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Henning
02-17-2018, 10:31 PM
Hello, as far as I understand koa is a very popular Wood for building ukuleles in Hawaii. It is understandable from the Point of view that you use what is the closest. So from Hawaii the use of building ukuleles in koa has spread to the USA.
But now is koa really such a good Wood to use in the top of a stringed instrument?
Isnīt it rather hard and dense, a Little like maple or perhaps rosewood?
Then it ought to be better suited for sides and backs. I donīt want to say it should be like that, only maybe.
Does an instrument in koa or acacia "open up" like an instrument in mahogany, cedar or spruce?
Does it take much longer time?
http://tonewooddatasource.weebly.com/wood-details-a-b.html

maki66
02-17-2018, 10:47 PM
Koa is acacia;
https://en.wikipedia.org/wiki/Acacia_koa

For obvious reasons it has a special meaning to ukuleles.
But is it the best tone wood? That depends on the preference of the listener.
It has a limited supply and high demand so the price of excellent koa tone wood is going to be much higher than excellent but otherwise equal tone wood
that has a greater supply.

Average Dried Weight: 38 lbs/ft3 (610 kg/m3)

Specific Gravity (Basic, 12% MC): .53, .61

Janka Hardness: 1,170 lbf (5,180 N)
http://www.wood-database.com/koa/

Compare this with Honduran Mahogany;

Average Dried Weight: 37 lbs/ft3 (590 kg/m3)

Specific Gravity (Basic, 12% MC): .52, .59

Janka Hardness: 900 lbf (4,020 N)
http://www.wood-database.com/honduran-mahogany/

Both are pretty close to each other. Neither wood is considered "hard".
I think the build quality has as much to do with the tone of the instrument as the wood type. Maybe more.
And this comes from a woodhead.

And just for giggles I'll add a list of acacia varieties;
https://en.wikipedia.org/wiki/List_of_Acacia_species

Brazilian rosewood is quite hard;

Average Dried Weight: 52 lbs/ft3 (835 kg/m3)

Specific Gravity (Basic, 12% MC): .68, .84

Janka Hardness: 2,790 lbf (12,410 N)
http://www.wood-database.com/brazilian-rosewood/

Maple is still medium-ish;

Average Dried Weight: 44 lbs/ft3 (705 kg/m3)

Specific Gravity (Basic, 12% MC): .56, .71

Janka Hardness: 1,450 lbf (6,450 N)
http://www.wood-database.com/hard-maple/

maki66
02-17-2018, 11:07 PM
One way to find out if you like one tone wood over another is to buy the same ukulele from the same builder with different sound boards.

http://shop.mainlandukuleles.com/category.sc?categoryId=3

Sell off the one(s) you like less?