# Instruments and Equipment > Builders and Repair >  Mandolin neck repair: the final solution?

## Bernie Daniel

This is an idea to make a final attempt to repair a neck break that has failed several times.  This is a pretty "hard core" repair and if it fails again the neck will next stop at the nearest trash can for incineration.

The fret board was taken off and the truss rod removed in this thread.

The diagram shows the plan. Basically the empty truss rod channel will be partially filled with a 0.2X0.5X10 (inches) carbon fiber bar which will be epoxied in to the bottom of the channel using StewMac clear, slow setting epoxy.  

The bar will extend from the dove tail joint, run under the nut and be embedded into the head stock up to near the end of the truss rod pocket.  Thus the CF bar will completely cross the the neck break line.

To provide additional support on the top or the head stock the truss rod pocket will be filled with epoxy and a truss rod cover made of aluminum flat stock -- which will run all the way to the nut (and butt up against it)  will be epoxied into place. Thus the TRC becomes a structural component of the neck repair.  Obviously that TRC will never be opened again.

The CF bar will be topped with a maple bar that glued in place with Titebond and will be leveled so that the fret board can be re glued to the neck.

Clearly this is either the last neck repair for this mandolin or it is the last time this neck will be in place on the mando!

Any other thoughts on this fix?

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## George R. Lane

Bernie,

I know nothing about this type of repair, but your plan seems to be well thought out. I say go with it. I am sure there will be somebody that knows this kind of repair will chime in.

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Bernie Daniel

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## ProfChris

I'm not an experienced repairer, but ...

Looking at the diagram, most of the strength is in the epoxy bond to the CF bar, and primarily along the back of the neck side from the break until the end of the bar. That is what resists the string tension, along with some compression in the aluminium truss rod cover.

Would a backstrap, bridging the neck break, be a useful addition? That would give you wood in tension along the grain, which would be pretty strong and also not subject to the leverage pressure on the CF bar/neck glue join.

Or is that either overkill, or too much of a change to the originality of the neck?

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## John Arnold

The backstrap repair has worked every time for me.........even after multiple previous failed attempts.

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Bernie Daniel

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## HoGo

> The backstrap repair has worked every time for me.........even after multiple previous failed attempts.


+1. Backstrap adds more strength where it is needed than all the epoxy/carbon/aluminum together. I think 1/8" thick maple piece would be more than enough.

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Bernie Daniel

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## Bernie Daniel

> +1. Backstrap adds more strength where it is needed than all the epoxy/carbon/aluminum together. I think 1/8" thick maple piece would be more than enough.


Thanks!  But the truss rod is already out so that train has left the station?  I think anyway?

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## Joe Mendel

I'd go with the backstrap anyway, even with the truss rod gone. It will add a lot of strength.

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Bernie Daniel

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## burt50

What is the back strap repair?

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## Bernie Daniel

> I'd go with the backstrap anyway, even with the truss rod gone. It will add a lot of strength.


Seems like a prudent idea.

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## Bernie Daniel

So the consensus is no one but me is excited about carbon fiber.  

I realize that the key to "the fix" that I propose is getting a strong bond between maple floor of t he truss rod channel and the carbon fiber bar.  My research lead me to believe that a strong bond between epoxy and CR is possible as it is used in both auto racing repairs and the aircraft industry and of course epoxy does bond strongly to wood. 

However I am not locked into filling the truss rod channel with carbon fiber.  Here is an alternative idea.  

Instead of filling the channel with CF suppose I fill it with precisely shaped a bar of hard maple or some other wood that that has a very high bending modulus of elasticity -- e.g., birch, hickory or black locust.  That way for sure I can get a very strong bond between the bottom of the channel and the wood re-enforcement bar?

Thus I effectively am converting the neck to a solid wood -- mandolins were made for years that way and did just fine?  In fact going to a truss rod weakened mandolin necks IMHO?

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## Bernie Daniel

> What is the back strap repair?


Essentially cutting out wood on either side of the break and, gluing in fresh wood and then reshaping it.

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## multidon

I think you are on the right track with your repair plan. Since the joint has already failed more than once, I would go with your original plan, and add the backstrap as well. With all three things working for you, the rod, the backstrap, and the aluminum plate, you are throwing everything you have at it. Hard to see how a repair like that would ever fail. The key is going to be to use a really high quality marine grade epoxy like West system or similar. Hardware store epoxy is not as strong as it could be due to the addition of unnessesary filler. They do this to dumb it down for the average joe. Hardener is actually a tiny amount when compared with resin, but the hardware store versions add filler to the hardener so “equal amounts” are used and it’s easier to measure, but the resulting product is weaker.

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Bernie Daniel, 

hank

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## Drew Streip

My very amateur thought is that there are four surfaces of the crack: outside back, inside bottom of truss rod channel, inside "roof" of truss rod channel, and outside front of peghead. 

Your CF rod fixes / reinforces inside bottom and inside roof; and your epoxied metal truss rod cover reinforces the front of the peghead. 

So 3/4 of the crack points would be fixed, but the back of the neck _could_ still be vulnerable to separating with another jolt plus the string tension. The backstrap would reinforce that weak spot. Then you'd be positive that the neck was stronger than original.

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## Jeff Mando

Bernie, extending the carbon fiber rod into the break area is a good idea, as well as using the new aluminum truss rod cover as a "mini front strap" to add strength, but the success of the repair is in keeping the break area from bending again under string tension, since the break has basically become the fulcrum of that force.  A back strap may help since it counteracts the string force.

Even if looks were not an issue, this would still be a difficult and iffy repair, IMHO -- especially considering the previous repair failures.  However, I have seen this type of repair done sucessfully with two scarf joints cut for maximum surface area for glue and adding a new section of neck wood basically going from around the 3-4 fret area and extending up into the tuner area, replacing the break area.  Obviously, a major repair -- but you could add a new truss rod this way, your peghead overlay would hide the front scarf joint, the back of the neck and peghead would show the new scarf joints, which could be hidden with touch-up and shading.  This is probably MORE work than actually making a new neck, so you have to decide how much you love that neck.

On the brighter side, you seem to like working on instruments and this mandolin has provided you with much experience and practice!  :Wink:

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## Jeff Mando

> So the consensus is no one but me is excited about carbon fiber.  
> 
> Thus I effectively am converting the neck to a solid wood -- mandolins were made for years that way and did just fine?  In fact going to a truss rod weakened mandolin necks IMHO?


In my way of thinking, going from a truss rod to no truss rod is a major "demotion" for lack of a better word -- carbon fiber or not......

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Bernie Daniel

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## Bernie Daniel

> In my way of thinking, going from a truss rod to no truss rod is a major "demotion" for lack of a better word -- carbon fiber or not......


Thanks for the comment and thoughts.  Funny you should say that I was over at Will Kimble's shop this morning looking at his new mandolins and talking about this repair.  Basically he said the same thing you just said. He had a period early in his building when he experimented with a no-truss, carbon fiber bar and eventually abandoned the idea.

Another thought would be to get my hands one some of the metal T-bar that guitar companies used to use before the days of truss rods. Some mandolin builders used it too?

One thing I have not puzzled through yet and why am surprised by the doubts expressed here by you and others who have posted is that I looked a bit into possible materials to use in stiffening the neck.

If you consider a property like Young's Modulus (aka the Modulus of Elasticity) which is a parmeter that quantifies the stiffness of an elastic material.  You find the following (all units in 10^9 N/m2 or Gpas (GigaPascals):

Pine = 9
Oak = 11
Aluminum =  69
Carbon Fiber = 181
Steel = 200

So there you see that CF is over 10 times as "stiff" or resistant to bending as something like a good hard wood (maple is a little, circa 10% more stiff then oak?).

What am I missing here?  The key is a good bond between the bottom of the truss channel and the CF - if I get that I don't see why I am not "golden"????

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## pops1

I think you would need a good bond not only on the bottom of the carbon, but the sides as well. I was going to suggest the same repair as Jeff, but didn't get around to it and am glad someone suggested it. Adding the carbon is a good start, but I would also agree to adding a backstrap to ensure the repair holds. If you drill some divots in the sides of the carbon it will give the epoxy something more to hold onto when bonding to the wood and carbon.

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Bernie Daniel

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## Jeff Mando

I think the carbon fiber rod will do a good job to stiffen the neck and keep it front bending.  That is not your problem here.  You have to prevent the peghead from bending under string tension.  You can't get the cf rod to extend past the break enough to eliminate that possiblility, IMHO.

You've already removed the fingerboard and the truss rod, PLUS the peghead is already broken, so if it were me I'd go ahead and try the scarf joint and add some new wood.  If you don't want to deal with two splices, you could just cut around frets 3-4 and add a new neck section and peghead.  That way the scarf joint would be bolstered by the fretboard and you can cut a new truss rod channel in the new neck section, THEN decide if you want to go with cf or a truss rod.  

Just my 2 cents, but you might want to watch some scarf joint repair videos, before you try to repair what you've got.

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Bernie Daniel, 

Paul Statman

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## Bernie Daniel

> I think the carbon fiber rod will do a good job to stiffen the neck and keep it front bending.  That is not your problem here.  You have to prevent the peghead from bending under string tension.  You can't get the cf rod to extend past the break enough to eliminate that possiblility, IMHO.
> 
> You've already removed the fingerboard and the truss rod, PLUS the peghead is already broken, so if it were me I'd go ahead and try the scarf joint and add some new wood.  If you don't want to deal with two splices, you could just cut around frets 3-4 and add a new neck section and peghead.  That way the scarf joint would be bolstered by the fretboard and you can cut a new truss rod channel in the new neck section, THEN decide if you want to go with cf or a truss rod.  
> 
> Just my 2 cents, but you might want to watch some scarf joint repair videos, before you try to repair what you've got.





> I think you would need a good bond not only on the bottom of the carbon, but the sides as well. I was going to suggest the same repair as Jeff, but didn't get around to it and am glad someone suggested it. Adding the carbon is a good start, but I would also agree to adding a backstrap to ensure the repair holds. If you drill some divots in the sides of the carbon it will give the epoxy something more to hold onto when bonding to the wood and carbon.


Thanks for the thoughts -- every bit of additional perspective is helpful!  

I'll reply to both comments as similar thoughts were expressed. 

Yes I agree that getting a very strong bond between the maple channel and the CF bar is the key to getting any benefit out of the bar.  I am pretty confident that should be possible.  In addition to looking at resistance to bending I also did some looking into epoxy adhesives.  It has already been mentioned in the thread that one should not use commercial epoxies as on those the polyamine catalyst is usually diluted to a concentration that will permit it and epoxide binding agent to be at the same 1:1 molar ratio when mixed equal volume.  I think Timbo mentioned the West System products. 

The West System products see very good and their Six10 product has huge bonding capability for both wood and CS.  In additon it dries hard and has a high modulus of elasticity -- so it seems to touch all the bases.   There is another very similar product called Thiox2:1 that is a little cheaper.

Also agree on scaring up the CF bar.  The tech support from one of the epoxy companies I talked to suggested scaring the CF with very course grade sand paper -- the kind used for floor sanders.

I'm not at all afraid of doing a conventional back strap. Whether I want to get into trying to match up two scarf joints so as to end up with exactly the right length of neck is something I would need to think about.  :Smile:

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## HoGo

Looking purely from static viewpoint, the string tension wants to bend the neck and headstock the bending creates tension on the outside of the bend and tension on the inside with neutral axis somewhere between (depending on exact crossection and materials) basicly anything that is close to neutral axis has very little effect, the further from neutral axis the more effect the material has. your CF ir right at the axis but the backstrap is as far as can be so it's effect is larger because that distance, not strength of wood. Straight grained wood strap is more than enough strong for this application and going to exotic numbers of CF is not necessary. On the opposite end the compression strength of the glued break is not much smaller than that of unbroken headstok so there is no real need for additional reinforcement.
If I were repairing that I would just glue it back together and add 1/8" backstrap going at least 2" in each direction from break. (tapering to nothing on both ends)

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## Bernie Daniel

> Looking purely from static viewpoint, the string tension wants to bend the neck and headstock the bending creates tension on the outside of the bend and tension on the inside with neutral axis somewhere between (depending on exact crossection and materials) basicly anything that is close to neutral axis has very little effect, the further from neutral axis the more effect the material has. your CF ir right at the axis but the backstrap is as far as can be so it's effect is larger because that distance, not strength of wood. Straight grained wood strap is more than enough strong for this application and going to exotic numbers of CF is not necessary. On the opposite end the compression strength of the glued break is not much smaller than that of unbroken headstok so there is no real need for additional reinforcement.
> If I were repairing that I would just glue it back together and add 1/8" backstrap going at least 2" in each direction from break. (tapering to nothing on both ends)


OK understood.

So would you go with option A equal strap on both sides of the break or option B putting more glue in play above the break?

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## rcc56

I would extend the backstrap at least 1" above the upper edge of the old truss rod pocket.
My point of view is that I would want the backstrap to extend over plenty of solid, undamaged wood in both directions.

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## HoGo

I would keep the lines smooth and use bent piece of maple (straight grained). You can extend the backstrap all along the headstock to make its end less visible there (Frank Ford has such guitar repair on his site) That would be easiest to do if you have drum sander - just add shim at the end of headstock to keep taper (if present) and sand away 1/8" from rear of headstock and then smooth the transition into neck at least 2" past the break. Bend long piece of maple rib stock to fit the curve and glue it in place with strong fresh HHG and flexible cauls. Trim excess wood and done.

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Bernie Daniel, 

Bob Schmidt, 

hank

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## Tom Haywood

These computer drawings are great. What are you guys using?

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## HoGo

Bernie's drawings are photo of the Siminoff drawings with lines added (I have no ide what program he used). I saved one of his, removed lines in Photoshop and drew in new curves in Photoshop as well. But for drawings I use combination of Photoshop and Illustrator or Rhino for 3D modelling.

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Bernie Daniel

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## Buck

I think you've gotten good advice already, but being a forum and all, I'll throw mine in as well.  (Free of charge, which some might think is too high a price!)

There are several problems with the CF rod as the primary source of reinforcement.  Even though it's running the length of the neck, the part supporting the break is still relatively small.  It's probably strong enough, but the glue area is still relatively small and my suspicion is that with that cross section it will subject to side forces that may compromise stability.  It does little to strengthen the short grain break, which is the root cause of multiple failed repairs.  Full disclosure - I am a mechanical engineer, not structural...

My strong preference would be for the back strap type repair, already noted on frets.com.  You'd remove the faceplate and reglue the headstock to set the alignment.  Then you would thin the entire back of the headstock by the thickness of the backstrap.  That would extend onto the neck shaft well past the break and be blended into the neck shape.  A new faceplate would be installed, and the original logo (pearl I assume) reused.  The larger glueing areas here would offer much greater support than the proposed permanent truss rod cover and short back inlay.

I think this method would support a truss rod as in the original construction, but I could live without the truss rod too.  Many instruments don't have one, and a mandolin will do fine without it.  The CF rod would be be helpful here, though not as the main source of strength for the broken section.  I am loath to argue with Will Kimble about mandolin construction, but other builders such as Paul Newson have built several fixed-reinforced necks with great success.  It's part and parcel of old Martin guitars as well.  You do have to be more careful with compression fretting and such, but once the relief is correct, it's likely to stay there.  

Summary - I could go either way on adjustable or fixed neck reinforcement, but believe the front and back strap repair has a far greater likelihood of success, near 100% if well executed.

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Bernie Daniel

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## Bernie Daniel

> Bernie's drawings are photo of the Siminoff drawings with lines added (I have no ide what program he used). I saved one of his, removed lines in Photoshop and drew in new curves in Photoshop as well. But for drawings I use combination of Photoshop and Illustrator or Rhino for 3D modelling.


I just used PowerPoint which is a primarily presentation program with very limited graphics design tools -- I probably could have spent a little more time on it and rounded the strap out but I was merely trying portray a concept.  Photoshop is a much more sophisticate drafting program and better to use for this purpose.  I don't think I have a working copy anymore on any of my computers....

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## ProfChris

Can I just say what a useful, thoughtful and well-tempered collegiate discussion this has been. I don't currently have such a repair to do, but it has equipped me for success if I do in the future. Thank you all!

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## Bernie Daniel

> I would keep the lines smooth and use bent piece of maple (straight grained). You can extend the backstrap all along the headstock to make its end less visible there (Frank Ford has such guitar repair on his site) That would be easiest to do if you have drum sander - just add shim at the end of headstock to keep taper (if present) and sand away 1/8" from rear of headstock and then smooth the transition into neck at least 2" past the break. Bend long piece of maple rib stock to fit the curve and glue it in place with strong fresh HHG and flexible cauls. Trim excess wood and done.


Just to make sure we are on the same page here before any wood is carved.

Would you envision the back strap to look like the first image just a rectangular piece the covers the break and protrudes into the head stock. First image,  (Note: this mandolin has a volute that I would not plan to retain in order to make the job easier).

Or do you see a back strap that includes the entire head stock width -- say up to the first tuner holes for example?  For this I could cut a thin 1/8 to 3/61" "slice" off from the sugar maple block for example and attempt to bend that entire piece into place. (second image)

PS you can see why I am note excited about putting a back strap on the beautiful maple neck!   :Smile:

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## Buck

Here's Frank Ford's page on the backstrap repair.  It covers the entire back of the headstock, which is how I would do it.  There's no advantage to making it smaller.

http://www.frets.com/FretsPages/Luth...phoverlay.html

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Bernie Daniel, 

Ivan Kelsall, 

Jess L.

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## Joe Mendel

What Adrian said! If you have a spindle sander, set up a fence so you can feed the headstock between the spindle and the fence removing 1/8" from the back of the headstock. Go about 2 inches past the break. Go slow, so you sand the wood away, not burn it. Then bend a 1/8" thick piece of maple to fit the back of the headstock and glue it in place. Trim & touch up and it should be a very strong repair.

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Bernie Daniel, 

hank

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## Bernie Daniel

> Here's Frank Ford's page on the backstrap repair.  It covers the entire back of the headstock, which is how I would do it.  There's no advantage to making it smaller.
> 
> http://www.frets.com/FretsPages/Luth...phoverlay.html


Thanks I intended to go look for that today!

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## Bernie Daniel

> What Adrian said! If you have a spindle sander, set up a fence so you can feed the headstock between the spindle and the fence removing 1/8" from the back of the headstock. Go about 2 inches past the break. Go slow, so you sand the wood away, not burn it. Then bend a 1/8" thick piece of maple to fit the back of the headstock and glue it in place. Trim & touch up and it should be a very strong repair.


Thanks so basically you are saying make a "strap" (1/8" thick) the would look like the second image I presented in post #29?  

I don' t have a spindle sander but I might be able to remove the wood I need using a sander on a drum and then clean it up with a cabinet scraper?

One other thought.  If I remove 1/8" from the head stock and neck I think the strap might have to be a little thicker than 1/8" so as to allow for error when carving back to shape?

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## HoGo

I would go for whole width of headstock (unless you have reason to fit it into channel like in first pic - that would work but it is infinitely easier to prepare flat surface across whole headstock), whether full length or not depends on your tools. With drum sander it is easy to thin the whole headstock, with handtools only I would go for 2-3" into headstock (full width). You want the surface be perfectly flat across and smooth bend along for best strength of glue joint (start with sanding blocksto create smooth bend along neck and finish with flat scraper to get perfectly flat surface across width).
Also I'd prefer straight grained wood for strength. Perhaps you can find a piece that has small part with very little curl (1-2" which will be right at the break) and transition into nice curl to match the neck shaft... if you really want curly wood, use thicker overlay. Always count with some extra wood for safety. You can build up the volute with another piece on top of the backstrap if you wish (I've seen that on decorated old time banjos)...

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## fscotte

I'd just use a 1/8" thick ebony veneer for the "backstrap". Just as if you we're building a new mando. Taper the veneer to a point past the crack. Use the CF rod as well.

Lot easier than than you think. You're just putting veneer on the back of a mandolin. It would look much better than a maple piece stuck in there, in fact no one would know any different.  You build mandos, this is nothing.

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Bernie Daniel

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## HoGo

Ebony can be brittle and may crack when bending at that thickness or even worse invisible cracks form that can lead to failure in future. Also maple glues better to maple than ebony so simple hard maple is hard to beat in this case.

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Bernie Daniel

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## Bernie Daniel

> Ebony can be brittle and may crack when bending at that thickness or even worse invisible cracks form that can lead to failure in future. Also maple glues better to maple than ebony so simple hard maple is hard to beat in this case.


Each round I learn more!  Thanks to all!

I think I have 3 or 4 thin panels (maybe 8" X 4"X1/16") of maple, with little curl.  In fact I do not know what kind of maple it is but it is very plain looking essentially little figure.  Does the repair have to be done with "hard" maple or would any quality maple wood work as well?

Thinking about these panels makes me wonder if I could take 1/8" of wood off the back of the neck and head stock and then heat bend in 2 or 3 of these panels to the instrument -- gluing each separately to make a "maple plywood" back strap?

They would be easier to bend and in theory would result in a tighter fit and, also in theory, be stronger because potential weak area one piece would likely be reinforced by the piece above or below?

Then the thought occurs to me that it might actually end up being *easier* to run the back strap over the whole back of the head stock? becasue then I would not have to content with the doing a blend on the back of the head stock? (Although I have a bunch of ebony veneer (paper thin) that I could use to cover it).

Always more questions! LOL

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## HoGo

> Each round I learn more!  Thanks to all!
> 
> I think I have 3 or 4 thin panels (maybe 8" X 4"X1/16") of maple, with little curl.  In fact I do not know what kind of maple it is but it is very plain looking essentially little figure.  Does the repair have to be done with "hard" maple or would any quality maple wood work as well?
> 
> Thinking about these panels makes me wonder if I could take 1/8" of wood off the back of the neck and head stock and then heat bend in 2 or 3 of these panels to the instrument -- gluing each separately to make a "maple plywood" back strap?
> 
> They would be easier to bend and in theory would result in a tighter fit and, also in theory, be stronger because potential weak area one piece would likely be reinforced by the piece above or below?
> 
> Then the thought occurs to me that it might actually end up being *easier* to run the back strap over the whole back of the head stock? becasue then I would not have to content with the doing a blend on the back of the head stock? (Although I have a bunch of ebony veneer (paper thin) that I could use to cover it).
> ...


Any good clear defect free maple should do OK.
I'd go for one thicker layer. It's not hard at all to bend it to such curve. You can wet it and heat it on clothes iron and clamp it against some curved object with similar radius to the neck transition. Then smooth the gluing surface on surfacing plate (I use large flat piece of plywood with rough sandpaper attached) to remove any kinks of the bend (likely to appear on curly maple)
Thin layers would be easier to bend but applying glue to so many surfaces and trying to press excess glue out will make the whoe asssembly want to slide in every direction or in case of HHG the glue will gel before you manage to add all layers. You can glue layers separately, but that's more work and more glue soak into the grain - possible problems during finishing. And the layered strap would be more noticeable than carefully selected single piece.
Use either shaped caul with layer of soft cork or "kerfed plastic (LDPE or such) caul" to clamp the strap in place and you'll get nice tight joint in one go.
Whether to do the backstrap on the whole length of headstock is just your decision. With my toolbox it would be easier to cut less off the headstock and then trim/blend the end of backstrap. (I also always use layer of black veneer on back of mandolin headstocks) You may find it easier to cut the whole headstock and not have to deal with the transition on the headstock end of backstrap... Also remember that larger area means larger caul (ore more than one) and more clamps and thus time to get proper pressure meaning, more time that is precious when using HHG. But heating room and the wood before gluing will help with that.

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## Jeff Mando

I wanted to add that while the repair is straightforward in theory, to get results like Frank Ford requires a lot of experience, IMHO.

Plus, it's a guitar, so the pieces are slightly larger, FWIW.  :Grin:

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Bernie Daniel

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## Bernie Daniel

> I wanted to add that while the repair is straightforward in theory, to get results like Frank Ford requires a lot of experience, IMHO.
> 
> Plus, it's a guitar, so the pieces are slightly larger, FWIW.


I agree!  :Smile:   I've looked at those Frank Ford pics about half a dozen times now......

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## Bernie Daniel

Thinking of going with a 3/16" hard maple back strap?

Have to experiment a little with bending a piece that thick though.

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## hank

I find it interesting that by using bent wood instead of carving a thicker piece you end up with the compression and stretch of the repair wood opposite of the failure crack.  I don’t know if this has and effect in strength but would reduce exposed endgrain.

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Bernie Daniel

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## HoGo

> Thinking of going with a 3/16" hard maple back strap?
> 
> Have to experiment a little with bending a piece that thick though.


Thicker will add more strenght but will be trickier to glue as it will not conform to the glued surface as easily as thinner piece (using cork lined cauls). I would dampen it slightly wrap in plastic wrap and heat it in microvawe for bending. That would heat the wood evenly all the way through and help clean bending. claming against a form of some sort would be best for getting good smooth bend with thicker piece.

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Bernie Daniel

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## Mando&Me

Thanks for this thread. I'm looking at the same situation, so this is useful. Thanks, everyone. 

M&M

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## Bernie Daniel

> I find it interesting that by using bent wood instead of carving a thicker piece you end up with the compression and stretch of the repair wood opposite of the failure crack.  I dont know if this has and effect in strength but would reduce exposed endgrain.


Thanks for that thought!   :Smile:   I have not been on this thread for a while but yes that thought occurred to me as well.  I have been doing other things and will probably start the back strap next week.

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hank

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## Bernie Daniel

> Thicker will add more strenght but will be trickier to glue as it will not conform to the glued surface as easily as thinner piece (using cork lined cauls). I would dampen it slightly wrap in plastic wrap and heat it in microvawe for bending. That would heat the wood evenly all the way through and help clean bending. claming against a form of some sort would be best for getting good smooth bend with thicker piece.


Thanks I really like that idea!  

I could remove the wood from the neck until I got where I wanted it to be then measure that angle between the head stock to the neck.   Then I could cut the same angle in a piece of 2X4 and use that as a form to clamp the hot maple (forcing the bend) into place until it cools?

I wonder how long one might microwave the wood or better what temperature one might take the piece of maple to?

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## j. condino

All of that work and mental anguish and time spent on the worldwide waste of time....

A new neck would take less effort and we'd all agree that it was solid......

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## Br1ck

Jerry Rosa has a Rosa Strings Workshop YouTube video where he cuts out the broken part altogether and scarf joints a new piece to bridge the gap. I believe he has one for guitar too. Interesting stuff there.

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Bernie Daniel

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## Bernie Daniel

> Jerry Rosa has a Rosa Strings Workshop YouTube video where he cuts out the broken part altogether and scarf joints a new piece to bridge the gap. I believe he has one for guitar too. Interesting stuff there.


Yes thanks I watched those -- the two on the mandolin repair are both about 1 hour long so they are perfect for my WiFi tablet when I am on the treadmill at  the fitness center!  :Laughing:   I think I watched both of them twice. Really great videos!

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## Ivan Kelsall

Regardless of what method you use to bend the wood for the backstrap,there will always be residual stress in the strap after bending. That's why we often see instrument sides coming adrift. So,unless there's a way of 'stress relieving' the strap prior to fitting it,then carving it to fit the 'bend' is IMHO,the way to do it. At least the strap won't be imposing any stresses right from the off,& as long as the strap is strong enough,it should be fine.
 I found this on the 'net :- 

_" When  a  piece  of  wood  is  bent,  it  is  stretched,  or  in  tension, along the outer   (convex) side  of  the  bend  and  compressed  along  the inner  (concave)   side.   Its   convex   side   is   thus   longer   than   its    concave side. This distortion is accompanied by stresses that tend to bring the bent piece back to its original straightness.  The purpose  of  softening wood with moisture and heat or plasticizing chemicals  is to restrict the development of these stresses."_.

 Note that it says ''restrict'' NOT *remove* any stress development,
                                                                                        Ivan  :Wink:

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Bernie Daniel

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## Bernie Daniel

> "Regardless of what method you use to bend the wood for the backstrap,there will always be residual stress in the strap after bending...."


I would guess that there is some truth to that for sure.  

But I'm not sure how much it amounts to in the "real world of luthiery"? 

I suppose it depends in part on how properly/effectively/efficiently the bends in the piece were made in the first place?

Thinking more about it if you bend a set of maple sides for a F-style mandolin and then decide not to use them and never glue them to the end and tail blocks do they ever become straight again?  I doubt it.  

They will probably relax to some "equilibrium state" with less bend then when originally conformed but never again become straight.

At that situation there is still stress but it is "internal" that is the stresses are within the piece of wood _per se_ and would not be imparted outside of that? 

So when you glue them in place it is only that "residual stress" -- i.e., the difference between the conformation immediately after the bending process is completed and the final shape of the cooled dry wood that has to be contained or contended with?

This would be much less (or at least less) than the total stress that was generated in the bending process?

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## Br1ck

I watched the Jerry Rossa videos again too. Someone got the deal of a century on an insane repair. The guy is very humble.

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## Bernie Daniel

> I watched the Jerry Rossa videos again too. Someone got the deal of a century on an insane repair. The guy is very humble.


Yes he is -- and very skilled as well.  His Rosa mandolins are supposed to be excellent but I have never seen one and I don't think there are too many around.  

In addition to musical instruments he builds all kinds of things to do specialty tasks including pieces of farm equipment.  Some people are born with the tinker's genius. He has nearly 300 instrument repair videos on YouTube and is up to 16,000 subscribers.  I hope the time he puts into these videos is worth the effort financially for him. 

Yeah he charged that guy supposedly only about $400 for all that work.  That two hours of edited video must have represented maybe 5 to10 times that amount of actual shop time?  What I find amazing is how he is able to match up colors and tones so well since he is color blind.

I hope he does another Christmas video with his picking buddies again this year.

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## Buck

Not to be overly critical, but I've watched several of the Rosa String Works videos.  He exhibits considerable skill on some repairs, but in other ways has seemingly total disregard for maintaining originality - finish touchups, using modern glue where it's unnecessary, and so on.  Under no circumstances would I allow that kind of work on any of my vintage instruments.

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## Jeff Mando

I agree there are certain standards for the repair of vintage instruments, but in my opinion, when a neck is broken in two and wood needs to be spliced in to fix it, then originality has already been lost and fixing the instrument becomes the goal over the glue choice, filler, putty, epoxy, whatever, etc......you're basically dealing with a lost cause, IMHO.

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## Buck

I couldn't disagree more, but in a kindly fashion I hope!  Originality is certainly hampered by such damage, but not so much as if a neck is replaced rather than repaired.  When I see a repairman using modern techniques where there is no good reason, I assume we do not share the same respect for vintage restoration methods.  It makes me doubt our compatibility.  I didn't mean to imply that only hide glue should be used for the type of repair in this thread, or to divert the discussion to glue types at all.  I wanted to emphasize the value of saving the neck over replacing it.  For that, it might be best to get advice from repairmen who value saving over replacing whenever possible.

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Jeff Mando

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## Bernie Daniel

> I couldn't disagree more, but in a kindly fashion I hope!  Originality is certainly hampered by such damage, but not so much as if a neck is replaced rather than repaired.  When I see a repairman using modern techniques where there is no good reason, I assume we do not share the same respect for vintage restoration methods.  It makes me doubt our compatibility.  I didn't mean to imply that only hide glue should be used for the type of repair in this thread, or to divert the discussion to glue types at all.  I wanted to emphasize the value of saving the neck over replacing it.  For that, it might be best to get advice from repairmen who value saving over replacing whenever possible.


Well for for starters that mandolin was not a vintage instrument?   Second, it seems that the owner of a $1000 mandolin most likely did not care about "originality" anyway he just wanted a mandolin that looked good and that he could play.  That makes perfect sense to me.  

To get a new factory neck for that mandolin from "The Loar" (I have no idea how you would do that?) and then get it fitted up and put on would cost at least half again what the instrument costs new? At least that would be my guess.  In  truth I doubt it could even be done?  But even if it could to spend that kind of money on that level of a mandolin would hardly be a wise investment?  You have an "original" $1000 mandolin for $1500 to $2000 invested???

As it was Jerry kindly gave him a $1500 repair for $400 - he didn't have to he just did.  Any other repair guy would have charged at least two to three times that -- in fact most would say probably say I can't fix that mandolin at a price worth your money? 

If Jerry fixes a vintage instrument he always fixes it in that way the owner wants.  Many owners (vintage instrument or not) care more about "play ability" and looks than in maintaining an instrument in original condition.  Those decisions are the owner's call of course.

Those are the reason why it is almost impossible to get an instrument into Jerry's shop he has a back log of work a mile long because he is very good and reasonable.

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## HoGo

BTW, how much would a new neck be in such case (headstock overlay, fretboard and truss rod could be reused)? I have no idea about US charges for such jobs.

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## Buck

To clarify, I was not talking about a video on repairing a modern instrument.  There are several videos showing repair of vintage instruments.  I guess I'm just set in another direction when it comes to vintage repair. Sorry if I offended anyone.

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## Jeff Mando

Two years ago, Gilchrist completed the repair of "The First Loar" mandolin with the ugly cracked top that was filled with putty and whatever?  It was known as a great sounding Loar prior to the repair and Gilchrist, himself, was concerned that it wouldn't sound as good after being repaired.  Turns out, everyone seems to like the repaired mandolin better.....(this was the subject of an MC thread showing pictures, etc.)

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Bernie Daniel

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## Bernie Daniel

> To clarify, I was not talking about a video on repairing a modern instrument.  There are several videos showing repair of vintage instruments.  I guess I'm just set in another direction when it comes to vintage repair. Sorry if I offended anyone.


Absolutely no offense taken at all Todd!! None!  :Smile:  

Everyone has their own philosophy on vintage instruments. And views change for everyone.  If you look back far enough you'll find the opinon proffered by me-myself on the forum that we don't really own vintage instruments but we are only their "caretaker" while we are alive. Don't really believe that anymore but it's still a nice idea -- just not too practical.  People own their legally acquired property and can do as they wish but it would be nice if everyone were sensitive to the bit of history that they own.

I would think you are correct that Jerry is more into repair then restoration with the goal of preserving vintage aspects.  The 1918 Gibson L3 guitar makes that point - -but I'll bet the owner was happy?

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## Bernie Daniel

> Two years ago, Gilchrist completed the repair of "The First Loar" mandolin with the ugly cracked top that was filled with putty and whatever?  It was known as a great sounding Loar prior to the repair and Gilchrist, himself, was concerned that it wouldn't sound as good after being repaired.  Turns out, everyone seems to like the repaired mandolin better.....(this was the subject of an MC thread showing pictures, etc.)


That is a great example of how the trade off have to be considered -- case by case.

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Jeff Mando

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## HoGo

I read a quote years ago going something like: good violin repair is one that makes instrument playable again, great is one that is invisible, and epic if it looks the same 50 years later....
Of course valuable violin repairs have pretty strict rules but some may apply to mandolins as well.
Gilchrist used some non-traditional approaches on that repair (most likely decisions of the owner selected from several possibilities) and only time will tell how it will hold.

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Bernie Daniel

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## Br1ck

I think Jerry Rosa looks at all instruments pretty much the same, a broken instrument that needs fixing at a price they can afford. He has whole videos on glue alone and why he goes modern. I don't think he really gets vintage instruments owners want to keep vintage. They just want them fixed. He gives them what they want.

By the way, the Godfather theme was played on a Rosa mandolin.

Three busted up guitars are now fixed and playing because I watched and learned from his videos. I watch everything he puts out and he is quick to point out where his methods may deviate from the norm, the most prominent being his glue selection.

The fact he can make a log splitter, or a portable saw mill, or a brass switch tip is an interesting diversion.

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Bernie Daniel

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## Bernie Daniel

> I think Jerry Rosa looks at all instruments pretty much the same, a broken instrument that needs fixing at a price they can afford. He has whole videos on glue alone and why he goes modern. I don't think he really gets vintage instruments owners want to keep vintage. They just want them fixed. He gives them what they want.
> 
> By the way, the Godfather theme was played on a Rosa mandolin.
> 
> Three busted up guitars are now fixed and playing because I watched and learned from his videos. I watch everything he puts out and he is quick to point out where his methods may deviate from the norm, the most prominent being his glue selection.
> 
> The fact he can make a log splitter, or a portable saw mill, or a brass switch tip is an interesting diversion.


I agree!  I wish he lived close to me!  :Smile: 

I have started working on the neck repair again (subject of this string) and I'm about at the point of bending the back strap. Might try that tomorrow.

What is the story of a Rosa mandolin and the Godfather Theme? That is a tune I like to play actually -- I play it in Dm but I think the TV show version was Bm?

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## Br1ck

I don't know how, but a Rosa mandolin ended up with a NY studio musician, you know , the kind of guy who can play anything, and the guy was on the Godfather recording session, had his mandolin, so played the part.

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Bernie Daniel

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## Drew Streip

> I don't know how, but a Rosa mandolin ended up with a NY studio musician, you know , the kind of guy who can play anything, and the guy was on the Godfather recording session, had his mandolin, so played the part.


Not to cast doubt here, but "The Godfather" was released in 1972 and Jerry Rosa didn't start building until a decade after that: 

"Rosa String Works was born out of my desire to play and build my own acoustic instruments.  Back in 1982 I couldn’t afford nor justify spending thousands of dollars on a mandolin since I was just a beginner.  So I decided to build my own.  I soon built another, then repairs started rolling in.  The rest as they say is history." 

https://rosastringworks.com/

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## Bernie Daniel

> Not to cast doubt here, but "The Godfather" was released in 1972 and Jerry Rosa didn't start building until a decade after that: 
> 
> "Rosa String Works was born out of my desire to play and build my own acoustic instruments.  Back in 1982 I couldnt afford nor justify spending thousands of dollars on a mandolin since I was just a beginner.  So I decided to build my own.  I soon built another, then repairs started rolling in.  The rest as they say is history." 
> 
> https://rosastringworks.com/


Was the theme used on the TV series the Sopranos too?  I can't remember.

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## hank

https://www.mandolincafe.com/forum/t...ather-Mandolin!!!

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## Bernie Daniel

Well if  we are done with the Godfather theme I like to get back to the topic of the neck repair!   :Laughing: 

I am about ready to start the back strap.  

Here are three images the mandolin with wood removed in preparation for gluing on the back strap.  

The Second image just shows a piece of curly maple that I will use to make the back strap out of.

The third image is a bending jig I made up from a piece of fir scrap wood that shows the profile of the bend I have make in order to get the back strap to fit on properly.

I have been practicing on ways to heat the maple so I can shape it fit in tight for gluing.

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## Jeff Mando

Good luck, Bernie!  Looks like you have it figured out.  :Cool:

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Bernie Daniel

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## HoGo

Looks substantial enough to hold well. Make sure to use flexible caul for gluing it on. I have cutoffs from old cork floor boards for this - 1/2" thick wooden core with 1/8 cork layer. I would cut thin kerf cuts 1/4" spaced across the piece (just like for linings inside mandolin) almost all through the wood so it will conform to the curve and provide good even clamping pressure.

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Bernie Daniel

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## Bernie Daniel

> Looks substantial enough to hold well. Make sure to use flexible caul for gluing it on. I have cutoffs from old cork floor boards for this - 1/2" thick wooden core with 1/8 cork layer. I would cut thin kerf cuts 1/4" spaced across the piece (just like for linings inside mandolin) almost all through the wood so it will conform to the curve and provide good even clamping pressure.


Do you mean kerf cuts on the caul not on the actual back strap piece I think?  

I'll see about doing that.  

Since I am "pre-shaping" the back strap on my bending block (see 1st image below) it will not take much pressure to fit it up  

The contour on this block matches the mandolin so when I heat the strap and force it into the contours of the block it is almost a prefect fit to the mandolin neck (see image 2 below)  

That strap was the first piece I tried to bend and it is about the thickness I need for the strap maybe 0.160".  

As you might be able to see from the poor image it is nearly a perfect fit and would only need to be forced about 0.06" in order to make it fit snugly against the neck for glue up?

I will wait a few days before doing the final bend and glue up in case someone points out something I am missing on this.  

Thanks for all the comments heretofore -- much appreciated!  :Smile:

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## pops1

Looks good Bernie, saving the original neck is work the time and effort IMHO.

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Bernie Daniel

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## HoGo

> Do you mean kerf cuts on the caul not on the actual back strap piece I think?


Yes, on the caul. That is large area and you need really high force to clamp it together and move the extra glue out of the space. I would suggest start clamping in the center and quickly add clamps towards ends so the glue has somewhere to escape.




> Since I am "pre-shaping" the back strap on my bending block (see 1st image below) it will not take much pressure to fit it up


It's not about the fit of the piece alone. Any trapped glue can work against you. I've seen CT scan of old Cremonese violin with chest patch where thickish layer of glue was trapped inside. You can bet that the restorer fitted the patch meticulously to the (millions worth) violin, but glue can be your worst enemy on such large surfaces.

----------

Bernie Daniel, 

Jeff Mando

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## Bernie Daniel

> Yes, on the caul. That is large area and you need really high force to clamp it together and move the extra glue out of the space. I would suggest start clamping in the center and quickly add clamps towards ends so the glue has somewhere to escape.
> 
> 
> It's not about the fit of the piece alone. Any trapped glue can work against you. I've seen CT scan of old Cremonese violin with chest patch where thickish layer of glue was trapped inside. You can bet that the restorer fitted the patch meticulously to the (millions worth) violin, but glue can be your worst enemy on such large surfaces.


I understand.  

You are getting at something John Hamlett has talked about and that is some glues have good adhesion but poor cohesion so the glue as a structural component is not reliable.

But maybe that won't be a problem on this job?  

I am going to be using a "professional grade" two component marine epoxy to glue the carbon fiber bars into the truss rod slot on the other side of the neck.  This material has very high adhesion, it has solids in it so it has very high strength, and dries hard and the dried material is highly resistant to flex. What is more it bonds to both wood and carbon fiber.  It is heavily used in boat construction to glue wood boat hulls below the waterline.  

So those two bars of CF that I will fit and glue into the truss rod slot will be "permanent".

Since I have the epoxy I am thinking about doing the entire job with it. Including gluing the fret board back on and also to gluing down this back strap? 

Since this epoxy does have very good cohesion it will be less sensitive to the concerns of glue pockets glue because it can also be used as a structural material and a filler.  For dang sure that joint will never fail as a result of heat or moisture.  

In fact, as the tile of this thread says this is the "final solution".  This is one job that I have no concerns over never being able to take it apart again.  If this neck ever fails again it is trash.

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## HoGo

I would personally use HHG (without adding any rods or such), but with this area Titebond should be good choice as well. Marine epoxy will hold as well as no one will ever want to open that joint.
The problem I mentioned is about large surfaces being glued. You need to apply just enough glue, not too much. If you apply the pressure evenly on the whole surface at the same time with shaped caul, any extra glue near center of the surface will have hard time getting out so clamping the joint from center towards edges is essential to avoid glue (or worse air) pockets. With epoxy any air can be your enemy but that is much less likely to happen with slow cure epoxy.

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Bernie Daniel

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## sunburst

Bernie, what do you plan to do here?

I fear that the butt  joint at the end of the piece, if left as is, will eventually be obvious no matter how it is dealt with.

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Bernie Daniel

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## Bernie Daniel

John it will be covered with a layer of ebony veneer (0.02" thick).  I have a life time supply of the stuff.  😀

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## sunburst

If it's not too late to work some kind of scarf joint-like thing into that, the line of the joint will probably telegraph through the veneer rather prominently. (Knowledge gained through experience.)
PM sent, by the way.

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Bernie Daniel

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## Br1ck

> Not to cast doubt here, but "The Godfather" was released in 1972 and Jerry Rosa didn't start building until a decade after that: 
> 
> "Rosa String Works was born out of my desire to play and build my own acoustic instruments.  Back in 1982 I couldnt afford nor justify spending thousands of dollars on a mandolin since I was just a beginner.  So I decided to build my own.  I soon built another, then repairs started rolling in.  The rest as they say is history." 
> 
> https://rosastringworks.com/


Perhaps a sequel.

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## Bernie Daniel

Waiting for the bonding to happen.  Eight clamps hopefully doing their thing.

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## Bernie Daniel

Clamping and bonding went well. Two pics: 1) fresh out of the clamps and 2) rough carving, the first session -- the easy part!  :Smile:

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## Buck

I really appreciate the progress photos.  My guess is this will solve your problem for good.  :-)

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Bernie Daniel

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## Bernie Daniel

> I really appreciate the progress photos.  My guess is this will solve your problem for good.  :-)


Thanks!  I hope you are right!

One more step getting closer now but still more fine carving and sanding needed.  Enough of this fun and merriment for today though........

PS if you look close, I think I matched up the curl pretty close. At least I hope so.

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## pops1

Looking good Bernie.

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Bernie Daniel

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## Mando&Me

Nice work, Bernie. Lookin' good. 

MM

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Bernie Daniel

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## Bernie Daniel

The back strap is done. So now it is time to work on the other side of the neck.

I inserted two carbon fiber bars that essentially fill the truss rod cavity.  They are stack on top of each other and glued in with Jamestown Thixo marine epoxy so most of the neck has a double CF bar in it. The truss rod is gone of course. 

The lower CF bar extends 1.5 inchs into the truss rod pocket and is flanked by two other 0.75 inch bars of CF -- then the entire cavity was filled with epoxy and then capped with a aluminum truss rod cover that is also glued down with the epoxy.

This epoxy dries rock hard and has a very high modulus of elasticity so it, along with the aluminum truss rod cover and the CF bars become part of the neck repair.   

This should be a pretty strong neck?

Needless to say this repair is *"final"* and it will never be opened up again.  

All you guys who like to be able to take things back apart will be grinding your teeth perhpas?  But this neck has been repaired four times in the past.  It was time for something different.

And don't worry I wiped the truss rod and head stock surface the isopropyl alcohol to remove any epoxy smears seen in the image.

After this cures the fret board is glued back on and for better or worse the repair is finished.  :Smile:

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## Jeff Mando

> ........this neck has been repaired four times in the past.  It was time for something different.


One way to look at it --- besides playing music on it between the repairs -- the mandolin has provided a great repair hobby for you!  :Cool:

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Bernie Daniel

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## Bernie Daniel

Now the fret board goes back on.  Waiting 24 hours for the epoxy to set.

Then make a new nut and string it up....

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## Bernie Daniel

Well the mandolin is back -- I think (hope). 

Here it is freed from it's bonds and clamps hanging alongside my other Gibson F-5 imposter.  

Still need to make a new nut, clean up some squeeze out glue (although most was taken care of by masking), and then fine sand and re-stain, install the hardware etc. 

Other points of interest.  The fret board is as flat as a pool table -- really nice. And it is light as a feather -- no truss rod.

Possible downside.  Hopefully, the fboard is not *too* flat?  I am counting on the string tension to produce a little relief - but not too much!  There is no capacity for adjustment anymore -- again no truss rod.  So I am not out of the woods yet!

I am kind of pleased that this rather unconventional approach to the repair actually came to fruition and turned out pretty much exactly as I had envisioned it.  That is a rare event really.

Also thanks for the many helpful comments and suggestions from this forum -- I probably would have screwed this up without them for sure.  I'll take some more close ups of the repair when I have time today.

The third mandolin to the extreme left in the pic is one I built earlier -- in case someone was wondering.  :Smile:

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## Bernie Daniel

Ebony veneer to hide the back strap on head stock. What a pain.  Lots of fine detail work left then the staining will hid a lot. This is a 40 - 45 year old mandolin so I want it the repaired area to look distressed.  Note on bank of tuners it right on the edge but I didn't do that! :Laughing:

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## Bernie Daniel

Back of the head stock has been sanded in Tru-Oil slurry to seal it.

The neck was re-stained with Trans-Tints. I'm not satisfied with it yet and the epoxy seems to have created a small area that I can't really stain well.  But that is all I'm going to do now until I string it up a confirm that it will be playable.

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Jeff Mando

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## Bernie Daniel

Just to "close the loop" on this thread so to speak.

For now the repair though slightly unconventional seems to have been a success.  The mandolin was strung up with D'Addario J74s (yes I still have sets of those).  The mandolin came up to pitch just fine.  I set the action at 0.06" on both the G- and E-courses and measured the relief this morning at fret 7 at 0.006".  It plays easily and sounds just as good if not better then before the repair.

The repair consisted of:

1) A 0.133" back strap of hard maple glued on with Jamestown Distributors Total Boat Thixo Marine epoxy.  This is a "professional grade" 2:1 epoxy meant for wet and underwater (boat hulls) bonding.  It is extremely strong and of course should not be melted by the heat or humidity issues a mandolin is likely to encounter. It is messy to work with like all epoxy cements but is very slow setting so that the worker has up to 37 minutes (room temperature = 70 degrees F) working time.  Total cure to a very hard and inflexible solid is 24 hours.

2) Filled the truss rod channel with two bars of carbon fiber. The lower bar protrudes about 1.5" into the truss rod pocket and across the old break.  The upper bar is the length of the channel only.  These were glued in and also glued together with the marine epoxy.

3) The truss rod pocket was filled with epoxy and bits of carbon fiber bar and the capped with a custom-made aluminum truss rod cover.  This THC is now "permanent" but it is shaped so as to butt firmly up against the nut/fret board and thus it becomes a structural part of the repair as it crosses over the old break line on the top (like the back strap does on the bottom). 

4) Fret board glued on with marine epoxy.

To be sure I am not necessarily recommending this approach to anyone at this time.  If all is well in a year I might just bump this thread and let you know how it is doing.  If if fails I will also let you know.

One again thanks to all who helped out!  :Smile: 

FYI the gray spot on the lower part of the head stock is bondo that I used to repair the cover plate broken with the neck - it will be colored black later.

----------

FLATROCK HILL

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## Br1ck

Well done and a gutsy solution.

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Bernie Daniel

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## Mando&Me

Have been following this thread with avid interest, since I will be attempting something similar in January. 

Thanks So Much!

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Bernie Daniel

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## Jeff Mando

Good work, Bernie!  I think you've got it!

Just curious, you said your mandolin was not a Gibson and you have had it a long time.  Do you know who made it?  I noticed a label in your picture, but couldn't read it.

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Bernie Daniel

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## Bernie Daniel

> Good work, Bernie!  I think you've got it!
> 
> Just curious, you said your mandolin was not a Gibson and you have had it a long time.  Do you know who made it?  I noticed a label in your picture, but couldn't read it.


Thanks for the thoughts.  I don't know who.  I have two of fake G-word F-5s (made by different individuals) supposedly in this (OH, KY) area.  I have some clues about who made the other one but not this one.  The label you saw in the pic is also fake L-word  :Smile: 

I was glad this repair worked (I hopefully permanently) because this is a really good sounding mandolin.   Seriously, it's right up there with a modern Kentucky KM-1000 or such -- that level or more.  Who ever made it knew what they were doing or really lucked out. Anyone could play this mandolin in a bluegrass band and not have any issues with tone or volume - at all.  In fact, it is on the loud, woody side of things mandolin.  I have to figure out what to do with it now - LOL.  As I really have a two good Gibson F-5s -- more than filling my needs these days. Some kid starting out playing bluegrass and wanting a mandolin with mojo that is strong and plays well should have this mandolin!  :Smile: 

So if the repair holds up for a year I will probably just sell it somehow with full disclosure of course.   But seeing the strength of this glue (see below) and knowing that the bonds are essentially "impervious" to heat and humidity (heck water!) this mandolin should last longer than anyone reading this post?!!  LOL

I did a lot of experiments with the epoxy before trying to fix the mandolin.  It is a one part polyamine to two parts epoxide resin so I was very curious as to how sensitive it was to exact mix ratios.  Also the glue ratios are 2:1 by volume -- don't know what that translates into by weight.  I kind of assume the density of the two components is the same but did not actually know that. The manufacturer could not supply me with that information either.  In the end I assumed equal densities and did initial trials with 2:1 by weight mixing.

IMO, even if the bond is not hyper-sensitive to the mix ratio you want to be as close to actual chemical stoichiometric  ratios as possible so that you do not have quantities of unreacted epoxide or polyamine floating around in the bond -- for lots of reasons.  Anyway, bottom line this glue is just like any other epoxy glue and it is easy enough to just eyeball the amount of the two components then mix and do the glue up.  Once if fully cured (24 hours) the bond is incredible.

I glued two pieces of scarp maple together in one test and there seems to be nothing i can do to break that bond. If I put one end of it in the metal vice and used a long enough lever (piece of pipe) on it i suppose I will either break the wood or I'd manage to tip over the bench. LOL. No interest in doing that.  This mandolin should be permanently fixed.

There are down sides. For example if you ever wanted to remove the fret board you'd probably have to mill or sand it off etc.  But probably no need -- the fret board is ebony and on the thick side so a leveling and new frets is all it is likely to ever need?  Right now its "perfect".

----------

Jeff Mando

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## hank

Great save Bernie!  I think she looks authentic to the untrained eye. Those screws on the truss rod-less cover add to the look but will mislead future I want to look in here types.  How does the response and sustain feel now that she’s back in service.  Can you tell any changes in behavior of your patient since the operation ?

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Bernie Daniel

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## Bernie Daniel

> Great save Bernie!  I think she looks authentic to the untrained eye. Those screws on the truss rod-less cover add to the look but will mislead future I want to look in here types.  How does the response and sustain feel now that shes back in service.  Can you tell any changes in behavior of your patient since the operation ?


Thanks! I think it sounds a little different but I really don't trust my tin ear for things like that.  :Laughing:  

It has always been a very good sounding and playing mandolin and I think it still is.  It feels a little lighter to pick up now (metal truss rod replaced with CF?).

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hank

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## Bernie Daniel

Well it has been over a year since the repair was completed and I thought a follow up might be in order?

The neck repair has held up perfectly -- the action (both the G and E courses) has not changed.  The neck is a flat as a pool table, the back strap is tight, and the mandolin plays very smoothly and sounds just great.  

Here are three pics taken this morning.

I'm saying that it's fixed!   :Smile:

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## MikeEdgerton

Nice work. Forty years from now some guy will buy it and post a message asking why it has a truss rod cover and no truss rod  :Smile:

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## Bernie Daniel

> Nice work. Forty years from now some guy will buy it and post a message asking why it has a truss rod cover and no truss rod


LOL! If they get to the point of discovering there is no truss rod they will have had to have done something relatively catastrophic to that mandolin.  You do raise a point though and I am thinking about gluing a note inside the f-hole explaining things, or maybe just little strip of paper with the url of this thread?

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## MikeEdgerton

I have repair stickers inside instruments I have done major surgery to. It's not a bad idea.  :Cool:

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Bernie Daniel

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## Bernie Daniel

Well its been about 2 1/2 years since this repair was completed and everything is stable.  The head stock intact, the fret board straight and level, the action is perfect, the intonation is right on, and it plays really well.  I've been playing it for the last couple of weeks and it sounds and looks like a really cool 20s-era mandolin.  

I have no need for it whatsoever and I probably should move it along.  

But it would be hard to sell because it is so heavily modified. Still with all the reinforcements especially the carbon fiber bars in the neck and the fact that it is bonded with marine epoxy -- this mandolin could take a hell of a licking and keep clicking.  It will not be affected by water.  That epoxy is used to glue wood on marine applications.  It laughs at  heat and moisture.

It will probably be around for 100 years or more!  Be very difficult to figure what it is worth so I won't bother.   :Laughing: 

Here is what it looks like now.

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## lenf12

Great looking mandolin you have there Bernie. I'll have to re-read this thread but thanks for the followup. Hope all is well and I vote keep the mandolin if it sounds good but it looks fine to my eyes.  :Wink: 

Len B.
Clearwater, FL

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Bernie Daniel

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## Sue Rieter

I went back and read the thread; it was before my time. I'd lean with Len and say keep it, but if you did decide to move it along, my bet is that there would be plenty of interest in a good sounding mando with that kind of character.

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Bernie Daniel

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## Richard500

Thanks, Bernie; just at the right time, since I’m about to fuss with my first repair on something probably valuable, a Calace from 1921 with a broken neck.  The many tips and theories you encountered before starting work are quite helpful, and the belt and suspenders solution you worked out may, as you say, last a very long time. It’s good to know that, in this particular area, even the experienced folk are engineering on the fly rather than hewing to one established repair.  It’s also good that sonic properties are unlikely to be altered here, and that success or failure will be obvious.

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## Bernie Daniel

Send me a pic Richard -- I will offer no advice because bowl backs are something I know nothing about. If you already have a thread on this please give me the link.

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