Collapsed top on a bowl-back

[Matt the Mead Maker]

I picked up an Oliver-Ditson (Vega?) bowl back mandolin with a collapsed top. From doing a little research, it seems that this problem is not uncommon with these old/cheap mandos and I was wondering if anyone here knew the cause.

It only cost me about $30 and I'm going to use it for a learning project. Were the tops just made too thin or is their bracing insufficient or was it something else? I don't want to re-create the problem when I put the new top on. Thanks for your help!

[Jim Garber]

The bridge (not original) is way too high. Probably one of the braces is loose and the strings are way too heavy. You need to first humidify the whole thing enough to work on the top. Patience... above all. Anything is possible. There are folks here who have dealt with this.

Actually Ditsons are pretty nice -- I think some were built by Vega and it might be worth restoring.

[Matt the Mead Maker]

Thanks, Jim. I agree that some of the Ditson mandolins are really beautiful and this one has its charms as well but I think it's a lower-end/student model. This one just doesn't have as much of the fine detailing that I've seen on some of the other Ditsons. Here are a few more pictures:

[Bill Snyder]

Matt have you considered trying to fix that top instead of replacing it?

[Matt the Mead Maker]

No I hadn't, Bill. I didn't even know that was possible. Do you have any links or advice for words to search on if it's already been covered here? This project is still a few months out and I'm just trying to gather information. All suggestions are appreciated!

[Bill Snyder]

Matt, maybe this link from frets.com will help.

[Martin Jonas]

Or maybe this link, describing Jon Springall's restoration of Jim Garber's Embergher. That one also had a partially-sunken top, caused by a loose brace, and Jon managed to repair it without taking the top off. Not an easy repair, though, and the risk is if you don't rehumidify and coax the top back into shape very slowly (over a period of many days), you're likely to crack it.

Martin

[Jim Garber]

I read your OP too quickly. I didn't see the mention of replacing the top. I was also referring to actually fixing the existing top. Jon did fix mine and it is fine now. I also had Jim DeCava fix a few other bowlbacks with warped tops.

Yours does look like a brace problem. I have a Washburn with a top that flattened over time the same way. As Martin and Bill have mentioned the key here is patience. Humidify (and monitor) over a period of days or weeks before even attempting to deal with the top. The key is also finding the right clamps to get into a small area.

[Matt the Mead Maker]

Thanks a lot for the great info, guys! #I'd much rather fix the existing top than replace it. #After I'm done building my F5, I'll start collecting or building the proper tools for fixing the Ditson. #Looks like that will have to include some kind of humidifying box. #If there's one thing I've got a lot of, it's patience and it looks like that'll come in handy with this project.

[Jake Wildwood]

I concur with the others' observations... you can fix that by humidifying it, cleaning up the underside, checking to see if the brace is broken or just loose, and then gluing the brace back together (or a new one in place) aided with a nice flat surface clamped to the top...

It's tricky with a small soundhole, though, and much easier on guitars... but a calm mind (that swears while NOT holding the instrument) will prevail!

[Jim Garber]

Or maybe this link, describing Jon Springall's restoration of Jim Garber's Embergher.

Hey Martin:
I didn't even know that page existed. Thanks for the link!

[Jim Garber]

Looks like that will have to include some kind of humidifying box.

I think most luthiers use that all-handy plastic bag for that purpose, tho I would like to hear if anyone has another method.

[Matt the Mead Maker]

Good call, Jim. It would be hard to improve on a plastic bag for sealing in the moisture. I guess I was imagining some box-type container with a humidifier on one end but that's probably overkill. Does anyone have a simpler way to humidify the mandolin?

[Loudloar]

I have a 1900 Martin bowlback with the exact same problem. #I believe these instruments are intended for light strings, and medium gauge can cause the top to sink. I loosened the strings and figured I'd repair it someday. Now a couple years later I looked at it and the top came up by itself. I still need to do a few things to it. I'll check the braces to be sure they're glued down, maybe add another light brace directly under the bridge. I know the bottom of the bridge needs to be flattened, it curved as the top sank.

To flatten your top you might try a technique I used to successfully repair a violin with a sunken top. (Learned this from a local violin luthier.) Make one or more small sandbags that will fit through the soundhole. Heat them in the oven until hot (maybe a couple hundred degrees F, not enough to scorch the wood). Dampen the underside of the top slightly with a wet cloth, insert the sandbags and clamp the top gently to flatten it out. Just don't force it too far. Leave it to cool for a while, preferrably overnight. It may take several sessions. Dampening the top is optional, you may try it dry first. But it didn't seem to work for me without a little moisture. It's a lot like bending sides, no?

For sure, you shouldn't replace the top. This is totally fixable.

Steve

[John Bertotti]

Grab a inspection mirror and look inside. Funny but in the pick the brace looks pretty straight. I can't help but wonder if the ends of the brace aren't loose. Get them strings off asap and toss that bridge.
I have a unadorned Vega and it is a fine sounding instrument. I would not even consider replacing the top till all repairs avenues were exhausted. Keep us posted on your progress. Search for some of the bowl back string threads, a lot of good recommendations on strings in them.

[BlueMountain]

Yes, I'd guess that almost certainly, the second brace is loose on both sides. The amazing thing is that it doesn't seem to have split the top yet, and the top seems to pop back into place. It's a relatively easy repair, compared to some, and you may not need to humidify it. But get those strings off of there.

I love that tool Frank Ford made, and I wish I could make one like it, but I'm not sure it would work on a bowlback. May be too deep. What might be easier is to cut a little arch with maybe an inch of rise out of a piece of wood, the length being the same as the width of the top, and attach it on each end to a couple wood stringers a couple inches long to spread out the support. Then humidify, then use a clamp between a brace or caul underneath the top to the top of this arch. This would PULL the top up into shape, rather than PUSHING it up from the bottom, and it would be just as easy to raise it a little at a time.

[Matt the Mead Maker]

To flatten your top you might try a technique I used to successfully repair a violin with a sunken top. (Learned this from a local violin luthier.) Make one or more small sandbags that will fit through the soundhole. Heat them in the oven until hot (maybe a couple hundred degrees F, not enough to scorch the wood). Dampen the underside of the top slightly with a wet cloth, insert the sandbags and clamp the top gently to flatten it out. Just don't force it too far. Leave it to cool for a while, preferrably overnight. It may take several sessions. Dampening the top is optional, you may try it dry first. But it didn't seem to work for me without a little moisture. It's a lot like bending sides, no?

Steve - that sounds like a really simple and do-able approach. #I'll definitely give it a shot!

Also, I was able to gently reach in there and feel the tone bar under the bridge. It's a little loose. I guess I'll deal with that after I get the top flatten out again.

Thanks to everyone for the great tips on repair as well as proper string thickness and bridge height!

[MandoHog]

Hey. I have a non-bowl back that has a sunken top problem too. I have been reading that many times a fix to an old top will kill the tone. I know every case is different, but has anyone found out the hard way about the tone of a mando with a repaired top?

[Rick Cadger]

Or maybe this link, describing Jon Springall's restoration of Jim Garber's Embergher.

Hey Martin:
I didn't even know that page existed. Thanks for the link!

The store referred to on that web page is about 5 miles from my house! I bought a fiddle mute there the weekend before last.

Wow. I never knew they could work on mandolins.

[Martin Jonas]

Wow. I never knew they could work on mandolins.

Well, they can since Jon Springall took over as their head of workshop a couple of years ago. Jon is an ardent mandolin fanatic, as well as an all-round nice guy, and he's a Cafe member, too (username "onthefiddle"). Check out his private homepage, where he has some nice photos of repairs to a Vinaccia bowlback (mine, as it happens) and scans of some mandolin arrangements of Chopin pieces.

Martin

[Rick Cadger]

Wow. I never knew they could work on mandolins.

Well, they can since Jon Springall took over as their head of workshop a couple of years ago. Jon is an ardent mandolin fanatic, as well as an all-round nice guy, and he's a Cafe member, too (username "onthefiddle"). Check out his private homepage, where he has some nice photos of repairs to a Vinaccia bowlback (mine, as it happens) and scans of some mandolin arrangements of Chopin pieces.

Martin

Excellent. Thanks for the info and the link.

[John Cadd]

I like to use a steamer to release hot hide glue .The steamer is designed to remove creases in clothes and general cleaning jobs.There are insulated extensions but the shortest fittings are best as the steam is superheated and dry. Extensions allow the steam to cool down too quick . The moisture only happens when dry steam cools down . If you were levering off a guitar bridge with a spatula just observe where the spatula edge meets the tiny gap between bridge and top .That gap is massive for a steam jet.Apply the dry steam jet right there and the glue gets blown away and softens the next inch. Very gentle spatula movement and steam will release the joint with no wood splinters at all . Then let it all dry out . Some moisture will be left but the dry steam will always work .
If the top is removed you can release braces more slowly with rolled up paper tissue up close to the join and taped in position.Then wet the tissue. Cover it with polythene and leave overnight .Water will find a way to soften the glue. Boiling water and a small artist brush will leave a clean flat surface .Dab away any water drops straight away .
Learn how all this works by using scraps of wood and glue to test your skill ,before hurting a nice instrument .

[Tavy]

I like to use a steamer to release hot hide glue .The steamer is designed to remove creases in clothes and general cleaning jobs.There are insulated extensions but the shortest fittings are best as the steam is superheated and dry. Extensions allow the steam to cool down too quick . The moisture only happens when dry steam cools down . If you were levering off a guitar bridge with a spatula just observe where the spatula edge meets the tiny gap between bridge and top .That gap is massive for a steam jet.Apply the dry steam jet right there and the glue gets blown away and softens the next inch. Very gentle spatula movement and steam will release the joint with no wood splinters at all . Then let it all dry out . Some moisture will be left but the dry steam will always work .
If the top is removed you can release braces more slowly with rolled up paper tissue up close to the join and taped in position.Then wet the tissue. Cover it with polythene and leave overnight .Water will find a way to soften the glue. Boiling water and a small artist brush will leave a clean flat surface .Dab away any water drops straight away .
Learn how all this works by using scraps of wood and glue to test your skill ,before hurting a nice instrument .

All good advice, but this is a 6 year old thread

[Charles E.]

A 16 year old thread.

[BillWilliams]

All good advice, but this is a 16 year old thread

I for one am grateful for the thread being reactivated as it pointed me to the work by Jon Springall on Martin Jonas's Vinaccia and the Chopin pieces.