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I'v'e found some nice figured wood I'd like to use for B&S's.
Is it OK to use flat, rift, or slab sawn for B&S?
If not, what is the downside of doing so?

the only woods that you can use sawn that way is maple and mahogany

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

John surely there's thousands of guitars out there with wood off quarter..... yes sides cup when off quarter and backs are less stable but these are things that can be worked round, well I think so anyway.

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Formerly JJH

I learn more from my mistakes than my successes

depends what you mean by that. I can tell you that there are few woods that are stable enough off quarter. Yes you will find an example but few woods will not be an issue down the road. As a builder that makes a living doing this I can't take a chance on sub standard material.
I will take something that is about 45 degrees off quarter but I won't personally build with it beyond that , other than using maple or Mahogany. You will run a high risk of cracking and warping. On a top I won't even think of anything that isn't quartered.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Sometimes I think you need to take the risk because of availability , e.g., most of the BRW seems very slab cut. Of course, a lot of it cracks.

I agree that if you wanted to for some reason to use some off quartered wood that Mahogany would be about the best choice. Not only is it stable but it less dense than a lot of other typical back and side woods. It is more easily restrained so to speak. But Maple is not particularly stable at all.
Why do you group Maple with Mahogany ?
Link

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

It is common to see maple and mahogany used quartered or flat and any combination. They are able to be used without as much trouble as other woods. I have seen them used on Martins and Gibsons.
Granted this is often used on lesser quality guitars. As a repair guy I don't see many maple guitars in the shop . I am not grouping maple with mahogany just stating a fact that these 2 woods are of the few that can be used in guitars on or off quarter. Maple being a wood of choice on Violins.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Why is flatsawn maple OK but not other woods? Flatsawn maple moves more with changes in RH than any other species commonly used in guitars.

If it's movement that's the concern, flatsawn cocobolo (for one) moves less with humidity changes than quartersawn maple. And it moves dramatically less than flatsawn maple. And that's bigleaf (western) maple which has a smaller differential of movement between radial and tangential orientations than other species.

One benchmark I look at when deciding whether a particular cut is OK to use for a back is the stability of quartersawn spruce. Not only are tops more prone to splitting due to the stress concentrations at the bridge and fingerboard, movement with humidity changes effect the action. So if the stability of quartered spruce is OK for a top, wood of similar stability should be more than adequate for a back.

Totally flatsawn cocobolo, BRW, and many other riftsawn species meet that level of stability.

Another thing to consider is how split prone a species is in certain orientations. For instance, there is nothing I've seen that splits as easily as quartered BRW. If a buyer was hyper-concerned about splitting, I'd steer them to just about anything over classic straight-grained, quartered BRW.

If stiffness is the criteria, then quartered is often better but that's not usually an issue for backs. If it was, flatsawn maple would certainly be ruled out.

As mentioned, quartered wood generally stays flatter when side bending but even that isn't always true. And again, if that's the issue then forget that quilted maple.

So in my book, there's a lot more to it than quartered vs off-quarter. Relative stability, beauty, rarity, and tendency to split play a part in my decisions. And as much as I hate to tempt fate, in more than 15 years, I have yet to have a guitar come back with a split.

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http://www.chassonguitars.com

Kent's right. I know many high end builders who like the look of the straight grain, but like it more when its slightly off quarter for exactly the reason Kent states -- less prone to cracking.

I was asked an opinion and I gave it. The more off quarter you go the more risk of instability you will have. Some woods can handle the off quarter better than others because of grain structure . I stand by maple and mahogany that they will be more useable then say most rosewoods . I bend about 200 sets of wood a year , and I have been doing this over 10 years . I think I have gained in site from a good bit of experience. Maple may move a bit but once set in the mold and glued up will do ok.
Rosewood when flat sawn is very prone to cracking from RH changes . I can't speak for cocobolo and I only used a few sets and all were well quarter. Bubinga is another that till be prone to cracking if too far off quarter. Mango , at least the few sets I used and sycamore seem to tolerate off quarter but they are not a common wood . I did generalize a bit but beginners want information and I stated my opinion .
Brazilian Rosewood , that is flatsawn is very prone to RH cracking . I agree that as you are starting out availability and expense are figured in. I use many local woods honing skills. Walnut and cherry also make great guitars . The more quartered , the better the stability. Also how it was dried has much to do with stability . kiln Dried is more stable than air dried. When the wood is braced is another factory .

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Kent,

Do you know of a resource that lists the stability of various woods in each orientation (quarter/rift/flat)? I'd be curious to see the data and be able to compare various woods.

Thanks,

Flori

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

One very important issue if your using flatsawn wood is it's storage(dry for along time is best)
Stickered - and the humidity in the shop when bracing & assembling the box.
I've used alot of the slab BRZ over the last 30+ years and NONE of mine have cracked.
I send an e-mail to all my clients in the fall reminding them to get the humidifier up & running.
For all guitars -even well quartered sets.

Mike

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Mike Collins

Humidity control is key . Martin will no longer honor cracks due to humidity .

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

http://www.woodbin.com/calcs/shrinkulator.htm

This one has some great features. You can plug in the species, width, starting RH and ending RH and it will tell you the actual change in width for radial (quartered) and tangential (flat) cuts.

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http://www.chassonguitars.com

Kent I have to agree with that assesment. After re-sawing several thousand sets some qs, riftsawn, flatsawn it is way to difficult to generalize. I have had qs sets that wouldn't stay flat for love or money. Some woods will come of the saw dead flat and stay that way
with no special care. Doesn't seem to matter what the cut is. The most difficult woods seem to be kiln dried so I tend to say away from them. I think the kiln drying process is rushed to move the wood out of the kiln as quick as possible, All quilted woods are flat sawn in order to show the figure at it's best. I'm sure everyone remembers that brain sapele with outrageous figure. All flat sawn. I sold several hundred sets and the only cracking I was made aware of was during bending. Besides all of the above finding QS exotic woods is becoming more difficult that ever.

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That's a great calculator Kent, thanks

Its quite obvious if you input a 14" back width and a RH drop from 45 to 30 how a back is going to perform (radial= quartersawn tangential=flatsawn)

And John Hall's experience with mahogany being fine flatsawn is mirrored in the results of the calculator.

Very interesting stuff. Thanks!