Guitar One: Plunging ahead

[charles Tauber]

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[CaffeinatedOne]

The rosewood is very hard and resists my efforts at talking it into being thinner. Maybe I should sharpen my card scraper. . .

[Shuksan]

In case you may not have heard of it, many builders use a veneer softener called Super-Soft 2 to make the sides more agreeable to bending. It's really good for hard-to-bend woods, but it's also a good thing even for the woods that are considered to be easy to bend. I now use it by default for bending sides and binding.

[CaffeinatedOne]

Originally Posted by Shuksan

In case you may not have heard of it, many builders use a veneer softener called Super-Soft 2 to make the sides more agreeable to bending. It's really good for hard-to-bend woods, but it's also a good thing even for the woods that are considered to be easy to bend. I now use it by default for bending sides and binding.

As it happens, the same luthier who lent me his silicone blankets also gave me a small amount of that stuff, so I have half a pint in a spray bottle to try out. Never tried it but everyone I encounter who has done so speaks well of it; apparently there are no long lasting effects on the wood but the short term effects are helpful. He brushes it on with a foam brush and allows it to dry prior to bending the side on a hot pipe.

[CaffeinatedOne]

Back wood is finally ready for assembly! The sides are now at the right thickness - about 0.08". Back is about 0.09". Still need to rout the back seam and inlay a strip of curly maple.

[CaffeinatedOne]

Life keeps intervening. But the side bending form is nearly completed. Yesterday I set up a set of spring loaded cauls to hold the side against the form as it cools in place. The only thing left to do with the side form is to affix an enameled steel webbing repurposed from a fireplace shield over the curves to allow the side a smooth transition from one bend to another. I knew I'd use that stuff some day.

[Truckjohn]

So... Make sure you put some legs under that sucker.

Also make sure you have provisions for clamping the sprung pieces down to the frame. The springs are great for keeping parts from wandering while you are heating up. They aren't so good at actually applying enough force to complete the bends.

Thanks

[charles Tauber]

I find it fascinating to see the many combinations and permutations of Charles Fox's 1970's side bender. It's also interesting to see how, in some variations, although aspects of the physical appearance are copied, the original functional principles are often lost.

The purpose of the steel rods is to "3-dimensionalize" the two plywood outside shapes. Ideally, the rods need to placed so that the circumference of each rod is tangent to the plywood guitar shape. If left proud, the side will kink at the elevated rod; if shy of the edge of the plywood, there is a step discontinuity between the 3-D shape and the plywood edges of the form. Not likely to break a side, but it may cause the side to ripple at that location or simply alter the shape a little.

As Truckjohn points out, the springs aren't going to do it, particularly at the waist. In the final position of the cauls, as you've shown in the photo, those springs will be streeeeeetched to supply sufficient downward force: your springs are way too long to apply sufficient force. It takes a fair bit of force to deform even a heated side into the desired curves.

You may also need something to keep the bottom of the plywood forms from moving outward when sufficient spring tension is applied to bend the sides.

Typically, to reduce spring-back, the waist is over-bend slightly, as are the ends. This is accomplished by making the forms a little more "severe" than the final guitar contour.

Hopefully, those suggestions will save you a few iterations in the side bending process.

[CaffeinatedOne]

This is helpful! My responses follow in the quote in bold face.

Originally Posted by charles Tauber

The purpose of the steel rods is to "3-dimensionalize" the two plywood outside shapes. Ideally, the rods need to placed so that the circumference of each rod is tangent to the plywood guitar shape. If left proud, the side will kink at the elevated rod; if shy of the edge of the plywood, there is a step discontinuity between the 3-D shape and the plywood edges of the form. Not likely to break a side, but it may cause the side to ripple at that location or simply alter the shape a little.

I was aware of that; the intention was to have the rods tangent as you suggest. I need better clamping technique (actually, what I need is any technique) when fooling around with the drill press. Kinda rough and sloppy. However, I have some light gauge steel mesh that came from a fireplace screen that is destined to be trimmed to fit and fastened with a pneumatic staple gun along the curved surface, so the wood will be resting against the steel webbed mesh. It should be stiff enough to let me avoid kinking and rippling. . . I hope.

As Truckjohn points out, the springs aren't going to do it, particularly at the waist. In the final position of the cauls, as you've shown in the photo, those springs will be streeeeeetched to supply sufficient downward force: your springs are way too long to apply sufficient force. It takes a fair bit of force to deform even a heated side into the desired curves.

Thanks to both of you for the heads up; I'll figure out an alternate clamping method, perhaps using cotton rope to truss it up like a boot. The side will be going on the form very, very hot - about 212 degrees F, which is the hottest the steam will get without pressurizing it. So that is a primary factor. I have heating blankets ready only as a plan B.

You may also need something to keep the bottom of the plywood forms from moving outward when sufficient spring tension is applied to bend the sides.

The side form has a couple 1x4 wooden spreaders affixed with three inch pneumatic nails, which should hold plenty well against the forces you're describing.

Typically, to reduce spring-back, the waist is over-bend slightly, as are the ends. This is accomplished by making the forms a little more "severe" than the final guitar contour. That's the plan. I might decide to trim the form a hair, but it is already somewhat exaggerated. When they've settled a bit, the sides will be clamped into an outside form with cam clamps.

Thanks for the suggestions - I'm paying attention!

[CaffeinatedOne]

As if trying to put a noise maker together wasn't enough, I'm building a work bench as we go. My utility table is a wobbly mess and, although I have a great old machine shop bench in the garage, the lighting needs work and the garage needs cleaning out. Besides the thing feels like 800 pounds whenever I try to move it. So I'm building a simple bench to use in the usurped bedroom that is becoming my *happy dance* shop. This is a gorgeous slab of Black Walnut I salvaged from a conference table that needed repurposing. Surface dimensions are 24" x 59" x about 2". Planning an apron and legs from 2 x 4 stock. In the meantime, at about 75 pounds, it slows the wobbles a little on the utility table.

[redir]

Could be some nice old straight grained East Indian Rosewood. I've got some of the same age and it tends to turn more brown in time. Anyway it's nice looking stuff.

[CaffeinatedOne]

I did some side cooking and bending today. The steam box was interesting to use and was almost hot enough to bend the sides. But "almost" is not enough.

I was nestling the first side into the waist bend and heard a *crack*. Pulled it out and there's a small fracture at the very edge of the side. Fortunately these are quite a bit wider than what I need and would have been trimmed in any event. So I can still use the side.

But my curiosity about steam bending has been adequately addressed. I'm moving to Plan B, which involves a silicone heating blanket method, about which you all know more than I. A luthier friend has lent me his silicone heating blankets, and I need to cut some aluminum strips to fit, but otherwise it's good to go.

I also got an impression about the spring tension on the waist caul that will mean a design change. It's violent. There's no way to increase pressure gradually. In theory, there's no need as the sides are already hot. But in practice, 212 degrees is not hot enough. I'll need to use a continuing heat and gradual bending approach.

I know, you told me. I admit it!

[Truckjohn]

Clamps for the side bending form are really easy. You are overthinking this stuff. By clamps - we just mean clamps. Rube Goldberg need not apply.

Here's a pic of one of mine.

[CaffeinatedOne]

Part of the problem with the side bending form I built was lack of proper support for the piece being bent. I understood the idea, but it took some splinters for me to see exactly how things can go south. So back to the drawing board it was, and I've amended the form a bit. The aluminum tape is to protect from sharp edges. The steel web is tightly stapled in place and the staples further set so they stay put. Stay tuned.

[charles Tauber]

I'm guessing you like "the journey". Nothing wrong with that.

I'm still using the same side bender I made 35 years ago, exactly like the one Charles Fox had at that time. Last year, I switched from light bulbs as a heat source to an electric blanket and controller. The light bulbs worked just fine, but curiosity got the better of me and I bought a blanket. (It works well, too.)

The point behind Charles' original design was that one could quickly and easily switch from one shape of instrument to another. This was accomplished by having easy-to-make plywood "inserts" that are "three-diminsionalized" using cross bars and the use of a slated press for the waist. The slats for the waist are bolted together and can quickly, and easily be loosened to conform to a different waist shape, then the bolts retightened to maintain that shape. With the plywood inserts already made, it takes less than 5 minutes to convert the bender from one shape to another.

I can't help but feel that your adaptation of his design somehow loses the advantages of his. Nothing wrong with adapting the design - since then, a number of true improvements have been made to his original design. But, you seem to largely be reinventing the wheel by starting with one that has corners. Again, nothing wrong with that, but it does seem to be the long way around the block. Certainly, you will learn things along the way that you might not have otherwise. Innovation is good, but so is learning from others' past experiences.