place. Mine were especially trying as I decided to profile them like the sides which also meant that they had to go in the form at an angle. This also meant that, as the back linings are profiled there is a right-hand and a left-hand lining and, because of the wedge body, they’re not reversible. The first lining I glued up didn’t seem to fit the side or follow the profile at all. Then I realised I’d made it ‘wrong-handed’ so I had to make another one. So when I made the lining for the other side I thought long and hard about which way round it had to go in the form and then made that one ‘wrong-handed’ too! (Told you there were cock-ups).

But before gluing in the linings I have to make the buttresses for the Carbon fibre struts. Two bits of wood and two wedges to help me drill the holes at the correct angles.

One of the holes being drilled.

Then they are sanded to fit the sides in the same way as I did for the tail block.

More sanding

And shaping the profile.

[Andyjr1515]

I like this build a lot

Proper facilities and proper engineering skills.  Great combination

 

[Dave Higham]

Thank you Andy.

[Dave Higham]

Gluing the first strut and its buttress in place. The CF tube is glued into the neck block and the buttress with epoxy and the buttress glued to the side at the same time with fish glue.

The same strut seen from the other side.

Both struts and buttresses glued in place.

The linings are then notched for the buttresses and glued in place. After a little more work with the radius dish, this is what it looks like. You can see from these photos the peculiar shape of the linings.

The front linings were much easier as they started out straight. I also made an improvement to the form by screwing on these guide pieces. It made it much easier to use.

[Gogzs]

Clinical work, I hope once this is done, you keep building and posting here. It's stuff like this that keeps me coming back to these forums, great job.

[Dave Higham]

I decided to have a go at an arm-rest bevel which meant I needed a much thicker lining in that area. I had a lot of helpful advice from Texan luthier Steve Kinnaird on how to do this so I followed his method. There are 7 laminations, each about  2.5mm thick, so I had to bend them roughly to shape on a hot pipe before gluing them together in situ. They are not yet, however, glued to the side. Here, 5 are glued and 2 to go.

All glued

If I’d thought about it a bit more, I’d have made this before gluing the tail block in place. As it was, I had to fit one end of the first 3 strips to the tail block (the 45° angle).

Smoothed out the steps inside.

Did a bit of spoke-shaving and sanding.

. . .and finished up with this.

Trimmed it to length, glued it in place, fitted and glued the other linings and this is the result.

And a view from the top.

I glued in some side strips. These are supposed to stop the sides from cracking if they receive a shock or, at least, prevent the crack from travelling. Some just use calico strips glued to the sides. Some think they are a waste of time and don’t bother.  In case you’re wondering how that hole in the side got there, it got there with the aid of a drill, a jigsaw and some files and sandpaper and it never crossed my mind to take any photos of the process. In this photo it still needed a bit of work; elliptical holes on a curved surface aren’t as easy as I thought.

Edited December 18, 2021 by Dave Higham

[mattharris75]

I've never seen linings look that good. Your work is ridiculously clean, just amazing. When I look at pictures of my own kerfed linings it makes me feel inadequate. 

[Dave Higham]

12 hours ago, mattharris75 said:

Your work is ridiculously clean, just amazing

I suppose I go to ridiculous lengths to make it look that way (or to hide the mistakes)

 

[Bizman62]

Così è (se vi pare)

[Dave Higham]

Time to start on the back and front plates. I don’t find joining the plates easy. I’ve tried everything except routing a slot between the two halves (which should be foolproof but I’d need to make yet another jig). The best join I ever got was by simply running them over a jointer, but my planer/thicknesser blades were knackered when I did this. I eventually got them good enough by a combination of improvised shooting board and sanding board. I joined them in the same way as the front, but of course it didn’t occur to me to take photos . . .

 

So, having joined the front and back and cleaned up the front I started on the rosette. Random mosaics were in vogue when I did this and I rather like them, (well, some of them) so I dug out my box of bits and sanded some of them to about 2mm thick.

I stuck them down onto a piece of 1mm ply.(The stuff they use to make model aircraft)

This overlay showed me what the finished circle should look like. Er… you may have noticed it’s not the same rosette. I’ll explain later.

Trimming to finished size.

Trimmed.

[Dave Higham]

After giving the area of the soundhole a couple of coats of shellac I then cut the recess in the sound board for the rosette and managed to do it without any tearout.

I glued the circle in with fish glue and, when that was dry, next day, cut a groove round the inside and outside for the purfling veneers

After giving the grooves another coat of shellac I glued the purfling strips in with CA. They were quite tight so just a few drops of CA were all it needed to glue them in.

I glued the purfling strips together before gluing them into the channel. I find it easier than wangling several separate strips in at the same time.

I took some of the surplus off with a block plane and then sanded the rest flush with the top.

[Nicco]

This is absolutely sensational. The engineer in me is loving the attention to detail and how meticulous your work is. It's a pleasure to follow along. 

[Dave Higham]

7 hours ago, Nicco said:

It's a pleasure to follow along. 

Thank you.

[Dave Higham]

I then moved on to bracing the back. Here are all the back braces clamped together to sand the 15-foot radius in the radius dish.

Starting to sand. Pencil lines on the surface to be sanded will show when  it’s finished.

And there are no pencil lines left.

Started by gluing the X-brace in place.

Then forgot to take photos until I’d glued and shaped all the other back braces.

I marked the positions of the back braces on the linings and cut recesses for them where necessary. The Dremel router base is mounted on a board long enough to span the whole of the body. This keeps it rock-steady whilst routing small notches in a narrow surface.

[Bizman62]

Yet another way to skin a cat!

The Dremel router base extension is a clever tool although most builders would just take a chisel. Both the Dremel and the chisel require a steady hand so you don't carve through the actual side but then again I've seen even that been deliberately done as the binding channel will cut that very edge of the side away.

Do you have a stopper pin or two on the bottom side of the extension to prevent cutting the side? Like so:

 

[Dave Higham]

On 1/1/2022 at 11:01 AM, Bizman62 said:

Do you have a stopper pin or two on the bottom side of the extension to prevent cutting the side? Like so:

No, no stopper pins. It would get a bit complicated as they would have to stop at a curved surface which isn't always the same. I just route up to the sides and it doesn't really matter if I cut into them a bit. I cut the braces a little bit short, to leave a gap between their ends and the sides. Braces have been known to expand in length (under extreme conditions) and push the bindings away from the top or back.

[Dave Higham]

Now to start on the front. I shall ramble on a bit here, so bear with me. When I started drawing up plans I found French luthier Christophe Grellier’s OM plan on his web site and then thought it wouldn’t hurt to ask around about bracing.

I’d been thinking about the PRS acoustics that Martin Simpson and Tony McManus were playing at the time. I’d had a brief chat with Martin Simpson at a folk festival in the UK, and he was genuinely enthusiastic about the PRS guitar he was playing.If you’re not familiar with Martin Simpson, there’s loads of stuff on You tube. For example:

https://www.youtube.com/watch?v=EAoQGSiVsy4

The PRS acoustic was developed for Paul Reed Smith by an independent luthier called Steve Fischer and has what they call Hybrid X-fan bracing. I’d also come across another luthier, Stephen Sheriff, who uses a similar bracing pattern. So, I thought, there’s no harm in asking, and I wrote to them both, asking if they were prepared to share information on their bracing systems. I wasn’t counting on getting a reply from either one; after all, they are both professional luthiers.

I’ve often said that the world-wide community of luthiers, both amateur and professional must be the most generous one there is. Even so, I was a bit gobsmacked by the answers I got from both Steves. In a nutshell, they both said ‘yes, I’ll tell you anything you want to know’. So, I finished up with a long email from Steve Fisher, explaining his bracing pattern and giving dimensions, etc. and an even longer one from Steve Sheriff with masses of information. He also sent me a full-size, fully dimensioned hand drawn plan of the guitar he makes which is the nearest to an OM and other goodies like radius templates and CF sheet which he uses for bridge plates. So there I was with an embarrassment of riches. I decided to start with the Stephen Sheriff version. By the way, he goes under the name of Edwinson Lutherie.

As I said, I’ve used the ‘tent’ method when joining fronts and backs but I’ve sometimes had trouble getting both halves aligned, as, especially if both halves are not dead flat or aren’t the same thickness, when I push the two halves down, the glue grabs and that’s it. So this time I did it in the go-bar deck. The go-bars hold both halves down flat and the wedges force the two halves together. There’s a strip of polythene film under the join area which stops them sticking to the base and helps them slide together when pushed by the wedges. It seemed to work OK.

Edited January 2, 2022 by Dave Higham

[Andyjr1515]

And those are just the back braces!

Awe-inspiring work.

[Bizman62]

17 hours ago, Dave Higham said:

No, no stopper pins. It would get a bit complicated as they would have to stop at a curved surface which isn't always the same.

In that case, shouldn't a single pin aligned with the router work? I can see a flaw in that as well: getting the pin close enough to the router bit can be challenging.

[Dave Higham]

On 1/3/2022 at 8:40 AM, Bizman62 said:

In that case, shouldn't a single pin aligned with the router work?

It might.

If I had a production line, making the same instrument time after time, it might be worth it.  But I don't. I make instruments as a passtime. It's a hobby I enjoy and in the past 15 years or so I've only made two identical instruments (a pair of ukuleles) and I found it a PITA having completed an operation on one, having to do it again on the other.

I started making bass guitars because I was plonking along on one in a little folk-dance band and thought 'I could make one of these'. So I did, out of the remains of an antique solid mahogany chest of drawers.

It was a 5-string neck-through all-mahogany with EMG Jazz Bass pickups

Then a 4-string bolt-on, padauk body, maple and walnut neck, Seymour Duncan MM pickup.

A semi-solid 5-string similar to a Rick Turner Renaissance in rosewood and spruce.

A 'headless' 5-string for which I made everything but the strings and the Glockenklang electronics.

Etc., etc.

I admit to sometimes thinking how I can make a jig or fixture to do some operation, and then think 'don't be daft, just grab a plane or a chisel and get on with it'!

James Olsen, who makes very beautiful and expensive guitars for the likes of James Taylor has a collection of routers, one for every operation that needs one. But he makes guitars in batches and they start at $20,000.

[Bizman62]

1 hour ago, Dave Higham said:

If I had a production line, making the same instrument time after time, it might be worth it.

Fully understood and my suggestion/question wasn't meant to criticize how you do things. Seeing tools and jigs like the last one simply make me think how they work and could they be easily improved. It's part of the way how I learn things, pondering pros and cons.

1 hour ago, Dave Higham said:

make a jig or fixture to do some operation, and then think 'don't be daft, just grab a plane or a chisel and get on with it'!

That's what I was thinking about when I saw your Dremel rig. A couple of strokes with a razor saw and chiseling the piece in between away. Or maybe just using the chisel...

[Dave Higham]

The front has a 25-foot radius and the front braces get the same treatment as the back braces. All the braces are clamped together to sand them so there’s less risk of wobbling than doing them one at a time.

Starting by gluing the X-brace and the cap.

Now I need a bridge plate. This will be laminated from a 0.6mm carbon fibre sheet and a piece of padauk about 1.9mm thick. Apparently padauk is a very musical wood and I had a whopping great plank of it.

They were glued together using 30-minute epoxy in the radius dish. The MDF caul was also sanded in the dish to a 25-foot radius.

The bridge plate was then trimmed to shape and a piece of cross-grained spruce sanded to the same thickness as the bridge plate and trimmed to fill the space between the bridge plate and the X-brace.

Here they are being glued in place. The same sanding caul was trimmed down to fit the bridge plate.