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Probably a dumb question, but I'm new to this stuff, so I'm allowed.

I'd like to try designing a couple of custom body shapes for acoustic guitars. I don't plan on straying too far from the norm...basically what I want to do is start out with a normal guitar shape (a Martin 000 or dread, for example), and just re-shape some of the lines to my liking, while keeping the same general design. Maybe widening or pinching in the waist an inch or two, changing the contours of the bouts, or shortening or lengthening the body a bit, but nothing more extreme than that.

What I'm afraid of is that I'll spend countless hours designing the shape, and making all of the molds/forms for it, only for the finished guitar to end up being a dud because of something I did (or didn't) do when designing it.

That being said, what I'd like to know is if there is any way of knowing how a particular change in a guitar's shape (pinching in the waist or lengthening the body, for example) will effect the tone of the finished product without actually building it first? And if so, are those changes actually a product of the guitar shape itself, or are they more because of the effects those changes in shapes would have on the total volume of the box?

Hopefully the question is easy enough to understand, but I can attempt to clarify if need be.

Thanks!

Well....
(1) It's all been done before (for the most part), and...
(2) There's a reason most guitars are like they are.

That being said - go for it and report back to us.
Don't let us stop ya.

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"Act your age, not your shoe size" - Prince

I am pretty sure that Chris means what he says when he tells you to go for it. He's correct that the basic shapes have become the norm for a good reason. But we all see numerous examples here from excellent builders who stray from the norm just a bit, and come up with wonderful customized shapes. Personally, I have always loved the subtle changes in shape that Lars Stahl builds into his guitars. They don't stray much from the norm, but they are always beautiful--just a bit more rounded here and a bit more narrow there, but always exquisite. There are so many others who have presented elegant customized designs here. I myself strayed from the norm when I built my 17" arch top. I pushed all the shapes and made it truly voluptuous in its curvature, but only a bit. It still fits a standard arch top case. I love my guitar. No one seems to stray farther than our own Padma, but the sound clips he posts always sound very good to me. I see no reason why you shouldn't follow your creative instinct. Go for it!
Patrick

This is the topic Ervin Somogyi and I have been talking about for awhile now. I've really learned a lot because of it (lots of 4-6 page in depth incredibly informative emails). If it looks good to you, go for it.

You can use G-thang to design and readily modify body shapes
it has templates of popular shapes you can use as the basis for modification
http://www.liutaiomottola.com/formulae/gthang.htm
you will need to output the drawing file to a cad program for printing

Yo, PoppaWoodie

You thinks you asks dumb questions ...NOT! Dude, you is always allowed. It part of the rules ... you know...do what thou wilt.

Me suggestions is simple..."just do it!" For me other suggestions ... see me first suggestion.

In this game ... first thing to get is ... there are no rules. Many guide lines but no rules.

To answer your question more directly, ya shape and air volume have their effects, so does wood and construction techniques and who built the sucker...but so what?

Again, just do it! and be great full for that opportunity to do it.


blessings
Padma


PS... please post pics...lots of pics.....we like pics.


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Audiences and dispensations on Thursdays ~ by appointment only.


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Here's my limited understanding/experience:
- Narrower waist = tighter, more controlled tone, as you'd expect. Pinching an inch is a major change.
- Longer body = more/lower bass, as long as you're starting in the normal range (a longer body lowers the 'main air' frequency as the soundhole is further from the tail).
- Changes in the upper bout are considerably less important than in the lower bout, both for soundboard and air resonance effects.
- Air volume is important, of course, but so is the shape of the air cavity. The waist width affects the air resonances. Alan C has mentioned some surprising experiments on the effect of body depth (~neutral, IIRC).
- No one is likely to hit a bullseye for a redesign on a first attempt, but I doubt some tweaks would result in a dud, as long as you are in familiar territory for dims and braces. Many makers have successful takes on the GA, modified D, small J, big OM, etc.

There are lots of good tools and drawings out there. For smoother curves and more control than G-Thang, DraftSight is a free Autocad clone. DFX files for 000, OM, D, and J are available from the MIMF forum library (login) and Grellier's site. (Those files have splines with many many points--time consuming to modify. Retrace your own spline on them with about 20 points, then pull and drag.)

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David Malicky

I've found that size makes a difference(!) but shape is not, of itself, a major influence on the sound. For example, I have a neo-classical body shape and a "classical" classical body shape. There are pictures on my website. These guitars can be made to sound virtually identical when the main modes are tuned the same and they have similar monopole mobility. How stiff you make the back, or the brand of strings you use (as well as many other parameters) can make a larger difference to the sound than body shape. So as others have said - just go for it. Provided it still looks like a guitar you should be OK. Very small differences in a guitar's outline can give a major difference in the look of a guitar.

This program by Jon Sevy is really easy to use and you can get great body shapes with just eight or so points. And you can print out full size on a home printer and tape the pages together to get a full scale print. With a bit of practice you can also do bridge shapes and headstock shapes.

http://gicl.cs.drexel.edu/people/sevy/luthierie/software/software.html

(you want the guitar design java application). Jon has heaps of great guitar stuff on his site.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

When you're designing your custom body, don't forget that you'll probably want a case for it.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

I think Woody just pointed out your most important consideration..........!!! Have fun...!
Tom

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A person who has never made a mistake has never made anything!!!

+1 to the post above - I've messed around quite a bit with solidbody bass designs, with CAD outlines of inside case dimensions as overall guidelines.

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The member formerly known as erikbojerik....

Ya beat me to it !


I agree with Padma and Chris , Yes there are alot of variables and yes they matter . The Majority have been tried already , However you will enjoy the experiment and learn from it . Ask questions here , but also trust your gut . And just do it . One of the things I like to do is just go online and pull up Guitar / Mando pics and see what others have done and get some creative juices flowing .

Main point is .. Have Fun !

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Go for it!
The hardest part I can see is how it looks.
Cphanna said Lars gits look good,
because they are subtley different.
I agree!
Then again, unusual and weird is good too! Here's one I'm working on that is a Weiss style shape, cut short,
and with a solid neck.
Next one will be different,
Less sharp inside corners, for easier finishing,
and a tapered body,
which I think will look better.

These days, yeah, most everything has been done at some point, reported on, and mostly ignored. The most apparent form of pioneering happens within ourselves, to see things firsthand. Very little is new to us, self discovery is the name of the game. Why do we have to go to Paris or Australia? Plenty of people have been there, and we can learn all about it, but when you experience it yourself, it becomes special to YOU.

Its actually really fun...I use Delta Cad and am in the process of building a 12 string I drew using what I liked from a couple of different guitars.
I draw virtually everything and make full size templates off my computer.. the cad program tiles them on regular size paper and then I just tape together, so I can make the molds , sides , braces, headstock, etc...best thing is everything fits!!!!!

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MK5acoustics.com

How long to you think til Taylor designs their body shapes in a wind tunnel?

They probably already doing it.
Top secret.

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Francis Richer, Montréal
Les Guitares F&M Guitars

Here's my 2 cents worth. Consider the Breedlove CM. They wouldn't be getting $7 grand for it if it sounded bad. I have never built a guitar to a standard plan yet people tell me they sound good. (maybe they just don't want to hurt my feelings) Try this, build your design free style (no forms or molds) and see how it sounds and feels. Tehn if it works build the forms. I have always felt it is more about the wood thickness and the bracing shape then the body shape. Just go for it.

I think the majority believes that most every aspect of the guitar is a factor in how it sounds. Unless you do a really shoddy job putting the thing together, a guitar is going to sound like a guitar. Every change you make to the shape, wood choices, strings, scale length, is going to be miniscule all by itself. Make a guitar, then make another one significantly lager/smaller, and with a wood choice on the "opposite end of the spectrum" RW/Maple and then you'll see a significant change.

You shouldn't worry about making a "dud". The only thing you should worry about is making the thing properly. Looks and sound are secondary to craftsmanship. Make really good glue joints, as solid a neck joint you can manage, and fret the thing correctly and you'll be fine! You can't design a guitar to be wrong unless you do something that just isn't done. Make a wooden guitar shaped box using familiar woods and a spruce or cedar top, brace the thing so that it's structurally sound, and attach a neck to it with a good solid joint. Design whatever body shape you want so long as you can keep track of how everything works. You don't seem to be wanting to do anything controversial here. It's not rocket science

Oh and find a way to test the body shape before you go further. One thing you can mess up is feel. Odd shapes may not sit well on the lap.

As usual, lots of good responses.

It's always better to build something that fits a standard case. Making cases yourself is a pain, custom cases are expensive, and it keeps you from getting too wild about the shape.

Provided you stay within 'standard' parameters, build quality and wood are probably more important than shape.

Size does matter: bigger favors bass. It's easier to make a loud small guitar than a loud big one. Changing the body depth has little effect on the pitch of the 'main air' resonant mode, but it alters the sound by 'spreading out' the bass response: a deeper body is likely to be more 'even' in the bass, and (maybe) less 'powerful' (which is not the same a 'not as loud').

IMO, a pronounced waist tends to a more 'interesting' and 'even' sound, particularly in the mid-range. Compare a Dread with a Jumbo.

There are lots of folks, particularly in the Classical world, who will tell you that if you don't copy some 'Olde Master' instrument to the millimeter, you're doomed. A quick turn around any of the shows, like H'burg or Montreal or Woodstock, should convince you otherwise IF you listen with your ears and not with your eyes...

Wow! Thanks to all of you for the fantastic replies! You've given me much to consider, and have also given me the confidence to go ahead with my designs.

From reading these replies, it seems like the shape of the guitar does have some impact on tone, but not significantly more than bracing, wood selection, string selection, etc. when each is viewed in isolation, which is exactly what I wanted to know.

What I think I might do is mock up my designs out of cardboard first, which will allow me to check that the measurements are correct, that the guitar fits in its case properly, and also that it sits comfortably in your lap when played (at least as much as I can tell without the neck being attached). If everything checks out, I'll start with the build, and believe me, there will be no shortage of pictures when that time comes.

Thanks again to all of you! I don't know where I'd be without this place!

One thing no one has mentioned is that, even though life isn't fair, your curves should be. At least, that's what I think I overlooked, causing a bit of a problem with a custom shape I designed. I had read that you should use a spline--such as a plastic ruler or thin piece of wood--as a guide for drawing curves for a guitar shape. But I forgot this and didn't: I just drew curves that looked good and made my mould to follow them. When it came to bending the wood, it didn't "want" to conform exactly to those shapes. I used shaped blocks to hold the sides to the mould at the upper bout, waist, and lower bout, but there were places in between where 1/16" or a little more wouldn't conform. The wood faired itself. Perhaps these gaps would have happened anyway, but I think not so much.

Something about the faired shape actually looked a little better to me, so I thought there was no problem. However, I didn't realize that where the sides were not pressed to the mould there was an opportunity for them to be slightly off 90 degrees. When I cut the binding ledge, using the sides as a reference, it was slightly uneven, and this became clear when I scraped down the bindings. Because bindings are thin, a variation of as little as 1/32" is noticeable. I know now that I should have left the sides a little thick and scraped the bindings down to the sides, rather than the other way around.

Anyway, if I'm correct that this problem was caused by not using fair curves, when designing new shapes you should use computer-generated splines or, if drawing by hand, a flexible guide.

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Tim Allen
"Never hurry, never rest."

My Freestyle standard. Fit's in a D case.
[url][url=http://www.flickr.com/photos/charlesfreeborn/6205080415/][/url]
NGF-Freeborn-img_3457 by Charles Freeborn, on Flickr[/url]

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Freeborn Guitars
and home of BeauGuard©

One solution for cases is to make the neck removable. Then a standard hard shell suitcase can be used if you need to travel by air.