Ukulele top question

[viento]

I'm building a baritone ukulele and don't know if I can use my very simple spruce top with wide annual rings.
Perhaps should I get a better quality spruce top or even a western red cedar top?
I plan to make the ukulele as an 8 string.
What do ukulele builders recommend?

That´s what I have (ruler in cm)

[Fathand]

Grain lines are an indicator of expected stiffness. Your's appear to be 3 to 4mm at the widest. I heard an amazing Collings guitar with some closer to 6mm. Your stiffness can be controlled by top thickness and bracing.

Ukes generally require less top stiffness than guitars due to smaller size and less pull from nylon strings. I built a Concert uke with similar wide rings at about 2mm, it sounded great. The top actually came from some 48 year old 2x8" lumber I have which I picked a good section to use.

Build your top to your desired amount of flex and brace accordingly for the 8 strings, I assume you have a plan?

[viento]

Thanks for your kind answer!
I'll take my spruce top and see how the sound gets.
If I am not satisfied, I will build a new uke and then use higher quality materials, perhaps with Western Red Cedar Top.
I bought a detailed plan from GenOne Luthier Supply that I am very happy with.
A friend printed it for me on his plotter in Architectural "D" (24 "x 36").
I changed some details eg.the peghead into a slotted one and the 4 strings into eight.

[Alan Carruth]

fathand wrote:
"Grain lines are an indicator of expected stiffness. "

That's the myth: in fact, if you measure the properties of a lot of tops there is no correlation between grain spacing and cross stiffness. The main variable is how well quartered the top is. If the ring lines are even a couple of degrees off perpendicular you start to lose cross stiffness.

Cross stiffness has an effect on sound, but it's not as important structurally as long-grain stiffness. Over time, as the top 'cold creeps' and bellies up the cross stiffness doesn't contribute much to keeping it flat.

Mark Blanchard did a long project on this, and decided that the 'right' cross stiffness depends on the shape. Something like a Jumbo, that's wide in relation to the length of the box, needs to have a top with high cross stiffness to vibrate right. A narrow shape, like some of the small 'Parlor' guitars, doesn't need a top with lots of cross stiffness. Mark cuts his tops to shape and looks at the way they vibrate, starting with his biggest and widest shape. If it's not right he cuts it down until he hits the shape that works for that top.

In your case I'm not sure I'd worry too much about it. The larger ukes tend to use a wide 'Jumbo' sort of shape, so you'd want something with pretty high cross stiffness. OTOH, if you're building it as a small Classical, which the uke is, and using fan braces, that's a really forgiving design. So long as you don't over build it you should end up with a really nice instrument.

[viento]

The body of this baritone ukulele is aboiut 35.49 cm = 13 31/32 "long.
It is therefore slightly larger than the smaller ukes.
The body is 25.36 cm = 9 31/32" wide.
When I bought the plan, I decided to buy a V-Brace plan just to give it a try.

Thank you for taking helpful care of my problem!

Here you can see the grain