arctop side crack

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arctop side crack

Postby Ryan Mazzocco » Thu May 09, 2019 6:45 pm

I've had a repair come across my bench that I'm little puzzled as to how to proceed and thought I'd seek a little advice from the smart people here.
It's an old Recording King archtop with a long crack along most of the bass side. there are some pretty wide areas where material has broken away.
Being an archtop I know it's going to be a real trick getting the cleats in there, and i'm going to have to splint some areas as well. So it's not an easy task to start.
Here's where it gets real tricky for me. The crack is right along the top edge of the kerfing on the back. So, I can't really "bridge" the two sides of the crack with cleats. Or if I put a reinforcing strip along the length of the crack, it still only touches one side and then runs into the kerfing. The way it is it's just kind of floating in space, able to go in and out. So, how do I connect it all as one solid piece and keep it in line with where it's supposed to be?
Thanks!
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Re: arctop side crack

Postby Barry Daniels » Thu May 09, 2019 8:08 pm

Shape some splints to fit the flat side on one half and the angled kerfing on the other half. Then use a Teeter tuning machine splint tool where a guitar string goes through a small hole in the sides and pulls the splint and a caul into place. You should have one of these tools for every 3 or 4 inches the crack is long. If you can't find any photos of this tool, let me know and I will post some.
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Re: arctop side crack

Postby Barry Daniels » Thu May 09, 2019 8:18 pm

Here is a Youtube video that shows one of these tools. He made his from plexiglass but mine are made from a single block of maple.

https://www.youtube.com/watch?v=0gjhTYHRtMg

The trick to using this tool in your situation is shaping those splints properly. When tightened up the crack must line up or you will end up with an offset which is not good.
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Re: arctop side crack

Postby Ryan Mazzocco » Thu May 09, 2019 8:44 pm

Barry,
Thanks for the tip. I actually have a couple spare wilkinsons that's I've been saving for just this type of thing. the part I was really worried about was fitting a cleat to the inside. I like your idea of shaping it to fit the kerfing.
So just to clarify:
When you say to "shape some splints," are you meaning regular cleats modified to fit the side and on the kerfing? or are you talking about the actual splint to fill in where wood is missing? or is this splint a longer piece that travels on the inside of the guitar the whole length of the crack? That was one option I had considered but thought it would really be a nightmare to fish that in through the F-hole.
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Re: arctop side crack

Postby Barry Daniels » Thu May 09, 2019 9:32 pm

Just a small block of wood maybe 3/4" square and only as thick as necessary to allow you to shape it into the oblique V shape needed to sit on top of the kerfing and on top of the sides, spanning the crack. Place one of these about every 3 inches. Make sure the grain runs perpendicular to the crack. This block should have a small hole in the middle to allow the guitar string to go through. Also need a caul backing it up to allow clamping pressure.
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Re: arctop side crack

Postby Ryan Mazzocco » Thu May 09, 2019 9:48 pm

Barry Daniels wrote:Just a small block of wood maybe 3/4" square and only as thick as necessary to allow you to shape it into the oblique V shape needed to sit on top of the kerfing and on top of the sides, spanning the crack. Place one of these about every 3 inches. Make sure the grain runs perpendicular to the crack. This block should have a small hole in the middle to allow the guitar string to go through. Also need a caul backing it up to allow clamping pressure.


Excellent! Love it.
Okay, one last question. Do I need to install the splint at the same time or can I do it in two seperate steps; cleats first and then install the splint?
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Re: arctop side crack

Postby Daryl Kosinski » Thu May 09, 2019 11:04 pm

If the back is off. why not scrape 1/8 inch the bottom of the kerf then glue in a backing splice. With the back and top on I got nothing.
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Re: arctop side crack

Postby Barry Daniels » Thu May 09, 2019 11:11 pm

The need for a splint makes it more complicated for sure. But you do the cleats first to get the sides of the crack level. Then clean the crack out and do the splints.
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Re: arctop side crack

Postby Ryan Mazzocco » Thu May 09, 2019 11:55 pm

Barry Daniels wrote:The need for a splint makes it more complicated for sure. But you do the cleats first to get the sides of the crack level. Then clean the crack out and do the splints.


Okay then. That sounds like a plan.
I honestly do feel a lot better about this now. Thanks for the nudge in the right direction.

When I get to it I'll add to this thread with some pictures of how the project is going.
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Re: arctop side crack

Postby Barry Daniels » Fri May 10, 2019 10:27 am

The challenge of this project will be getting the cleats shaped properly so that the sides of the crack are level when everything is clamped up. You should definitely go through dry runs until you find the correct angle.
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Re: arctop side crack

Postby Ryan Mazzocco » Fri May 10, 2019 11:54 am

that's what om doing now. I'm going to take my time with this. the guy isn't in a huge hurry.
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Re: arctop side crack

Postby Barry Daniels » Fri May 10, 2019 12:32 pm

Now that I think about it, you will need to have a spool or cam clamp pulling the top and back together, placed directly over the tuning machine clamps because the oblique angled cleat will tend to push the crack open.
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Re: arctop side crack

Postby Bryan Bear » Fri May 10, 2019 1:07 pm

This may be a dumb thought but. . . when you make the cleats that fit the side and kerfed lining angle, could you add a thin spline to the side of the cleat that would push in between the kerf and give you a bit more glueing surface? Please forgive my crude drawing but the darker brown is what I am talking about slipping into the kerf of the lining. I know it wouldn't be a perfect fit since the kerfs flex but the spline to lining joint is going to be endgrain so every little bit helps.

kerf cleat.jpg
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Re: arctop side crack

Postby Barry Daniels » Fri May 10, 2019 5:12 pm

That is not a bad idea.
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Re: arctop side crack

Postby Barry Daniels » Sun May 12, 2019 5:27 pm

How is the repair going, Ryan?
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Re: arctop side crack

Postby Ryan Mazzocco » Sun May 12, 2019 7:30 pm

As expected... very slowly lol
it's one of those "back burner" kind of jobs. I test fit a few pieces but haven't found the that sweet spot of the perfect angle quite yet. I think it's going to take a couple tries anyway because about halfway to the waist the kerfing changes to a bit larger size and sits just a bit taller. I want to be able to figure out the right spot so that when I drill the hole it positions the cleat in the right spot to make solid contact with both the kerf and the side. Once I get too far beyond the F-hole I won't be able to guide it much, even with my violin post setter tool which I have found very valuable for working on archtops and semi-hollows.
This is another one of those jobs where I know I'm not getting paid enough to do it, but I want to do it because of the challenge and being able to add the experience to my bag of tricks. So I'm piddling around with this in my spare time rather than taking up more valuable time to do more profitable jobs.
But thank you for asking. I'll be sure to keep you up to date. I really appreciate your advice.

Bryan, Hey how's it going! That is a really interesting idea. I'm thinking that not only would that help with gluing surface area, but IMO more importantly could help keep it aligned. I often have trouble keeping the grain oriented the right direction when gluing in cleats. The only thing I would add is that I would need to take a bit off the leading edge of the side piece so it woudn't bottom out on the back edge of the kerfing before the other two surfaces make contact.
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Re: arctop side crack

Postby Barry Daniels » Sun May 12, 2019 7:39 pm

I think Bryan's idea would work well if you had the back off and could fit the part by hand, but working sort of blind like you are, the kerfing filler piece would be impossible to fit into place. It would complicate your job unnecessarily.
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Re: arctop side crack

Postby Ryan Mazzocco » Fri May 17, 2019 9:46 pm

Update:
Not much to update really, but I'm going on vacation for the next week and wanted to mention what's been going on.
I got 3 tuner clamps put together and made up a whole heap of cleats once I got the angle figured out.
Next step is to break the old repair apart, clean it out and begin the new repair process. Maybe I'll get to that in about 12 days...
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Re: arctop side crack

Postby Ryan Mazzocco » Wed May 29, 2019 9:31 am

Well, I'm back at it. I got a chance to do some work on this guitar. I also decided to start over and make my cleats over again because I didn't like the shape of the the first ones I made.
But First here are a few pictures to show exactly what I'm dealing with here:
RK1.jpg

RK2.jpg

RK3.jpg

RK4.jpg

So, as you can see, the crack runs just about from tail block to head block and there is quite a bit of material missing. At some point a repair has been attempted, but that will need reversed and hopefully I can do this properly.
Here's a picture of the inside through the F-hole...
Rk5.jpg
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Re: arctop side crack

Postby Ryan Mazzocco » Wed May 29, 2019 9:41 am

And now the repair begins....

After new tooling, many attempts at testing and dry fitting the actual repair begins....
RK6.jpg
These will be the cleats I'm using...

RK7.jpg
I'm using one of the old cleats as a caul

RK8.jpg
One of my new tuner clamps in action. I made 3 of these.

RK9.jpg
Here's a picture of the cleat in place as viewed through the F-hole

RK91.jpg
And here's a view through my inspection camera.


I'll continue to work my way around the body until I have a cleat every 2 to 3 inches around the body, then I'll start figuring out how to do the patch and finish repair.
The guitar is very worn and rough looking. This repair doesn't need to disappear, but I do want to do as good a job as I can do without making it look nicer than the rest of the guitar.
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