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PostPosted: Mon Jul 23, 2018 3:40 pm 
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Cocobolo
Cocobolo

Joined: Thu Nov 27, 2014 10:35 am
Posts: 254
Location: Hopkinton, MA
First name: Robert
Last Name: Ionta
City: Hopkinton
State: Massachusetts
Zip/Postal Code: 01748
Country: USA
Focus: Build
Status: Amateur
I’ve got a mid-60s Gibson bass that (naturally) fell off its stand and broke its neck. It’s not completely separated. The headstock veneer at least is holding it together. I think if the veneer was removed it still would not completely separate. I’ve done a few of these headstock breaks and have found that I can inject hot hide glue with a syringe and get clamps on it within a minute when I don’t have to fuss around positioning the broken piece. I am confident I can do that in this case.

What I’m not so confident about: there are multiple moving fracture lines. I can spread the crack open to inject glue into the largest one but the smaller ones don’t open wide enough to get any needle I have into them.

I’m too chicken to try to break the thing all the way off and anyway I think that’ll do more harm than good.

So how can I get glue into those smaller fracture lines?

Thanks for any and all advice!

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PostPosted: Mon Jul 23, 2018 3:59 pm 
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Cocobolo
Cocobolo

Joined: Thu Nov 27, 2014 10:35 am
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Location: Hopkinton, MA
First name: Robert
Last Name: Ionta
City: Hopkinton
State: Massachusetts
Zip/Postal Code: 01748
Country: USA
Focus: Build
Status: Amateur
Ok. Here I go, responding to my own post, like an idiot. But what the heck...

I have 2 ideas:

1. Deposit some HHG along each of the small cracks and use compressed air to force it inside. What worries me about this is that the air will cool the glue and cause it to gel before I get it clamped.

2. Repair the main crack with HHG and clamp. Then wick some CA glue into the smaller cracks.

Any opinions about those ideas?


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PostPosted: Mon Jul 23, 2018 5:04 pm 
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Koa
Koa

Joined: Thu Nov 04, 2010 1:46 pm
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First name: Freeman
Last Name: Keller
Focus: Build
Status: Amateur
I've done similar repairs but always with AR, I don't have the chops or confidence with HHG that I could get it done in time. With AR I've used a variety of tools to work the glue up inside the small cracks - I keep a few pieces of guitars strings and some scrap purfling that seems to work well.

Image

And you are right, don't break it all the way open. It gets infinitely harder to align everything and apply clamping pressure unless you build some really creative jigs.


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PostPosted: Mon Jul 23, 2018 5:12 pm 
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Cocobolo
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Joined: Fri Feb 18, 2005 6:18 am
Posts: 265
Location: United States
First name: Frank
Last Name: Ford
City: Palo Alto
State: CA
Zip/Postal Code: 94301
Country: USA
Focus: Repair
Status: Professional
I think if you use air pressure to force hot hide glue into the crack you'll be guaranteed of premature gel and glue failure.

This is a job I'd likely do with epoxy. West System or another good grade of slow-set (NEVER the 5-minute stuff) will penetrate farther into tight cracks than pretty much any other glue because it stays liquid for a long time and creeps slowly - you know just like it tends to get all over your hands and everything when you're working with it.

I'd support the instrument with neck aimed downward at about 45 degrees, and start dribbling, injecting, pounding or otherwise getting as much into the joint as possible for half an hour. Then I'd use the standard rope trick* to pull the headstock back, and watch for the next hour or so, wiping as much squeezed out glue as possible. After wiping like crazy, I'd coat the surface with regular rubber cement to help keep epoxy from sticking to the finish.

Next, I'd clamp things back together as well as I could with wax paper to prevent sticking to my resilient cauls. Cleanup can be a careful bit of business with razor blades and scrapers, but the result is usually worth the extra effort there.

* Here's the rope trick: http://www.frets.com/FretsPages/Luthier ... clamp.html

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Cheers,

Frank Ford

FRETS.COM
HomeShopTech
FRETS.NET



These users thanked the author Frank Ford for the post: fumblefinger (Mon Jul 23, 2018 9:09 pm)
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PostPosted: Mon Jul 23, 2018 5:12 pm 
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Cocobolo
Cocobolo

Joined: Thu Nov 27, 2014 10:35 am
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Location: Hopkinton, MA
First name: Robert
Last Name: Ionta
City: Hopkinton
State: Massachusetts
Zip/Postal Code: 01748
Country: USA
Focus: Build
Status: Amateur
Thanks Freeman. Maybe I’m just being overconfident in my chops with HHG. I haven’t been using it that long and I doubt I’ve done anywhere near as many repairs as you. To be honest, I’ve been using it because I’m afraid of getting things misaligned and then having no recourse because of the glue now in the joint. I figure with HHG I have another chance to heat it up and adjust. But I’m pretty sure I can’t work glue into those little cracks fast enough for this one.


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PostPosted: Mon Jul 23, 2018 5:15 pm 
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Cocobolo
Cocobolo

Joined: Thu Nov 27, 2014 10:35 am
Posts: 254
Location: Hopkinton, MA
First name: Robert
Last Name: Ionta
City: Hopkinton
State: Massachusetts
Zip/Postal Code: 01748
Country: USA
Focus: Build
Status: Amateur
Ahhhh! Thanks for the rope trick! That looks very doable. I was working on a fancy-ish clamping scheme to accomplish the same thing but that looks a lot simpler.

I’ll investigate the epoxy. Thanks again!


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PostPosted: Mon Jul 23, 2018 9:04 pm 
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Koa
Koa

Joined: Thu Nov 04, 2010 1:46 pm
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First name: Freeman
Last Name: Keller
Focus: Build
Status: Amateur
All the necks I build have a scarf joined head - this is basically the same thing, just not as pretty. I use AR glue for them too and have never had a problem.

This particular 12 string neck was an epoxy job that went bad - for some reason the epoxy didn't kick off and remained soft in the joint. The joint opened up again, I clamped the neck down to the work bench and gently put a clamp on the end of the head pulling it open. I spent about half a day futzing around inside the joint with pokey tools and alcohol wipes until I felt that I had most of the epoxy out. I debated doing it with epoxy again but decided to go for the AR. No rope tricks, just a couple of hunks of UHMW and a lot of clamps

Image

However to hedge my bet (and because it was a 12 string) I did put a little carbon fiber spline in the joint and then covered it with a back strap

Image

Probably overkill but the repair is about four years old now and is holding up perfectly


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PostPosted: Mon Jul 23, 2018 9:15 pm 
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Cocobolo
Cocobolo

Joined: Thu Nov 27, 2014 10:35 am
Posts: 254
Location: Hopkinton, MA
First name: Robert
Last Name: Ionta
City: Hopkinton
State: Massachusetts
Zip/Postal Code: 01748
Country: USA
Focus: Build
Status: Amateur
Nice work!


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PostPosted: Mon Jul 23, 2018 9:29 pm 
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Koa
Koa

Joined: Thu Nov 04, 2010 1:46 pm
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First name: Freeman
Last Name: Keller
Focus: Build
Status: Amateur
bionta wrote:
Nice work!


Thank you. Just like yours will be, some of the hardest work is making it not too obvious.

Image


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PostPosted: Tue Jul 24, 2018 7:33 am 
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Cocobolo
Cocobolo

Joined: Thu Nov 27, 2014 10:35 am
Posts: 254
Location: Hopkinton, MA
First name: Robert
Last Name: Ionta
City: Hopkinton
State: Massachusetts
Zip/Postal Code: 01748
Country: USA
Focus: Build
Status: Amateur
Freeman wrote:
bionta wrote:
Nice work!


Thank you. Just like yours will be, some of the hardest work is making it not too obvious.



Looks great. I'm not sure what I'm going to do about that yet. I may take it to a finishing expert if the owner is willing to pay for it. There's someone in my area who specializes.


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PostPosted: Tue Jul 24, 2018 10:31 am 
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Cocobolo
Cocobolo
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Joined: Fri Feb 18, 2005 6:18 am
Posts: 265
Location: United States
First name: Frank
Last Name: Ford
City: Palo Alto
State: CA
Zip/Postal Code: 94301
Country: USA
Focus: Repair
Status: Professional
Yep, Freeman, that's about the most solid repair possible, and considerably stronger than the original construction! I have seen only a few of these backstrap overlay jobs fail, and those were clearly a matter of high heat exposure. Pretty much the best repair after the failure of a previous gluing. Unlike dowels, or splines, the backstrap still allows a bit of flexibility to resist shock, has terrific gluing surface and because the wood is bent, it asn't split apart.

_________________
Cheers,

Frank Ford

FRETS.COM
HomeShopTech
FRETS.NET



These users thanked the author Frank Ford for the post: DanKirkland (Wed Jul 25, 2018 10:37 pm)
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 Post subject: Re:
PostPosted: Wed Jul 25, 2018 10:38 pm 
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Koa
Koa

Joined: Wed Feb 17, 2016 8:54 am
Posts: 591
State: Texas
Country: United States
Focus: Repair
Frank Ford wrote:
Yep, Freeman, that's about the most solid repair possible, and considerably stronger than the original construction! I have seen only a few of these backstrap overlay jobs fail, and those were clearly a matter of high heat exposure. Pretty much the best repair after the failure of a previous gluing. Unlike dowels, or splines, the backstrap still allows a bit of flexibility to resist shock, has terrific gluing surface and because the wood is bent, it asn't split apart.


Frank you are a gentleman and a scholar.


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