"temporary" brace glue?

tjp · #1 03-01-2012, 12:28 AM

I've been playing my first build for about a month and a half now, and it is settling in nicely, especially for slower, single note stuff. Really, really nice. Far better than I expected. It is possible to overdrive it though, for lack of a better word, with hard strumming. I suspect the back, since I braced it really lightly thinking it would be active. I'd like to reach in and put an extra back brace in the lower bout as an experiment to get a sense for things. I would also like to take that brace out if I don't like it, or to permanently glue it if I do...what kind of glue should I use? I don't want to heat it if I don't have to. If I just used a few drops of LMI, you think I could pop the brace off when I'm done?

Not worried about cosmetics in the box. This guitar isn't going anywhere.

gitnoob · #2 03-01-2012, 03:31 AM

I've had similar ideas -- I'd love to be able to tweak the voicing at will.

If I were you, I'd start by muting the back. Just wrap your body around the guitar -- it'll kill the back, especially at the lower frequencies.

If you still suspect the back after that, you might try tuning it by changing the mass rather than the stiffness. See this thread for ideas:
http://www.acousticguitarforum.com/f...d.php?t=241422

If you really want to stick a temporary brace in there, perhaps double-stick tape would work?

mb propsom · #3 03-01-2012, 10:22 AM

First of all, what is the topwood of your guitar? Some species, most notably WRC are generally great for fingerstyle but "break down" under a harder attack like strumming.

Mystic · #4 03-01-2012, 12:16 PM

put the temporary brace on the outside.

tjp · #5 03-01-2012, 01:04 PM

Some good suggestions and questions. It's a Sitka top, mahogany back 00. What got me thinking along these lines was some discussion I've read recently about active vs reflective backs. I know mine's active, I just want to see what happens if I lean it toward the reflective side.

gitnoob · #6 03-01-2012, 01:13 PM

I did an experiment once.

It was on a Silver Creek (which I torture quite a bit).

I thinned the back, expecting to make it more "active" and to drop the back resonance. I thinned it quite a bit. The resonance frequency didn't drop!

I'm still not sure why, but I suspect that the stiffness of the braces just overwhelmed the stiffness of the plate itself.

Those back braces are pretty stiff -- arched and tucked. I'm not sure you can replicate that stiffness easily by gluing on another one post-build.

BTW, the back thinning did affect the tone. Seemed to increase the "Q" (probably by removing the finish). More lively and more "sparkle."

tjp · #7 03-01-2012, 03:28 PM

Thanks guys. We're going to do a little experiment this weekend. Get a piece of brace material, profile the back to match the back of the guitar, and stick it in various places of the outside of the back using some high strength double stick tape. Best case, I learn something. Worst case, I have some fun and learn absolutely nothing while drinking a couple of beers and giving the wife yet another reason to question my sanity.

Misty44 · #8 03-01-2012, 04:23 PM

I have an old Sigma DM-4 that I use as a testbed (I like gitnoobs's active word "torture", it's more accurate), and have used popsicle sticks to support temporary top and back braces in my attempt to learn about the inside mechanics of guitars and their effects on tone.

The trick is to conform the brace to match the surface radius as precisely as possible,

I've also used double-sided tape with some success, not the thin scotch tape from a dispenser type, but a heavier-duty one made by 3M (I think), comes in a roll. Can be cut to fit, adheres like crazy, and can be easily removed without leaving a sticky residue. Great for adding-mass experiments, along with poster-board adhesive clay, which doesn't dry out and leaves no "oily" residue.

Tinkering can be addictive, and a whole lot of fun. And I figure that no matter how I spend my Saturday afternoons, I'll always get those raised-eyebrow looks from my wife, her way of silently asking me "really?".

Good luck!

tjp · #9 03-02-2012, 10:40 AM

I messed around with it some last night. Picked up some good double stick tape at the craft store, cut a piece of 1/2 in square brace material to length, then using my typical, highly scientific methods, I tapped the back until I found the "loose" spot and stuck the brace on there. I'm an engineer in my professional life, and I get plenty of precision at work. I like to go by feel when I get home.

Wow. What a difference. It was suddenly a strumming machine, with no loss of the great qualities I spoke of earlier. Overall balance was improved as well. Next step is to play with brace dimensions a little, then put it inside the guitar, again using tape and play it for a bit to make absolutely sure I want to go permanent.

That tape is stout stuff by the way. I was a little afraid I was going to pull finish off when I pulled the brace off.

When I glue it on the inside, I think I'll use the popsicle stick method - body is too deep to use tennis balls.