Selecting sitka spruce. Too heavy?

[Thibaud]

Hi,

I am going to build my second guitar and I am going through the process of selecting tops using Trevor's method.

I have a Sitka spruce top "master grade" that is causing me doubts about its weight. My sitka top have a predicted weight of 186 grm.

Since no data are listed on the table 4.5-3 on sitka spruce, I am basing my observation on the paragraphe below the table.

It says: "All the above wood except the Port Orford cedar and western redcedar samples 17 and 18 made excellent guitars."

Those samples are all above the 169 gramms.

Would you reject that particular piece of wood or is it normal for sitka as it is a heavier wood?

Here is my spread sheet. The first line is my piece of wood, the second line is the first Engelmann spruce listed in the table as a comparaison.

http://www.anzlf.com/download/file.php? ... w&id=22548

Thanks for your help
Best regards
Thibaud

[GregHolmberg]

Thibaud--

It makes me happy to see my spreadsheet being used!

I had the same thought about that paragraph. He seems to be implying that for this guitar, a 390x490mm OOO size, that 169g (the POC, #11 and #12) is too much. Also, he said that sample WRC #17 was too heavy at 165g. The Engelmann averaged 146g.

These are his standards for a "master grade guitar". I'm sure many good guitars have been made with 165g tops. So I guess you just have to decide what your personal standards are. This might require iterative refinement over several builds.

By the way, your piece is showing an e-long of nearly 16. Are you sure? That seems very high. Check that f-long value. Are you sure you have the right peak in the frequency graph?

The density of your Sitka does seem high at 479. The species' average is 425. That's a 13% variation, which is normal, but you're looking for something exceptional in the other direction (lighter).

Average Sitka came out at 2.80mm and 172g. Yours at 186 is 8% heavier.

I think that maybe Sitka just isn't the absolute best choice for tops. The best appears to Engelmann, WRC, and Lutz.

Pacific Rim Tonewoods provides density and E values for its pieces ("Sonically Graded"). I did the thickness calculation using numbers they posted for one of their pieces of Lutz, and got 2.27mm and 132g. That's an exceptional piece of wood. And you can see the numbers before you buy. So you know what you're getting. I haven't bought from them yet, but when I need such a piece of wood, I will go there.

By the way, 𝜈LR and 𝜈RL for Sitka Spruce are 0.372 and 0.040. But I don't think that will make much difference in the thickness calculation--probably less than 1%.

Greg

[Thibaud]

Thank you very much for your help and your spreadsheet. All the credit goes to you on that one

Well, my first acoustic had a moon spruce top with a weight of 153g and it does sound really good so I would like to stick to that range. I do understand that sitka is heavier however my piece doesn't seem too good even for sitka. I have double checked all of my data and nothing has changed.

I have changed 𝜈LR and 𝜈R with your values instead of the book average values. It makes the top even heavier

I took a look at Pacific Rim Tonewoods. This is a fantastic idea! Buying wood hoping for the best could be frustrating and here is a solution.

I think sitka is maybe not the best wood indeed (if there is such a thing) but I think I will focus more on localy sourced wood since the alps are very close to me and seems to produce high quality wood.

If anyone else has other toughts on this particular case I would be happy to have more advice.

Building a guitar is such à long process as everyone know. I don't really want to make the wrong choices

Thanks for your help
Thibaud

[GregHolmberg]

Thibaud--

I think these folks provide a similar grading service in your part of the world: https://woodntones.com/the-abies-project

They work with Rivolta Woods in Italy (outside Milan). https://riwoods.com

You might also contact Giuliano Nicoletti at https://www.iuliusguitars.com/ in Sorbiers, France. He sources his Spruce from somewhere in the Jura mountains, but I don't know exactly where.

Update: he gets it from Bernard Michaud of Le bois de lutherie, Fertans, France. https://bois-lutherie.com/

Greg

[DaveO]

Good to hear from you all. My name is Dave Olson, and I’ve been working with PRT on the sonic grading system, measuring density, longitudinal Young’s modulus, and damping, and providing a system for delivering this wood to the community of Luthiers. The work has been helped immeasurably by our friend Trevor Gore, who many of us have in common on this forum.

If there are any questions about our system, please let me know either in the forum or by email [email protected]

Cheers to all, Dave Olson