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CS257 neck fix

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fhryder
Posted 2012-02-21 9:16 AM (#450757)
Subject: CS257 neck fix



Joined:
February 2012
Posts: 6

Hello All:
Been playin guitar since the early 1950's
got an Ovation eleven hundred and something in the early 80's
but I lost it when my daughter left home several years later
sad to see both of them go
I was left with my 12 string Fender which is all I've played ever since

Decided last year to get back in, and learn fingerpicking
and so got a new CC24NBM, best sounding guitar on the wall
around Christmas I got an early CS257 with the neck problem
it sounds even better than the cc24 (solid top vs laminate I think)

anyhow I have developed a modified fix for the Ovation cracked neck which I would like to share.

Frank
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Nick B.
Posted 2012-02-21 9:21 AM (#450758 - in reply to #450757)
Subject: Re: CS257 neck fix



Joined:
December 2009
Posts: 686

Location: Route 66, just east of the Cadillac Ranch
Welcome to the group Frank. Hopefully one of the moderators will be along shortly to give you access to the other forums. I'm anxious to see your fix.
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Damon67
Posted 2012-02-21 1:31 PM (#450782 - in reply to #450757)
Subject: Re: CS257 neck fix



Joined:
December 2006
Posts: 6992

Location: Jet City
Share away Frank
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fhryder
Posted 2012-02-23 6:49 AM (#450883 - in reply to #450757)
Subject: RE: CS257 neck fix



Joined:
February 2012
Posts: 6

I recently acquired an early CS257-CGB, (picture 1. in /Albums/cs257-cgb neckfix) it's pristine except that it has the Ovation neck problem.With heavy strings the neck lifted more than 1/16 in and with time would only get worse.
Having studied the repair techniques on this board and on smashedguitars.com, I concluded that neck repair requires a bit more than just a reglue. Photos of disassembled guitars revealed a well braced bowl bulkhead at the neck joint, I concluded that the neck should be more securely attached to this than a glue joint could provide. How to do it?
The bowl is about 1/4 in thick at the point it is glued to the wooden neck, a screw at a 10 degree angle near the edge of the bowl could pass through this bulkhead and enter the strongest part of the neck. Deck and drywall screws have larger thread spacing and are less likely to pull out. (picture 2.)
A screw by itself would put create a high pressure point on the plastic bowl and risk crushing so I used the base of a snap fastener as a washer to spread the force over the surface of the bowl, and to redirect it by 20 degrees flat to the surface of the bowl. (picture 3)
After drilling a pilot hole to a point just short of the truss rod and enlarging the portion through the bowl to relieve stress, I overtightened the strings to really open up the crack and injected cyanoacrylate (crazy glue) then released the strings and tightened the neck with a carpenters clamp closing the crack completely before tightening the deck screw home.
After letting it harden for a week I restrung it with 007-044, light strings When I measured the 1st and 6th string clearances at the 12th fret I found it to be about 5/64, nice low action, plays easy, sounds great. Then I cleaned the glue joint and sealed it with a final layer of crazy glue so that any subsequent cracking would be clearly evident.
I really want to thank all those who contributed photos of their repair jobs, particularly photos of disassembled guitars which enabled me to scale bowl and neck dimensions and precisely locate and orient my reinforcing screw . (picture 4. )

Frank
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Mr. Ovation
Posted 2012-02-23 7:13 AM (#450884 - in reply to #450757)
Subject: Re: CS257 neck fix


Joined:
December 2001
Posts: 7209

Location: The Great Pacific Northwest
Hi Frank,
Interesting project. The only thing that isn't clear, or maybe I missed it, is how you "concluded that neck repair requires a bit more than just a reglue" I would think a screw would be the last resort as that is not nearly has strong as a glue joint. A friend of mine (actually it was MWoody) recently instructed me on the proper way to glue wood together, and I was totally amazed at the result. Also seems to me that a screw in that area would actually weaken the structure to where one day you'll be playing and ker-snap... you'll be holding the neck in one hand and bowl in the other. Also, so my knowledge (and I could be wrong) it's my understanding and experience that Crazy Glue is worthless on wood. Might as well use water for glue, at least water would expand the joint and maybe cause two parts to stick together.

I don't mean to diss your project. It looks interesting, and if it works... well that's really all that matters. I would not have thought it would work, but I'm sure we all have stories of things that maybe on paper "shouldn't" work and turn out just fine.
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fhryder
Posted 2012-02-23 8:06 PM (#450908 - in reply to #450884)
Subject: Re: CS257 neck fix



Joined:
February 2012
Posts: 6

Hi Miles:

Thank you for your observations, I guess in an effort to be concise I sacrificed some clarity.

I will address the issues one at a time. First my statement "neck repair requires a bit more than just a reglue " goes to the design of the Ovation CS257 neck attachment. I've uploaded picture 5. to the album showing the plan and profile of a neck joint failure. You will see that the dovetail joint does not continue all the way to the bottom. In fact at the bottom there's no dovetail at all, nothing but a gob of glue forming the bottom joint. In fact there's a lot of glue up the sides as well, not my idea of a nice tight dovetail joint.Thus while the dovetail accurately secures the alignment of the fretboard at the top, it does not in my opinion do an adequate job of securing the neck to the bowl at the bottom. A simple reglue will not fix these issues.

Consequently any stress caused by string loading, or a drop shock, is carried only by a glue joint in tension. A standard string set , say (.011-.052) has a tension at standard tuning of about 140lbs. which by applying a bit of physics means that the bottom of the neck joint is under tension of about 55lbs. So that quantifies the steady state, I won't attempt to quantify the stress of a drop shock, or someone sitting on it, or a small child or animal jumping on it, but that seems to be the circumstances when and where the joint fails .

That's why I began thinking that a bolt or screw securing the bottom of the neck might help. My choice, a high strength deck screw, small, so as not to unduely disturb the structural integrity of the neck, while transferring the force to as large an area of the surface of the bowl as possible.

That's not to say I won't suffer your nightmare scenario, however I have a nightmare scenario of my own in which the neck and screw remain intact, but the screw pulls right through a crushed hole or slot in the ruined bowl.

to be continued...

Frank
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fhryder
Posted 2013-08-02 10:13 AM (#473789 - in reply to #450757)
Subject: Re: CS257 neck fix



Joined:
February 2012
Posts: 6

CS257 neck fix ... one year later

Thought I should let you know how I made out with this repair so her we are one year later.

As I said I finished the job with a layer of crazy glue all around the seam between the neck and the body
so that if it cracked again it would be clearly evident at the surface.
No cracks have appeared.

The previous owner had replaced the tuners with a set of GOTOH tuners, they do not slip.

This guitar can hold it's tuning for weeks at a time. it's great

and it also sounds great crisp and clear it really rings

So I'm very satisfied with me deck screw neck fix.

Frank
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fhryder
Posted 2013-08-02 12:32 PM (#473796 - in reply to #450757)
Subject: Re: CS257 neck fix



Joined:
February 2012
Posts: 6

edit:
line 1 : here
line 9 : my
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fhryder
Posted 2017-06-13 4:12 PM (#535517 - in reply to #450757)
Subject: Re: CS257 neck fix



Joined:
February 2012
Posts: 6

CS257 neck fix ... five years later

It has sat in the case for the past 3 months
It sounded fine and when I checked the tuning with a counter
it was spot on.

The cs257 is a great sounding guitar ( I play acoustic only )
and the shallow bowl means it doesn't slip around as much as the full size ones

So I think we can say the deck screw fix is a success in the long term.

Frank
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