Double bass pegbox repair - which glue to use?

[Shawn Elgaaen]

Folks,

I’m looking for insight from a few of you with experience addressing a similar repair challenges.

I’ve got a double base that was knocked over onto the scroll.  The impact split the pegbox along the grain at the upper peg for the D string.  The break is clean and fits back together nicely.  My dilemma is which would be the best glue to use.  I know that hot hide glue is preferred; however, my experience is that hide glue doesn’t give much time for positioning and clamping with good squeeze-out of the excess glue.  I am wondering if it would be better in this situation to use a Titebond II or Titebond III wood glue. 

Any words of advice?

Edited February 26, 2020 by Shawn Elgaaen

[violguy]

Have you tried fish glue?

[Giovanni Corazzol]

Hello, no matter which glue you will choose, I believe that you will have to make some counterforms to make the clamping force spread more evenly without the pieces sliding. Chuck Traeger covered this kind of repair in his book on bass restoration: "Gluing will not be sufficient to hold the tuning box together"  and he suggested using brass screws to make the repair stronger. "I use small brass wood screws, which I insert into pre-drilled holes and countersink the heads as much as possible".

[Bill Yacey]

This would be another instance where I personally would use G2 epoxy, as it's a glue joint that will be under high stress.

[HoGo]

2 hours ago, Bill Yacey said:

This would be another instance where I personally would use G2 epoxy, as it's a glue joint that will be under high stress.

I don't think there will be high stress in the joint. It's right through the last hole and mechanic gears don't apply pressure like tapered pegs do, they will just bear on one side of the hole facing nut so no direct stress on the joint. The surface of break is clean and jagged whch will lock well during gluing and provide adequate surface. I would go for regular hide glue and clamp with shaped blocks as needed. I would be aware of application of the screw right through the break - I would pre-drill the hole while the clamps are still on or I would drill out 1/8" or so hole almost all the way through the side and insert some soft wood dowel (basswood or such) for the screw to hold in (but would pre-drill small hole anyway).

Now I see that the break is quite angled where the screw hole is visible so what I would re-consider what I wrote above. Perhaps it would not be needed at all.

[Evan Smith]

9 minutes ago, HoGo said:

I don't think there will be high stress in the joint. It's right through the last hole and mechanic gears don't apply pressure like tapered pegs do, they will just bear on one side of the hole facing nut so no direct stress on the joint. The surface of break is clean and jagged whch will lock well during gluing and provide adequate surface. I would go for regular hide glue and clamp with shaped blocks as needed. I would be aware of application of the screw right through the break - I would pre-drill the hole while the clamps are still on or I would drill out 1/8" or so hole almost all the way through the side and insert some soft wood dowel (basswood or such) for the screw to hold in (but would pre-drill small hole anyway).

Now I see that the break is quite angled where the screw hole is visible so what I would re-consider what I wrote above. Perhaps it would not be needed at all.

That is what I also observed.

It would appear that the tension of the string held it together and caused it to break beyond the tuner.

I would bet a dollar against a donut that the tuner could be placed  in it's home and the string tightened up full tension  before the piece is even glued. (just to prove the point)

There shouldn't be a lot of stress on that joint,,, fresh hide glue, solid clamping, and,,,,,, happy camper.

A set of full plates would give it a bit more protection,,,

[bkwood]

If the break is clean and fits together nicely I don't see why hide glue is a problem. If it fits perfectly you shouldn't need to clamp it either, just hold it with good hand pressure for a few minutes then put it where it won't be disturbed and carefully clean up the squeeze out. Tight bond is likely to leave a more visible crack.

I did a somewhat similar repair with a dowel not too long ago, but that repair had string tension on it. I'm not sure you need to do that.

[Shawn Elgaaen]

This is great info.  Thank you all.

I’ve decided to to go ahead with the hot hide glue.  Worst case, if it doesn’t hold, I’ll have to clean it up and do it over again.  I just wished I had more confidence in hide glue as a permanent solution.

I agree that the position of the break should have very little impact on the structural integrity of the lower portion of the pegbox and peg holes.  In fact, the strings were still under full tension after the scroll was broken off.

 

[jezzupe]

The entire concept behind Hide glue is it's ability to be separated. In this case, this is not a glue joint that we will ever want to be separating. so in my opinion, just because this is a musical instrument, does not mean we "have" to use "Hide glue" for structure breaks in "parts" that are not intended to be separated for any kind of repair purpose.

Therefore ergo, in this case you have many options, some of which will require no clamping, just a "perfect fit" with a simple seating firmly and that's all you will need.

this is one of the few instances when I would suggest a slow set epoxy as Bill has suggested, I'm a big fan of Smiths brand, but there are many with extreme bonding strength that will more than suffice.

Your concern with epoxy is 1.applying the right amount, and 2. squeeze out. To minimize the squeeze out, I suggest first masking as close to the crack as you can get with an extremely low tack painters tape, use a tooth pick to load up the crack on each broken piece, then use a small model brush that you have "pre dehaired" {pluck it so it does not deposit brush hairs in you glue} and then stipple {tap} the glued pieces in order to work the glue into any crevasses and to help control the amount of glue. Then, using some type of prop get the instrument in a position that makes it so the scroll part will be sitting in a "gravity neutral " position that will make it so when you push the two together that the scroll will not flop off when you walk away.

Anyway, depending on the epoxy, the general procedure is after you have mated the pieces, wait a "bit" then pull them apart , and then re-mate them, position them perfectly, walk away for a bit, make sure you are neutral position, then, after an hour or two, GENTLY use a small brush dipped in mineral spirit/paint thinner/white spirit to gently remove any squeeze out, let it dry for a bit, them GENTLY remove the tape, if you allow the tape to stay on, there is a good chance it will get glued to the wood and be hard to get off without it turning into a varnish touch up....the better you mask the crack, the less clean up you will have to deal with

You may opt to use some clear tape {so you can observe the joint} on top of the masking tape to act as a gentle clamp that will allow it to hold its position once fitted if a good neutral position is hard to find

I also suggest masking the majority of the instrument off with low tack tape and painter paper to act as a "just incase", you do not want to slop either paint thinner or epoxy on the instrument.

You could also simply use yellow wood glue, you will need to make proper cauls for clamping however.

Some may disagree with my advice, but I see no reason to use a seprable glue for an intended permanent glue repair

[bkwood]

I guess I disagree on the basis that being a separable glue is irrelevant. It's a perfectly good bond that's easier to work with than epoxy, which seems unnecessary for this fix.

[HoGo]

The main problem with Epoxy it's nearly impossible to get invisible glue line. With HHG it is quite the norm on clean fitting surfaces. Epoxy is thick and almost impossible to squeeze out of such ragged crack. And most epoxies REQUIRE some thickness of the joint for mximum strength. You can use strong fresh HHG and just hold it in place for couple minutes till the glue grabs and use two small clamps though the D string tuner hole to hold the scroll in place till the glue dries keeping the bass with scroll over the joint during the drying.

[jezzupe]

17 minutes ago, HoGo said:

The main problem with Epoxy it's nearly impossible to get invisible glue line. With HHG it is quite the norm on clean fitting surfaces. Epoxy is thick and almost impossible to squeeze out of such ragged crack. And most epoxies REQUIRE some thickness of the joint for mximum strength. You can use strong fresh HHG and just hold it in place for coths is quite thin compared touple minutes till the glue grabs and use two small clamps though the D string tuner hole to hold the scroll in place till the glue dries keeping the bass with scroll over the joint during the drying.

Smiths is quite thin compared to many others and I've never had the issues that your describing with it, It does not have to have a thick seam of glue. I am also VERY familiar with several other brands of epoxy and while many of them are thicker, I've never had issues with tight joints or "invisible" or not that visible crack repairs.

Again, as Bill points out, this appears to be a high stress joint area where the tuning key will be applying force the the blown out hole, I personally would want it to be a one time repair and I would feel more confident about that with epoxy personally.

Also being overtly familiar with hide glue , if one were to go that route I would opt for the fish glue, as it has open time and cold application, may b a little stronger, depending

But based on the angle and the break location, personally I go epoxy, but then again thats why I keep saying "personally"

My concerns with Hide glue based on the question even being asked, is the persons skill level with working with it. You get it wrong one time to the point where it needs to be water wiped clean, you could swell and "poof" the breaks grain, thus losing your perfect key lock.

IMO you have one shot with a water based glue to get it married, if you mess it up and have to clean it, you might loose that perfect union. Because one does need to factor in clamping and cauls or not, I could see a good mix of hide glue properly setting up without the need for clamps, but based on the break, it could be difficult to achieve a neutral position, so clamping may be needed, therefore making the "one shot" deal even more complicated, keeping in mind this is a bass scroll, it's probably got some heft to work against gravity and based on how steep the break angle is, I could see it needing some supporting clamps , again making for a very difficult fast maneuver that has to be completed.

[HoGo]

12 minutes ago, jezzupe said:

Again, as Bill points out, this appears to be a high stress joint area where the tuning key will be applying force the the blown out hole, I personally would want it to be a one time repair and I would feel more confident about that with epoxy personally.

OP says the strings were still under full tension after the scroll was broken off so all the stress goes towards the undamaged part of head. So all it needs is good gluing job with whatever glue one is familiar with and can get reliable tight joint. Most violin folks don't use epoxy as much as HHG and I prefer it as well for instrument repair. I know strengths of epoxy and used it several times on broken stocks of biathlon rifles where HHG would look nice but probably wouldn't hold for too long.

[Giovanni Corazzol]

@jezzupeI am not familiar with epoxy glue, so thank you for the detailed explanation of your method!!

 A friend of mine who makes celtic harps showed me how to use the West System epoxy to make a structural bond in wood. he said that since this kind of epoxy is thinner than other kinds (the common DIY glues I was more familiar to) it can be used to create "glue rods" that are formed when the glue fills the holes that have been drilled into the two parts before gluing. These glue rods become effectively locked into the holes because the epoxy also permeates the surrounding wood. My understanding is that generally, epoxy glues have a high internal cohesion but they do not have adhesion to wood fibers as high as other glues like water-based pva/alipahtic, or hide glue (the last one having the better adhesion, but quite poor cohesion and that's why the hide glue line should be as thin as possible without being "starved").

my thoughts on clamping the pieces (if the OP chooses to go this way): with the machines removed, a piece of wood can be roughy shaped to adapt into the tuning box and long enough to support the scroll. the support can be fastened to the back of the pegbox with a clamp and left in place. It will be placed against the bottom of the pegbox.  A wooden wedge covered with cardboard or cork sheet can be fastened to the curved rear side, using some plastic cable clip-holders that go through the machine hole. I believe that this set-up won't take much time for preparation and it makes the gluing with hot hide glue fast enough. Having someone for help in placing the clamps would be better though.

[Brad Dorsey]

If you want to clamp the pieces, we had a discussion a while back that may give you some ideas:

https://maestronet.com/forum/index.php?/topic/341319-clamping-broken-peg-box/

[jezzupe]

6 hours ago, Giovanni Corazzol said:

@jezzupeI am not familiar with epoxy glue, so thank you for the detailed explanation of your method!!

 A friend of mine who makes celtic harps showed me how to use the West System epoxy to make a structural bond in wood. he said that since this kind of epoxy is thinner than other kinds (the common DIY glues I was more familiar to) it can be used to create "glue rods" that are formed when the glue fills the holes that have been drilled into the two parts before gluing. These glue rods become effectively locked into the holes because the epoxy also permeates the surrounding wood. My understanding is that generally, epoxy glues have a high internal cohesion but they do not have adhesion to wood fibers as high as other glues like water-based pva/alipahtic, or hide glue (the last one having the better adhesion, but quite poor cohesion and that's why the hide glue line should be as thin as possible without being "starved").

my thoughts on clamping the pieces (if the OP chooses to go this way): with the machines removed, a piece of wood can be roughy shaped to adapt into the tuning box and long enough to support the scroll. the support can be fastened to the back of the pegbox with a clamp and left in place. It will be placed against the bottom of the pegbox.  A wooden wedge covered with cardboard or cork sheet can be fastened to the curved rear side, using some plastic cable clip-holders that go through the machine hole. I believe that this set-up won't take much time for preparation and it makes the gluing with hot hide glue fast enough. Having someone for help in placing the clamps would be better though.

Smiths and West's could be considered similar. The apply and then pull apart and then re-mating helps with the cohesion. I agree with the clamping, something like what you have described will have to be done.

And yes someone helping could make all the difference in the world. Any of my advice is based on an assumed working alone, my advice may change if there are 4 hands instead of 2.

 

[jezzupe]

16 hours ago, HoGo said:

OP says the strings were still under full tension after the scroll was broken off so all the stress goes towards the undamaged part of head. So all it needs is good gluing job with whatever glue one is familiar with and can get reliable tight joint. Most violin folks don't use epoxy as much as HHG and I prefer it as well for instrument repair. I know strengths of epoxy and used it several times on broken stocks of biathlon rifles where HHG would look nice but probably wouldn't hold for too long.

I did not see his second post, somehow my eyes saw the hole blown out, but if its only the scroll north of the holes, then I would agree that epoxy is not "as needed" based on the the repair not being something needed to work against the tension.

[jezzupe]

also, while on this subject, about Cauls for curves, If one goes to the classified {craigslist} one can often find people giving away hot tub covers,many of these are made from 2 to 3 " styrofoam that is a rather firm, yet compactable with clamp pressure, you can use a serrated steak knife to cut it to conform to what ever shape may be needed, it can be hot glued together in case you need a very thick form.

You can also use rigid foam insulation , but it tends to crush too much, you can back it with wood if needed which can help, if that works in the clamping layout

for real precise forms you can use a hot knife sold for cutting foam to get more accurate cauls if needed 

Balsa wood also works well in certain applications

foam forms can have a piece of wax paper placed between them and the work to prevent sticking.

Some of the more intimate problems one can have with these types of repairs is "seeing" if when dry fit together, does it stay put, this can lead to "searching" for a position, searching for a position can lead to repetitively puling apart and putting back together the break, that can lead to you perfect union becoming unperfect  by upending fibers and chips, which can sometimes interfere with a keylock, thus forcing one into well done cauls in order to "smash" things back together, and with these types of angle/curves that can be easier said than done.

So IMO there is lots of logic behind not wanting dry fit the repair over and over in search of the perfect neutral position/ clamoing of cauls.

And so again because of epoxy ability to form a tack bond,as long as it stays put, it won't need clamps, thus not need to be dry fit often.

this could be one of those breaks that when put together it really key locks well and does not want to sluff off, if so, great, use hide glue. If it is difficult, I would recommend Fish glue, based on its open time and cold set,or the epoxy, again in this case not so much for the strength as much as the ability to hopefully skip clamps and cauls 

[Craig Cowing]

Personally, I'd go with Titebond II. I have used it extensively for a couple of decades for woodworking projects in general and don't know of a wood glue that holds better. And as someone pointed out above, this is not a joint that needs to be re-done in the future. You don't want it coming apart.

[Jeffrey Holmes]

I understand I work on another class of instrument than the bass that's illustrated... and I would think the OP will use whatever they think best at this point... but I feel I've got to say I would, absolutely, use a nice, clean, fresh, strong (250-315 gram strength) hide glue for this repair, and (for me) nothing else. No "creep" and a good strong bond with little/no glue line.  

Hide glue, especially of the strength I mentioned, can chip glass.  If you forget to watch the pot and  it dries out in a glass glue pot liner, you'll quickly see that for yourself. It, of course, has a relatively short working time.

No matter what adhesive is used, or what the working time is, the success of the repair will depend on how well the alignment is maintained by counter forms or clamping cauls...  prepared and tested well before the glue is applied.  I've found tin (not aluminum) foil and Bondo is handy for making many of these sorts of counter forms (get some help from someone who has used the stuff before going cowboy. It heats up as it cures and must be removed from the varnish surface before it reaches a temperature that will harm the instrument).  Dental plaster is also useful... and (I haven't tried it on a scroll form, but I know others who have) "smart plastic" could be handy. Plain old wood comes in handy too.

At Oberlin, we've had the occasion to try several methods of aligning and clamping pegbox/scroll breaks, but I'm convinced that decent counter forms are critical in contributing to a nice job... and cutting down working time once glue is applied.

A colleague, Christian Schabbon (who sometimes contributes here) solved the challenge of alignment on this project: Scroll & pegbox repair

[jezzupe]

31 minutes ago, Jeffrey Holmes said:

I understand I work on another class of instrument than the bass that's illustrated... and I would think the OP will use whatever they think best at this point... but I feel I've got to say I would, absolutely, use a nice, clean, fresh, strong (250-315 gram strength) hide glue for this repair, and (for me) nothing else. No "creep" and a good strong bond with little/no glue line.  

Hide glue, especially of the strength I mentioned, can chip glass.  If you forget to watch the pot and  it dries out in a glass glue pot liner, you'll quickly see that for yourself. It, of course, has a relatively short working time.

No matter what adhesive is used, or what the working time is, the success of the repair will depend on how well the alignment is maintained by counter forms or clamping cauls...  prepared and tested well before the glue is applied.  I've found tin (not aluminum) foil and Bondo is handy for making many of these sorts of counter forms (get some help from someone who has used the stuff before going cowboy. It heats up as it cures and must be removed from the varnish surface before it reaches a temperature that will harm the instrument).  Dental plaster is also useful... and (I haven't tried it on a scroll form, but I know others who have) "smart plastic" could be handy. Plain old wood comes in handy too.

At Oberlin, we've had the occasion to try several methods of aligning and clamping pegbox/scroll breaks, but I'm convinced that decent counter forms are critical in contributing to a nice job... and cutting down working time once glue is applied.

A colleague, Christian Schabbon (who sometimes contributes here) solved the challenge of alignment on this project: Scroll & pegbox repair

Thanks for that, some cool tricks in that repair

[Shawn Elgaaen]

Thank you for all of your insight and suggestions. I have learned a great deal.

Well, it is glued together.  The repair didn't turn out as perfect or as invisible as I would have liked but I believe it is structurally sound and fully functional.  

This instrument belongs to an elementary school and has other areas of damage and repair which it has accumulated over its 41 years of life.  So, it’s more my pride than anything that is affected by the less than perfect outcome.  The school is simply happy to have it back.

I did cut a counter form for the scroll and a wedge for inside the pegbox and attempted to dry-fit the pieces with clamps.  Because of the unwieldy size or bulk of the double bass and the counter form, I found this approach extremely awkward and unhelpful so I abandoned it.  An extra set of hands, a much larger work bench and perhaps bench-mounted clamps probably would have done the trick to make it work.

What I ended up doing was sliding several heavy rubber bands onto the pegbox so I could easily pull them into place once the glue was applied and the parts mated together.  I then took a deep breath and proceeded to apply fresh hot hide glue to both pieces, rung them together then held them in place for fifteen to twenty seconds before pulling the rubber bands into position.  Then, after checking the alignment of the parts on all sides the best I could without moving the bass, I wrapped a good length of 3/4” wide elastic from my wife’s sewing supplies around the joint like an ace bandage.  Fortunately my wife donated the elastic voluntarily.   Then, as a few of you suggested, I forced myself to walk away and leave it undisturbed overnight and most of the next day. 

If I run into a repair like this again, I believe I will invest more time to crate a way to position and hold the parts more securely and apply uniform clamp force more quickly.  I also need to get me some fish glue to experiment with.  The idea if longer working time before the glue sets is appealing to me.

Best wishes to you all!

[Rue]

Whoa!!! Awesome!!!

Turned out better than I thought it would.