Guitarrón - split heel

[Light]

The one significant advantage I see to screws is that it obviates the need to make a caul or other form fitted device to place over the back that I can use to clamp the repair. The screws will pull the split parts back into place and clamp them while the glue sets. Then the screws could be removed and the holes filled, if they are going to cause differential expansion problems in the future of the instrument.

Clamps will give you a better joint. The screw pulls at only one point. Clamps spread even pressure over the whole joint (at least, if you use them right). A dowel being used to support the joint isn't there in the place of clamps, and if you have a lot of good long grain figure you probably don't even need to reinforce the joint.


Light

"Cowards can never be moral."
M.K. Gandhi

 

[muttley600]

A glue joint is way stronger than a screw in that application. Also if the glue joint fails the screw isn't going to hold on. The forces acting on the neck are not good for a screw joint. You need to get even pressure across that joint for it to work well. Screws don't allow for movement of the timber into which they are screwed.

If your dead set on doing it with screws and glue go ahead. All many have done is point out to you that it not the best solution and will possibly make it worse. That has been echoed over at mimf by those voices in the know. Amy for example. At the end of the day it is your instrument. Go with what you feel happiest with,

 

[Milnoque]

The challenge is that the back of the instrument is radically arched and the heelcap is at a radical angle in relation to the surface of the neck. Creating a caul to properly clamp this joint is not going to be simple task. The caul will have to spread the clamping load across the back of the instrument and hold in place under pressure. It will probably have to involve a frame that anchors to the other end of the instrument to keep things from slipping out of alignment during clamping and a pad that matches the contour of the back. I can't think of an easy way to describe it in a thread.

 

[danw]

I see what you're saying. Like a frame that includes the heel-clamping caul on one end and wraps around the endpin area on the other, to stabilize the position of the caul and keep it from sliding down towards the neck when you put the clamping pressure on. I wonder if you could do this with a strap (or two), instead of having to build a frame. The only thing I'd worry about there is the strap pressure caving in that back; I don't know how heavily these things are braced.

Oh, and a related question: Isn't the advantage of using hide glue that if the joint fails you can put new glue in and it will stick to (and mix with) the old, so you don't have the issue of cleaning the old glue out? Or am I mixing that up with something else?

Keep us updated if you get this thing fixed; I'm curious to see how this works out.

 

[Light]

The challenge is that the back of the instrument is radically arched and the heelcap is at a radical angle in relation to the surface of the neck. Creating a caul to properly clamp this joint is not going to be simple task. The caul will have to spread the clamping load across the back of the instrument and hold in place under pressure. It will probably have to involve a frame that anchors to the other end of the instrument to keep things from slipping out of alignment during clamping and a pad that matches the contour of the back. I can't think of an easy way to describe it in a thread.

Just because something is difficult doesn't mean you shouldn't do it right.


Light

"cowards can never be moral."
M.K. Gandhi

 

[muttley600]

I see what you're saying. Like a frame that includes the heel-clamping caul on one end and wraps around the endpin area on the other, to stabilize the position of the caul and keep it from sliding down towards the neck when you put the clamping pressure on. I wonder if you could do this with a strap (or two), instead of having to build a frame. The only thing I'd worry about there is the strap pressure caving in that back; I don't know how heavily these things are braced.

Oh, and a related question: Isn't the advantage of using hide glue that if the joint fails you can put new glue in and it will stick to (and mix with) the old, so you don't have the issue of cleaning the old glue out? Or am I mixing that up with something else?

Keep us updated if you get this thing fixed; I'm curious to see how this works out.

Not really, yes hide glue will make future repairs easier in some ways but you still need to get old gue out first so the joint will close properly. It is true that pva and similar glues don't take well to "itself", hide does. The real benefit of hide glue when it is used properly is that it is very strong, very thin and very hard. Yes rework is easier but thats not the best of it. It is harder to use.

 

[Light]

It is harder to use.

Well, that depends on what you are clamping up. Braces are a breeze, as are bridges (particularly if, like me, you like to use vacuum clamps). When my dad glues on tops with hide glue, our shop manager or I spread half the glue while dad does the other, AFTER he heats all the parts with a heat gun (which really is helpful).



Light

"Cowards can never be moral."
M.K. Gandhi

 

[muttley600]

Well, that depends on what you are clamping up. Braces are a breeze, as are bridges (particularly if, like me, you like to use vacuum clamps). When my dad glues on tops with hide glue, our shop manager or I spread half the glue while dad does the other, AFTER he heats all the parts with a heat gun (which really is helpful).



Light

"Cowards can never be moral."
M.K. Gandhi

Yep, I heat all parts up a little just to stop it gelling. There is no question that a spare pair of hands is helpful when clamping up with hide glue. The secret for me is getting it fresh, keeping it at the right temp and making sure you have all you need to hand. Braces I use a go bar deck, bridges I have clamps and cauls Ive made. The hardest is binding by far.

 

[Milnoque]

I see what you're saying. Like a frame that includes the heel-clamping caul on one end and wraps around the endpin area on the other, to stabilize the position of the caul and keep it from sliding down towards the neck when you put the clamping pressure on. I wonder if you could do this with a strap (or two), instead of having to build a frame. The only thing I'd worry about there is the strap pressure caving in that back; I don't know how heavily these things are braced.

If you think the job through, a pair of straps could work very well. Straps will spread the load such that there should be no risk to the back. The challenge will be to compensate for the fact that the straps will stretch as the load is increased. Strap or no strap a clamping caul will have to be made that fits the back and heel on one side and is parrallel to the face of the instrument on the other.

 

[stevieb]

...Frank is a friend of mine, and I can promise you he would agree with me...

"Frank was a friend of mine. You, sir are no Frank."

 

[Light]

"Frank was a friend of mine. You, sir are no Frank."

No, there is quite a bit less of me than Frank.


Light

"Cowards can never be moral."
M.K. Gandhi

 

[crazydoc]

I suggest Elmer's Carpenter's Glue and decking screws. That usually fixes most anything around here.

I finally am fixing it. You win!

 

[crazydoc]

This is really a cheap Chinese POS, so I don't mind just going for the simple fix.

This shows how they screwed the bridge on from below. So one more screw in this instrument won't hurt.

 

[crazydoc]

Here's the heel from the inside, showing that the heel and neck extension are two different pieces of wood, and don't really look like they were ever glued together. You can see the crack in the side extending out to the left of the "joint."

 

[crazydoc]

The loose brace. Nothing holding the top and sides together except, apparently, glue.

 

[crazydoc]

So here's the 2 1/2" deck screw through the neck and into the heel, after liberally applying Elmer's white glue to the crack. The screw pulled it together pretty well.

 

[crazydoc]

The top clamped onto the side where it split off, again with Elmer's. The loose brace was also clamped and glued.

More pics when it's dry and restrung.

Also, this thread might be better off in DIY/mods, instead of electric guitars and basses.

 

[crazydoc]

After gluing, here's the inside at the heel. Didn't pull the neck piece all the way down - I should have put another screw in here through the top.

 

[crazydoc]

The brace is not tight enough either, but it will suffice.

 

[crazydoc]

The heel from one side.