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I am considering my first foray into laminated sides. I would like to vacuum bag the laminates to make sure of good even adhesion. However, the bag doesn't easily fit into a bending jig. Is it possible to laminate first, then bend using heat? I am expecting to use epoxy as the laminating glue.

I wouldn't do that. After you heat it up you will break you adhesion and likely weaken the adhesive compared to having bent first and then laminated. Never tried it that way though so I can't be sure.

However I've gotten great results with a standard mold and a truck tire Intertape cut into a solid strip.

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Thanks Joey, but I'm not sure what I'm looking at in the picture. I see the mold and the inner tube straps. Then there is something on top that looks like hardboard. There is clearly a gap between the "hardboard" and the mold. Is there a vacuum bag in there? Or is there no vacuum bag and the jig is applying direct pressure to the laminates? If no bag, how are you keeping the laminates from sticking to the "hardboard" and mold? Also, I'm pretty sure that is not actually hardboard. My guess is that hardboard will not bend to a guitar shape (especially in a cutaway). So what is that?

The folks that I know who have laminated sides for double sided guitars bent the laminates individually and then clamped them on a plug/form after the bending was done as Joey indicated.

Just searched on search key "double sides" and found four pages of info, some of it great info. Look for posts from Tim McKnight who was doing killer double sided guitars fairly early on.

A few suggestions:

1. You should get a copy of John Bogdanovich's book on building classical guitars, and also buy the parts of his online video series that deal with laminating sides. Both are excellent guides.

2. Question the assumption that a vacuum bag system is required. Joey's method above does not use a vacuum system, nor does Bogdanovich's. If someone here at OLF uses vacuum, they will chime in with suggestions, but I have looked at a few different ways of doing this, and none involve a vacuum system.

3. Gluing straight, then bending, is probably a bad idea, so please don't try it. The sides will fight you, the glue will probably let go and refuse to re-adhere, and some parts of the sides could snap. I made some custom herringbone purfling not long ago, and through trial and error learned that I was much better off bending some of the elements of the purfling first, then gluing them together, rather than gluing them up straight then bending.

Good luck with the new project.

The board on top is walnut that is already bent. What looks like a gap is actually a curly Narra side already bent and pre-shaped. It looks like a gap because the walnut slat is still way over sized. Once the glue dries I'll trim the excess Walnut so that they have the same profile shape. I like to pre-shape the profile prior to radiusing the rim in order to cut time down "driving the bus" or however you accomplish that task. For me what's worked best are these steps.

1. bend all 4 sides
2. sand/scrape all sides
3. glue the sides and clamp them down (this is the step pictured above). For me that's a simple mold, a tire inner-tube and wax paper. The glue doesn't stick to the tire so you just need to line the mold with the paper. Or you could treat your mold with Bates non-stick compound- Somagyi does this and uses doubled up wax paper as well because he uses epoxy, which can go through a single sheet. I use regular old titebond 2 and work fast so for now I've found paper to be quick, cheap and easy.
4. pre-shape sides
5. radius sides for the top and back
6. glue in kerfing
7. repeat step 5

Hahaha, that is a great description. On my first build I didn't pre-shape. I drove the bus for what seemed like hours. My second build I had more confidence and shaped pretty close to the plan before putting into the dish. I spent a fraction of the time at wheel.

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I abandoned vacuum techniques and use a form with clamps.

I don't think your inner tubes will give sufficient clamping pressure. Also, there needs to be a caul or something to keep the sides flat across the width. I can see some bowing in your setup.

What you see bowing is the overhanging Walnut side. That is half my mold though and I have 3 clamp cauls that fit the upper and lower bouts and the waist that I can use in addition to the tire If I feel it's necessary. I prefer to do both sides in their half mold so that I don't need to trim the sides until after the glue dries and I'm ready to fit them together. I'll go back and double check it anyway. The phone pictures are kind of crappy but I was pretty satisfied with just the tire last night. I haven't glued these sides up yet, just setting it up to check fit.

I recently posted my method using a 2'x4' vacuum bag, including video, here: laminated sides setup. It worked well for me, and it was fast.

My sides are a full .120" thick. Some mentioned adhesion issues. One an even more basic level than that, I just can't imagine bending that very well.

I went back and looked and you were correct, there was a buldge. I'm working out a solution with what I have on hand. Thanks for pointing that out.

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There was a recent thread on gluing and clamping techniques for double sides. It'll give you some ideas. You can profile and bend both sides together. Really helps to get a perfect fit.

I am a huge fan of double sides.

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I use a stainless steel bending slat on top for a caul. Then lots of clamps on top of additional cross bars. There is a lot of surface area so it takes a lot of clamping force to get things tight. That is why I gave up on the vacuum bag because it would leave big glue filled pockets in various places, especially the waist and cutaway.

I also was unhappy with vacuum bagging and went back to clamping with backing. I usually use a solid inside form that I had used for bending. There are various ways to make the outside clamping backer form fit. Whatever you use, I think it is best that one side of the sandwich (in my case the outside) is left slightly flexible. If both sides are completely rigid, it is about impossible to get and exact fit, and you do not really distribute the pressure, anyway.

"I think it is best that one side of the sandwich (in my case the outside) is left slightly flexible"

I use kerf kore for the outside caul. It conforms to the veneer/mold sandwich very well and provides a smooth surface against the outside surface of the sides.

Looking at threads for "double sides" I realize that I actually had something very different in mind.
I have some CF cloth that I ordered wrong for my tops. Rather than just let it sit there I was considering making sides with a lamination of maple-CF-maple.
This is all very flexible, at least until the epoxy has set, so pre-bending doesn't seem necessary. But I got the message loud and clear:
Do not make the lamination first and then bend to shape.


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