$100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Eddie McRae » Fri May 04, 2012 11:53 pm

Resawed some cherry for the backs. Got them joined/glued and then rough cut to shape. Glued cherry marriage strips on both. While thicknessing both backs, I wound up with a little tearout and few voids so I decided to mix some cherry dust with clear epoxy and went ahead and filled them rather than having to worry with levelling them later.
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Eddie McRae » Fri May 04, 2012 11:58 pm

Inlayed herringbone back stripes on both backs. Had enough length left over to to the butt strips on both bodies.
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Eddie McRae » Sat May 05, 2012 12:06 am

Got one of the tops braced and scalloped. And yes, I realize my scalloping on this one is a bit unorthodox. I had trouble making up my mind whether to scallop any at all and I finally decided to scallop one and leave the other unscalloped. But considering the guitar that I used for comparison for these builds, I just couldn't bring myself to take out that much meat....so, as a compromise, I decided to go this route. Sort of a half-scalloping, so to speak. I'm almost certain that it wound up being far more trouble than it was worth but I guess we'll see.
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Mark Swanson » Sat May 05, 2012 7:53 am

That looks interesting Eddie. You left points in the centers of the braces where it's usually scooped out. Looks like you do a fine job of carving though! The only comment that I'll make is that usually the upper braces of the X are left full and not scalloped, the bracing needs its strength there and the scalloping isn't needed there. But you're still Ok I think, my opinion anyway.
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Eddie McRae » Sat May 05, 2012 8:22 am

Thanks Mark. Actually the upper braces aren't scalloped so maybe the picture is misleading. They're just tapered down 2.5" from the outer edge to a thickness of 1/8". So I think the only non-typical thing I did here was leaving the center peaks in the scallops. And my reasons for that were actually 2-fold. First, the obvious, a little more structural integrity and added strength. But secondly, I wasn't sure about adding a great increase in bass response to this guitar.....especially considering how happy I am with the tone of the guitar that this one is modelled after. Not quite sure what kind of differences it'll actually make but I guess I'll find out! LOL As for my carving....funny you brought that up. I actually strayed from my norm on this one and went old school and did all the carving with chisels. I normally pre-shape using the rounded end of my benchtop belt sander and then, once the braces are glued, do most of the final shaping and scalloping with a grinder/36 grit disc, using a very light touch. I'm alot quicker that way and get just as good results. Carving this one the old-fashioned way took me a good bit longer but I'd just gotten a new honing guide and wanted to try out some newly sharpened chisels. You know how it is......gotta play with the new toys!
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Mark Swanson » Sat May 05, 2012 9:11 am

Yes I do! Well it looks like you have a good handle on it Eddie, good work.
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Eddie McRae » Sat May 05, 2012 9:26 am

Incidentally, my first acoustics were built years ago using Jim William's book as reference, which I still use alot. My treatment of the upper section of the X-brace comes directly from that book. In this case, I wind up with a little over 2.5" of full X and about 2.5" of tapered-down section to the outer edge. Do you recommend a different approach there?
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Mark Swanson » Sat May 05, 2012 9:50 am

That's funny, I learned a lot from that book too! Well, many people do things differently but most see it as a benefit to leave the upper X the full height its whole length, until you have to taper at the linings. That part of the top will not benefit from having a looser brace there because not much if any tone production comes from the top at that location but stiffness there is all important.
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Jason Rodgers » Sat May 05, 2012 11:15 am

To follow up on the scalloping questions, any reason you left more peaks than is typical?
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Eddie McRae » Sat May 05, 2012 11:38 am

I explained above....the guitar that I modelled this build after has unscalloped bracing and has great tone. My line of thinking with this half-scalloping is that it will allow a little added bass response without going overboard. Basically, in a nutshell, when it came right down to it, I just got scared that a completely scalloped bracing design might take it a little further than what I want. This has actually become sort of a "lab rat" situation for me because the 2nd guitar will not be scalloped and I'll be able to compare the difference as they are identical otherwise.
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Eddie McRae » Sun May 06, 2012 8:33 pm

Glued the scalloped top on the first body.
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Eddie McRae » Sun May 06, 2012 8:36 pm

Got the first back braced and glued it on the first body.
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Eddie McRae » Sun May 06, 2012 8:39 pm

A couple of pictures of the first body closed up.....
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Eddie McRae » Sun May 06, 2012 8:50 pm

Chose a more traditional bracing structure for the second top without any scalloping. Also followed Mark's suggestion and left height on the upper sections of the X-braces.
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Eddie McRae » Mon May 07, 2012 4:58 pm

Completed the bracing on the second back and glued the top onto the second body.
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Eddie McRae » Mon May 07, 2012 5:00 pm

A couple of shots of the second body all closed up....
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Eddie McRae » Mon May 07, 2012 5:05 pm

At this point, with all I have left to do on these along with other customs in progress, I really don't see any way possible for me to finish by deadline. I'm still gonna try but I'll be very suprised if I make it.
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Eddie McRae » Mon May 07, 2012 10:30 pm

Twins....
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Mark Swanson » Mon May 07, 2012 10:53 pm

They look good!
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Re: $100 Local Materials Challenge, Eddie McRae, Grand Auditorium Cutaway Acoustic

Postby Eddie McRae » Mon May 07, 2012 11:23 pm

Thanks Mark. I've had an issue arise with these that's never happened to me before. Perhaps you may have a little insight because I can't figure it for the life of me. I drafted a drawing to determine the neck angle for these a week or so ago so I could go ahead and cut the heels and get the fretboards glued on. Correct angle came out to 3.5 degrees which worked out perfect with the 25' top radius and worked out so the fretboard extension would require little to no fitting. When I mock fitted the necks today, one fit perfectly as per the drawing......but one was 1.5 degrees off. I thought at first that the front face of the body had to be out of plumb, but when I checked it, it was fine. I checked everything I could think of and it finally dawned on me to check the top radius. And that's where I found the problem. The top with no scalloping held it radius perfectly but the top with scalloping was a good bit flatter. It's still radiused but it's definitely not 25'. Actually the radius gauge shows it holding to 25' from side to side but it's flatter from end to end. You can't see it with the naked eye but it certainly made a difference in neck fit. I corrected the neck angle so the problem itself is solved but I'd sure like to know what happened to cause this.
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