How to flatten a badly warped mandolin top?

[Frank Capo]

My friend rescued an old STETSON bowlback mandolin from the trash. It is nicer than most garden variety bowlbacks - some nice fretboard inlay and bindings/rose, nice tuners and buttons, rosewood back.
Its an angled top - has the seam that "folds". The top however is badly warped - especially the top right quadrant. I removed the top quite cleanly with a hot knife. Is it possible to soften, flatten and reform the top? What do you suggest? And if it can be reformed, will it hold its form? Thanks

[Ronnie Nichols]

Those old "taterbug" mandolins are usually not worth a lot nor do they produce the sound most of today's mandolin players prefer. If you want to hone your repair skills, this may be a good instrument to do it on. I just wouldn't expect it to be a profitable venture. You've heard the old saying about putting a $100.00 saddle on a $50.00 horse. I've been guilty of doing extensive work on cheap instruments myself. It may be possible to reform the shape of this top. I'd suggest using heat or steam. You could make some kind of jig to hold it until it dries. As far as it holding its form, that is a good question. It may need some reinforcement on the underside to encourage it to stay in place. I think wood has a memory and it always seems to gravitate toward where it has been for a while. I hope your project goes well.
Ronnie Nichols

[Bob Webster]

Given that you're 99% guaranteed to have to refinish the top, and to echo Ronnie's input, I'd also recommend heat AND steam. If there are no braces in the way (or that can't be temporarily removed), I'd reach for the steam iron in a heartbeat. Create a set up that will allow you to clamp the top after treatment with a heated caul of some sort and then steam the back side of the top using the iron at lowest steam setting. You can expect that the top will swell locally and attempt to form some sort of tubular structure but that should abate after the top has been allowed to cool and dry during clamp-up. Best of luck.

Best regards,
Bob

[Frank Capo]

Thanks. Not a money making deal just feel its to nice to put back in the trash and will give me some additional repair experience. The braces are off and since I removed the top it already started flattening somewhat by itself. But yes it will need steam and pressure, and the iron is a good suggestion. I just dont know how well the wooden multicolored soundhole "rose" and edge "purfling?" will hold up. Also not sure how well the fancy celluloid batwing-shaped inlay/overlay will hold up though its pretty flat under the soundhole...

[Bob Webster]

Yowee. Forgot about all those other doodads on the old bowlbacks. The soundhole stuff will probably survive with a little post-treatment CA. The celluloid overlay will probably have to be removed beforehand, though. Here's where alot of us jump back and yell "FFRRRAAANNKKK!". Can't imagine he doesn't have something at frets.com that would cover this.

Bob

[Frank Capo]

Well, its nice an flat now with no distortion. the rose and purfling etc conformed well. I simply wet it and set it between two 12x12 ceramic floor tiles. First without clamping and then clamped tight as it relaxed. Its now drying between the tiles. The test will be if it will stay flat after I get the braces back on. the braces seem to have a slightly convex form. Not sure if they were originally cut that way... In any event that may help to counter to bowing and keep it flat.

[Jim Bancroft]

If the original bracing is flat sawn I'd probably replace it with 1/4 sawn bracing of the same size and dimensions as the original. You might beef up the bracing, slightly, if you feel that would stabalize things better.

Jim

[Len Biglin]

Hi brothers , in my limited experience on bowl-backs , they do have a slight dome on the braces , each end of a brace will pop away from the deck sometimes .The main reason I'm here though is to ask if anyone knows how they make these things ? how do they coop the back ? The neck joint? And then you get the ornamental ones that use pine for the neck but cover it in R/W veneer ! Oh and dont forget the inside lined with paper ! Does anyone GET this ?

[Frank Capo]

Thanks for the additional advice. I reglued and significantly straightened the top. I put it down for the holidays but now am
reevaluating the top to see if I can improve it further before proceeding to reattach the top. The bowl itself is a masterpiece of craftsmanship - it seems that it would take an extraordinary sum of labor to assemble one from scratch - sadly with a nominal payback in terms of value.

[Ned Knepp]

My brother and I though about building a bowl back mandolin several years ago. Actually HE thought about it, I took a look and delegated myself as the "assistant". The best sources of material we found were related to lute building and repair.

From what I learned the best way to support the bowl as you build is to create an mold then fit the pieces around that. I've seen some pictures of them made of very carefully shaped wood but the one that looked the easiest, at least for a "one-off", was shaped foam. You really have to be precise about the shaping and joining of the segments or the whole thing will go south quickly. In the end, my brother chickened out and decided that carving a mandolin was easier and would probably sound better to boot. ( That turned out to be something that even I could do.)

Right now, I'm happy to get tight joints between the straight edges of two or three pieces of wood. The prospects of lots of pieces of wood, that curve and twist to boot is too daunting for me.

Ned