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In another thread Todd had mentioned that figured redwood can be good given some allowances for bracing and top thickness. I did't want to throw that thread off track, so I'll ask here. Todd can you give a little detail on the allowances you are talking about? I assume you mean leaving the top a little thicker and thinning the braces out a little. Am I correct? I wouldn't mind feed back from others as well. Thanks

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Kyle

I have seen a few custom Breedlove guitars in the past few weeks and all of them have had noticeable and almost scary depressions in front of the bridge. The bridge roll looked to be on the order of 4 degrees or so.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Thanks for the answer Todd. Do you think bracing with adi, which from what I understand is stiffer, would help? Along with going a little heavy on the x brace and bridge plate?
Brian, you didn't indicate but I assume these Breedloves were figured redwood tops?

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Kyle

Thanks for all the info Todd. I'm going to be bracing a top in the next month and this is valuable information going into it. One of these days I hope to get the time to drive out to Germantown and meet you and some of the folks that hang out.

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Kyle

Kyle, how are you measuring stiffness, and are you measuring the stiffness of your brace stock?

No, I've never tested brace stock. To be quite honest the last guitar I did, which was my third, was the first that I did any deflection testing on the top. From what I understand of deflection testing, it's a comparison of recorded data. Unfortunately my data consist of one Sitka top, being fairly new to guitar building. When you are testing your brace stock are you getting it to rough dimensions ( 1/4" x 3/4") then testing? The thought never occurred to test brace stock but makes complete sense.

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Kyle

Sounds like a good time.

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Kyle

That's the cool thing about deflection testing. Once you have established stiffness parameters that work for you, they should translate into any species of top wood you choose to go with.
The only thing I wonder in regards to that is if different woods have different amounts of cold creep....

I use them on smaller guitars.
L.

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Cut to size.....Beat to fit.....Paint to match.

Adi will indeed generally be stiffer at a given size, but you can also just leave the braces a little taller to get the same stiffness increase with sitka or lutz or whatever.

I'd also go on the large side for glue area, like 5/16" X brace, since you're gluing to a lot of endgrain.

I suspect dealing with the low stiffness would be somewhat similar to my quest to make rosewood topped guitars... except instead of going super thin to get the weight to just a little above normal and ending up with lower stiffness that way, you go thicker and end up with the weight a little above normal but still lower stiffness due to the runout

Here are the tricks I've developed so far to deal with it:
1. Use more braces. 3 fingers, for example, so the unsupported spans of top are smaller and thus not so squishy.
2. Notch braces into eachother, so you can control the stiffness at the junctions rather than having it be purely defined by the stiffness of the plate.
3. Support behind the bridge. Either make the bridge plate much larger, or use a pattern like lattice or fan braces in the lower quadrant. I'm currently liking 5 fans.
4. Strong upper bout structure is a must. I like the L shaped headblock style, glued to the upper transverse brace, not just coming close to it. A-frame should be fine too, if sufficiently tall and notched into the headblock and UTB (again, don't leave high flexibility points at brace junctions).

Here's the latest incarnation, although used with super stiff straight grained redwood on my harp guitar:

It's about .100" thick and still quite stiff by itself, but with 300lbs of tension on it so relative to that it's pretty thin. I probably could have gotten away with 2 fingers since it's stiff enough that it wouldn't be squishy between them, but I think 3 taller fans would show more localized distortion around them than these 5 shorter fans, and the 3 fingers make it all nice and even. I've had strings on it since Friday and it's holding up like a champ, and sounds pretty darn good. I'll be using this exact pattern on my next rosewood top (adjusting for differences in body shape and bridge position, of course), and would most likely do the same for curly redwood.

Let's go ! (schedule permitting). I will bring some of the Everclear I have sitting here - never mind- I may need that for the shellac.
I can supply some dry high quality cigars (I don't smoke but they were gifts) - they just need a humidor -

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It's this new idea from recent decades that everyone gets a participation award. - MUX

Carbon fiber

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MK5acoustics.com

There's a good book around which shows you how to measure the material properties of the wood you're about to use (using either a static 3 point bend method or a dynamic tap test method) and then tells you how to use those material properties to derive the thickness that you need to reduce that panel to in order to get a consistent vibrational performance from guitar to guitar. It takes both the stiffness and density of the wood into account because the modal vibrational frequencies (which determine a guitar's sound) are dependant on both. So you can figure out the thickness you need for any type of wood top attached to a standard bracing pattern (with instruction on how to design the bracing, as well).

Regarding using figured wood tops, Schleske, in his 1990 Catgut Acoustical Soc. paper, related long grain run-out to damping; basically the more run-out, the higher the damping. He was talking spruce, but I don't see why his measurements wouldn't hold for redwood. Figured wood is just lots of reversing run-out. Have to say, having used "good" redwood, with all its splitting and splintering, I wouldn't be in any great hurry to use figured redwood in a guitar I'd sell to a customer.

Make it mid Pacific and I'll drop by...

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

There you go again, I just can't seem to keep up with the guitar speak around here. What, pray tell is a zero clearance insert?

And I totally agree redwood is just so darn pretty.

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Thank You and Best To All

Wood is completely supported on back side of the cut so as to prevent tearout/splintering during blade exit.
On a bandsaw or tablesaw, it's accomplished with an actual insert that hugs the side of the blade.
If cutting by hand, additional stock placed underneath accomplishes same effect. With some woods, simply taping the cutline helps.

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Always have plenty of sandpaper; it's rough out there!

That's what I thought it was but didn't get the context so good. Thanks for the explanation.

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Thank You and Best To All

I only used hardwood for my bracing.

How's tomorrow afternoon look?

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A man hears what he wants to hear, and disreguards the rest. Paul Simon