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Cello Repair
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10137&t=51992		 Page 1 of 3
Author:  LuthGate [ Thu May 30, 2019 4:03 pm ]
Post subject:  Cello Repair
Hello all! I am trying to repair a Cello that is around 18 years old but never used. It is possible the Cello was dropped on the foot. It was inspected by a professional and he noted some issues which I am trying to address. The main issue is the foot sits at an angle. I took the top off the Cello and it appears that the piece of wood that holds the foot has broken. I am gluing this back together (see below). Once the glue is dry, I was going to laminate a piece of plywood over the entire foot block. The main issue why it was crooked was the hide glue in that part of the Cello had separated. When it goes back, I think it will line up correctly again. I have never worked on any instruments but I am a general woodworker. My other though was to add a "truss rod" of sorts from one side of the Cello to the other in order to maintain integrity of the foot piece. I have put images below if any one can offer advice I would appreciate it!
Author:  Chris Pile [ Thu May 30, 2019 5:39 pm ]
Post subject:  Re: Cello Repair
That's called a tail block. No - a "truss rod" is a horrible idea.

Why didn't the "professional" handle the repair?
Author:  LuthGate [ Thu May 30, 2019 5:53 pm ]
Post subject:  Re: Cello Repair
She was a Cello professional, not a luthier. I was selling this and she came out to look at it. She pointed out the problems and indicated the Cello sounded very good and thought it would be worthwhile to get it fixed. The Cello new was around $1000.

Thanks for the info. What do you suggest? That part of the Cello around the tail block is slightly warped in. I think the Cello was damaged and then sat damaged for 10 years and developed a "memory" (warp) in this area. Since my glue-up it is much better and I could just glue the top back on and it would be "nearly" straight. I could do the truss rod thing but I am guessing this is not a good idea due to diminished sound quality?
Author:  Chris Pile [ Thu May 30, 2019 11:33 pm ]
Post subject:  Re: Cello Repair
Just put the top back on it and be done with it.
THEN - never do repairs again, okay?
Author:  B. Howard [ Fri May 31, 2019 4:25 am ]
Post subject:  Re: Cello Repair
So normally we would pull the back to make extensive repairs inside the box, never the top.

It was worth $1000, but you'll be lucky to get $100 based on how brutally the top was torn off of it
Author:  LuthGate [ Fri May 31, 2019 6:06 am ]
Post subject:  Re: Cello Repair
B. Howard wrote:
So normally we would pull the back to make extensive repairs inside the box, never the top.

It was worth $1000, but you'll be lucky to get $100 based on how brutally the top was torn off of it


Well that makes a lot of sense now that you mention it. All the videos and repair sites I saw all showed taking off the top but it does make more sense to remove the bottom. Anyway the only thing I have done so far is put a few drops of glue in the tailblock and clamp it back to its original form. I've also cleaned up the top edges so they are about ready to receive the top. I have hide glue on order it should be here today. I had planned on getting some threaded bar stock and make a bunch of clamps for the top. Someone else told me I could probably wrap the top on with rubber tubing instead of clamps. Does that work ok?

Also today's cost for this model is $1000. I paid much less and had it listed for $350. What you are seeing in those pics is 95% hide glue. The top separated rather easily when I ran my knife around the edges. The original assembly appears to have been very sloppy.
Author:  LuthGate [ Fri May 31, 2019 6:10 am ]
Post subject:  Re: Cello Repair
Actually I take that back. The ribs had separated from the top, not the bottom. I had to remove the top to fix the damage.
Author:  LuthGate [ Fri May 31, 2019 6:57 am ]
Post subject:  Re: Cello Repair
My glue-up seems to have done a lot for straightening out the foot post. I think I will not need to shore up the block with a truss rod. I just glued the lamination piece to the tail block.

You can see before and after pics of the rod and also my lamination piece of plywood below.
Author:  Barry Daniels [ Fri May 31, 2019 8:59 am ]
Post subject:  Re: Cello Repair
It looks like the end block was split. I would glue a cross grain reinforcement block over the end block. Obviously, the block will need a hole in it for the end pin to pass through. This block will also help to align and stabilize the end pin.

I would also glue in some triangular blocks on each side of the end block to get a little more grip on the sides. These minor repairs would strengthen the area and take nothing away from tone.
Author:  LuthGate [ Fri May 31, 2019 9:20 am ]
Post subject:  Re: Cello Repair
Barry Daniels wrote:
It looks like the end block was split. I would glue a cross grain reinforcement block over the end block. Obviously, the block will need a hole in it for the end pin to pass through. This block will also help to align and stabilize the end pin.

I would also glue in some triangular blocks on each side of the end block to get a little more grip on the sides. These minor repairs would strengthen the area and take nothing away from tone.


Thanks that is what I did this morning. I like the triangular block idea for reinforcement I will also do that.
Author:  Barry Daniels [ Fri May 31, 2019 9:33 am ]
Post subject:  Re: Cello Repair
Good call on the baltic birch ply reinforcement. It will not split. This is what I use for end blocks in my guitars.
Author:  Mark Mc [ Sat Jun 01, 2019 6:34 pm ]
Post subject:  Re: Cello Repair
So - that doesn’t look so bad after all! It looks like you have got the tail block fixed up OK. Go ahead and add the reinforcements on either side of the block, then you are ready to close it up. This is no small feat for a cello. I understand your choice of hide glue, as it is traditional. But the short working time with hide glue is going to be a real challenge for such a big glue job. I only make guitars - much smaller than a cello - and I can’t manage to glue a top or back on with hide glue within the available open time. I use hide glue for many parts of the guitar but Titebond for this job. If you want to use hot hide glue you will probably need to work in sections. I don’t know how the cello makers handle this issue, but I am sure there are some videos out there to help you.

How to clamp the top is another question. Spool clamps on threaded rod are fine. But boy are you going to need a lot of them! Here is a solution I have found, using sections of PVC pipe as a clamping tool. But I still think working in sections will be your answer.
http://www.anzlf.com/viewtopic.php?f=5&t=5758
Author:  profchris [ Sun Jun 02, 2019 5:55 am ]
Post subject:  Re: Cello Repair
I've glued up guitar back and tops with hot hide glue, working in sections. I paint the glue on around 1/8 of the rim, leave it a couple of minutes, paint on a second layer of glue and then clamp about 2/3 of that length. Once the clamps are on I heat the section gently until the wood is hand hot to the touch, tighten clamps, remove squeeze out. Leave 30 mins or so, then repeat (leaving the last clamp on the previously glued section to stop the heat opening it up). So I guess a dozen separate operations in all. It goes pretty easily.
Author:  profchris [ Sun Jun 02, 2019 5:56 am ]
Post subject:  Re: Cello Repair
Forgot to say I heat with a heat gun, which requires care not to scorch the wood. A hair dryer is slower but safer.
Author:  LuthGate [ Sun Jun 02, 2019 8:10 am ]
Post subject:  Re: Cello Repair
I was told to use surgical tubing to "wrap" the cello and apply enough pressure all around it. I hadn't thought of titebond. That is a great glue and what I usually use in woodworking but it is a permanent bond. There would be no way to ever remove the top again, which isn't necessarily bad. How long is the working time with hide glue? Would I have time to paint on all the way around the ribs, put on the top, clamp both ends and the center (where it counts most) and wrap it in surgical tubing? I would say it would take me @ 1 minutes to coat the top edges in hide glue. Then another 1-2 minutes to locate the top and put on the initial 6 clamps or so. Also I am not sure how messy hide glue is should I put painters tape around the ribs to catch squeeze out? I supposed I could glue in "reverse" and put the top down with the bottom of the top facing up, apply the glue around the edges or the top, then put the cello body on. That would avoid squeeze out mess on the cello. I'll have to think this through carefully before proceeding. I was actually under the impression that hide glue had a fairly long working time.
Author:  LuthGate [ Sun Jun 02, 2019 8:21 am ]
Post subject:  Re: Cello Repair
OK - So I just ready up on hide glue that applying on a cold surface could give well under a minute of working time. But heated up glue can have a near infinite working time. One suggestion I found was to heat up the room where the glue is being applied. I am wondering if I could put the cello in the miday sun here and let it heat up for 2-3 hours. We are currently getting around 90 during the day and I suspect with full sun, I could get the surface of the cello to 110 or so. Not sure if that will damage the cello I don't see why it would though. I do have a heat gun but the article I was looking at was talking about getting temps up near 140. I can't imagine that is good for an already finished cello.
Author:  Barry Daniels [ Sun Jun 02, 2019 8:39 am ]
Post subject:  Re: Cello Repair
Use fish glue. It has great open time.
Author:  Chris Pile [ Sun Jun 02, 2019 8:47 am ]
Post subject:  Re: Cello Repair
Quote:
I hadn't thought of titebond. That is a great glue and what I usually use in woodworking but it is a permanent bond. There would be no way to ever remove the top again, which isn't necessarily bad.


Titebond is NOT permanent. That is why it is used so much in instrument making. Titebond II is permanent. Please don't use that on this cello.
Author:  LuthGate [ Sun Jun 02, 2019 10:40 am ]
Post subject:  Re: Cello Repair
Chris Pile wrote:
Quote:
I hadn't thought of titebond. That is a great glue and what I usually use in woodworking but it is a permanent bond. There would be no way to ever remove the top again, which isn't necessarily bad.


Titebond is NOT permanent. That is why it is used so much in instrument making. Titebond II is permanent. Please don't use that on this cello.


I did not know this! I will get some titebond then and use that. Thanks!
Author:  Mark Mc [ Sun Jun 02, 2019 2:26 pm ]
Post subject:  Re: Cello Repair
Titebond Original (the red label) is heat reversible. It is the most popular glue used in luthiery, by far. Fish glue also has a following, but I have no personal experience. Wrapping as a form of clamping can be quite successful. You don’t need super-high pressure on this joint. Some people use string, jute, cotton cloth. The problem is that it covers the glue squeeze-out (and gets stuck to it). Long rubber bands (made from bicycle inner tubes) have the advantage of not adhering to the glue. But you will still have to deal with clean-up after it dries. Not good on your already finished wood, which you don’t want to be sanding. Whatever you do here, you will want to to some practice runs before actually putting the glue down.
Author:  Barry Daniels [ Sun Jun 02, 2019 3:48 pm ]
Post subject:  Re: Cello Repair
Titebond Original, fish glue, and HHG can all be easily removed from finished surfaces with a damp rag. Just takes a bit of time and gentle rubbing to dissolve the gubbers.
Author:  LuthGate [ Mon Jun 03, 2019 8:52 am ]
Post subject:  Re: Cello Repair
Can anyone tell me if I can put a bit of Varnish along the separation line between the top and the ribs once the glue is dry? Also a couple of nicks here and there I'd like to touch up while I am at it. I was going to touch it up so that it visually looks better. I am gluing up today with Titebond. I got a whole mess of clamps on sale so I will just clamp it all.
Author:  Barry Daniels [ Mon Jun 03, 2019 9:23 am ]
Post subject:  Re: Cello Repair
I don't see why not.
Author:  Dave Baley [ Mon Jun 03, 2019 12:17 pm ]
Post subject:  Re: Cello Repair
One of the difficult aspects of amateur instrument repair is the ethics of full disclosure.
If you intend to keep this cello to learn to play or put in the corner as a decoration, or if you plan to donate it to a local school music program, you probably don't have an issue.
If you plan to sell it, you really should tell any prospective buyers that it was a) broken and b) repaired by someone (yourself) who has no experience or knowledge about cello repair.
This may not be a problem with some buyers but given the number of cellos out in the world that have either never been broken or, if broken, were repaired by a professional, you may have a limited number of people willing to pay very much money for it.
My recommendation would be to find a local school that wants a cello, tell the instructor the history, and donate it to them so some student who may not be able to afford a cello can have a chance to learn to play one.

Dave
Author:  LuthGate [ Mon Jun 03, 2019 12:52 pm ]
Post subject:  Re: Cello Repair
Dave Baley wrote:
One of the difficult aspects of amateur instrument repair is the ethics of full disclosure.
If you intend to keep this cello to learn to play or put in the corner as a decoration, or if you plan to donate it to a local school music program, you probably don't have an issue.
If you plan to sell it, you really should tell any prospective buyers that it was a) broken and b) repaired by someone (yourself) who has no experience or knowledge about cello repair.
This may not be a problem with some buyers but given the number of cellos out in the world that have either never been broken or, if broken, were repaired by a professional, you may have a limited number of people willing to pay very much money for it.
My recommendation would be to find a local school that wants a cello, tell the instructor the history, and donate it to them so some student who may not be able to afford a cello can have a chance to learn to play one.

Dave


I completely agree with you and of course would disclose the Cello history. I have actually already prepared a tag that will be visible though the F hole as to the date and nature of the repair. In addition I plan on burning in my woodshop brand (inside). I have put @ $200 into the repair (new strings, new bow, etc) in addition to my own time for a Cello worth around $300. It is not for the money I assure you! I might keep this around awhile in case one of the kids wants to play it or might donate to our local high school. I hate to have an instrument sit around not being played they tend to degrade.
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