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A local hardwood supplier stock this. In some places it is called Eucalyptus. To me it looks a lot like mahogany, and it is touted as a mahogany alternative.
Anyone here use it? Anyone know if it is suitable for necks. Lighter or heavier than mahogany?
I don't have any doubt it would make a decent solidbody electric, at least for the body, but I wonder about it's working properties and suitability as neck stock, with an appropriate fretboard material.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

Possibly Eucalyptus Grandis, aka Rose Gum. Never used it, but try asking on the ANZLF. If it behaves like most eucalypts it will likely be not too stable - not necessarily a bad thing if you intend mating it with an ebony fretboard - the assembly will likely stay straighter in humidity changes as there will be a closer match between the coefficients of expansion with changes in RH.

Text book density is 620kg/m^3, low for a eucalypt, but higher than S. American hog., with about twice the Young's modulus of hog, so good stiffness.

It could also be Lyptus, which is a cross between E. Grandis and E. Urophylla, which can have an appearance similar to Honduran hog. It has the typically high density of a eucalypt and the well known high degree of movement associated with most eucalypts.

If it were me, I'd be inclined to give E. Grandis a go, but I'd pass on the Lyptus.

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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

Trevor, thanks. Eucalyptus Grandis is indeed another name for what I am talking about, according to the lumber place. You mention mating neck stock with ebony for a fingerboard. Would I get similar stability with EI Rosewood or Grannadillo, or is there something specific about the ebony?

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

The problem that many run into with necks is seeking out a really stable neck wood (for the obvious reasons) then mating it with a really unstable fretboard wood, like "ebony". By "stable" I mean moves very little with humidity change. If you mismatch the stabilities you get a type of bimetal strip - it just bends as the humidity changes, acting like a hygrometer. The ebonies are amongst the woods that move most with humidity changes, especially long grain. Macassar ebony is generally more stable than the African/Indian ebonies, with the rosewoods having around half the movement of the A/I ebonies (in general). So to avoid the neck bending with humidity changes it's best to match the coefficients of expansion with humidity change* (not a number often published) of the neck and fretboard wood. It's a bigger issue with classical guitars as they usually don't have truss rods that can be used to straighten things out.

Eucalypts, generally, move a lot, but there are exceptions. Again, I'd say ask on the ANZ Luthiers Forum, as there are some specialist tree guys who hang around there who'd likely be able to advise you.


* Not the same as shrinkage when drying. The best indicator normally found is "stability or movement in use", which is not a very objective descriptor.

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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

One of my semi-local wood dealers has started pushing it as a readily available, sustainable plantation grown wood. I have no experience with it. Here's what his literature has to say:

[quote="James Ringelspaugh"]One of my semi-local wood dealers has started pushing it as a readily available, sustainable plantation grown wood. I have no experience with it. Here's what his literature has to say:

Same here. Under $5/bf for 4,5 and8/4 lumber.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

You've mentioned this before, and I wonder whether the long grain shrinkage you've observed in ebony is a result of reaction wood (which in any species would be more prone to long grain movement).

I've seen plenty of classical guitars with very stable necks of Spanish cedar with ebony fingerboards. I've seen them when they were dried out enough that the frets stuck out, and when they were damp enough to raise the seam where the two woods joined. In many cases, the neck was still very straight. I've also worked on my share classical guitars with badly bowed necks. Very rarely do these have back bow. I just repaired a nice classical that had been humidified to the point where the plates swelled and broke the binding-side seams. The neck was straight. These days it may be hard to find ebony stock that's free of reaction wood. Ebony is getting scarce. There are lots of good reasons to use another wood for fingerboards. I hope classical players become more accepting of this. Still, I haven't found ebony and Spanish cedar to be a bad combination.

Sweet! Thanks for all the info, folks. Trevor, I'll have a look on the ANZL. Much appreciated.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

Can't say, Eric. We sure know that wood ain't what it used to be.

When guitars leave my climate controlled shop they see everything from 15% RH to 95% RH, but typically around Sydney will see ~60-65%. After 6-12 months an ebony fretboard neck will considerably quieten down in how much it moves, but it is impossible for me to predict where it will stop moving in terms of neck curvature, which is why I always use adjustable truss rods (CL and SS). If I had a large number of boards from essentially the same stock, I could probably get a better prediction, but I don't, so I have to do what I can with the wood I have.

I was lecturing at Sydney Classical Guitar society summer school earlier this week. I had two students come to me with fret buzz problems. Both guitars (one ~ 7 years old made in Aus, one from the '70's made in Spain) were headed into backbow country. The Aus. one had a cedar neck, can't remember what the Spanish one had. Humidity was in the 70's. I think the high action (compared to SS) seen on classicals hides a lot evils.

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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

I couldn't agree more. (SS action is pretty variable too.) When I'm setting up a classical, "straight" means +or- .0005" (.013 mm), measured with a machinist's straight edge (not the "luthier models").
When I'm evaluating a guitar, "straight" means can I mill the frets to get to "set-up straight" without removing more than 10% of the fret height.

Often, "back-bow" is inferred from one or two high frets.

You and I are lucky to work in a forgiving climate. We have that in common with Antonio Torres. I send guitars out into environments that range from 4% humidity to 100% humidity. I try to be patient with customers who have abused their guitars. I do everything I can to prevent unpleasant surprises.

I guess this bothers me. You and I are fond of data. Are there data to suggest that ebony moves more along the grain than other woods?

There is very little third party data on longitudinal movement. However, according to USDA, in round numbers, wood shrinks approximately twice as much tangentially as it does radially whilst the longitudinal shrinkage is ~10% of tangential shrinkage. Obviously, there is a lot of within-species and across-species variation. For example for hog, (S. Macrophylla) the T:R ratio is much closer to 1:1. Longitudinal figures can be computed from T and R data and the volumetric shrinkage. The data for coefficient of dimensional change per 1% change in RH is published by USDA for a variety of species, but the data is incomplete. However, the magnitude of the coefficient tends to follow the magnitude of the shrinkage data, the data for which is much richer.

Following a procedure derived from USDA methods (and noted on p 4-7 of the Design book) I put together a table of shrinkage coefficients derived from USDA data and CIRAD (France) data. Of the T and R coefficients, African ebony has the largest radial (R) coeff and the second largest tangential (T) coefficient after one of the eucalypts (Karri). Cutting a long story short, and with all the above caveats, the coef. for a piece of ebony longitudinally is likely between 3 and 7 times that of EIR. This correlates with my experience of rosewood vs. ebony fretboards in that I have a lot more trouble with ebony, but I've not figured out whether it's 3 or 7 times as much!

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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

I'm a little skeptical. I used the USDA numbers to calculate the longitudinal shrinkage from R, T, and V values on a half dozen woods. I got values of 1.1% for persimmon, and .2% for EIR. So far, so good. That fits with what you're saying. Spanish cedar was .08% (believable), but Ipe comes out with a negative number. In other words, it expands lengthwise as it shrinks in width and depth. Maybe there's a typo in there, or maybe the values don't correlate well enough with each other to justify these sorts of calculations. Elsewhere, the USDA's Wood Handbook gives the range of longitudinal shrinkage for all woods as being .1%-.2%. Where do they say that it is roughly 10% of tangential?

Yep, I got some negative numbers, too; 3 or 4, having checked across ~30 species. I've never come across a wood that expands as it dries either, but that's as good as the published data gets (and is another example of the necessity to make ones own measurements).


In their data. My analysis of their data brings up that figure. The actual average figure I got on the population I took (discarding negatives) was 12.16%, but quoting anything other than ~10% would be somewhat heroic.

Edit: PS Was back at Sydney Classical Guitar Soc. Summer School again today. Had another student come to me with a back bowed neck. Humidity ~70%, pretty normal for round here, so I dunno, maybe these guys keep their instruments under humidity control at home.

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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

So would this be a reason to use an ebony stripe in a classical neck. if you were to use an ebony fretboard?

It sounds like Rosewood would be a superior fretboard wood.

How about Wenge?

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Old growth, shmold growth!

Absolutely. You see that a lot in classical guitars. And now you mention it, none of the current batch of back-bows had the skunk stripe.

That's my view from the stability point of view. Macassar doesn't give me as much of a problem as the black ebonies, though. The main issue is that a lot of classical players view rosewood as inferior and say they don't like the pores in rosewood. They've never bothered me, though, but I also play SS so I'm used to it.

Just did some quick numbers (off the the Wood database) on Wenge. Approx. three times the longitudinal shrinkage of EIR. Big pores, too!

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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

I don't seem to see longitudinal shrinkage listed. How are you figuring that?

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Old growth, shmold growth!

I reviewed my arithmetic, and found a crucial error. Actually, Persimmon, EIR, and Spanish cedar all have negative values. Ipe is the only one that actually shrinks!

Trevor, you mentioned the Wood Database, so I used their figures to calculate longitudinal shrinkage for ebony, EIR, and wenge. Wenge comes in at 1.7%, both EIR, and ebony have negative values: EIR= -.2%, ebony= -.7% (so they're both expanding as they dry out, with the ebony expanding three times as fast as the EIR).

Just for fun, I decided to see what rounding errors did to the figures. All of the values are given to the nearest .1%. Ebony's radial shrinkage of 6.5% could be anywhere from 6.45 to 6.549. Those rounding errors mean that ebony's longitudinal movement is somewhere between .5% shrinkage, and .9% expansion.EIR's is between 1% shrinkage, and .3% expansion. The margin of error is bigger than the differences we're talking about.

The USDA states that longitudinal expansion is .1%-.2%. Factoring in the rounding errors, there's no reason to think that any of these woods don't fall in that range.

It's not listed. You work it out from the T, R and volumetric. The T, R and L shrinkage must "add up" to the volumetric shrinkage (if you get the math right!).

I've found quite a lot of the data on the Wood Database is the same as that published by USDA, for example EIR, so I would say that many of the Wood Database numbers are lifted straight from USDA. I got 0.17% longitudinal shrinkage for EIR.


You make a good point about the rounding errors. When I did the sensitivity analysis (longitudinal) I got a range for EIR of 0.012% to 0.330% shrinkage and for Wenge 0.281% and 0.608% shrinkage, so I'd still be saying that EIR is more stable than Wenge and I'd stick with my ~10% of tangential given that the USDA's figure is such a generic range, probably because they couldn't extract better numbers from the data! Their range is *only* a factor of 2!

Back in real life, I still see more problems with the black ebonies than I do with most other woods. Could also be because most "decent" classicals have black ebony fretboards, so the population is much larger!

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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