Cocobolo Tops

Hello again,

We are experimenting with Nicaraguan cocobolo tops and I wanted to see if anyone has any experience with cocobolo or even rosewood tops. Many people compare the sound quality of Nicaraguan cocobolo to rosewood. In fact, it has the same genus name as Brazilian rosewood.


For the wood nerds like me, there is an interesting article about cocobolo in Wood Magazine:


http://www.woodmagazine.com/material...es-1/cocobolo/


We have only made 2 ukuleles with Nicaraguan cocobolo tops, which were both custom orders for special customers. We were so impressed with the volume and sustain of the cocobolo that we are now experimenting with 6 more. It is an exciting new frontier we are discovering!


I mostly wanted to see if any UU members have any experience with cocobolo (or even rosewood) soundboards and to see if anyone has any thoughts or advice for us as we move forward.


For example, cocobolo has a high strength-to-weight ratio, and we are thinking about using thinner tops to enhance sound even more. Any thoughts or advice on that idea?


Thanks again for your help,


Kevin

"Popular opinion" is that hard and heavy woods like Dalbergia Retusa are a lousy choice for an acoustic stringed instrument top, and I have never seen it done. Therefore I very much look forward to hearing of your actual results.

I am known as a light builder. My guitar backs in rosewood are typically just under .070", whereas my Koa guitar backs are around .080, perhaps a hair above. I have made Jatoba guitar backs at .055, and my Koa uke backs are between .035 and .050+ depending on the Koa. Many here have question these numbers, but my instruments sound great ("they say", and I agree) and I haven't had a catastrophic failure for over 40 years!

Bruce,

Thank you for your thoughts. I am a complete rookie compared to you, but my understanding of construction theory was similar to yours. When my first customer requested a custom cocobolo top I warned him that he might lose out on sound quality, but he had fallen in love with his first cocobolo ukulele and he wanted to go ahead with the cocobolo top anyways. We were both pleasantly surprised the the range, volume and sustain that the cocobolo top produced.

Like I said earlier, we are currently experimenting with 6 more cocobolo tops. I am looking forward to posting a sample for the 'expert ears' in the UU community to evaluate. Hopefully we are stumbling upon something good here

Thanks again,

Kevin

There is a classical guitar builder who has built a few all brazilian guitars. I haven't had the opportunity to play one but I have heard from a very reliable person that they sound surprisingly good. Yes, that's contrary to conventional wisdom but it has made me curious. And if stiffness/weight ratio was everything, why all the flamed koa tops? Or flamed anything?

On the other hand, Cocobolo is more than 30% denser than Brazilian, on average. It would take a serious paradigm shift for me to understand how one of the densest woods around could work as a top. But shift happens...

Hi Kent,

Thank you for your input. Do you know that name of the classical guitar builder that works with Brazilian? You make a good point about the flamed tops as well. Maybe it is time to shake up conventional wisdom a little bit. It's definitely worth giving it a shot

I am looking forward to sending you a video demo to hear your thoughts.

Thanks again,

Kevin

i plan to try a laminate of Brazilian veneer with cedar veneer for a top...one day. id rather use that then cocobolo, cheaper too

Hi,

I built a complete rosewood (neck, sides, front and back) ukulele. I can't find the pics on this computer. Will post some tomorrow.
Cant make any educated comments on how it sounds or compares, it was the second ukulele I built, starting on number 4 soon and I am still learning and making mistakes as I stumble along…

Daan

Hello again,

The cocobolo soundboard experiment is coming along nicely. Cocobolo has a high strength-to-weight ratio, which has allowed us to start using 1.75 mm (.070") soundboards, and 2 mm (.080") backs and sides. It is amazing what a difference it has made to the volume and projection of sound. We are very impressed with the improvement.

We are now experimenting with a 1.5 mm (.060") soundboard and 1.75 mm (.070") backs and sides. This might be pressing our luck, but I guess if we don't give it a shot we will never know

Here are a couple of links to some video sound samples:

http://www.cocoboloukuleles.com/index.php/video

https://www.youtube.com/watch?v=nt-wLdSA78Y

https://www.youtube.com/watch?v=Z0AqhGApBX8

Very nice! I have a bit of a passion for rosewood tops as well. Put an Indian rosewood top on my test mule guitar (steel string) and it sounds quite nice, though severely underbraced and dying a slow and painful death. Over 3 years old now, and I can't believe the bridge is still holding on, since it's been partially lifted for most of that time, and the top is all squiggly. But I'm working on a real one now, which I'll use a better bracing pattern and leave them taller to stiffen it up. I'm expecting good things from it.

Brazilian should be the best rosewood for soundboards. Same density as Indian, but about 15% stiffer according to the numbers on wood-database.com. Honduran rosewood is an interesting one because it's very dense, but off the chart stiff, so it ends up being about the same stiffness and weight as Brazilian if you make it super thin. But maybe more crack prone at the thickness you'd need to go for a soundboard. Cocobolo should be worse, being more dense and less stiff than Honduran. But African blackwood is the ultimate challenge, being even a little lower stiffness than cocobolo, and a lot heavier. It would really need to be veneer thin to get the weight down, and I'm not sure if you could brace it up adequately, without just doing a full lamination with a softwood plate, which sort of takes the fun out of it I don't think I'll ever attempt it. But perhaps I will try cocobolo, now that I've seen and heard yours I have the perfect set, too. Some offcuts included with a guitar back/side set I bought, which are 10 3/4" long. Close enough to the 11" standard for concert size.


I'm not sure whether it's really important to use low damping woods for the soundboard, especially when going super thin and getting most of your stiffness from bracing, but my instinct says it is. i.e. rosewoods are better than ebonies for exploring high density tops. Not to mention the humidity expansion, which is a bigger deal on the soundboard where it directly affects the action height by raising and lowering the bridge. I'd recommend avoiding flatsawn rosewoods as well for that reason, even though it doesn't have the effect on cross grain stiffness that it does for softwoods.

Also, my feeling is that rosewood tops will work better on the smaller models of each instrument. That is, soprano/concert ukes, parlor/00 steel string guitars, small classicals like FE17. Reason being, mass is the challenge. And the mid to large sizes are balanced for very lightweight softwoods. Small size, the soundboard is lighter by surface area, and can be lighter still because the necessary stiffness is less. Plus the higher mass gives lower resonant frequencies, countering some of the trouble that the small size causes with softwoods.

What is the status of cocobolo in Nicaragua?

Down in Panama, cutting cocobolo is now illegal. Of course, we now have idiots cutting down trees and smuggling the logs to China. (I had some trees take from a property while nobody was looking.)

Wicked, sorry to hear about your cocobolo trees. That must have been devastating.

We buy all of our tonewoods from a legally registered source here in Nicaragua. They give us the correct paperwork each time we make a purchase. They explained to me that if we export 'raw' cocobolo we could run into problems, but that if we export it as part of a finished product we are fine. The goal is to avoid a lumber company from clear cutting the forests and exporting it to China. However, they want to encourage the small artisan woodworker to make a decent living. We are lucky to have access to such beautiful wood!

Well, I wish you luck.