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Black Locust
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10101&t=17425		 Page 1 of 2
Author:  Greenman [ Sat May 31, 2008 3:55 pm ]
Post subject:  Black Locust
[:Y:] I meet a local woodworker with a sawmill that has a pile of black locust that was sawed over a year ago. I am going to go through it and pick some pieces that are quartered for sides and backs. I plan to resaw it and experiment with it. I have read some interesting things on the forum about it. I just wanted to throw that out there to get some input and see if anyone else might be interested in some as well. First I have to see what shape it is in. Just want to be sure it is worth the cost and effort. I realize it is a plain looking wood but the tonal qualities are suppose to be good. Thanks Bill Sterling-Greenman
Author:  Don Williams [ Sat May 31, 2008 4:21 pm ]
Post subject:  Re: Black Locust
Yes....!!! Interested in a set...most definitely. According to Al Carruth, the tonal properties, damping etc., are almost identical to Brazilian Rosewood. It just doesn't look anywhere near as pretty.
Author:  Mike Collins [ Sat May 31, 2008 4:38 pm ]
Post subject:  Re: Black Locust
I'd buy a set also!!!
If Don & Al say it's good-THEN it's good!!
bliss Mike
Author:  Link Van Cleave [ Sat May 31, 2008 5:39 pm ]
Post subject:  Re: Black Locust
I would be interested. Or I should say I am interested.
Link
Author:  Alan Carruth [ Sat May 31, 2008 6:23 pm ]
Post subject:  Re: Black Locust
I had heard that locust might be a reasonable substitute for BRW. I had one set that was given to me several years ago, and finally dug it out to check the assertion. I tested one of the back halves, and am now in the process of finishing the guitar.

The back I have is reasonably well quartered, and has tight grain. The density was 672 kg/m^3; lower than that of the Indian I've tested, which runs from about 750-850. The Young's modulus of the locust was about 13,000 mPa along, and 2250 mPa across the grain, in the lower part of the range for IRW. The damping factor, however, was significantly lower than most of the IRW I've tested, with Q values along and across the grain respectively of 142 and 92 for the locust sample, and 87 and 89(!) for ten samples of IRW. Only one of the IRW samples I tested had a Q value over 100 in either direction. High Q = low damping = long 'ring' when tapped.

BRW is generally denser than IRW, with higher stiffness and lower damping. Locust would appear from these numbers to be more like Indian than Brazilian, with the exception of the damping factor. The interesting question is which, if any, of these properties is important in the final guitar.

I'm building a classical guitar with this set: they're a bit trickier to get a good sound out of, and more sensitive to material problems, IMO. I am using a struturally nice Englemann top with a bit of a cosmetic challenge: some water stain that I could not work around. I'm in the process of building up the French polish now, in hopes of having it ready to take to Montreal, so it will be a little while before it's strung up and playing. The tap tones seem very good.

One thing that must be kept in mind here is that I'm working off a sample of one; not a 'scientifically valid' thing to do. "All Indians always walk in single file, or at least the one I saw did". Still we have to start someplace. I'd urge anybody trying out 'new' woods to do some simple testing and post results, so that we can start to get a feel for how these things might compare with the 'traditional' woods. One certain benefit I can cite for this stuff; they won't confiscate it at the border as they could my BRW instruments!
Author:  jhowell [ Sat May 31, 2008 7:20 pm ]
Post subject:  Re: Black Locust
I would be interested in purchasing a set also! Please put me on the list.
Author:  Lillian F-W [ Sat May 31, 2008 8:34 pm ]
Post subject:  Re: Black Locust
I'd be interested too.
Author:  Jim Kirby [ Sat May 31, 2008 9:19 pm ]
Post subject:  Re: Black Locust
Yes I'm definitely interested as well.

Jim
Author:  Ken Franklin [ Sun Jun 01, 2008 1:21 am ]
Post subject:  Re: Black Locust
Count me in.
Author:  bluescreek [ Sun Jun 01, 2008 6:31 am ]
Post subject:  Re: Black Locust
thank you Al for your insight and information. I am most interested in your measuring methods and equipment you use.
john hall
blues creek guitars.
Author:  pharmboycu [ Sun Jun 01, 2008 7:58 pm ]
Post subject:  Re: Black Locust
I am very interested in the so called "alternative woods" and while I cannot build at all, I would love to play a guitar made out of Black Locust once one is made. If one of you all do decide to build with it, may I play it for a minute or two? I promise not to wear a belt and to take the keys out of my pocket. ;)
Author:  Alan Carruth [ Sun Jun 01, 2008 8:22 pm ]
Post subject:  Re: Black Locust
John Hall asked:
" I am most interested in your measuring methods and equipment you use."

There are several good ways of measuring these things, and all of them have advantages and drawbacks. Density, of course, you get by measuring the length, width and thickness, and weighing the piece.

Probably the lowest tech method for finding the Young's moduli is by deflection, and there there are several accounts of how to do that. I'm pretty sure, for example, that Dave Hurd covers it in 'Left Brain Lutherie', although I loaned out my copy and haven't gotten it back.

Deflection testing won't give you the damping numbers; for that you need to vibrate the piece. If you have an FFT program on your computer you can tap the piece, run the transform, and get the Q value from the spectum by calculating the bandwidth of the resonance. The main issues there are getting a long enough signal for decent resolution of the Fourier Transform, and figuring out which peak is what.

I use my signal generator to drive a back half that's supported on foam pads. When I find the lengthwise and crosswise bending modes, by using Chladni paterns, I find the peak frequency and the half power band width. Those numbers, along with the size and weight of the piece, allow me to calculate the Young's moduli and Q values.

As usual, there are inherent problems with this approach. For one thing, the math assumes that the bending is 'simple': when the plate is bending along the grain it's not bending at all across the grain, and vice versa. This is not always true, and when it's not the results will reflect a sort of mix of the long grain and cross grain properties. As in any case where you're looking at the product of a number of measurements you're limited by your least accurate measurement. In my case, that's probably the thickness, since I can only measure that to the nearest .05mm at best, and the thickness can vary more than that from point to point. Other things, such as air drag and background noise, can also effect the results. On the whole I suspect some of my numbers are only good within, say 10%; hardly lab accuracy, but good enough for shop uses. If you're interested in more details I'll be happy to provide them.
Author:  Mike OMelia [ Sun Jun 01, 2008 11:06 pm ]
Post subject:  Re: Black Locust
Anybody got some pics? (finished and unfinished)

Mike
Author:  bluescreek [ Mon Jun 02, 2008 4:28 am ]
Post subject:  Re: Black Locust
thanks Al If I could call you that would be great. You can send me your phone # through my web site or if you have a site I can send you the contact info there
my email is tippie@epix.net
thanks agian
Author:  Matt G [ Wed Jun 04, 2008 6:26 am ]
Post subject:  Re: Black Locust
Wow, more talk of locust... thanks AL that is very intresting.

I have cut many locust trees here on cape cod in my day. I have`nt used any for guitars, but i can tell you the logs do sing.

The other thing i know about them is they grow really fast. I have a 20' tree that is only about 4 years old in my yard. i`m sure it will take a few more years to grow a wide enough trunk to be usefull for instruments. I`m keeping an eye on it.

If the brazilian cousin of this wood grows equally as fast, it makes it hard for me to belive that Brazilian could ever go extinct. Locust gives off suckers, and one tree can take turn into many very fast.

if only i has the gear to saw some sets for you guys... theres a lot of it here

Matt
Author:  Dennis Leahy [ Wed Jun 04, 2008 8:51 pm ]
Post subject:  Re: Black Locust
I found reference to Black Locust being used for marimba bars. That's a promising sign.

I actually have some material, with just enough to get one or two side sets around the huge bug holes, cracks, etc. Until it is resawn, I'm not sure I have anything. The stuff I bought sight-unseen for backs turned out to be wavy flatsawn material - barely rift at one edge. So, I'd be very interested in trying a set or two, and will buy it or trade for it. If you end up with more back-sized billets than side billets, I'd love to get a couple of extra backs to mate with the sides I "may" have. I would also be OK with narrow back sets (parlor sized), if that helps.

Thanks,

Dennis
Author:  Dennis Leahy [ Wed Jun 04, 2008 8:54 pm ]
Post subject:  Re: Black Locust
slackkey_mike wrote:
Anybody got some pics? (finished and unfinished)

Mike

Mike, it looks like Ash with a yellowish-tan stain. Pretty boring wood compared to all the highly figured guitar sets you see. But, I really want to make some guitars using North American "exotics", so I don't mind that there is no "bling."

Dennis
Author:  Arnt Rian [ Thu Jun 05, 2008 1:26 am ]
Post subject:  Re: Black Locust
I have nothing to add to this discussion except an observation: Some of the woods that seem to have similar acoustical properties to BRW are also the same woods that are favorites among makers of traditional bows. Black locst and of course osage orange are regarded by many as some of the worlds finest bow woods. I wonder if BRW would make a good bow ;)
Author:  Mike Mahar [ Thu Jun 05, 2008 9:21 am ]
Post subject:  Re: Black Locust
Arnt, Do you mean the kind of bow used to shoot arrows or do you mean the violin kind? Do other languages use the same word for both or is that just English?
Author:  Arnt Rian [ Thu Jun 05, 2008 10:53 am ]
Post subject:  Re: Black Locust
Mike, I meant bows for shooting arrows. We use the same word for violin bows and archery bows too, BTW ('bue'). Another related anecdote: Snakewood is the only wood I know of that is popular for both violin and shooting bows...
Author:  Alan Carruth [ Thu Jun 05, 2008 2:07 pm ]
Post subject:  Re: Black Locust
The violin bow making course that they held at the University of New Hampshire used osage at least one year as a practice wood. I bet it would make a good violin bow.

The key common factor may well be low damping. This probably links to low hysteresis; the ability to return to the initial shape immediately, rather than taking a 'set'. Willow makes terrible archery bows, I imagine: you don't even have to heat the stuff to bend willow violin liners.
Author:  Schoonie [ Thu Jun 05, 2008 2:33 pm ]
Post subject:  Re: Black Locust
I have not used Black Locust, but I have made one reso from the local Osage (Oklahoma). I have also built Osage archery bows. Another way that Black Locust and Osage are similar is they are very resistant to decay. Osage has been used for decades around here for fence posts. They saying is they will wear out 2 post holes. I have found this to be true.
While bending Osage sides in a Fox style bender, they had almost total spring back! I ran them through twice with the same results. I ended up just going straight to the mould while hot the third time.

Kent
http://www.schoonoverresophonicguitars.com
Author:  Dennis Leahy [ Thu Jun 05, 2008 3:57 pm ]
Post subject:  Re: Black Locust
Alan Carruth wrote:
I had heard that locust might be a reasonable substitute for BRW.

...The damping factor, however, was significantly lower than most of the IRW I've tested

... low damping = long 'ring' when tapped.

BRW is generally denser than IRW, with higher stiffness and lower damping. Locust would appear from these numbers to be more like Indian than Brazilian, with the exception of the damping factor. The interesting question is which, if any, of these properties is important in the final guitar.

...

I recently had a chance to (unscientifically) compare Black Locust, Osage Orange, and Yellowheart (the South American "cousin" of Osage Orange) tap tones. I'd say that Al has made a good observation, comparing Osage Orange and Black Locust more favorably with East Indian Rosewood, and only the Yellowheart stood out as truly being "metallic" or "glassy" similar to (or perhaps even more pronounced than) old, dry Brazilian Rosewood.

I have asked the question on a couple of luthier forums about which wood to use (or which wood characteristic to look for) for a baritone guitar or acoustic bass guitar. The "glassier" woods are often mentioned, but I'm too much a beginner to know if that is true or if it is myth that just keeps getting repeated. In a way, the selection of a glassier wood (apparent higher pitch tap tone) is counterintuitive for bass, unless it is true that wood with higher damping, selected for a back, somehow interferes with the vibrations to promote a "muddier"-colored tone.

Anyway, I think we should take the opportunity to grab any high quality rift to quartered chunks big enough and straight enough for instrument sides as well as 2-piece or even 4-piece backs. Black Locust and Osage Orange in fence posts and firewood can't sing.

Dennis
Author:  Alan Carruth [ Fri Jun 06, 2008 2:32 pm ]
Post subject:  Re: Black Locust
The Osage I've tested has bee pretty much a drop-in replacement for BRW in properties. The guitars I've made from it have pretty well born that out.

It has occured to me that, with lower damping and density than IRW, the Locust mght actually be a reasonable substitute for Mediterranian Cypress. I may be finishing up my very first Flamenco!
Author:  Vincent Simokovich [ Fri Jun 06, 2008 5:43 pm ]
Post subject:  Re: Black Locust
Alan Carruth wrote:
John Hall asked:
" I am most interested in your measuring methods and equipment you use."

There are several good ways of measuring these things, and all of them have advantages and drawbacks. Density, of course, you get by measuring the length, width and thickness, and weighing the piece.

Probably the lowest tech method for finding the Young's moduli is by deflection, and there there are several accounts of how to do that. I'm pretty sure, for example, that Dave Hurd covers it in 'Left Brain Lutherie', although I loaned out my copy and haven't gotten it back.

Deflection testing won't give you the damping numbers; for that you need to vibrate the piece. If you have an FFT program on your computer you can tap the piece, run the transform, and get the Q value from the spectum by calculating the bandwidth of the resonance. The main issues there are getting a long enough signal for decent resolution of the Fourier Transform, and figuring out which peak is what.

I use my signal generator to drive a back half that's supported on foam pads. When I find the lengthwise and crosswise bending modes, by using Chladni paterns, I find the peak frequency and the half power band width. Those numbers, along with the size and weight of the piece, allow me to calculate the Young's moduli and Q values.

As usual, there are inherent problems with this approach. For one thing, the math assumes that the bending is 'simple': when the plate is bending along the grain it's not bending at all across the grain, and vice versa. This is not always true, and when it's not the results will reflect a sort of mix of the long grain and cross grain properties. As in any case where you're looking at the product of a number of measurements you're limited by your least accurate measurement. In my case, that's probably the thickness, since I can only measure that to the nearest .05mm at best, and the thickness can vary more than that from point to point. Other things, such as air drag and background noise, can also effect the results. On the whole I suspect some of my numbers are only good within, say 10%; hardly lab accuracy, but good enough for shop uses. If you're interested in more details I'll be happy to provide them.


I would definitely be interested in how you are using Fast Fourier Transforms Al. I am using MATLAB.

Vince
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