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I have not yet built my first acoustic, although I have built several electrics and a crossover acoustic/electric instrument. I plan to build or at least begin to build my first acoustic this year. I will be using the Cumpiano method. Workboard, sanding boards, sanding stick, the whole nine yards.
My question is in regards to a body wedge. I know most might caution to build just a standard guitar for the first go around, but seeing as I will be playing this one, and seeing as I have some physical issues which were discussed in another thread, I really want to at least contemplate incorporating a wedge and an arm bevel into my build.
I would create the wedge by forming it on the section of the sides that the top is attached to. The bevel as well. Since in the Cumpiano book the top is glued to flat kerfing I don't see a problem with getting the proper radius like I might if using a sanding stick to get the radius of the back kerfing. I hope you guys are following me, as I have a hard time articulating what I mean, so I'm relying on your experience to picture what I'm talking about, but using such a technique to sand a radius into kerfing that spans the sides of an instrument that is wedged shaped seems it may be problematic. The top doesn't have this issue, at least as far as I can see.
Does anyone foresee anything that would cause a major issue incorporating these features using the Cumpiano method?
And please, I'm not wanting to revive the ongoing debate over using body molds and radius dishes as opposed to "free assembly" building methods. I have chosen my method. Now I'm looking for the collective wisdom of this wonderful place to help me look ahead a bit and maybe foresee things I have not considered. Thanks.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

I don't see an issue with the wedge. In fact Cumpiano experimented with wedge designs. Might drop him a line, he's pretty friendly with the e-mails.

As far as the arm bevel, I've been pondering that myself. Post pics of the process you come up with, pretty please?

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Old growth, shmold growth!

I hope to post a build thread, amateur though I am. But we shall see.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

No problem doing a wedge with freeform assembly. I'm confused though... you're talking about trying to tilt the soundboard, rather than the back? How would you get the proper angle planed into the sides when they're still loose and flexible? Much easier to get the sides glued to the soundboard/headblock/tail block while it's all still square, and then plane the tilt into the rim at the same time as doing the normal depth tapering.

And anyway, forcing a radiused top to conform to flat linings is just as much built-in stress as forcing the back to conform to an imperfect radius on the rim. So don't worry about that.

IME, the biggest difficulty of wedge construction is binding. First getting the channel cut, then getting the strips to conform to the compound curve. If possible, stick with more flexible binding wood like curly maple, rather than rosewood or other really stiff types.

Thanks, all of you. This is why I posted. After looking at things again I understand why the wedge would work better if done on the back, but I'm having another problem visualizing something.
The Cumpiano method of forming the long radius of the back(from tailblock to neck block) iirc uses a taper cut into the back of the sides from somewhere near the center of the waist to the neck block. After that a large sanding board is used to basically get rid of the "peak", gradually sanding that into a long radius. How do I achieve or keep that long radius on a pair of sides which are not of equal height? Or am I over thinking things?
Also while I'm here anybody got a link to a good tute or resource for such a wedge?
Thanks.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

You will do it the same way, except now you are working on a tilted surface .. if you want to visualize it differently, block the side you have made narrower (the edge on the bass side of the guitar) up until the whole back is level, as if there is no wedge at all, and then sand ...

when I have done them its with a bowl .. you are just bowl sanding on an angle, until the whole rim has been touched.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Tony, thanks. Simple and effective. Appreciated.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

Exactly what Tony said. I'm thinking a wedge would be fairly easy to do on the Cumpiano workboard as the process immediately lends itself to exactly that.

Pay special attention though to the neck block treatment as there's a discontinuity that appears there unless care is taken to remove it. Cumpiano's book deals with that very well.

Since writing that book, Cumpiano's adapted his workboard shim and neck block hold-down to be more stable.

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Old growth, shmold growth!

Experiment all you like and post your findings. I'm working on a double wedge at the moment but I built a form to do it. it tapers from the head block to the tail and also the top side to the bottom side in order to shift the fret board a few degrees in hopes of a minor degree of comfort. I'll let ya know how that works out if I ever string the sucker up.

I'd be interested in the results.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

http://www.cumpiano.com/Home/Guitars/Sp ... -page.html

Here's an article about Cumpiano's wedge guitar he made on commission, and there's also a picture of the guitar on the workboard.

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Old growth, shmold growth!

Cool! Thanks for the link. Way more wedge than I was contemplating, but good to know it's do-able.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

I've done a bunch of wedge bodied guitars, mostly retro-fits on factory guitars, and all on a solera with no mold. Tony has it right. I use a sanding dish with the same radius as the braced back to fit the rim to the back which works great, but there's no reason you have to.

The binding is more difficult, but not impossible. Don't expect perfection, think things through, and you'll be fine.

FWIW, a 3/4-1" difference between treble and bass side depth seems most popular amongst my past customers.

James, thanks!

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

Way too much for me. The only wedge I've built so far is a 15" lower bout with about 5/8" difference between the sides, and still feels a bit much. I'll be sticking to 1/2" or less in the future. Like fan frets, I consider it to be an improvement to the design of the guitar, but too much of a good thing is a bad thing.

And it doesn't matter whether the top or back is tilted... what matters is the resulting angle on the fingerboard affecting your left hand wrist position. Although tilting the top would actually be a little bit more comfortable if not doing an armrest bevel, since it would reduce the angle between the side and top there.

I wonder how it would sound if you tilted just the soundboard, but kept the neck in its normal position with a cantilever fingerboard extension... so the string-height-at-bridge is a lot higher for the bass strings than the trebles.

Well...Here are said results. Major case of failure due to guitar hitting cement floor followed by therapeutic foot in guitar ordeal. Moving on to the next one....

Actually, what matters in regards to the wedge in this instance is the thickness of the depth of the body where I have to reach my right arm across it to strum the guitar. The left hand position doesn't have anything to do with it. At least in this instance. Nor in the link to the Cumpiano guitar. The wedge was to obtain relief for the player's right shoulder, to avoid having to rotate that shoulder out to reach across the guitar. That's my purpose as well. Body depth as it relates to the right shoulder and arm is the thing here.
And Joey, FWIW, my guitar might end up like the pics you just posted, LOL. Sorry to see that, btw.
James, since you've done this several times, can you give me your observations on how this changes the character of the tone of the guitar?

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

AAAAAAAAAAAAAAAARGH! So sorry! That's horrific.

I guess it depends on how you normally hold the guitar. If you can't pull the lower edge closer in toward your body, then the narrower upper side will result in tilting of the soundboard (and neck with it) relative to your body. I normally have the lower edge in contact with my right hip bone (skinny, no belly in the way), so I can't really pull it any closer. Thus, I feel the tilt.

Ahhh, it's just a year's worth of work. No biggie. That box had so many mistakes that a foot in box scenario was inevitable. I learned a lot and will use that knowledge moving forward. The next build is already well under way.

You are absolutely right. But with the issues I've got I normally tilt the treble side of the soundboard out and the bass side of the instrument in when sitting so that it's easier to reach across that lower bout, while sitting, anyway. It's a natural position for me at this point, so I didn't even consider it. And I've got a big old belly in the way, so no part of the guitar will be resting on my hip bone any time soon, LOL.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

Glad you've made it into a positive! Certainly got the experience if not the guitar!

Still, my heart goes out to you!