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Yet another top brace glue up
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=13360		 Page 1 of 1
Author:  jhowell [ Thu Aug 23, 2007 12:24 pm ]
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The top wood is Lutz and the bracing is Adi from John Hall and is going into a deep bodied 00. This was my first with HHG and its made me a fan of the glue.

The general layout:



On the gobar deck. I use short sections of ACE hardware yardsticks here and there so to not have to put gobars on the already rounded bracing.


The bracing has been lightened up a little. All of the carving was with a 1/2" chisel and some sandpaper. I tapped with an old piano hammer. Just tried to get a good ring from the top.


Author:  Marc Lupien [ Thu Aug 23, 2007 1:45 pm ]
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Jim, I am by no way an expert, having built only three acoustics before switching to electrics, but I think that the lower bout portions of your X-braces are not "substantive" enough...  Of course, il may be that I overbuilt my guitars...  Other opinions?
Author:  KenH [ Thu Aug 23, 2007 1:47 pm ]
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Nice job Jim!


Just out of curiosity, what are the 2 holes drilled in the top near the neck block for?  Is that a Maple bridge plate?
Author:  Bruce Dickey [ Thu Aug 23, 2007 3:50 pm ]
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While I agree with Marc that the x braces appear quite "cutaway", I think as Todd and Hesh do, that it will work fine.

A recent measure of an Olson in my shop, revealed the x brace to be only 1/2 inch tall at the x brace. The x'es were scalloped too, so they were close to 1/4 inch tall at the low point of the scallop, similar to Jim's OO bracing revealed here.

Jim, were it me, I think I'd remove some additional mass from the upper x braces, maybe curve those squared lines a bit and taper the braces from base to top in more of a vee shape, pointier on top. Just to get rid of mass without affecting strength much at all.

Great job so far, really nice looking workmanship. Of course these are merely suggestions, but I really think it would make a better guitar.
Author:  Arnt Rian [ Thu Aug 23, 2007 7:51 pm ]
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Well, you didn't exactly ask for our opinions, but as long as you posted pictures and you already have some opinions I'll give you mine too...

The bracing looks nice and I think it will be fine structurally if the woods have normal stiffness and the top isn't too thin, but like Bruce I would take some more off the sides of the braces to make them sharper to lose some weight without losing much strength. This in in regard to all the braces below the soundhole, the ones above look fine. In general I would make the transitions between the 'peaks' and 'valleys' smoother and try to avoid some of the 'lumpiness' in their profile, perhaps make the peaks less substantial. I see that the lower peaks on the tone bars are quite a bit larger and closer to the rims than I would have put them, I like to make the top more flexible that close to the side. If the tone bars are not inlet under the x-brace I would shave them down to nothing at the intersection as the increased flexibility of the brace end would make it less likely to come unglued later on. I also think the x-brace intersection would be stronger if you capped the joint with wood instead of cloth.

As I said, these are all just opinions based on pictures and not actually handling the wood; if you are happy with they way the top feels and rings now and you'd rather not do anything more to it that's OK too, these are all suggestions based on personal preference.
Author:  Bruce Dickey [ Fri Aug 24, 2007 12:29 am ]
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Jim,

As you already have the cheesecloth wrapped over the x-brace, it appears you felt you were done with the shaping.

I'm sure you've noticed many of us cap with a slice of spruce these days, rather than cloth. That's a preference thing too, but could add substantial strength to the intersection without much change in mass.

I mainly wanted to say, it would be good to grab a set of plans and really pay attention to getting the braces really close to standard tolerances and shapes.

For me, I have a copy of dred plans that came with a Martin kit. Most of my guitars so far have followed that general scalloped Martin plan. Your's is very similar.

I notice your very minimal fingerbraces and just wanted to say those really look good to me. I might just change to make mine look more like those.

I think Lance uses a similar bracing scheme as found on Dana Bourgeois guitars. Through trial and error you find what works. It'd be worth a look at that website to see Dana's bracing scheme.

I kinda followed the logic of Charlie Hoffman, about going with something tried and true and not varying much from it. He does add a little back fingerbrace off the lower tonebar to enter and support the large area of the lower bout.

Others do a brace, like Mario Proulx, behind the bridge plate. I think John Kinnaird does that too. So there are many variations and they all work with predictable outcomes. I think some of the behind the bridgeplate stuff comes from trying to offset the belly bulge that can occur on acoustic guitars.

Great subject matter, folks generally find a way they like and stick to it. If you don't change a thing on the top above it'll still sound like a guitar. It has all the requisites. Good luck in your building.

Someday soon I plan to deviate from true Martin bracing and build a guitar for myself based on the Lowden.
Author:  jhowell [ Fri Aug 24, 2007 9:17 am ]
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Guys--

The opinions are very much welcomed! I'm really new at this game and am trying to soak up as much as I can, where ever I can.

The Lutz top is very stiff and I was surprised (probably shouldn't have been ) at how much stiffer the adi bracing is over the sitka on my last top. I made a conscious decision to go very light with this one. Hopefully not too light. I sketch my bracing patterns for each build and record all dimensions and intersection angles in the hope that if I hit on something that sounds fairly good, I can come close to repeating.

I closed the box last weekend, so what you see is what I got!    My last top had a spruce cap on the main X intersection, but these braces came already formed in cross-section, so I used a fairly heavy linen patch (the stuff that I FP with) soaked in LMII white glue as the brace. The top is now sitting on a nice set of EIR back and sides that are essentially at dreadnaught depth.

The two holes are, I believe, artifacts of most of the pieces/parts of this kit from John being Martin parts. There are registration holes in the top of the neck block that allow the top to be accurately placed in the Martin manufacturing process.

So anyways, thats pretty much how I ended up with what I have. This one is a gift for one of my brothers and he will get to be the guinea pig to see how it stands up to playing.

Sorry about not posting sooner. I'm an IT dude in a plant that upgraded its ERP system about a week ago and my spare time has been well taxed.

Please keep the comments coming!
Author:  Bruce Dickey [ Fri Aug 24, 2007 4:22 pm ]
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[QUOTE=Bruce Dickey] Jim,

As you already have the cheesecloth wrapped over the x-brace, it appears you felt you were done with the shaping.

If you don't change a thing on the top above it'll still sound like a guitar. It has all the requisites. [/QUOTE]

Thanks for the picture Jim. That's a great way to get some feedback. What shape a guitar is this anywho?
Author:  Bruce Dickey [ Fri Aug 24, 2007 4:24 pm ]
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00, I just re-read your post.

This is similar to the one I built with my neice, three years ago. Your brother will be thrilled.
Author:  jhowell [ Sat Aug 25, 2007 1:28 am ]
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Bruce--

I hope so, he has no clue that it is being done for him.

Hesh--

The new shop is working out well for being a shared space with the washer and dryer. The top three improvements are being able to get to all four sides of the work bench; having a concrete floor that makes me quite a bit less paranoid about spilling anything liquid; and now having a gobar deck that is off the floor.

Thanks again to all for the comments. This forum is a really inspiring and insightful place to spend some time. The bar, for me, is raised with nearly every visit.
Author:  KenH [ Sun Aug 26, 2007 12:22 pm ]
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Since we are showing pictures of our bracing, I'll throw mine in the hat. This is a recent dread with an Adi top. I am experimenting with "mario's magic tonebar" which is an extra and much smaller tone bar placed at a skew to the other tonebars. I am also letting out of the bag one of my other secrets to better tone, which is an Osage Orange bridge plate. I use no x-brace cap at all. My x-braces are well fitted and glued together so well that I feel that any additional materials would add weight that isnt needed. Even though this bracing is pretty thin, I still feel that I can go lighter on the bracing. Also make note that the transverse brace isnt shaped in this picture.


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