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I just finished thicknessing the top of my latest build, which is redwood/tasmanian blackwood baritone.
Unfortunately I thicknessed it a little too thin, trying to sand out couple of low spots around the rosette. Now I'm left with 2.2mm (0.086inch) redwood top for baritone. It seems a little bit risky.
Do you think I can still pull it off by making the bracing stronger? or should I just make a regular standard tuning guitar out of this redwood?

I thought about making laminated bracing (spruce, wenge, spruce). Is it a good idea? Would the top handle bigger pressure from the strings this way?

This is my first redwood top guitar, so I can't comment on stiffness of this top. All I can say is that it's not sinker redwood and LMII graded it AAA.

Body shape is OM btw.

Top thickness relates to the Young's modulus of the wood, primarily along the grain, the tension you're going to put on it, the size of the guitar, particularly the span between the tailblock and the main cross brace, the bridge height, and the brace pattern.

What you're trying to do is make the top stiff enough to reist bridge torque over the long term. Lowering the height of the strings off the top reduces torque, so that's one way to get by with a thin top. The down side of that is that you'll tend to have a bit less of the even-order partials in the mix, and those tend to be the most 'harmonious'. If the strings are really low to the top it can make the guitar hard to play.

Lower string tension also reduces top belly and dish. Again, there are limits as to how low you can go and still have a workable string, particularly when tuning low.

A thin top tends to 'belly' or 'dish' between the braces, and the larger the unsupported span, the greater the distortion. Using a lot of braces, closely spaced together, can support the top well. The Smallman 'lattice' tops are pretty xclose to the limit on that, although you could think of 'sadndwich' tops as being even further along on the same line.

Usually baris are big guitars, as part of the way to get that low tone is to have lots of air in the box. Think about making it wider instead of longer.

Young's modulus in softwoods relates pretty directly to density, so if that redwood is particularly dense, it might still be stiff enough. The only way to jknow for sure is to make a measurement.

Long story short: there are lots of ways to 'save' a top, but they might not al give you the sound you're looking for.

More things to think about: You didn't mention the scale length, string gauge and tuning you intend to use. There is no real standard that I'm aware of and the resulting string tension can be in a pretty broad range. You need to start there and build accordingly. Regardless of any of that though, 2.2mm redwood is mighty thin for a bari. IMO it is almost certainly too thin unless you are using an alternate bracing pattern with shorter spans between braces, as Alan mentions. I would use an oversized bridge plate too.

Another thing to be extremely careful of....redwood has low peel strength and bari bridges usually have a good bit more torque on them. If I were to use redwood, I would be inclined to use a bridge with a larger footprint and no odd shapes on the back edge that will form stress concentrations. And be extra careful when scoring the finish not to go into the wood.

Good luck.

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I'd have to say you should go for a new top 2.2mm is far too thin for a conventionally braced baritone and it is so soft, you will inevitably get thinner when finish sanding,

I hadn't really settled on scale lenght yet. It would have probably been around 27.5-29 (fan fret). I would have used elixir 16-70 strings on it.
I looked into lattice bracing but I'm afraid im not experienced enough to pull off something as complicated as lattice bracing.

I'm thinking about making 25-25.75 standard tuning fan fret out of it. I also plan on using double x bracing and adding couple of small fingerbraces here and there (to reduce the unsupported span). Making the x laminated (spruce, wenge, spruce) sounds also like an interesting idea. In my limited knowledge it seems to work well with supporting very thin top.

Any suggestions? How's my plan?

I have used tops as thin as .080", but not redwood on a baritone. I think you should just buy another top. They are not that expensive. Use this one on a OM or 000 instead.

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You're attempting a multi scale baritone and you're worried that making lattice bracing is complicated????!!!!

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