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Looking through guitar builds; I'm new to guitar building; I see that most use an outside mold. I've always used an inside mold making violins and violas. Only about a dozen of them, just enough to sort of know what I'm doing. So to make the arch top I'm building I made an inside mold. It was pretty easy to make.

I made it so it can easily have the back glued on, and it will slide out, or glue linings on both sides, and it SHOULD wiggle out. If I didn't put a cutaway in it, it would easily come out that way.

$6.00 for a 2 X 10 X 4' piece of Fir? from Menards. Curly grain, insect holes. Very cool looking. It should work, I'm about to bend the sides now.

I made a new post on my blog showing more photos and stuff, but this is what it looks like.

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The mold looks great. It will interesting to see you build with it. I thought of making an inside form for ukuleles, like a violin with a place for the end blocks, although I never did as I picked up a complete set of outside ukulele molds at a ASIA auctions. With my guitars keeping the rims square until the top and back are glued on keeps me from using an inside mold. With the outside mold I can leave the body in the mold with spreaders side to side and and heel to tail, until both the top and back are glued on.

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My idea is to build like a classic Italian violinmaker. My premise for this is that GB Guadagnini sees his grandson's guitar, looks it over, plucks it a little, then looks inside and says,
"Whatsamatter you guy? Forget everything I taught you?"
I'm not worried about symmetry too much. More of an organic approach. Not very common anymore. I'm going to retire in 3 months. I've been a machinist for 40 years, and while there is a place for precision, there is a place for letting things just flow too. I'm not going to get bent out of shape over things. I trimmed the ribs from 2 mm to 1.7 or so for the tight bends. But that's the kind of things that matter.

The ribs are bent! Tomorrow I'll trim them up a little dry, and glue them.

I don't like my Chinese bending iron at all. It was WAY too flat when I got it, and even after a lot of filing, (had to stop when I saw bolt holes!) it still is horrible even for violins. It truly is next to useless on guitars. The fairly mild maple wasn't too much trouble.

In its credit, It IS tall enough for an Arch top.

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Why be normal?

Strong pun, just slipped in there. Well done.

One of the things that many of us struggle with is: When is it best to do things your own way and ignore conventional wisdom, versus having the humility to admit that the pack has it right? I go back and forth, depending on the subject.

I hope that the internal mold thing works out for you. But, there really are good reasons why most guitar builders go off in a different direction from violin family builders and use outside molds instead of inside molds. At some point, you might want to experiment with the outside mold and compare it to what you have done this time. Good fortune as you move forward!

Fleta built his classical guitars with an inside mold. An early 1960's guitar, Making a Concert Guitar, by Eric V. Ridge uses an inside mold. Both of these luthiers like the OP, built violins first.

Some builders don't use a mold at all, only a work board. I think the pursuit of a completely symmetrical outline is a relatively new thing.

I've been looking up a lot of things. I just watched an interesting video where a guy just builds on a board, (the belly, not the back) and has an ingenious, simple way to glue the sides on. Just a few simple wedges.

https://youtu.be/mFCGX-nRaxE

The outside mold IS a "challenge." I guess that's a polite way to describe it! It will work, but I probably wouldn't do it again.

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" I just watched an interesting video where a guy just builds on a board,"

Yes, he built his first guitar on the kitchen table. He has progressed a bit since then but I believe still uses the traditional Spanish methods for the most part.

You are right that is a really neat way to apply pressure on the sides. You may not be aware that Romanillos is a hugely respected builder, author of several books.

Building on a workboard is very much the traditional Spanish way of doing things.

Dave

I learned to build on a wooden beam that goes from the nut to the butt of the guitar. One is a nice maple, and the one in the picture is pine. This one has some deep cuts on it to accommodate a raised rosette. When it is time to glue the back on, I use wooden cam clamps, as in the picture (I don't see a picture in the preview, so maybe I did it incorrectly). When I glue in the linings and things I switch to a guitar shaped plain board so I can apply a little pressure without worrying about getting things out of alignment. It seems the workboard with the slots around the perimeter, like Romanillos has in his book, is now almost universal. But I never have felt that I am missing something by doing it without a solera.

Here are the pictures, showing the beam.

Interesting thread, I generally use an outside form but I built once with no form (not recommended but doable if you're not too anal about symmetry ). I enjoy seeing how other folks build and sometimes I change my methods based on what I learn.

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"Music is what feelings sound like"

Ken I might have sounded a bit condescending, it wasn’t intended, my assumption was that as you were starting out building that you weren’t too aware of the state of the art. Sorry.

Thomas I also don’t care too much about absolute conformation to a mould and once I have linings glued in usually glue top and back out of the external mould. My argument would be that that is the shape that the sides, with their linings want to take so fitting the top and back to them is sensible. The box will fit together with less stress. I am prepared for some flak over this!

Dave

A mold may make sense when building a guitar without the integral neck, since it would be more difficult to hold on to the guitar without something like a vacuum clamp. Also, when laminating sides. Right now, I put new strings on a guitar I built in 1997, and the sides are still very accurately curved and square to the top and back. But almost everything on the internet seems to show the solera like Romanillos and then more recently, Bogdanovich. It was only a few years ago that I noticed how much classical guitar construction has changed and how far behind I was. So I clearly was unaware of the state of the art. I bought Bodanovich's book, and later, Romanillos', and I still cannot see what the advantage is over the older ways of construction of classical guitars. Steel string guitars have pretty much always been built with a mold. Hauser, Ramirez, and the older builders didn't build with the raised portion of the workboard, or a mold, and good serviceable guitars were made. Romanillos did not use the type of setup pictured in his book, in the 1970s. He had a plain guitar shaped workboard without anything to guide the sides. And he used a violin type clamps to glue the back on. In the end it is the result that counts, so we should all use was works in each of our situations.

I've not used a Fox side bender, but maybe it does not have enough heat to set the sides. I bend my sides with an old cello side bender which is a teardrop shaped heavy aluminum casting with a heater inside. I overbend them just a bit at the waist, and then bend it back a little, which seems to help keep the shape. The waist gets slightly scorched, but it is easily scraped. Also, I have the Overholtzer Hauser mold, but it does not get the sides hot enough, so I touch it up on the side bender. But I can bend pretty thick sides and linings. One thing I liked about Bogdanovich was his lining laminating mold. I'm not sure why Bogdanovich uses a mold, since he laminates the sides like Ramirez and they are very stiff. For me, I like the flexibility of building on a beam, where I can build any shape without having to have a mold collection.

As to stress, there sure are differences of opinion. When I started building, Overholtzer's book had come out. In it, he advocated for stress-less building. To me, this is another thing that does not seem too important. The whole structure will be stressed once the strings are in tune. In the more traditional way of building guitars, stress was built-in by bending the top a little to get the set of the neck. I think Richard Brune said that he felt Hauser's tops were built pretty flat, and it was the curvature of the underside of the bridge that actually arched the top. But like everything else in guitar building there are many opinions, and the good news is that very good guitars can be made with diametrically opposed building methods.

I made a fancy violin mold out of aluminum. It was adjustable. It was far too complicated! I threw it away. But I met a guy at the VSA that I went to once in Indianapolis. He made a mold he calls a Skeleton mold that is the same idea, but bare bones. It looks like you could do the same for a guitar. Really nice guy. Thought he was British, but he is in California. He won an award. Good for him.
I have the link to his blog, but I see that it was in The Strad magazine as well. Maybe that's where I saw it first. I like thinking outside the box.

https://www.andrewcarruthers.com/wp-content/uploads/2016/02/Skeleton-mold-article.pdf

The beam idea seems great with an integral neck. I suppose it would still work on an archtop for locating the blocks. The ribs would just have to be bent accurately.

I use the form to get the sides close, and the linings smooth the shape out. The linings can have a big impact on the final shape.

Dave m2, I don't know nothing! I also have a fairly thick skin. Thinking about it more, it does seem that sides out in the open will have less stress on them. But then again, to we want induced stress? Do we want stiff sides, or wimpy sides that just separate the top and back?

More questions to follow.

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Why be normal?

The Skeleton mold reminds me of the SoloEtte, which is like a skeleton guitar.

We see two functions for the mold - shape retention (i.e., the sides remain square and true over time) and holding the work for operations. Guitars are large enough and awkward enough to hold that ease of being able to achieve solid vertical, edge, and horizontal positioning becomes as important as maintaining good geometry.

This begs the question: how are you handling the 'holding' part of the functional requirements using an inside mold? Is there some sort of specific clamping scheme or specialty fixtures used? Inquiring minds want to know!

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If for no other reason, I see inside molds being less practical than outside molds for this specific reason:

The inside faces of the sides of a guitar have linings, and often some cross-grain side braces, but the outside faces do not. The presence of the linings (and maybe braces) makes it harder to fit an inside mold and take it out at the appropriate time. In contrast, the outside faces of the sides do not have these impediments. So, we get what we want from an outside mold with less hassle.

Other than storing them. I agree that the outside mold is less of a hassle and they provide support though closing the box.
When I was working through using an inside form for soprano ukuleles I was going to have the blocks spot glued in to an inset in the form, then I would glue the sides to the blocks, glue the back linings, then the back and slip out the mold. The back is basically used at that time to hold the form. Then the top linings and if required side splints are installed.
I know from retopping guitars that most of them will splay open slightly if the top is removed without an outside form. I thought I could away with it on the smaller instruments.

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I have to bend the linings for the second side now. I did the cutaway side first. Might as well get it out of the way; right? The linings are clamped with 50 or more of those little metal spring clamps in an old Tupperware box. I have over a hundred of them. Much stronger than clothespins. I use quarter sycamore because I found that it doesn't snap as easy. I couldn't get spruce to work at all, and who has willow sitting around the shop? !.8 mm twice for violins and they won't snap. But I found that you can snap it at 3 mm thick; so I soaked them overnight, and that works better. They look cool when you cut them back.

3 mm plus the 2 mm of the ribs gives 5 mm glue surface. Good enough?

An outside mold would be MUCH easier, but this will work. The sides will bend a lot when they are off the form. Hopefully I left the plates big enough on the outside. I have a bad habit about that. You would think that I would learn? With the guitar I have some leeway with the binding. A violin overhang that goes from 1.0 mm to 3.5 mm is frowned upon. Unless del Gesu did it.

I'm not del Gesu, so I don't get a bye.

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I usually laminate 3 layers of linings at ~ 0.085" (2.2ish mm) each to give me about 6.5 mm linings plus the side thickness. Laminating the linings like this make the rim pretty stiff even when you take it out of the mold.

Remember that you will cut away a good deal of the thickness when you cut your binding rebates. I would go with thicker linings if I were you.

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I generally like to make it from plywood. That piece looks like it could break if you were a little overzealous with the expanders.

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This was my idea on the edge work:

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I took the sides off the form yesterday. It worked good. As I thought, the sides came out a little bigger than the form. There are 3 sport I'll need to glue on a small strip of maple that will be hidden by the inlays on the back and the binding on the side. It's something that I always do, but at least on a guitar it can be hidden. You would think that I would learn. I need to trim back the linings, round the bottom block smaller, and cut the recurve on the inside of the back. When the recurve is in, I can glue the back on, and see if the belly fits!

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