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Charity Acoustic


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OK, well...I've always wanted to do an acoustic, and at the encouragement of my wife (isn't she great!), I took the plunge to build one for the charity auction that our church is running to raise money for a new building. Lacking a thickness sander, I got me the back & sides and plans from LMI and I'm off and running with the Cumpiano book as my reference.

That was about a month ago....with the goal to finish it in 6 weeks. So what happens? Work gets crazy, no way I'm getting done in time (surprise). So I'll have to hold my own auction when its done and donate the proceeds.

Its going to be a dreadnought with a florentine cutaway. So here we go: 3A Sitka spruce top being glued up; its pretty nice, 10-14 lines per inch and no flaws.

topglue.jpg

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Backstripe routed out with 1/4" straight bit and glued in with epoxy. Here I'm flexing the top ever so slightly over the spruce center strip, anticipating the arch that will come from the back braces, so that the epoxy fills in any small gaps in the channel.

I'm digging the grain on this EIR and how non-oily it is. Reminds me of walnut.

backstrip.jpg

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Back braces glued and shaved.

The braces are all quartered Sitka spruce. I did the Cumpiano trick of splitting the billet with a chisel, then choosing pieces where the grain was already running with a slight radius, and radiused the braces accordingly so that there is almost no run-out.

backbraced.jpg

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I used the "drilled router baseplate" tip in Cumpiano's book to rout out the channel for the soundhole rosette (also from LMI). Used a flat-end 1/4" bit.

This shot shows the rosette fitted into the rout....ooops (that's why you practice on scrap). Those of you who've done this before will know exactly the mistake I made.

rosettegoof.jpg

The second practice-rout was perfect.

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Here's the top with the soundhole cut out, and the braces glued up and shaved. I've been tapping and tapping, there wasn't a huge change in tap tone until the X-braces went in. Now I guess I'm at that ?huh? stage of wondering what kind of tap tone to shoot for as I continue to shave the braces (removing material mostly from the outside-edges of the X-braces).

topbraced.jpg

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Work craziness and a SW vacation (Grand Canyon-Zion-Bryce) got in the way. Got me wondering what kind of lumber you could get from a Joshua Tree. :D

I did get a little work done before leaving though. Know what to do with a bass neck-through blank gone wrong? Yep...chop it, stack it, and turn it into an acoustic neck blank. Flame maple, ebony, flame maple & padauk.

neckblank1.jpg

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I've been tapping and tapping, there wasn't a huge change in tap tone until the X-braces went in. Now I guess I'm at that ?huh? stage of wondering what kind of tap tone to shoot for as I continue to shave the braces (removing material mostly from the outside-edges of the X-braces).

The way I learned is to start the project with a tone in your head that you want to achieve. You already stated you want a lower response for the piezo element. Think of what you want the highs to do, and the mids, and whatever else you are looking for. When you start to tap it listen to how the top responds all over. Is the bass area too tight or too loose? Does it have an overall resonance that you like? Taking material away will loosen that area and lower it's frequency response. Leaving too much wood will dampen that area. You can add material as well if it needs it to tighten things up.

My personal approach is to leave the treble side stiff and loosen the bass side gradually changing the stiffness as I go across the braces. So far it yeilds a nice even response that I like. It is perfect for fingerstyle and light strumming. I have used the same bracing and carving for heavy strummers but I carve everything a bit stiffer all the way around for that. I listen to the different areas by tapping them in sequence. You can hear the pitch rise as you move from bass to treble.

You have to play with the idea and use this guitar as a test. Only when it's done (and probably after a few more) will you know if you are onto something with the tap tuning. It is a method of hearing the results of what you are doing and takes experience to know how the little things affect the whole.

Other builders go for an even response across the top. Some shoot for specific notes for the back and top. Some go by weight alone of the finished top. Sone don't do any of it at all and rely on the design and wood choices. I have played guitars built with each of these techniques and they all sounded wonderful. For me this works very well and I will continue to tap the tops to determine where and how much to shave away from my braces.

I think tap tuning is a valid approach among many and it is not really that easy to teach. Experience is the teacher in this case. One of the best bits of advice I was given (by one of my mentors Harry Fleishman) is to take detailed notes and compare them with the finished guitar. You will learn so much that way.

Sweet looking guitar by the way! It is cool to see an acoustic project on this forum. I was going to start one a while back but I got flooded with electric guitar orders. This makes me want to get back to it!

~David

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Thanks David, that helps a lot. So far, the response is pretty even as I tap across the bridge area, but then again so is the bracing. It hadn't occurred to me to shave the bass side more than the treble side, that's a great idea.

I've been tapping and listening the whole way, as each set of braces were glued down & shaped. Before the X went in, it sounded like a floor tom, with a nice long ring. With the X unshaved, it was like a high-tom but damped. I can hear it open up a bit as I shave the X, but now I'll lean toward taking more material off the bass side.

I sized my braces exactly to Cumpiano's specs, I'm removing material mainly from the sides...but hardly touching the tops, and not at all where they contact the soundboard (footprint).

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I think Myka nailed it from start to finish. Tap tuning is not an exacting science. Setting a goal or sound for a guitar when you start, and keep it in mind as you move through the project. I tap as a reference tool. I believe it has become easyier to get what I want with each new carve because I learned more from the last. I suppose after a couple hundred I will figure out what I am doing.

I noticed something I wanted to point out on your bender form. It may just be the picture I am not sure. Be sure all the cross supports are dead flush with the forms side. If they are not when you are bending the sides will cup, and may even crack at the re-curve. I like to have a few extra cross braces at the tight curves. It is a super good idea to keep the side very evenly supported while you are bending.

That neck is going to be a beauty. I love laminates. One thing to watch on the lams (and bear with me I usually carve a tight spanich style heal) is the thickness of the heal, and where the lams lay out in relation to it's width. If the lams spread a bit too far you will carve into them and out of them (can look cool, or not so much). If you are going for a wide heal it may not even be an issue. (just a thought).

It is looking very, very, very good! You make it look effortless.

Peace,Rich

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Thanks Rich. I haven't yet decided on the heel width, it is one of those things that will come to me as I start. I'll almost certainly leave some of the outer maple exposed the whole way down.

Yep, the cross-supports are dead flush to the sides of the bender. The way I made it was to screw the two pieces of MDF together, shape them, drill for the bolt holes, then separate the sides. Then I went back and used a 1" forstner bit to very precisely drill a small countersink for the cross-supports (which are just 1" diameter aluminum tubing, 0.1" wall thickness) so that the bender profile is tangent to the supports all the way around, and the sides are perfectly parallel.

I'll be making a caul for the waist and just use a pair of bar clamps to slowly move it into place and hold it down, nothing fancier than that.

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Thanks Rich. I haven't yet decided on the heel width, it is one of those things that will come to me as I start. I'll almost certainly leave some of the outer maple exposed the whole way down.

Yep, the cross-supports are dead flush to the sides of the bender. The way I made it was to screw the two pieces of MDF together, shape them, drill for the bolt holes, then separate the sides. Then I went back and used a 1" forstner bit to very precisely drill a small countersink for the cross-supports (which are just 1" diameter aluminum tubing, 0.1" wall thickness) so that the bender profile is tangent to the supports all the way around, and the sides are perfectly parallel.

I'll be making a caul for the waist and just use a pair of bar clamps to slowly move it into place and hold it down, nothing fancier than that.

Cool,

Regarding the waist clamp. I picked up a screw at Rockler (basically same as a bench vice screw) for $19.00. It is smooth and does a super job (well worth a few bucks-IMO). The great thing about this style bender is that you can make new sides and you have all the hardware so after the initial investment you have a very flexable tool.

It's really great that you are showing all the tools you are making. That is the biggest part of making acoustics. Well.... That and you have to be good at wiping glue. :D

Peace,Rich

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Kind of following on from Myka's post regarding shaving the bass and trebble side struts differently, what would happen theoretically if you used two different types of wood for the soundboard, something trebbly for the trebble side and err..bassy for the bass side :D

Just something that I was thinking of the other night.

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Kind of following on from Myka's post regarding shaving the bass and trebble side struts differently, what would happen theoretically if you used two different types of wood for the soundboard, something trebbly for the trebble side and err..bassy for the bass side :D

Just something that I was thinking of the other night.

I don't think it would have the effect you are imagining (but it is good thinking). Actually if you wanted to try something like that you could use a one piece top and it would have a tight grain side and wide grain side. That would most likely yeild a slight difference in stiffness form side to side. I say go for it! build one and try that theory :D

Rich

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