RE: Shape the sides to fit a domed back in five minutes.

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RobF

Posts: 1611
Joined: Aug. 24 2017

RE: Shape the sides to fit a domed b... (in reply to Andy Culpepper)

I get a sore back making kerfed liners on the table saw.

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 20 2019 4:49:47

mango

Posts: 158
Joined: Apr. 2 2019

RE: Shape the sides to fit a domed b... (in reply to Andy Culpepper)

quote:

I did make one of those side patterns but mostly I use an interior form that fits inside the guitar when the sides are in, before the back linings are glued. It's made out of MDF and has 4 bolts tapped into it so it can be adjusted up and down for different guitar widths.

Interesting idea! That interior form is shaped like the plantilla then, but probably thicker and with adjustable height? And how did you find the shape of the edge of that form, where you trace the line from?

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 20 2019 11:25:19

RobF

Posts: 1611
Joined: Aug. 24 2017

RE: Shape the sides to fit a domed b... (in reply to Stefan Leon Kelly)

I think there are many ways to build a good guitar. There may be stylistic camps and ‘schools’ that favour differing methodologies and aesthetics, but the end result, to my mind, should be that the maker is able to build an instrument that is true to their own aesthetic and musical values by following a sensible method that gives them satisfaction and pleasure.

I know the use of dishes doesn’t get a lot of love on the Foro, but there are a lot of highly competent and successful makers out there using them to make beautiful instruments.

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 20 2019 15:57:59

RobF

Posts: 1611
Joined: Aug. 24 2017

RE: Shape the sides to fit a domed b... (in reply to mango)

Hi Mango, The exercise you’re doing with your program can get you a template if you increase the granularity, so you’re on the right path. You don’t have to build any taper into the template, just place it on the side blank at an angle so the desired end block depth tapers to the desired heel depth.

Also, there’s nothing to prevent you from using a higher radius longitudinal arc than lateral. In other words, if you don’t like the look of a 15’ dome, then you could make the longitudinal arc 25’ then use 15’ for the lateral braces, for example. Or take it one step further and drop the upper bout brace height a touch. Just take care not to get crinkles in the back, but that’s the whole point of fitting it.

I think the best path for a new maker to follow is to select a method, any method, and stick to it without too much deviation for their first build. The other methods will still be available to be explored in subsequent projects. That’s part of the fun of this. But trying to reinvent the instrument or to deviate all over the place, while not necessarily being a recipe for failure, is almost certainly not going to make the actual build process any more enjoyable and is unlikely to make a better guitar.

Just my 2 cents, of course.

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 20 2019 16:22:19

Andy Culpepper

Posts: 3023
Joined: Mar. 30 2009
From: NY, USA

RE: Shape the sides to fit a domed b... (in reply to mango)

quote:

Interesting idea! That interior form is shaped like the plantilla then, but probably thicker and with adjustable height? And how did you find the shape of the edge of that form, where you trace the line from?

This is sort of off topic from Stefan's original post because this still requires planing down the sides and heel/foot, but here's a picture of my jig. It's been a while since I made it but I think the profile of the edge was taken from a guitar I liked. It sort of tapers up from the heel to an inch or two past the waist and then gets more flat. But I always eyeball it and adjust with the plane until I get a pleasing line. Oh and it's MDF laminated onto 1/4 inch ply. And the tapped threads are hardened with thin super glue.

Images are resized automatically to a maximum width of 800px

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 22 2019 0:22:37

JasonM

Posts: 2055
Joined: Dec. 8 2005
From: Baltimore

RE: Shape the sides to fit a domed b... (in reply to Andy Culpepper)

That’s a nice idea Andy.

As far as radius dishes go, I’m glad I used one for my first guitar. One less thing to go wrong. Probably the only thing that didn’t go wrong lol. Although I like the more traditional look that the pros here use, I don’t look at my guitar and hate the way it looks either.

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 22 2019 23:46:44

Andy Culpepper

Posts: 3023
Joined: Mar. 30 2009
From: NY, USA

RE: Shape the sides to fit a domed b... (in reply to JasonM)

quote:

That’s a nice idea Andy.

As far as radius dishes go, I’m glad I used one for my first guitar. One less thing to go wrong. Probably the only thing that didn’t go wrong lol. Although I like the more traditional look that the pros here use, I don’t look at my guitar and hate the way it looks either.

Oh I didn't know you used one. Your guitar doesn't have "that look" that I was referring to. Maybe it's just when certain makers use too much of a radius.

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 23 2019 1:23:59

Echi

Posts: 1132
Joined: Jan. 11 2013

RE: Shape the sides to fit a domed b... (in reply to RobF)

I noticed that the new generation of makers trained by Stephen Hill and Pablo Requena make good use of a radius dish for their backs.
Probably the dish has a a gentle radius which makes it just barely noticeable. The average customer wouldn’t notice any difference.

It’s a little off topic, but do you think a 3 ply laminated back, made with quality woods of the same species and grain orientation would produce a noticeable effect in the overall tone?
I’m not so sure it would.
I know some makers are laminating backs even with nomex.
It probably would be a lot of work for no or little purpose but a laminated back would let you fit a domed back to flat sides, similarly to a violin.

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 24 2019 12:41:11

RobF

Posts: 1611
Joined: Aug. 24 2017

RE: Shape the sides to fit a domed b... (in reply to Echi)

I know a few classical makers who are making their backs with Nomex or wooden cored laminates, but I think when wood is used as a core layer for a back it’s generally cross grained. While laminated sides have been around for a long time, a number of newer makers are laminating in a relatively thick kerfed wooden core. Depending on the thickness and rigidity of the backs and sides, liners and even the back braces can be eliminated.

I think the main rationale is to prevent the top from losing energy through the sides and into the back, with the goal of increasing loudness. I’ve never encountered a flamenco made this way, maybe there’s some out there. I’ve heard some pretty nice sounding classical guitars that were made using modern style laminations, however.

Just an aside, I was given an old Gibson J55 with a broken headstock that I may or may not ever get around to repairing. It’s from the 1970’s and has a pressed laminate back with no back braces. The person who gave it to me said it was a good sounding guitar. I also picked up a similar vintage Aria classical at a garage sale for $20 that needs work to get the action down. But sonically, it kicks butt, loud and good tone to boot. I think it’s made with pretty well all laminates (maybe not the top, I’d have to check). As the old saying goes...plus ça change...

*edit* To address your original speculation, while the laminate would likely have some form of impact on the tone, I agree with you that it might be so little as not be noticeable. There are so many other factors at work. Maybe if a solid back was replaced with a laminate (or vice versa) then one might hear an effect, but even a replacement with a similar style could also have some amount of discernible difference, however slight.

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 25 2019 0:53:28

Stephen Eden

Posts: 914
Joined: Apr. 12 2008
From: UK

RE: Shape the sides to fit a domed b... (in reply to RobF)

I think having a domed back is pretty common place. I don't see any disadvantages to using one and a couple of very good advantages to using one.

Echi - Pablo Requena introduced the 25' radius backs to Stephen Hills course. Before that Stephen hated the radius back too. I don't know if he has made the change to using them on his own instruments. They use a 25' dish which is about the same for a lot tops.

I use a 15' dish for my backs for no other reason than that was what Pablo was using when I first started building guitars. I have used a 25' dish on some guitars where I was aiming for a more traditional look. Mainly because I don't like how inaccurate the traditional method is. It probably doesn't matter as wood is so pliable.

With regards to looks I don't think it matters. So many makers have their own take on what is right that they all end up looking different any way. I have seen some top makers use a difference of 10mm from tail block to heel! and it looks like a wedge.

There have been very few people through my workshop ever even notice that my guitars have a radius back. Most if not all players are only interested in how the guitar sounds and plays. Craftsmanship comes next you want the guitar to be well built obviously. Some are interested in the sound board bracing but so far none has said 'oh I have to have a traditionally shaped back'. So why make life harder?

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REPORT THIS POST AS INAPPROPRIATE | Date Oct. 25 2019 9:07:45

Andy Culpepper

Posts: 3023
Joined: Mar. 30 2009
From: NY, USA

RE: Shape the sides to fit a domed b... (in reply to RobF)

My (ignorant) comment with regards to using a radius dish has now been removed. I didn't mean to cast aspersions on anyone's craft. I think I have just seen a few examples where a steeper radius has been used and the way the heel looks is not to my taste personally.

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 26 2019 1:34:20

RobF

Posts: 1611
Joined: Aug. 24 2017

RE: Shape the sides to fit a domed b... (in reply to Andy Culpepper)

When I used to do dovetailed necks I found matching the heel to the slope of the back could be a bit of a pain. The top of the cap can be sanded to get it in line, but really the line of the lighter heel wood has to be done right for it to work.

Also, if I mess up the bee-stings into an integrated heel cap I’ll chisel it off and replace it with a separate cap. I had to redo the second cap once because I went too deep removing the first and didn’t like the line I got. In that case, I removed the second cap, restated the slope and added a couple of veneer layers to follow the line of the purfling to avoid having a too thick cap. Once the third cap was on it turned out looking quite good, like the whole exercise was intentional, lol.

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 26 2019 3:17:38

RobF

Posts: 1611
Joined: Aug. 24 2017

RE: Shape the sides to fit a domed b... (in reply to Stefan Leon Kelly)

This thread has had some focus on the doming method followed by Bogdanovich and Romanillos, where the lower bout doming on the workboard lies above the plane of the board. (*edit* I just realized I posted this in the wrong thread, but there is something side related at the end so I’ll leave it here.)

I’ve just finished bracing a top with a lattice pattern, which holds the dome very well. I thought I’d post a couple of pictures of the top as it shows the rationale of why they’re doing it that way quite effectively. The upper bout on this top is flat while the lower is domed, I probably should have put the weight on the sound hole side of the brace to show that more clearly. But the point of this is to show the natural unstressed lie of the top after the dome is introduced. For reference, the workboard pictured is flat (also note that the board is not pushing up on the center of the lower bout, the top will hold this shape when hanging freely, the flat board is just there to help show the effect).

Just an aside, this is a classical, I’ve never used lattice on flamencos.

Also, as the thread is related to side bending, here’s a handy little jig to hold the bent sides while preparing to box. I always touch the sides up on the pipe before assembly, but this helps to minimize spring back prior to that. Oh, and in the spirit of the thread, these sides were preshaped.

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Attachment (3)

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 26 2019 15:52:08

ernandez R

Posts: 739
Joined: Mar. 25 2019
From: Alaska USA

RE: Shape the sides to fit a domed b... (in reply to RobF)

Rob,
nice tread drift. I just cycled three sets of ribs in my newly fabricated double wide fox like bender and was thinking of a simple way to store them to prevent spring back. Your simple fixture with the dowels is perfect…

Just as many ideas about proper doming as builders I suppose. For the new builder such as myself it is good to get exposed to many ideas. I have thought about making a rib profile template but unless one is building with CNCed parts I think one could get trapped. I still get tricked by the waist and end up with a gap there, nothing that won’t be hidden by the bindings but still bothersome. Perhaps a proper template would save me the hassle ;)

For myself i do not see the top or bottom as being anything near a sphere section. I still trying to sort it all out and find the process of adjusting the rib kerfing hight and angle one of those zen processes right up there with chiseling out a rosette groove: one can use a power tool or whatever but using ones hands and eyes really connects one to the wood, bond line, and curves of of our creation.

HR

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 26 2019 22:22:39

RobF

Posts: 1611
Joined: Aug. 24 2017

RE: Shape the sides to fit a domed b... (in reply to ernandez R)

quote:

Rob,
nice thread drift.

I probably should split it into two, but then I’d have to find the other one.

Yeah, the dowel jig only takes a few minutes to make and it’s quite useful. For multiple sides you can stack them and then loop a cord around them longitudinally a couple of times, then do a gift wrap style turn above the waist and wrap it around the waist a couple of times, then back up over the longitudinal wrap, pull it all snug and tie it off with a bow. Much easier done than said.

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 27 2019 1:18:25

JasonM

Posts: 2055
Joined: Dec. 8 2005
From: Baltimore

RE: Shape the sides to fit a domed b... (in reply to RobF)

Andy, no hurt feelings here.

Rob, your pics inspire me to clean my work bench. And I second the dowel rib holder. Great idea.

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 29 2019 0:02:03

Echi

Posts: 1132
Joined: Jan. 11 2013

RE: Shape the sides to fit a domed b... (in reply to RobF)

Nice thread, with very useful contributions.
Andy, as you know the radius dish was introduced by Martin Co. to fit the back with a more standard and predictable procedure.
Obviously it doesn’t belong to the Spanish traditional assembly method and as a consequence the opinion about it are quite polarised.
For sure it works effectively for many people and without drawbacks as Seden pointed out.

Rob, you have a very clean shop and your guitar look flawless.

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 29 2019 10:36:00

RobF

Posts: 1611
Joined: Aug. 24 2017

RE: Shape the sides to fit a domed b... (in reply to Andy Culpepper)

quote:

Andy, no hurt feelings here.

Ditto for me too, Andy.

And thanks Jason and Echi.

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 29 2019 16:18:51

aaron peacock

Posts: 141
Joined: Apr. 26 2020
From: Portugal

RE: Shape the sides to fit a domed b... (in reply to RobF)

How is the back radius created?
Is the bracing pre-curved like the top?
How does pressure in a radius-dish, top or back, not merely stress the joints....(points where go-bars errr go?)

Here's a visual non-sequitur for your viewing pleasure.
I'll bet it does nothing sonically pleasing for the guitar but it sure looks cool...
I'll not ask how to cut a wiggly brace to follow such lines lol...

https://i.pinimg.com/originals/4f/60/0c/4f600cb34464903439b5efc57f9ab8a1.jpg

Images are resized automatically to a maximum width of 800px

Attachment (1)

REPORT THIS POST AS INAPPROPRIATE | Date May 8 2020 22:28:30

RobF

Posts: 1611
Joined: Aug. 24 2017

RE: Shape the sides to fit a domed b... (in reply to aaron peacock)

That looks like something Victor Diaz might do. Is it yours?

REPORT THIS POST AS INAPPROPRIATE | Date May 8 2020 23:13:14

aaron peacock

Posts: 141
Joined: Apr. 26 2020
From: Portugal

RE: Shape the sides to fit a domed b... (in reply to RobF)

Hello Rob,

No, I can barely plane a true surface, let alone goof around like this.
It's something I was admiring in a thread of similar backs on Pinterest.
I have never seen the bracing of such a back.

I inquire merely if the back bracing is pre-shaped for the doming and if complex middle-work or multi-peice backs alter the equation...

Also, if go-bar placement is a general concern with domed backs, fancy or otherwise.

I'm hacking away on my first solera at the moment, and will likely destroy much ugly low grade wood before I can even begin to ask appropriate questions here, let alone do work as shown above, lol... thank you nonetheless!

... by the way, at what point do such decorations negatively affect the tonality, sonority? I was under the impression that one could have a very active thin back for flamenco, and yet this indicates 'tank with steel strings & a truss rod' and some djembe-making thud wood, perhaps good for another style?

respect to all the actual luthiers here. I'm a wanna-be going for my first build...

REPORT THIS POST AS INAPPROPRIATE | Date May 9 2020 0:45:49

RobF

Posts: 1611
Joined: Aug. 24 2017

RE: Shape the sides to fit a domed b... (in reply to aaron peacock)

Yes, the back bracing is pre-shaped to define the doming. If that’s one of Victor’s backs, he has some fairly innovative bracing ideas using laminations and I-beam concepts. I think he shows some examples on his Facebook page.

But, of course, I have no idea whose back that is....

REPORT THIS POST AS INAPPROPRIATE | Date May 9 2020 1:55:47

Andy Culpepper

Posts: 3023
Joined: Mar. 30 2009
From: NY, USA

RE: Shape the sides to fit a domed b... (in reply to RobF)

Yes, if you're building an arched back you would curve the braces prior to gluing and then press them into a dish, like gluing top braces but usually with more arch.

With something like the above picture I always assumed you would actually inlay it into the back plate at a shallow depth rather than attempting to join it into center. It seems crazy to me to try to get a decent joint on that all along the seams, and I don't know how you reinforce them. But it wouldn't change how the back braces are glued, you would just take that back down to thickness and then glue whatever bracing you're using on the inside.

_____________________________

Andy Culpepper, luthier
http://www.andyculpepper.com

REPORT THIS POST AS INAPPROPRIATE | Date May 9 2020 2:02:01

aaron peacock

Posts: 141
Joined: Apr. 26 2020
From: Portugal

RE: Shape the sides to fit a domed b... (in reply to RobF)

Thank you Andy and Rob.

I-beams! I've seen some, and funny flying(floating?) braces with holes!
(reminds me of airplane wings...)
(more typical of classicals?)

Inlay. makes sense. I couldn't imagine trying to butt-join those curves but now I'm sounding a bit pervy, so I'm off to bed, instead...

..Victor Diaz... interesting top bracing system... thanks again

REPORT THIS POST AS INAPPROPRIATE | Date May 9 2020 2:16:15