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form-less guitar building
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Author:  Tai Fu [ Wed Nov 02, 2011 3:48 am ]
Post subject:  form-less guitar building
Does anyone have any comment on building a guitar without a form, which Cumpiano suggests in his book because "it gives better freedom when deciding the shape of the guitar".

I am thinking this could save me a lot of plywood if I don't have to build a form, but what he suggests in the book doesn't involve radius dish (or maybe he cut the radius dish into guitar shape) or using go-bars for clamping, instead he used a bunch of cam clamps.

Right now I am just thinking how do I incorporate Cumpiano's technique to include radius dish and go bars, but without cutting the dish because I prefer to leave them the way it is (other than to glue it to a backing board)?
Author:  mqbernardo [ Wed Nov 02, 2011 6:08 am ]
Post subject:  Re: form-less guitar building
in my only guitar (a classical), i´ve built without a form and without a radius dish - with a slightly scooped at the lower bout solera. it did have the periphery flat, so it was easy (to some extent) to get the sides perpendicular to the top. i guess that with a radius dish it would be difficult to get the sides to align properly at 90º. IIRC Mr. Cumpiano also used a flat solera in the book, but with a cork sheet so it could accept and adapt to a domed top.

on my next guitar i´m thinking of getting side forms for better consistency (and maybe laminate the sides with some nootka cypress). plywood is still not that expensive.

cheers,
miguel.
Author:  mqbernardo [ Wed Nov 02, 2011 6:12 am ]
Post subject:  Re: form-less guitar building
i´ve re-read my own reply and found it not of much help (as usual...) Sorry,Tai.
Author:  Michael.N. [ Wed Nov 02, 2011 6:56 am ]
Post subject:  Re: form-less guitar building
Building without a form or mould is entirely possible but building a modern Classical/SS without a Solera is another matter.
You can build without a Solera but it wouldn't resemble the method of the vast majority of Classical Guitar builders.
I rarely use any mould but tend to use 'work forms' - basically flat boards cut out to slightly larger than the final Guitar outline. These are for early Guitars that don't have the dome feature - a true flat top. You still end up using plywood though. It's hard to avoid unless you really do want to build straight onto a soundboard or the Back. It's possible but scary and a lot can go wrong. Here's one that I did, built straight onto the Back - no workboard:

Image

If I were to build a Classical in this manner I would probably glue the fan struts on first, shape them and give a very slight curve to the two harmonic bars. Glue the bottom block and top block/neck to the soundboard. You can glue little wooden 'tabs' to a drawn outline of your plantilla. It effectively becomes a mini mould. You can see the idea here at around 1:17

http://www.youtube.com/watch?v=SVWlM4vzKUU
Author:  RaymundH [ Wed Nov 02, 2011 8:24 am ]
Post subject:  Re: form-less guitar building
These guys have it down pretty good:

http://froggybottomguitars.com/guitars/the-sj-blog.html
Author:  DennisK [ Wed Nov 02, 2011 9:17 am ]
Post subject:  Re: form-less guitar building
I build formless. You won't get shapes absolutely symmetrical, and sides won't always be perfectly vertical, but if those things don't bother you then it's a lot more enjoyable than cutting up tons of plywood.

The style lends very well to true flat top, or dome top with flat perimeter, but not so well to the radius dish style with a radiused perimeter. A form is very useful there, to assemble the rim first and then sand it in the radius dish while the form holds it steady. You could try assembling the freestanding rim with solid linings to stiffen it up, and then hand plane the radius into it, and give it a final light sanding in the radius dish to get a good mate for clamping to the top using the dish as a caul.

Of you could skip the dish altogether, and just plane the approximate radius into the sides after bending... of even before bending, if you're doing an existing shape where you can make side templates and mark where the high and low points of the radiused rim will be, and freehand some curves between them. Then glue to the top with dentellones (also angled on their tops to support the radius).
Author:  jfmckenna [ Wed Nov 02, 2011 9:20 am ]
Post subject:  Re: form-less guitar building
I used to use a mold but now prefer to work on an open board. The method that Cumpiano uses is to make a 'solera' by lining a poster board cut out of your guitars shape with 1/8th inch cork probably about as wide as your linings.. So when you mount the top face down and clamp it such that you can apply pressure to the bridge patch then the top essentially domes under pressure. Then you glue the sides on. I've used this method on at least 20 guitars or more and I've found that it works quite well.

A radius dish and a go bar deck will work well just the way it is.
Author:  Bryan Bear [ Wed Nov 02, 2011 9:54 am ]
Post subject:  Re: form-less guitar building
I have built instruments with and without molds. At first I was resistant to building molds/form because I wanted to use different shapes and was low on storage space for all the forms afterwards. starting out, I went completely free form, then I wanted to start using a dish to radius my rims and glue braces so I tried really minimal outside molds made from scraps. That worked, but not nearly as well as making a good solid form. You can be successful either way, but I think your expected work volume can help you decide. I'm pretty sold on the benefits of forms outweighing the freedom of not using them (even as a small time hobbiest). If I decide to do something funky that I know I will never repeat, I can see myself doing another free form build, but by and large I will make molds. For me, the little time upfront saves more time and frustration later in the building process - if I'm building more than one of that shape it is a no-brainer. If you are planning to do this for a living, I can't imagine the cost of some extra plywood should even factor in. If a mold is right for your goals get the plywood and don't look back, if not. . .

As for Cumpiano/go-bars/molds, I think most people have read that book and learned quite a bit, but have also incorporated other methods. The great thing about that book is that it gets you building without setting up a huge shopfull of tools. Over time, people adopt other methods to speed up/simplify the process. At lest that is how it is going for me.
Author:  dunwell [ Wed Nov 02, 2011 11:48 am ]
Post subject:  Re: form-less guitar building
I use a rig similar to Cumpiano's with the baseboard slotted to take big dowels cut from a piece of banister. I also made pieces of hollow form dish that I cut to the profile of my instruments. I bolt these to the baseboard and then slide the big dowels up to the hollow form to define the location of the ribs. You can see this in action in my Luthier Pages link off the home page of http://http://dunwellguitar.com/. Follow the links to the the Let's Build A Guitar pages.

Alan D.
Author:  theguitarwhisperer [ Wed Nov 02, 2011 12:17 pm ]
Post subject:  Re: form-less guitar building
It's possible to get symmetrical shapes and perpendicular sides using the moldless formula. It's also possible to dome tops that way as well. It just takes a little more time than with a mold, and different techniques.

To get the shapes symmetrical you have to bend the sides very accurately. I use the method Todd Stock describes with the fox style bender and get no springback and sides that conform perfectly to my outline.

To get the sides perpendicular I use cam clamps to clamp the sides down, and manipulate the clamp so that the sides are perpendicular, it's actually quite simple.

To incorporate the dome into the top, a 1/8th inch thick masonite shim is installed onto the workboard, with supports for the neck block and tailblock during clamping, no cork needed.

I sand a very slight bevel into the masonie, up to the outline of the guitar to accomodate the domed top.

This is a very basic workboard, some people get super creative, and scoop out the actual wood in the workboard to accomodate the dome of the soundboard, and cut slots into it for spool clamps, and so forth.

Cumpiano and Froggy Bottom guitars have very similar methods and building backgrounds.

I went up north and spent time in Cumpiano's shop, and learned his techniques, which are slightly different now than in his book, but updates are on his website.
Author:  jfmckenna [ Wed Nov 02, 2011 12:27 pm ]
Post subject:  Re: form-less guitar building
FWIW From my experience I think accurate bending of sides is fairly equally important weather using a mold or not.
Author:  Quine [ Wed Nov 02, 2011 12:28 pm ]
Post subject:  Re: form-less guitar building
I think you would have to be really good at bending sides to build without a form. The two main benefits of a form is to hold the bent sides in shape while drying and to keep the sides square while tapering/radiusing and gluing on the top/back. I've seen other methods to do that....but it seems like about the same amount of work making fixtures.
I make my forms out of any junk wood I can find. It doesn't need to be very strong to do its duty
Author:  Tom West [ Wed Nov 02, 2011 12:51 pm ]
Post subject:  Re: form-less guitar building
Talk to Bruce at Sexauer Guitars,he is the king of formless building. He hangs out at the UMGF.
Tom
Author:  Jeff Highland [ Wed Nov 02, 2011 2:09 pm ]
Post subject:  Re: form-less guitar building
Whilst Froggy Bottom are assembling without external forms, it should be noted that they are bending the sides using a solid form cut from laminated plywood and using a bending blanket. The solid bending form is cut for each model so you would expect the sides to have good dimensional accuracy.
It takes very little extra to produce outside forms at the same time.
I just cut a bending form and external forms for my classical shape from a $25 sheet of ply.
For one off builds I would just use my adjustable solera.
Author:  BlueBellyGuitars [ Wed Nov 02, 2011 4:14 pm ]
Post subject:  Re: form-less guitar building
I have 3 body shapes & have built them all from left over construction wood. I you see any jobsites around you, stop & see if they have any good plywood scraps. Or look up masonry contractors. A lot of times they will have scrap plywood left over from building concrete forms. The only guitar I have built w/o a form was from a solid chunk of wood cut to the shape of side material. Huge waste of wood, but it was a one off & I had the perfect piece for it.
Author:  Bill Hodge [ Wed Nov 02, 2011 8:38 pm ]
Post subject:  Re: form-less guitar building
An important note to Alan Dunwell,

Norton (Symantec) has your site listed as a known malicious website. You might want to look into it because you've likely been hacked and had a trojan or virus incorporated unbeknown to you.
Author:  segovia [ Thu Nov 03, 2011 2:27 am ]
Post subject:  Re: form-less guitar building
http://www.collinsguitars.com/teaching2.html

Apparently no forms here.

I am interested in this approach as there are pros and cons with a mold the cons in my view are

1, potentially forces badly bent sides into a shape it doesn't want to go
2, I can get in the way of gluing the blocks
3, internal clamps holding the sides against form add to the restricted access to the inside

J
Author:  Michael.N. [ Thu Nov 03, 2011 4:06 am ]
Post subject:  Re: form-less guitar building
Many of these methods aren't true formless building. They usually have some type of buttresses that act like an adjustable mould. Instead of having contact all around the periphery of the sides (as in the more usual mould) there are a number of contact points/buttress that determine/support the outline.
Author:  David LaPlante [ Thu Nov 03, 2011 7:32 am ]
Post subject:  Re: form-less guitar building
"Free" building eliminates the need for specific fixturing and allows one to easily make "one off" designs or replicas of historic instruments.

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TorresSE151AReplica-II 007.jpg

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TorresSE151AReplica-II 016.jpg
Author:  dunwell [ Thu Nov 03, 2011 9:01 am ]
Post subject:  Re: form-less guitar building
Bill Hodge wrote:
An important note to Alan Dunwell,

Norton (Symantec) has your site listed as a known malicious website. You might want to look into it because you've likely been hacked and had a trojan or virus incorporated unbeknown to you.


Yikes!! Thanks for the heads up. I'm running CentOS and am patched up to date, wonder how that happened. I'll kill it and clean it up today.

Alan D.
Author:  charlton [ Thu Nov 03, 2011 9:16 am ]
Post subject:  Re: form-less guitar building
RaymundH wrote:
These guys have it down pretty good:

http://froggybottomguitars.com/guitars/the-sj-blog.html


See the photo with the signing on the underside of the top? That's some marvellous hand writing.
Author:  dunwell [ Thu Nov 03, 2011 11:19 am ]
Post subject:  Re: form-less guitar building
dunwell wrote:
Bill Hodge wrote:
An important note to Alan Dunwell,

Norton (Symantec) has your site listed as a known malicious website. You might want to look into it because you've likely been hacked and had a trojan or virus incorporated unbeknown to you.


Yikes!! Thanks for the heads up. I'm running CentOS and am patched up to date, wonder how that happened. I'll kill it and clean it up today.

Alan D.



Ok, OK, we can calm down. What happened is this. If you look at my original message I pasted in a URL complete with the "http://" part. I then highlighted it and selected the "URL" button to make it a link and didn't notice that that button adds on another http:// to the front. <sigh (I need an emoticon that says Sigh) So when you try to access that you should get a 404 site not found error. But for some reason Bill's browser turned it into http://http//dunwellguitar.com, dropping the additional colon. For reasons unknown this then gets flagged as a malicious site.

In any case, all is well and you can connect to my site if you wish without fear of spam or men in camo riding black helicopters swooping in on you, etc.

Thanks to Bill for helping figure out what was going on.

Laters,
Alan D.
Author:  Bill Hodge [ Thu Nov 03, 2011 11:28 am ]
Post subject:  Re: form-less guitar building
Confirming that it's safe, I just visited there. I didn't even notice the double "http://". Where's the forehead slap emoticon when I need it? duh
Author:  segovia [ Fri Nov 04, 2011 3:16 am ]
Post subject:  Re: form-less guitar building
When free building (moldless) what is the technique used to get the radius on the kerf linings after gluing ?

J
Author:  DennisK [ Fri Nov 04, 2011 10:08 am ]
Post subject:  Re: form-less guitar building
segovia wrote:
When free building (moldless) what is the technique used to get the radius on the kerf linings after gluing ?

J

For the top, dentellones. Sand an angle into the tops of them individually. The perimeter itself is flat, but the dentellones still help support the dome. More angle on the ones around the waist where the top's arch has to stretch down the most to reach the flat plane, and less around the tail block and wide part of the lower bout. Above the waist, especially right as you approach the head block, it depends on how much the top of the block is angled to match the neck angle.

For the back, kerfed linings and a finger plane. I glue the sides on at constant width, then taper them from tail block to head block by saw/block plane/whatever, and work it until the rim is all in the same plane (lays flay on the workbench with minimal gaps anywhere around the edge), but also about 1/8" above the blocks. Mark a reference line all the way around the sides about 1/8" down from the edge, and finger plane the approximate contours of a domed perimeter (lowest at the blocks and outer limits of the lower bout, highest at the waist). Then glue kerfed linings, and more finger plane work to angle their tops to the dome shape. Then it's on to final voicing of the top, now that its perimeter is constrained so you can really hear it :)

I glue the back on with spool clamps, so it conforms to any imperfections in the perimeter shape. Also interesting to clamp on the back and then tap on the plates to tune the top/back coupling effect (long echo when tapped). Although I haven't figured out if this actually helps anything, since the effect comes and goes throughout the rest of the build process. For one thing, the tap tone is way lower pitched than it is after gluing the back and removing the clamps, because the clamps are so heavy (mass loaded sides :)). For another, the bridge isn't glued on yet and that drops the top quite a bit. Bindings might change it too.
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