Thinning out thick tops

[johnM]

I recently aquired a decent F mandolin from a small builder at a very good price but it has a very thick top. It sounds ok and plays good but it wouldn't ever hold up in a jam with a couple other instruments. It's got a couple other problems that make it almost worthless to the average player but to me its got some emotional attachment. So i'm thinking of thinning the top a little, which i'm certain will help its "pop".

I've heard you have to pull the back off these to re-carve them from the inside but I really don't want to go there. Has anyone had any experiance regraduating thick tops from the outside of the instrument?

Here's my idea. I remove the tailpiece, bridge and measure the radius of the top. Then I could thin the top with a hand sander to a predetermined thickness(with your help). I would then give it a coat of black stain and varnish.

For all the people that think i'm crazy, I do a fair amount of wookwork, furniture building for a hobby/neccessity and have access to a ton of tools and equipment.

I have other mandolins but that doesn't mean I want to destroy this one so any help will greatly be appreciated.

Thanks

[Chadmills]

How thick is "very thick"?
Tom

[johnM]

Its 1/4 - 5/16 at the F holes. Its not in front of me but it noticably thicker than my other instruments.

[ftlstrings]

can you reduce the top thickness without needing a significantly higher bridge to maintain a playable action on the instrument?

~M~

[Jim Rowland]

Thicker than I make them. Thinning a closed carved mando box is certainly possible,but can be very tricky. It sounds as if you could safely lose a sixteenth of an inch at the F holes,but without a Hacklinger gauge you will have to guess how much to take off (or how much you have taken off) the other surfaces. It's a lot of trouble,but the only semi-safe way is to carve or sand a little,string up and try,sand or carve a little..etc. Even then you will not know for sure if you have reached optimum thickness,or if it will hold over time under pressure. An alternative is to leave it strung up and remove small amounts of wood from the outside in, strumming and listening. Nothing guaranteed in any of this advice.
Jim

[markishandsome]

A power sander seems a little heavy-handed for something like this, especially since without popping the back off you'll have no idea how far to go. If you did remove the back you'd need to remove the tone bars to remove that much wood. You could thin the center from the outside and the recurve area from the inside i guess. At some point you'd be better off making a whole new top, or just reserving this one for quiet evenings at home and bringing one of your other mandolins to a jam.

[grandmainger]

If volume is what you're looking for, frets.com's super light bridge for increased volume? There might be a few quick fixes to try before going at it with the sandpaper!
Germain

[Dale Ludewig]

If it's that thick at the F holes, that's really thick. If the rest of the top is comparable, you've got a lot of mass to move with the strings. On the other hand, it is a lot (capital L) of work to remove the back and do this. You'll have to judge how much it's worth to you to do this. A Hacklinger would be good, but they cost almost $400 before you even start the work. And you may well wind up having to refinish at least part if not all of the instrument. I'd think a lot before I jumped into this project. JMHO.

[johnM]

Thanks that's a lot of information.

I have not started "yet" but I agree there's a lot of mass to move and I would never attempt to remove the back by myself. So If I were to attempt this it sounds like the only way to get the thickness anywhere near close with the instrument in tact is with a Hacklinger gauge sanding the top, correct?

I also think that the power sander is needed to get started, then I would definitly finish by hand sanding but I'm very concerned about taking too much off. Grow, I think your advise to take a little off the outer edges while its strung up would work also.


Its not just volume i'm looking for, I just know that this thing is being held back by the copious amounts of wood on the top.

If I were to attempt this and succeed, what would you'all suggest for a black face finish and a light coat of varnish.

Thanks in advance.

jm

[David Newton]

If I were the builder of this, I would want you to call me about it. Give him the courtesy, at least.

[Antlurz]

Without knowing if the builder followed normal practice on shaping the inside profile, you might be lighting your candle with a blowtorch. In fact, if the top is as thick as you relate, I wouldn't assume anything about the inside profile.

Ron

[buddyellis]

Sounds like a good learning project, personally. I'd pop the back so you can get a caliper on it. Yes thats alot of work. But it is a great change to learn, especially if the instrument isn't that valuable.

[g_mc]

In the thread on thickness calipers, I believe there's a design that allows you to go through the f-holes and get a measurement. Fairly simple and inexpensive to build. You might take a look and see if it would be of any help to you.

[PaulD]

Not that I have any idea what I'm talking about, but in following this thread I was thinking "remove the back" while I kept my mouth shut and read what the experts have to say. It would be a Lot of work, as Dale pointed out, but it sounds like a lot of work to sand/scrape the top while blending all the details, refinishing, then possibly remaking the bridge. Assuming you like the top profile the way it is, it seems like it's worth consideration. Obviously it means rebracing, but as Buddy stated you could use a caliper and know exactly where you're going with the graduations.

If the builder is continuing to build it might be good to include him or her in the process if possible. Maybe the builder knows of the problem... we don't know that... but I figure it may be why you say you got a good price on it.

That's probably not worth 2 cents! Let us know how it goes!

pd

[buddyellis]

To me, it really depends on the value of the instrument. If we are talking about a Kentucky or something like that, It'd be fair game AFAIC, and at my current skill level. I personally would feel confident in playing with something like this, as often the best way to learn is on an inexpensive or unimportant instrument, and to 'just jump in'. But that's me.

The type of finish is going to determine how hard it is to clean up after getting the back back on. If it's poly you are probably looking at a full refin to get it 'right'. If not, you can probably touch up the back and sides depending on how bad your back removal goes. Is this instrument bound on the back? That adds to your problems, though not hugely IMO.

An instrument with a poly finish is going to be MUCH harder IMO to clean up than something that is varnished or Nitro. If you like the top outside profile, it's best to remove material from the outside, as you save the finish. If it's poly you might wanna wack the whole thing anyway, so it might not matter.

As an aside, of the top is thick, the back may be too, so you can regrad that while you have it apart.

P.S. when I say 'varnished' I mean 'spirit varnish' Oil varnish is a bit more touchy.

[Dale Ludewig]

Paul, please! Those aren't braces. They're tone bars and do nothing as far as reinforcing the top goes.

[Bill Snyder]

...#Is this instrument bound on the back? # That adds to your problems, though not hugely IMO.

I would think most luthiers would rather deal with a bound back. If you do a neat job of removing the binding first you have less finish damage to deal with. You just have to rebind after regluing the back.
FWIW I would not suggest you attempt recarving without being able to measure the thickness at several points on your mandolin before you start and as you go. That is unless you won't be too upset with it imploding at some point.

[PaulD]

Paul, please! Those aren't braces. They're tone bars and do nothing as far as reinforcing the top goes.

I stand corrected, Dale! I should have said he would have to re-tone-bar the top if he regraduated from the inside! Actually... after rereading my post, I should have stuck with my original instinct and avoided the temptation to post. I'm not sure it was even worth 1 cent, but that's the second time today I gone against my gut when I shouldn't have!

pd

[Bill Snyder]

Don't feel bad about your post Paul, I am no expert (far from it, and I try to make that clear from time to time) but I still speak (type) up from time to time.

[david blair]

I just finished remodeling a friends Gibson flat top guitar. Using metal scrapers I shaved off a LOT of lacquer. It was thick. After removing all that gook I applied a thin coat of hide glue mixed with stain to seal and level anything bare. I also removed the plastic bridge (which was bolted on), glued on a new rosewood Martin style and made a bone nut and saddle. It's a much different guitar now, and the finish has a super smooth vintage feel.
Without looking at yours my first thought is to shave off all the unneccesary lacquer, and perhaps thin out the recurve area on the top and back before taking anything from the arch. If you remove to much there you may end up with a neck angle issue. A lot of volume could be gained from a well fitted ebony bridge, saddle and heavy gauge strings. Removing wood from the recurve area can add bass. #
Good luck!

[Adam Tracksler]

it sounds to me that you like the mandolin, i would suggest sending it to a luthier to have the work done. Another suggestion is to send it to Steve Perry at Gianna Violins (NFI, and no personal experience, but people seem to have gotten good results from it) and have some mandovoodoo done to it. -- actually, if it were mine, i'd get it mandovoodo-ed

--ad

[Stephen Perry]

I'd just get another mandolin. Seems a great deal of trouble from the outside. I may be influenced by the violin world, where we attempt to preserve original varnish. Wouldn't one lose control of the recurve, and isn't that critical?

From inside seems more reasonable. We do this all the time on violins.

Sanding also seems an odd approach from my perspective. I use gouges, planes, and scrapers. They seem rather fast when sharp. Again, that's a view from the violin side of the world.

Still, popping off the back doesn't look too hard. Then one could examine the graduations in detail. Perhaps the back is very thick, too.

[Hans]

An instrument that's 1/4" thick at the ff holes is so far off that sanding from the outside would really change the arching of the plate. Removing the back, carving off the tone bars and re-graduating from the inside is the only way to do this right. Don't know if that's worth it.

[Mario Proulx]

Is it truly 1/4" at the F holes? If it really is, I'd question the rest of the instrument, also. If the maker more than doubled the thickness of the top as is implied here, he/she didn't study well, and everything else is questionable at this point, also. Perhaps it's a StewMac or other's kit that was simply slapped together at the supplied thickness, which leaves a lot of wood for the maker to do the final graduations.

This could be a mess. What's the finish? Is the back bound? Does the top's arching look 'right'? What of the back; Spruce is many times easier to carve than Maple, so I hate to think of how thick he/she left the back....

input; need more input.

[EdSherry]

Personally, I would think it would be less work to take off the back and work from the back than trying to regraduate from the outside, which would require you to refinish the top when done. #By working from the back, you avoid the need to refinish the instrument.