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PostPosted: Sun Feb 25, 2018 9:57 pm 
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Koa
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I was hoping that some with experience building with the neck block (or tail block) supporting buttresses can share their experiences. I've tried on a couple of guitars, but always have a problem with figuring out how to anchor the carbon fiber rods to the guitar side.

Getting the angle from the top of the neck block to the bottom of the waist is complicated enough. Actually drilling the neck block to receive the rod at the correct angle has been VERY challenging. Then figuring out how to receive the rod at the bottom of the waist against a curving surface has me spending hours of trial and error fitting, cutting and re-cutting little pieces of wood, drilling and re-drilling holes to receive the rod, etc.

What shape or size piece is the rod inserted to? How do you fit the piece to the curvature of the sides? How do you test fit the length of the buttress rod? How do you glue/clamp it all together? Is there an efficient, simple, repeatable way fo doing this that I'm just too dense to see? I very much like what these buttresses to for me, but it is becoming a bottleneck in the production that introduces too many opportunities to mess up. I'd love to see what others have come up with.

Thanks!


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PostPosted: Mon Feb 26, 2018 4:38 am 
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I haven't done them myself, but Burton LeGeyt has a documented build in the tuts section which including buttresses if that helps http://www.luthiersforum.com/forum/viewtopic.php?f=10117&t=29270&p=395888&hilit=neck+buttress#p395888
P.S. the whole thread is amazing to read.

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PostPosted: Mon Feb 26, 2018 12:51 pm 
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Brazilian Rosewood
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I didn't terminate the tubes at the waist because I thought it more of a "half step"; that angles were too steep to do much good. The photo shows pretty much how the blocks were shaped. The neck block was 2 piece and the holes drilled on a set up radial drill press, the rear holes drilled more or less freehand. The top kerfing was cut away and that enabled the tube to be glued and the rear buttresses slid onto the sides from the top. Those buttresses must be first dry fit and the length of the tube cut for a tight fit. Tubes were 3/8".

Image

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PostPosted: Mon Feb 26, 2018 1:15 pm 
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Thank you Hans. I had done full length buttress but didn’t like that they showed through the sound hole. Opening them like that is a nice solution.


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PostPosted: Mon Feb 26, 2018 3:36 pm 
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Burton's approach is very interesting and unexpected. In a nut shell he glues wooden balls to the end of the CF rods and then drills out holes the size of those balls. The balls allow the rod to rotate in 360 degrees to align properly. Elaborate, but genius. I'm not sure how well tooled up I am to duplicate that, but it's worth thinking about.


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PostPosted: Mon Feb 26, 2018 6:29 pm 
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Brazilian Rosewood
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rirhett, Prairie State by Larson's used one "tone tube" like you did (Fender did also on their Villager 12 strings), works fine on a ff hole instrument, but not so hot on an oval or round center sound hole. It is also a repairperson's nightmare. The two tube system works well and repairpeople don't seem to mind it.
The first time I tried it, I worried about vibrational effect with such a long span, but as long as it is well glued and the tubes are cut to proper length (tight), I can detect no disadvantage. Larsons called them "tone tubes", but I don't know if they contribute anything to the quality of tone. Never speculate much. However, since installing them in the first 12 string, I've used them in 12's and 6's ever since.

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PostPosted: Fri Mar 02, 2018 5:48 pm 
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Here's a couple of shots of the one I did that on. I chose to run the braces into the sides at what I thought was a natural angle. I haven't done any more that way and don't plan to unless I build something that needs it structurally.

Attachment:
DSCF0572.JPG


Attachment:
DSCF0575.JPG


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These users thanked the author SteveSmith for the post: rlrhett (Fri Mar 02, 2018 6:34 pm)
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PostPosted: Sat Mar 03, 2018 9:17 am 
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The issue is more twist of the neck block, so I'm not sure how reinforcing the neck block from neck to tail helps that? On the other hand in Steve's photos, one can see that the buttress is looking to support the top of the neck block from twisting inward.

Another way to prevent twist is to make the neck block a "C" shape, attaching the C to the UTB and first back brace, thereby creating a very stiff upper bout that resists twist.

Andy


Last edited by AndyB on Sun Mar 04, 2018 10:16 am, edited 1 time in total.


These users thanked the author AndyB for the post: SteveSmith (Mon Mar 05, 2018 8:58 am)
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PostPosted: Sat Mar 03, 2018 10:02 pm 
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Brazilian Rosewood
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Well Filippo (oops), Robin, Andy, or whatever you care to be called, works for me. By the way, it's called neck block rotation. Pretty obvious how it works. Fifty or 70 years will tell. I'll be dead. I happen to like the way Larsons did it with some modification. They're dead. But they have 80-100 years on their instruments.
To each their own...take what you need, leave the rest...

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