Double Bass Repairing Braces on Romanian Flatback

[gandalf1]

Hi Folks,

I have ~12 year old Romanian flat-back bass with the red polymer finish (yes, one of those…). I am the only owner, having bought the bass new. I’ve noticed a rattle/buzz when playing an “A” on the G string (at the second “fret”). Unfortunately when amplified, the bass booms like crazy when this note is played, as the amplified sound is reinforcing the buzz, making the bass practically unplayable.

I put it on the bench and it seems that a couple of the cross braces have become separated from the back at their ends, which I am presuming is the problem. In reading other threads on this forum, the first piece of advice is to call the luthier, so I gave Arnold S. a call yesterday. In chatting with him it quickly became apparent that the cost to have a professional repair the instrument will exceed its value.

So here is my conundrum: The bass itself is plays well (Arnold has had it a couple of times over the years for a new fingerboard and a setup, and the instrument plays and sounds as good as it possibly can be expected.) For my needs, it sounds and plays fine, and though I play regularly, a new bass is not an option (as well as the added headache of trying to get rid of this one). In lamenting this to Arnold, and as someone who has been interested in working on my own basses for years, his closing comment was, simply, “Then you need to fix it yourself”.

And thus I write.

First, the situation. A few pictures are attached. Fig_1 is the instrument itself for reference. As you can see the back of the bass is warped inward near the part just before the knee (Fig_2) . The braces in question are the two topmost horizontal braces on the back (Fig_3) (where the back is curved) The topmost brace is thick (maybe 1.5” thick and 1.5” wide) and is located near the knee in the back where it starts to angle towards the neck joint. The second brace is smaller (maybe 1” x 1”) located below the bigger brace near the upper violin corners. The topmost brace has popped on both sides, with the gap larger on the left (E-string) side (Fig_4, Fig_5) than the right (Fig_6). The lower, smaller brace has separated only on the left side (Fig_6), with the right side still attached (Fig_7). (Incidentally Figs. 5-7 were taken with an inexpensive inspection camera from the hardware store---very handy).

The gap for the larger brace is substantial, maybe 3/16” at the edge (Fig_4, Fig_5).

As I see it I have four options available:

• OPTION 1: Glue/wedge braces through f-holes. I can reach the seam between the brace and back through the bass-side f-hole and was thinking of attaching a small syringe with glue that I can get to the joint (or using a syringe + a tube on a wooden dowel to get the glue to the joint--a detail).
  
• OPTION 2: Drill small holes for glue and screws through back (sacrilege I know!!)+ glue/wedge through f-hole. I also have a fine (23-gauge) pneumatic pin nailer that would be virtually undetectable.
• OPTION 3: Remove top + R/R braces, refit, and reglue.
• OPTION 4: Remove back and rebuild.

-----------------------------
Some thoughts:

Options #1 and #2 are comfortable in my skill set.

I think Option #4 is comfortably beyond my skill set.

Option #3 is probably beyond my skill set, but I am willing to give this a try, if the consensus is that (a) removing the top is not as terribly daunting as it looks, and (b) would provide for a better repair. Additional benefits of #3 include doing any modifications for tone (not that I would embark on them, but the potential is there), and getting over my phobia of doing any serious work on my bass. The obvious disadvantage, of course, is that I make a complete mess of the instrument and render it scrapwood.

#2 (drilling/screwing+ gluing) I know this likely violates the senses of many professionals on this list, and with good reason. However this bass is not an heirloom instrument, and if a 1-hour repair can get me several years of service out of it, I would have a hard time not taking this option.

Then there is the issue of glue choice for Options #1 and #2 (#3 and #4 would allow normal hide glue). If white glue was used on the original braces (I cannot tell, in fact there isn’t much of any glue residue on the braces that I can see) there is the issue of other/new adhesive not sticking to it. Glue choices include a) hide glue, b) liquid hide glue, c) white glue d) wood (yellow) glue, e) two-part epoxy, and f) silicone. Yellow, white, and liquid hide glue are pretty much ruled out for the same reasons they aren’t used elsewhere. Epoxy isn’t a bad choice due to its minimal shrinkage and gap-filling qualities, although there is a permanence to it that scares me.

I have granular hide glue and a glue pot, and some limited experience working with it. I will use traditional hide glue if this is the overwhelming recommendation, but there is the issue of adhesion to the old glue (white or hide, depending on what they used).

Believe it or not, I am attracted to silicone as the top candidate at this point , because it has good gap-filling qualities (think bathroom caulk), excellent grip to most other surfaces, and flexibility. It can also be removed fairly easily if and when I were to attempt a major repair in the future. I am almost certain that this will stop the rattling, however silicone doesn't have much strength as an adhesive, and will likely do little to help the brace in its original role of supporting the back as intended.

Note that whatever glue is used will have to span a gap of up to 1/8” between the foot of the brace and the back of the neck. Without taking the top off, there is no way to otherwise compress the brace against the back when gluing. I can also make up some wedges and work them into the gap before or during gluing.

A little about me: I do not have an enormous amount of woodworking experience, although I have many of the tools, and I have over 30 years experience with mechanical repairs of all kinds. I’m a mechanical engineer by training and profession, and I work at a university, with a big part of my job doing engineering research. Thus ‘thinking outside the box’ is something we do all the time, and I’m not adverse to implementing a clever/untested solution. I own and have read the books by Chuck Yaeger and H.S. Wake.

Arnold had graciously suggested attending the Oberlin workshop in June, with this as my "project". This is also an option, although I have some scheduling issues that might be insurmountable, and I fear that the typical skill level there would be far beyond mine. I am looking into it now. Yet another option might be to make a temporary repair now and plan to attend next year.

Anyway, if you have gotten this far, thank you for reading. Any and all comments in terms of how to proceed, glue choice, what to avoid, things to watch out for, tools, and general opinions are be most welcome. If you would like additional pictures, information, or measurements, please let me know and I will provide them.

Thank you all for such a great resource,

-Jon Longtin
Stony Brook,Long Island, NY

 

[gandalf1]

Here are two braces in question (left pic) and the gap as seen through the e-string f-hole (right pic).

-Jon

 

[gandalf1]

Gap on left side in both upper brace (left pic) and lower brace (right pic) on left (e-string) side as taken form an inspection camera.

 

[gandalf1]

Gap on upper brace (right pic) on right (g-string) side, and absence of gap on lower brace on right side (left pic).

-Jon

 

[Matthew Tucker]

I'd suggest making a hole in the treble side C bout so you can get your hand in there to make the repairs. Measure your forearm first to see what size hole you need! Then you have a soundpost-adjusting port as well, and you'll be the envy of all the tweakers in the neighbourhood.

[edit] on looking closer at the warped back and the chunky braces, Option 3 is the go. If you are patient, careful, and persistent it's not THAT hard. But if you just want to try to glue the brace ends and get back to playing, my previous suggestion may be a way to go ... it is NOT easy working through FF holes, even just to try to works some glue in there! And trying to screw into the brace ends will not IMO work very well. [/edit]

 

[Jake deVilliers]

Please, no epoxy. Why not take the back off and fix those braces the right way?

The hard parts will be the alignment when replacing the back and the cosmetics of the varnish repair. If you remove the back very carefully there will be less damage to repair and if you re-glue the plate a quarter at a time you should be fine with the alignment.

You could go old school and drill 3/16" holes in all six blocks to aid in re-positioning the plate correctly.

 

[KUNGfuSHERIFF]

Not that I'm qualified to carry water for either of the gentlemen who posted above, but as a person in similar circumstances to you, I may have something to add to the conversation.

Opening a bass for the first time is terrifying. So are the second and third. Maybe the fourth too, I'll have to let you know. This encourages you to go slow, which is for the best. The good part of working with hide glue is that you get a few chances to do the job correctly, all of which you will need. At least I did. Look here:

http://www.talkbass.com/forum/f3/need-advice-repairing-mortone-basket-case-775510/

I played that bass for a few minutes before work this morning. So far it hasn't exploded. I hope it keeps not exploding, because it's a fun bass to play. If I can get that mess back into playing shape, I'll bet you can fix this.

I agree that Option 3 is the way to go. If the braces were simply loose you'd have more leeway, but because the back plate is out of true, that is the first problem you need to correct. Those braces will never go back into place on a warped back.

Once the back is off and the braces are removed you will need to fabricate a flat, heated surface that is large enough to fit the back. You could probably use a simple spray bottle to moisten the wood and make it flexible before you clamp it down and hit it with low heat. I've used a steam iron to reshape broken ribs, but this is too large a job for too small a tool.

I've heard that many Romanian instruments are put together with yellow glue, which you will want to remove as nothing will stick to it. White vinegar and elbow grease should do it.

Through trial and error, I've decided that re-gluing a top or back in one shot is too much for one person. What I've done for partial top removals (and will test when I close up the nightmare I'm working on now) is to start at one point -- the button, in your case -- and work my way down the shoulders six inches at a time, slowly gluing and clamping.

Again, I'm not a luthier, but these have been my experiences.

 

[Schoolhouse]

The back needs to come off. Refit or replace the braces. You would get great help at Oberlin, but this repair needs strict attention to humidity control which is hard to achieve in the mid-west in June. One of my clients has a similar bass with the Poly finish stripped. It is a decent sounding bass.

 

[Schoolhouse]

When the back is off you could use "go-bars" (wooden sprung bars) to glue the braces against a flat or slightly dished dished subsurface. Again, control of the humidity is crucial. The back has to be dry. Most of the Rumanian braces are excessive, making them smaller won't hurt. Some guys would argue for a diagonal brace, it's worth investigating. I've never had the guts to try it.
Tom

 

[Matthew Tucker]

i would say the hardest part won't be re-aligning the top or back, it will be getting that back to lie flat again! It has cupped like that due to drying and shrinkage on the inside - the wood was not properly seasoned and now varnished on one side has dried unequally. If you use heat you will risk separating the center joint. You don't want that. Remove the braces and see if you can get the black to go flat or very very slightly convex. You may have to use warm sandbags and be patient. THEN replace the braces when its all very dry. I usually make my braces taller and stiffer in the middle and lower and more flexible at the ends. If they can flex a little at the ends they are less likely to unglue.

One more note - you can do the repair either by removing top or back, but in my experience a top is easier to refit than a back, as the back has the button and often a bend in the upper bout, whereas the top is flat. But on the other hand it would probably be easier removing and refitting the braces if you take the back off. Check the neck / FB alignment. Is it centered between the FFs? if not, if you remove the top you have an opportunity to re-align the fingerboard a little as well.

Oh so many choices!

 

[basswraith]

I had to re do the cross bars on a bass just like yours 2 years ago for the same reasons. This is not a "do it your self" job.
This is for the pros. Getting the back off with out destroying the button is challenging. These basses are assembled with white glue. Its a bitch to get them apart with out destroying them.
Getting the back to fit back onto the body was extremely difficult and frustrating. It has to line up with the button and there needs to be equal over hang around the edges of the bass. Not an easy thing on basses that are not dry yet.
I did it, but man, that took every thing I had. I chose a more modern approach to back bracing. There was a positive audible difference.
Michael Hartery

 

[gandalf1]

Matthew, Jake, KFS, Thomas, and Michael,

Thanks to each of you for the thoughtful replies.

First, I'm encouraged that no-one has yet said "Forget it, you deranged, inexperienced fool. This is certain madness!!"

It also sounds that regardless either the top or the back needs to come off. This is what I needed to hear, and I am thus inclined to go this route (I was secretly hoping this would be the verdict anyway, as I really want the chance/challenge to actually open this thing up and get over my fears of doing this).

So now the question is one of removing the top or back. The verdict between you all seems more or less equally split. I've been reading all day (don't tell my employer!) as many threads as I can find here. I came across one about removing the back (http://www.talkbass.com/forum/f3/removal-back-159596/), and there were several concerns mentioned:

1. The back tends to be glued on more strongly than the top, as it is assumed the top is the standard portal for interior work and will thus be glued on less strongly for removal eventually.
2. There is the issue of damaging the button
3. There is the issue of maintaining the neck alignment

Also there is a cut in the back where it bends (the knee) (see attached figure), that, to my inexperienced (but engineering-oriented) eye looks like a perfect opportunity to tear apart upon removal.

In sum: I'm somewhat afraid to remove the top. I'm really afraid to remove the back!

Thomas, thanks for mentioning the mechanism as to why the back has arched in the first place. I was wondering all day if it was a chicken-and-egg situation: did the braces pop off, resulting in the back warping, or did the back warping cause the braces to pop. It sounds like it is the latter.

Thus a question: Does the back _have_ to be straightened? Would I be able to remove the top, remove the braces, and place an arch in the braces that follows the contour of the back (think a crude bass bar repair), then reglue with fresh hide glue and finally plane the braces down to a more reasonable 3/4" thickness or so (this will also help with the braces not fighting changes in curvature of the back). Is this reasonable? Just a thought.

I also don't mind trying to straighten the back (with the top removed) using a sandbag (great idea!) or similar, possibly with some mild heat and moisture. Again, if I have to let the bass sit for a couple of weeks for this to happen, I don't mind, as I have a spare.

One other slight nod to the top (vs. back) removal: there is already a slight gap in the top just screaming for a palatte or butter knife!

On the other hand, I didn’t plan to remove the neck if I pull the top (or back). If I pull the top, the fingerboard will be in the way to some degree, but I think I can live with this.

I like the dowel alignment trick, by the way, on the top or back. That seems to make a lot of sense, and, again, this is no heirloom instrument, so I am not worried about preserving the unblemished character of the thing.

Matthew, Incidentally, I have watched your top removal video carefully several times. Seeing you do this successfully was part of the reason for even considering Option #3 (top removal) in the first place.

Thomas, regarding humidity issues, thanks for the thoughts. I’ve given that some thought. The bass will be worked on in my basement in the Northeast (= high humidity, especially heading into spring/summer), but I can readily construct a plastic tent (think Dexter’s kill room, if you watch the show), and run a dehumidifier to drop the humidity to 35-40%. I can also control temperature, e.g., increasing it to 85-90 degF for the re-glue with hide glue.

Matthew, regarding heat and weight, I have a 1000W dual floodlight that should make short work of heating the back as needed. Also, as far as I can tell, the neck appears to be well-centered between the f-holes.

Michael, I agree with you completely that this is a job for a pro, and is probably beyond my skill set. I would, without hesitation, take that route, but unfortunately the cost of the repair will easily exceed the value of the instrument, and there is the longer-term issue that other problems are likely to arise. I am thus faced with trying to sell this instrument as defective at pennies on the dollar for what I paid for it, and get another, or try to repair it. I guess in the final analysis I see this as an experiment, or tuition. I admire you people who repair and build these instruments immensely, and I appreciate the craftsmanship and skill that you have honed over decades. If nothing else than to get a better appreciation for your craft, I figured I would take a stab at this myself (and the generosity of knowledge and advice that folks of this forum have displayed over the years has factored strongly into that decision). Also, frankly, as an engineer and as someone who has not hesitated in the least to tear something apart to fix it since being a wee lass, the temptation to take a whack at repairing it is almost overwhelming. Thanks for the candid advice. I know this is not going to be easy.

I'm not in any particular hurry on the repair, in that I have a spare bass that I can use for as long as needed.

In sum:

• I need to decide on whether to remove the top or the back.
• I have a preference for the top.
• This is uncharted territory for me.

Thanks again to each of you for the feedback. I'm mentally starting to prepare for major surgery for this bass. If successful, this will be a big achievement for me.

Thoughts welcome on the above. Once I decide which to remove (top vs. back) I'll put a plan of action together on how to proceed and present that to the thread for feedback.

Unfortunately it looks like Oberlin is out for me this year, given prior scheduling commitments. I’ll have to fly solo (well, think of it as flying with instruments with this forum). Worst case, I’ll bring the thing in a box to the workshop next year!

Again, a final note of thanks. I still am amazed at how generous people are with their time on this forum. It’s a wonderful thing. I appreciate all of your comments and help, and look forward to getting into this repair.(I suppose it goes without saying that I'll be relying heavily on the fourm for help with this. Kind of like that group-therapy thing where you close your eyes while standing up and then fall backwards while others catch you before you smack the floor...)

Thanks again,

-Jon

 

[gandalf1]

Michael,

I didn't catch the picture you attached before my earlier post.

That's very cool what you have done with the bracing!

-Jon

 

[basswraith]

Gandalf
Thanks.
If you are going to do this ...take off the back so your clamps will get to the right areas. Also the back is less likely to split as your taking it off. The top is.
... but I wouldn't do it
MH

 

[Matthew Tucker]

Tops may be glued on less strongly than backs only if they are done with hide glue. If not, it's anyone's guess. The top removal in my old video only works like that with dilute hide glue. With other glue it can be harder. But if there's a chink in the armour and you can get a knife in already ... there's a clue where to start, I reckon. Leave the neck/fingerboard intact and work around it. You WILL need to repair some edging when you have got the top/back off. It is easier to repair the spruce than the maple (It IS a carved bass, right?) but the spruce is more likely to split than the maple (What he said ^) Choices, choices. Aaaaarhh.

Personally, I wouldn't dowel all the corner blocks, even if you get them lined up you'll still have to massage the ribs into position and then you'll need to fill and touch up the dowel holes, they'll be visible. Perhaps just the tail and neck block under the FB/tailpiece? Or, you can always PIN them with a nail hammered half way, then remove nails and re-insert for positioning later. Then REMOVE the pins when all glued! A small nail hole is much less hard to fill and touch up.

Careful with heat. The back is glued up the centre seam (it IS a carved bass, right??) and you really don't want to have that start to come undone.

And ... just another way of looking at "the cost of the repair will easily exceed the value of the instrument". I hear that often. But what IS the value of the instrument in it's current condition? You say it's "practically unplayable". Therefore, I'd say its value is close to zip. So if if costs you, say, $1000 on a repair, you'll end up with a bass that cost you $1000. What's the bass actually worth when playable? might be a good deal.

 

[gandalf1]

Thanks Matthew,

Yes, it is definitely carved: top is two pieces of wood joined at the center; back is three pieces joined: a center strip just over 12" wide, and two wings, 7" wide each.

Yes, choices, choices. It seems the consensus is now shifting to removing the back.

Yes, it does appear that the instrument was assembled with white glue.

Your economic arguments are certainly sound. But I seem to be struggling with "death by a thousand cuts". I had a new fingerboard and bridge put on a few years ago that wasn't cheap, and I am under the impression that this repair, done by a pro, would come in closer to $2,000+. At that price point, I think I would rather go the extra mile and get a better bass. Also, from what I gather these instruments seem to be plagued with long-term issues (white glue, unseasoned wood, stiff and overbuilt, yielding less than ideal sound) that makes it more difficult to justify investing in them long term.

I've never been crazy about the sound of the bass itself, which has always been on the thin side, given, I presume, to a rather thick top and Sherman-tank bracing on the back. On the other hand (and probably for the same reasons), it sounds pretty good amplified, which is virtually all of my playing (jazz/folk). People seem to like my sound, and I am reluctant to break that.

Another (very) longer-term vision---and this is the engineer in me speaking---is to eventually do measurements and acoustical tuning of the instrument (resonant modes, mode matching, Chladni patterns, even numerical simulations) of the instrument to make it sound better. Modifications I had in mind would include top regraduation, bracing alteration, even making a new top, if needed. This is a very long-term vision, but the first step begins with the confidence to make changes to the instrument itself...something I haven't been able to bring myself to do to this point. In this regard I am at a cross-roads.

And thus player/owner has his own complicated choices to make, above and beyond the repair at hand.

As you say, choices, choices, arggghhh. Nothing is easy.

Looks like removing the back is slightly ahead as the favored approach.

-Jon

 

[basswraith]

Keep it simple.

 

[Steve Swan]

I'd sell it to a bass repairman, who can work on it in his spare time and use it for a rental. For your climate, you're probably better off starting over with something that isn't a flatback.

 

[360guy]

I vote for the diagonal bracing. I've done it with good results. The propellor will help keep the back flat.

As far as cost v. value, remember to factor in your learning. That will probably be priceless.

Also, I'd advise planning it one bite at a time. This is a long project.

 

[uprightben]

The picture you posted of the back seam at the knee looks like the seam might be loose, the varnish is definitely cracked like the seam is open. That might help you decide to remove the back.