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Archtop Laminating


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I've never seen anything on this, but if you are talking about the kind of forms from say plywood that you would get on a 355 it is most likely impossible. They use extreme heat and pressure to make these kinds of 3D shapes...any attempt I have ever tried (in say boat building) has caused far too much stress except in very large and gentle shapes.

A curve on one plane though is easily achieved and bracing is enough to keep shapes like this. As soon as you curve something in one plane, the difficulty in bending in another is many times harder...try it yourself with something like cardboard...you will see that you will need a lot of compression to make such a shape.

A real archtop, like a violin is made by carving the back and front from a solid piece...quite an art.

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There are a couple of good sites out there. The method I used was to just use thin wood, and clamp it to the sides and the formed center block. There is a little under 3/8 height difference and it bends well with those changes. I have a mold for the sides and the center that keeps them secure, then I put bar clamps across the body, anchored to the workbench (The body between the bench and the clamps with the clamps going horizontally across the body.) I then use wedges to push the top down to the center block gradually over several seconds to let it give a little. You could use a heat gun if it get stubborn. My tops are solid curly maple a little under 1/4 inch thick. There is a point a little under 1/34 inch thick where the top gets flexible, it's a magic thickness.

I spread glue on the middle and the rim and slip the top under the bar clamps, clamp the neck and center of the bottom and start clamping the heck out of it. It's quite funny to see. It does work.

Oh, the whole thing is raised off the bench (The mold) so I can clamp the edges to the mold all around. I think I use about 25 clamps to get it done.

Here are some links to get you started. This covers the mold. They sell top and bottom plates. I just made mine and pressed them into the shaped mold with clamps.

http://www.upnorthstrings.com/es335body.pdf

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Luthier's Mercantile sells a book by Jim English all about making laminated archtop electrics. It's worth picking up.

I have to totally disagree on this, the book is a waste of money. When this book gets into any technical detail it references Benedetto's book. So if you want to know about archtops and the details get the Benedetto book. And then there's the chapter about how to make your molds, forget it. He casts plaster off an old Guild without protecting the guitar and then uses his van to "clamp" them together. He fails to offer any useful advice on how to actually craft a model from scratch and make a decent mold from it. There also is no alternatives to the van mentioned so those of us that would want to do this in their own shops are at a loss once again with this book.

You are much better off testing out some of your own ideas than getting this book. Just my $.02

One way already mentioned is to bend solid wood to a curve. This can work but I prefer to make my arches so that they are not under tension. I use a mold that I press veneer onto in layers using a vacuum bag system. If you use standard veneer thickness and laminate about 4-5 sheets together the pressure needed is not excessive and you could get away with using clamps but you would have to have a male and female form. The trick with both techniques is carving the molds. Take your time with this and you will have good results.

This picture is of a guitar I did that has a solid carved spruce top with a veneer over the top:

019-11.jpg

~David

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