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 Post subject: Double bass neck repair
PostPosted: Thu Sep 21, 2017 11:28 am 
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Mahogany
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First name: Nathan
Last Name: Peirson
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I am currently working on a double bass that fell over and started the neck popping out of it's neck pocket.
It tore some of the wood free from the pocket sides, but the neck itself is in great shape. I was able to clean all the old glue off, remove some of the chunks of the pocket sides and glue them back into place. There are obvious gaps in the neck pocket walls; pieces that were not able to glue back in. My question: can I fill the gaps with epoxy putty and then glue the neck back in, or should I shave down the walls and glue in shims?


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PostPosted: Thu Sep 21, 2017 3:28 pm 
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Cocobolo
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Deep down, you already know the answer to this one. If the epoxy repair fails, the next guy has a real mess to clean up before he can fix it right.



These users thanked the author bobgramann for the post: Hesh (Wed Oct 11, 2017 6:14 am)
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PostPosted: Fri Sep 22, 2017 12:15 pm 
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Mahogany
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Here is an update. I did a test of 2 different wood epoxy putties. I am not endorsing either, but using Mohawk and Quickwood putties, I put a good pad of each on the end of some quartersawn 8/4 Doug Fir, waited 24 hrs, leveled them to the same level, approx 3/32" proud of the fir. Using Titebond II, I glued another piece of wood to the 2 pads of putty, waited 24 hrs and tried to break the bonds. The only thing that failed was the secondary wood piece. Basically, the bond held to the quartersawn end of the fir and the wood splintered off the other. I wouldn't use this for large deep areas, but I think that for smaller 'craters' it might be a viable solution. Both putties held up, and I put it under a fair amount of stress.


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PostPosted: Fri Sep 22, 2017 12:44 pm 
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Cocobolo
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If the bass has any value (i.e., it's better than a $600 Chinese painted plywood bass), I wouldn't use either epoxy or Titebond II. Even Titebond Original is difficult to remove. Sooner or later, that bass will have to be repaired again. A repair with epoxy is the last repair that can be done in that area without a lot of reconstruction the next time. A repair with hot hide glue, which requires that all of the gluing surfaces be perfect before gluing, is a lasting and serviceable repair. If the bass has value, you may wish to take it to a professional bowed instrument luthier. Some instruments require epoxy or metal hardware in a neck repair, but when you make that choice, you are making decisions for the future life of the instrument. If you take it to someone who has done many of these and he/she determines that epoxy is the only way, then you can be more comfortable going that route, knowing that the next fall might be the last. A repair on a good instrument needs to be reversible.



These users thanked the author bobgramann for the post: Hesh (Wed Oct 11, 2017 6:14 am)
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PostPosted: Fri Sep 22, 2017 4:44 pm 
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Brazilian Rosewood
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I have done a similiar repair in my shop . I used an angled dowel to pin the repair , For the missing pieces I would find whatever is a good maple match , glue it on and shape it to the overall neck shape very carefully . HHG is your friend.


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PostPosted: Fri Sep 22, 2017 9:05 pm 
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Mahogany
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It's a cheap bass. Cheaply made. It is a straight tenon neck and took a lot of time getting all the clear glue off. The tenon didn't even touch the bottom in many places and the gap was apparently filled with the glue. I have a feeling it may have been epoxy. If this had been a carved top bass I would take a completely different approach.


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PostPosted: Fri Sep 22, 2017 9:48 pm 
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Cocobolo
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Okay. I won't be so upset about epoxy on a throwaway bass. Another warning about epoxy, though: when I first started building guitars, I tried epoxy for the heel block and peghead scarf joints on one instrument. Over less than a year under string tension, both joints crept revealing the joints with palpable edges. I was glad that it was on an experimental instrument. I don't use epoxy for anything in my building now.

That said, I still wouldn't use glue or epoxy to fill any gaps. I would reconstruct the surfaces with real wood.


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PostPosted: Fri Sep 22, 2017 10:09 pm 
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Koa
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Even the "throwaway" old Laminate Kay bass' seem to have found an ongoing life in live gig performance.... Probably because they don't crack and split like a good old solid wooden unit when you haul them around from place to place.... Nobody ever thought they would still be around - but they just keep hanging around because they are tough.

Remember - the glue is only supposed to be there to keep the joint from falling apart.... The glue doesn't maintain geometry or act as part of the structure... It just keeps the wood from shifting too much.

Caution: Neither straight epoxy nor wood filler is "structural" for thick fillets under significant load. That stuff is made to hide nail holes.... In structural use - it will fail.. Maybe not in 2-3 months... But it won't last 5 years... To make that stuff work in a structural fillet- you generally need a lot of fumed silica filler or finely chopped glass... And then it turns to rocks and ruins your edge tools. And if you thought the next guy would curse you for epoxy - go ahead and fill that epoxy with 60%+ glass... ;).


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PostPosted: Thu Sep 28, 2017 4:46 pm 
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Mahogany
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First name: Nathan
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Well, discretion being what it is, I have decided to just chisel out the bad wood and laminate in some maple I had in stock. Took longer, but I really couldn't justify the epoxy putty. Thanks to all. I needed to see what the thought about putty was in the larger builder community and I thank you for your honest input.


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PostPosted: Thu Sep 28, 2017 5:51 pm 
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Pix when you're done, OK?

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PostPosted: Wed Oct 11, 2017 4:53 am 
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Mahogany
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The only epoxy in this repair is on the broken button, an extension of the back, never meant to be demounted. I had to refit a few neck block splinters that stuck to the heel.

http://lumberjocks.com/Texcaster/blog/43520

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PostPosted: Thu Oct 12, 2017 3:34 pm 
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Mahogany
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First name: Nathan
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I would love to post some images but I can't find instructions. Any help?


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PostPosted: Thu Oct 12, 2017 5:09 pm 
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Mahogany
Mahogany

Joined: Thu Oct 20, 2016 7:22 pm
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First name: Nathan
Last Name: Peirson
Country: USA
Focus: Build
Status: Amateur
nathanpeirson wrote:
I would love to post some images but I can't find instructions. Any help?

ImageImageImageImage



Sent from my iPhone using Tapatalk


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PostPosted: Thu Oct 12, 2017 5:11 pm 
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Mahogany
Mahogany

Joined: Thu Oct 20, 2016 7:22 pm
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First name: Nathan
Last Name: Peirson
Country: USA
Focus: Build
Status: Amateur
nathanpeirson wrote:
nathanpeirson wrote:
I would love to post some images but I can't find instructions. Any help?

ImageImageImageImage



Sent from my iPhone using Tapatalk

Saw the post about sharing from iPhone. That worked! Here are a few of the shots showing damage, new inserts and final. Still need to work the finish a bit.


Sent from my iPhone using Tapatalk


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PostPosted: Thu Oct 12, 2017 5:31 pm 
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Cocobolo
Cocobolo

Joined: Mon Oct 17, 2011 4:10 pm
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First name: Bob
Last Name: Gramann
City: Fredericksburg
State: VA
Zip/Postal Code: 22408
Country: USA
Focus: Build
Status: Professional
Nice save! Congratulations.



These users thanked the author bobgramann for the post: nathanpeirson (Thu Oct 12, 2017 5:34 pm)
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PostPosted: Thu Oct 12, 2017 5:46 pm 
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Brazilian Rosewood
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Nice Job!
Remember, the rule of instrument repair is no matter the value, first, do no harm.

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These users thanked the author Haans for the post: nathanpeirson (Thu Oct 12, 2017 8:21 pm)
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