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Can anyone explain this repair?


keyboardclass
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Is that the saddle at the bottom? If so, the pin is an assembly artifact, and that made a weak spot for the crack to originate from, but it's not exactly the cause of the crack, which would have probably happened eventually, anyway (I say that because it's a wide open gap, not just a crack, indicating some inherent stress).

To fix this type of crack correctly it's necessary to take the top off, so there's a temptation to rub some glue in, hope for the best, and leave the full-scale repair to the next guy, hoping the crack doesn't run right up to the other end in the meantime (which it probably never will do.)

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The two factors that may have created stress there are the pin and saddle as has been mentioned, but the photo doesn't show the sides of the saddle. Most saddle cracks originate from either end of the saddle if the saddle is too tight, however, the pin made a weak spot in the middle of the saddle and the pressure may have released there instead. If there is no gap at all on either side of that saddle it may be necessary to make a little space to relieve the pressure contributing to that crack.

I don't like the fact that it appears to have had glue rubbed into it, but it isn't actually closed. It indicates it probably wasn't reinforced internally, the stress that caused it is still holding it open, and since hide glue isn't a great gap-filler it isn't a tight enough glue job. Those three factors all say to me it should be closely watched and taken in for proper repair at the first sign that it is either growing longer or the crack shows any flexibility when pressed under your thumbs. 

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14 hours ago, Brad Dorsey said:

As Michael said, there's a good chance that your top would have cracked without the pin; the stresses around the pin just encouraged the crack to form in that particular spot.

In my limited experience, I have not seen a crack in the center above the saddle without the presence of a locater pin. I don't consider them saddle cracks per se because they can happen even with a properly fit saddle.

I have seen the center seam open without the presence of a pin, but that can have different causes. Interestingly, I have also never seen a locator pin open the center seam; it always seems to crack the wood on one side or the other.

Saddle cracks seem to occur mostly on either side of the saddle.

Again, in my limited experience.

 

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The photo isn't detailed enough to tell if we're looking at a wood crack or an open center seam, although it's a bit raggedy so at least some wood looks like it has been split off.  

I expect center pins can be done in ways that might cause a crack... i.e. using a tapered pin, and hammering it in.  I presume this would be the method used for inexpensive, high-production instruments.  I use a steel pin for locating a top for assembly, but then remove the pin and glue in a slip-fit piece of wood to fill the hole (but not pin it to the endblock).  I can't imagine that a crack would be caused by this type of pin.

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Sometimes people drilled a hole, and used a length of gut string to thread a cleat onto. After gluing the crack, apply glue to the cleat & quickly pull into place, keeping it tight until dry. The other end of the string can be pulled out, but it leaves an open hole to plug.

Looks like in this case, all the small drills were missing that day ;)

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2 hours ago, Wood Butcher said:

Sometimes people drilled a hole, and used a length of gut string to thread a cleat onto. After gluing the crack, apply glue to the cleat & quickly pull into place, keeping it tight until dry. The other end of the string can be pulled out, but it leaves an open hole to plug.

Looks like in this case, all the small drills were missing that day ;)

Yes, this is an old technique commonly called "fishing a cleat".

These days, we aren't much into drilling holes in tops, but in some circumstances, it may be less destructive than other methods.

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3 hours ago, keyboardclass said:

I assumed you introduce it sideways.

How would you clamp it securely?

The following link is to an old thread (I posted it in 2014) when dealing with a number of saddle cracks during that winter.  To avoid serious backups at the shop, I need a quicker, relatively non invasive, but reliable way to deal with this problem. Works better than fishing cleats on a thread through a hole I think!  :) 

Long saddle crack repair without completely removing the top.

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2 hours ago, Jeffrey Holmes said:

How would you clamp it securely?

The following link is to an old thread (I posted it in 2014) when dealing with a number of saddle cracks during that winter.  To avoid serious backups at the shop, I need a quicker, relatively non invasive, but reliable way to deal with this problem. Works better than fishing cleats on a thread through a hole I think!  :) 

Long saddle crack repair without completely removing the top.

I liked that post, I then tried it withing a few months and it worked great.  As far as "fishing" cleats, it's a common repair technique on guitars (a lot on ribs).  Jeff, the way you hold the cleat tight is with a homemade (or Stew mac now makes them) wood block using an individual guitar tuner on the outside.  This is StewMacs, but it has some limitations.

StewMac Crack Repair Tools Crack Clamp

I use a .016" guitar string if it's a rib crack on a student cheap chinese cello (usually all this is used for) because it's always super stubborn to pull together.  If all comes together well, then I use a .010" guitar string.  Tiny hole to be filled.  On the inside pulling the cleat, I use a "thingy" that screws down on the string with a tiny nylon washer. It's something used in model airplanes for elevator control.

StewMac Crack Repair Tools Clamp Tie Block(this is similar)

 That pulls up against the cleat on the inside using the tuner block on the outside.  A total compromise, but it's usually done on a $1000 student chinese cello to keep it structurally sound.  Works quite well.   

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3 hours ago, Jeffrey Holmes said:

How would you clamp it securely?

The following link is to an old thread (I posted it in 2014) when dealing with a number of saddle cracks during that winter.  To avoid serious backups at the shop, I need a quicker, relatively non invasive, but reliable way to deal with this problem. Works better than fishing cleats on a thread through a hole I think!  :) 

Long saddle crack repair without completely removing the top.

You can buy clamps that allow you glue cleats through the f holes. I actually made a couple of longer ones that can reach just about anywhere. I suppose that if I was doing a budget repair on this, I would: 1) Release the top from the lower bouts to see if there was a chance of clamping the crack back together. 2) Carefully remove the wood pin. 3) Attempt to clamp the crack back together. 4) If successful, glue the crack, and clamp closed. 5) Glue some cleats through the f holes. 6) Re-glue the top.

https://www.metmusic.com/tools/clamps/met-music/

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2 hours ago, Jeff White said:

I liked that post, I then tried it withing a few months and it worked great.  As far as "fishing" cleats, it's a common repair technique on guitars (a lot on ribs).  Jeff, the way you hold the cleat tight is with a homemade (or Stew mac now makes them) wood block using an individual guitar tuner on the outside.  This is StewMacs, but it has some limitations.

StewMac Crack Repair Tools Crack Clamp

I use a .016" guitar string if it's a rib crack on a student cheap chinese cello (usually all this is used for) because it's always super stubborn to pull together.  If all comes together well, then I use a .010" guitar string.  Tiny hole to be filled.  On the inside pulling the cleat, I use a "thingy" that screws down on the string with a tiny nylon washer. It's something used in model airplanes for elevator control.

StewMac Crack Repair Tools Clamp Tie Block(this is similar)

 That pulls up against the cleat on the inside using the tuner block on the outside.  A total compromise, but it's usually done on a $1000 student chinese cello to keep it structurally sound.  Works quite well.   

Hi Jeff; I think you misunderstood... or I misunderstood keyboardclass... I was asking keyboardclass how a loose (not tethered to a line) cleat fed through the endpin hole sideways could be clamped.... or accurately positioned for that matter.  I'm sure it could be done, but I imagine it would be  Rube Goldberg affair.  :) 

1 hour ago, FiddleDoug said:

You can buy clamps that allow you glue cleats through the f holes. I actually made a couple of longer ones that can reach just about anywhere. I suppose that if I was doing a budget repair on this, I would: 1) Release the top from the lower bouts to see if there was a chance of clamping the crack back together. 2) Carefully remove the wood pin. 3) Attempt to clamp the crack back together. 4) If successful, glue the crack, and clamp closed. 5) Glue some cleats through the f holes. 6) Re-glue the top.

https://www.metmusic.com/tools/clamps/met-music/

Hi Fiddledoug;  I'm with you on steps one and two... but since the lower bouts would  already be open, and very into the Cs (or easily could be opened that far if needed), I'd use the method described in the link I supplied rather than trying to position the cleats through the ffs on a box already glued back together.  Easier to clean things (glue) up around the cleats with some access from the lower bout as well.

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" Hi Fiddledoug;  I'm with you on steps one and two... but since the lower bouts would  already be open, and very into the Cs (or easily could be opened that far if needed), I'd use the method described in the link I supplied rather than trying to position the cleats through the ffs on a box already glued back together.  Easier to clean things (glue) up around the cleats with some access from the lower bout as well. "

Hi Jeffrey,

I did read your link, but I guess that it wasn't clear to me exactly how far open you have to spring open the top (gap mm?), and what kind of clamps you're using to clamp through that gap. Thanks!

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