Official Luthiers Forum!

I am curious if anyone has tried it and how it would work.

For the last 10 years or so I have had this chunk of Cherry that is fairly well quarter sawn. A few years ago I cut some of it to use for sides and back for a small parlor sized guitar (maybe a tennor uke, not sure yet) I bent the sides and set them aside. I was thinking it would look pretty cool in all cherry.

The back piece seems to have a pretty good tap tone so it got me thinking...

I have not tried searching for this but was wonding if anyone knew how it would work?

Thanks for your input,

Cheers,
Bob

I've used a lot of cherry over the years, but not for soundboards. I have used walnut or soft maple, which are similar in many respects, for soundboards a couple of times.

The Young's modulus of a material is a measure of how hard it is to stretch or compress it. Most of the resistance to bending something like a beam or a guitar top comes from stretching and compressing the wood near the surfaces. Knowing the Young's modulus allows you to predict how stiff the thing will be at a given thickness. I test this on all of the tops I use, and much of the B&S wood as well. These numbers vary from one piece to another, of course, but with enough experience you can make some generalizations.

Cherry and walnut tend to have Young's modulus values for bending along the grain that are similar to spruce; but they're anywhere from 1-1/2 to 2 times as dense. To make a top with the same stiffness you'd need to leave it just as thick as a spruce top, but it would weigh much more. Most of the weight of the top is in the top; bracing usually accounts for about 1/3 or less of the total.

Many people make hardwood tops thinner than they would if they were using spruce, and beef up the bracing. It's hard to get the weight down to equal that of a spruce top, and with the relatively flexible areas between braces the treble response is not as good.

Because of the extra mass a hardwood soundboard will be harder for the strings to drive, particularly at high frequencies. The sound tends to be 'warm' and 'sweet', but lacking in treble 'brightness'. There is also less power output. My most recent use of walnut for a top was on an acoustic-electric bass guitar, which was designed to be played amplified most of the time. In that case I wanted a heavy soundboard to reduce feedback problems at high gain levels.

If you decide to use cherry try to find nicely quartered stock, as it will be more stable. It also has a strong 'ray' pattern that looks good.

Thank you for the info Alan,

I had this idea for a guitar or uke that would be all Cherry with Maple bindings.

It sounds as if it would work as long as I can drive the top well enough to get it moving. That would probably exclude making a small parlor or a uke since the small top would restrict the movement. I do however like the "thumpiness" of a ladder braced guitar so it may work well for that sound.

I know nothing about Young's modulus so maby I should start there and do some research.

I am not aftaid of failing since every fail is an oppurtunity to learn somehting.

Thanks again for you input and advice.

Cheers,
Bob

Stiffness is thickness cubed times Young's modulus.

https://www.wood-database.com/common-name/ lists the Young's modulus for many species. Black cherry is 10.3GPa, whereas sitka is 11.03GPa. But cherry is 35lbs/ft³ whereas sitka is 27lbs/ft³. So to get equal stiffness, the cherry will have to be 2.3% thicker (cube root of 11.03/10.3), meaning the weight will be 33% higher (1.023x35/27).


That is opposite of my thinking. A small top is naturally lighter weight, so the wood's stiffness to weight ratio is less critical than on large guitars, and might even be beneficial to get the resonant frequencies lower since you can only go so far with reducing stiffness before it caves in (unless you use the forbidden art of the zero-downforce tailpiece bridge).

OK, that is something to ponder... My thinking was that because it is a smaller area it wouldn't move as much...

I am really not well versed in the "numbers" of guitar bulding and have so far just " flown by the seat of my pants". Wifh only a couple of acoustic builds so far I have a lot of learning to do. I have relied on tapping, thumping and flexing and at this point it hasn't done much for me yet.

Thanks for your advice Dennis, any bit helps.

Cheers,
Bob

I find it useful to understand the mathematical relationships between things, but in the end the numbers are only good for comparison and theorizing since I don't know what specific values are "good". I tap and flex my way to a random chance of success too.

Glad I am not alone. I doubt I will live long enough to learn what a "good" tap tone really is.... At 72 I don't think I will build enough guitars to figure it out. But I can still learn...

Thanks much,

Cheers,
Bob

As Dennis said, you can get away with denser wood on a small instrument.

'Average' numbers on wood can be misleading. Density can easily vary by 20% or more +/- from an 'average' for a species, and stiffness by even more. I've got two pieces of European spruce that were cut from the same plank, within 4" of each other, and one of them is noticeably denser, but it's long-grain Young's modulus is 50% lower then the other. The best redwood I've tested had a long-grain Young's modulus more than three times as high as the worst. Long-grain stiffness in softwoods tracks the density pretty nicely for the most part, but cross grain stiffness can vary by a factor of ten.

I'll note that some folks get very good at judging stiffness by 'feel'. Dr. Karl Roy, who was the head master at the German state violin making school at Mittenwald could reliably distinguish a difference in stiffness of 3%, which is about as well as the test methods I use can do. He developed that skill over decades and hundreds of instruments. Most people are not nearly as good as they think they are.

That's why I measure stuff.

This may be an answer that is overly scientific for your liking, Bob, but it's more-or-less my standard answer when anyone asks about hardwood tops. They can be made to work well, but it's not the easiest thing to do...

Here's a link to a thread from 2014...

viewtopic.php?f=10101&t=43138&p=569628#p569628

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

http://www.goreguitars.com.au

Thank you Trevor,

That is a stunning guitar! That is somewhat what I have in my "minds eye" with doing one in Cherry only with maple binding. I would love to hear what it sounds like (as was mentioned in the post).

I already have 2 guitars started so this one will be a while before I even start on it but this gives me some encouragement to try it. It will also give me some time to study up on how to do it.

I really want to thank you for the link and showing that it can be done.

Cheers,
Bob

Black Cherry is pretty heavy, at 560 kg/m^3. Sitka averages 425, Engelmann 385.

A Sitka panel would make up about 60% of the mass of the soundboard (braces and bridge being the other 40%). The higher the mass, the quieter and less responsive the soundboard is to the strings. With a Cherry panel, I'm sure it would be a lot more than 60%.

I used Trevor's thicknessing formula and averages for the species, and found that an Engelmann top (no braces) would be 159 g, and Sitka top 175 g, and Black Cherry 255 g. So that's 46% heavier than Sitka.

I think that would be fine for a back, but too heavy for a top.

Greg

Greg,
Thanks for posting those numbers, Prior to reading this I was in the process of looking some of this up.
As I said I am not well versed in "guitars by the numbers" and should learn a bit about.

I like the idea of using local wood seeing how the price of some of this stuff is going through the roof.
I do have a small stash of top, back and side wood but would like to see what other options are available.

Thanks much,

Cheers,
Bob

In the testing I've done the Young's modulus (E) along the grain for all softwoods tends to 'track' the density in the same was for every species. 60% of all samples I've tested fall within 10% +/- of the Young's modulus value predicted by the density. That's pretty good for a natural material. Since long-grain Young's modulus is the most important thing determining the thickness of the top, you can pretty well use any softwood for a guitar top, so long as you make it the right thickness.

Low density tops end up being lighter, so long as they fall 'near the line' on the graph of long-E vs density. Stiffness goes as the cube of thickness times E. Leaving the low density top a little thicker raises the stiffness faster than the weight.

In my shop my students and I have used a bunch of different softwood species. All of the spruces have acted like spruce: Red, White, Black, Engelmann, European, Lutz, Sitka, and maybe some others. Don't get hung up on the on-line stuff: spruce is spruce. We've also used Western Red cedar, Douglas fir, Western hemlock, White pine, Pondarosa pine, Redwood, Lawson's cypress, and a couple of others who's names escape me. Despite the published 'average' numbers, all the redwood I've seen that was worth using has been about as dense as the 'average' Red or Sitka spruce. The only low-density stock I've come across was some 'salvage' wood that had very low long-E and a tap tone like cardboard, which I sent back. I'll note that redwood can have what seems to be a lot of built-in stress, so you have to be careful, particularly if it's figured. Redwood, Doug fir, and WRC tend to lack toughness: they're 'splitty'. I don't use those for bracing. White pine has a very soft surface; use a larger bridge footprint and a good pick guard.

Note that when I say 'softwood' I'm using the botanical term. Some soft woods, such as Balsa, are botanically hardwoods, and don't necessarily follow 'the rule'.

Keep in mind, too, that there is a lot of variation is any wood species. You can't always tell just by looking at it, and labels don't mean as much as you'd like. There's no substitute for measuring the properties of the piece you want to use. Some hardwoods, such as balsa, and Spanish cedar, can be low enough in density and high enough in long-E, to work as top wood, and some softwoods won't. These days it's not hard to do the measurements, and both Gore and Hurd ('Left Brain Lutherie') give good instructions on how. Daniel Haines published articles on this in the 'Journal' of the Catgut Acoustical Society, which I believe are available on line, as did Morton Hutchins. There is other material on this general subject in that source as well.

We here in the US are blessed with abundant sources of all sorts of usable lutherie woods. The only one that's really hard to find a good substitute for is ebony: there are lots of hard close grained woods out there, but hard, close grained, and black...

Quite a few Cherry ukes have been made - I've made one myself - and the wood works fine for that. I'd say the sound is a little more biased to the treble than mahogany. As a plus, it usually bends much easier than mahogany!

So I'd think you could make a decent parlor guitar from all Cherry, basing the design on all-mahogany guitars. The average density of Black Cherry is pretty much the same as Honduran Mahogany.

One thing to watch out for is finishing - Cherry is notorious for taking up finish unevenly, resulting in a blotchy appearance. I found that wiping on thin shellac for 3 or 4 base coats worked, but you'd want to try out your planned finishing process on offcuts.

I've used a lot of cherry on various kinds of instruments, and I've never had a problem with any clear finish. It takes up stain]/u] very unevenly, as it soaks into the end grain, but I've never been one to use stain. I've used some pretty highly figured cherry, too.

Much of the cherry you find in lumber yards comes from Pennsylvania. They hunt deer with shotguns, and you sometimes get 'shot' cherry. You can see the tracks of the pellets, but the lead dissolves away fairly quickly. The wood is usually harder and a bit darker than normal, and can have an unusual figure that can only be called 'characteristic'. It has something in common with both quilt and curl, but is irregular. There are black resin pockets where the lead was. I did once get some walnut with a lead slug in it. When I ran it over the newly-sharpened jointer and saw that shiny metal spot I said something like; "Golly gosh-darn [u]heck!!", more or less. The jointer was much less bothered than I was...

I have said that in my shop once or twice before. I probably got it from you. I've learned so much from your posts; I assume this is just another example. . .

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

OK... My Brain hurts

I spent a good part of last night searching info on Youngs Modulus and am even more confused that when I started.
I should probably mention that I don't think have the left half of my brain... I am a very "Right Brain" artist so I don't do math...

I think the best way for me to figure this stuff out is to just do it and see what happens. As I said in an eariler post, I am not afraid of failing since you always learn in the process.

I really apreciate all the help and info you all have given, and it appears that Cherry can be used for a soundboard but it takes care to get it right.

Thanks again,

Cheers
Bob