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I've just decided to use a beautiful piece of sinker redwood and East Indian rosewood for a classical (Hauser plan) for my next project, instead of the steel string I was originally planning to use it for.

I've never used sinker redwood before --- any tips from anyone as to thickness, etc., when using this wood?

Here's a link to the photos (already cut out for the originally-planned Taylor-style Grand Concert size --- it will be adapted to the Hauser plan). (I can't figure out how to attach the images here.) http://theamateurluthier.com/retirement/htmlpages/2015taylor2.html

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Kathy Matsushita
San Jose, CA USA
http://theamateurluthier.com
Facebook: https://www.facebook.com/kathy.matsushita

I have used Sinker Redwood on one guitar. It was very pretty and sounded good. I did have a problem with the redwood wanting to split. This may be a characteristic of all Redwood. I wicked some CA glue into the end grain around the perimeter. This may have helped some.

That's a good thing to know...Thanks!!!

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Kathy Matsushita
San Jose, CA USA
http://theamateurluthier.com
Facebook: https://www.facebook.com/kathy.matsushita

Redwood is pretty stiff, and not as light as Cedar, but I built one Redwood/Brazilian classical, and I had to go back and take off the bridge and thin the top to get the response from it I was looking for. When I built it originally, I thought, "Well, I should probably use Cedar thickness specs for the Redwood." I was wrong. It had nice tone, but was not responsive. It sounded great when recorded, but it just seemed slow, somehow. I thinned the top into the lower 2's (2.3 - 2.4) from about 2.7 in the center, originally. I don't know exactly, but I just thinned until it sounded great and had excellent pop with the bridge off. When I put the bridge back on, it was a completely different instrument. Still had the nice tone, but really had great response and projection. So, I say build it closer to Spruce specs than Cedar specs, maybe a little thinner in the center, but not too thin at the edges. I don't know if you have evenly thinned tops or not. I do not. I taper my tops, usually from the bridge region of the lower bout to the wings and even more to the tail, but leaving it thicker between bridge and soundhole. Mostly I do this based on feel. Usually works for me, but I just didn't know how to handle Redwood. It makes a great classical guitar. Amazing bass response.

You may want some other opinions!

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Waddy

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Sound Clips of most of my guitars

I've never built a classical so can't help there. Working on my second build with Sinker Redwood. Worked it pretty much the same as cedar...
I would not wick CA a long any end grain though. Just like with spruce and cedar it will stain the top (unless you seal the end grain with shellac first) and you'll never get it out.


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Waddy...Thanks for the tips. So far I've had one other response (on Facebook) as to thickness. Dave Fifield told me I should probably shoot for around 115 mil (which I later figured out meant .115"), which is around 2.9 mm. so that's kind of close to what you are saying....

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Kathy Matsushita
San Jose, CA USA
http://theamateurluthier.com
Facebook: https://www.facebook.com/kathy.matsushita

Good point, Rod!!

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Kathy Matsushita
San Jose, CA USA
http://theamateurluthier.com
Facebook: https://www.facebook.com/kathy.matsushita

Really depends on the properties of the specific set. Redwood is highly variable to begin with, and the level of mineralization just mixes it up even further. Does it ping or thunk? What's the density? Not sure you can do an accurate Young's modulus measurement when it's already cut to shape, but maybe with one of the offcuts. Or just do what I do and flex it by hand and tap on it until you like the sound and feel

Yeah...it's never an exact science, is it???

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Kathy Matsushita
San Jose, CA USA
http://theamateurluthier.com
Facebook: https://www.facebook.com/kathy.matsushita

I've made 7 redwood soundboard guitars, 3 of which sinker. I find that the plates should be thinner than usual to get a good tap out of them. I usually go to 2.5mm on the drum sander, and then they probably get down to 2.2-2.3 when the box is closed. Be careful gluing the bridge, as it can definitely start to peel if you don't have clean gluing surface.

I saw Dave's response to your Facebook post. I will just say, I disagree, but agreement is not a requirement! I also know other classical builders who would disagree, as well. I do agree that you have to assess each piece of wood for what it is. I have never left a guitar top as thick as 2.8 mm. (One was close though, Italian Spruce, and I actually left it close to 3 mm in the wings, but you could have wrapped it around a post the cross grain stiffness was so weak. Great guitar though) It really depends on what you want out of your classical guitar. You can get a nice sound out of the thicker top. I have a video, of my Redwood guitar, but I don't think Johnnie (the player) want's it publicly posted. I might be able to strip the audio from it. It sounds great, it just does not have the response that would make it attractive to competitive players in classical circles, where response, power and projection are critical qualities in a guitar.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

I know....people's opinions vary widely. I did see that GustavBuhund's reply (below) was closer to yours, as well. I think the only way I'll be able to decide is when I start to thin it down, flex & tap it, and just kind of go by intuition!!!

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Kathy Matsushita
San Jose, CA USA
http://theamateurluthier.com
Facebook: https://www.facebook.com/kathy.matsushita

first redwood top for a CL was a PITA even though i was super careful. The top was 18 yrs old air dried The bridge area sunk, and the wood had a tendency to split along the grain I would use shellac around the s,hole prior to routing and the bindings as well. Gud luck kathy PS I would use 315 HHG on bridge glueing

Not sure about the thickness for a classical, I used it on a steel string. My thickness end up closer to spruce than cedar If that held true for a classical I would be at 2.2 mm to 2.3 mm. I would not run CA on the end grain to keep it from spitting. I used CA to glue a rosette in a sinker redwood and a stain ran through the wood like a celery and dye experiment and ruined the top.

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http://www.Harvestmoonguitars.com

So, so far there are about 3 of you who recommend somewhere in the range of 2.3-2.7mm. Hmmm....

About using CA to keep it from splitting. What if I shellacked the end grain first (as I do when using CA to glue in purflings)?

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Kathy Matsushita
San Jose, CA USA
http://theamateurluthier.com
Facebook: https://www.facebook.com/kathy.matsushita

I used sinker redwood once, on a steel string. Sealed the routed rosette channel with shellac before gluing and had no problems with wicking. (But test with a piece of your scrap first!) Like John, I ended with a thickness in the spruce range. That said, the top has shown more bellying and telegraphed the braces more visibly than my others. It was also difficult to keep everything flat when scraping/sanding and the top was extremely susceptible to marring while handling. Sinker redwood is gorgeous under finish, IMO, and I do like the tone I achieved, so I would definitely use it again.

I hope you'll keep us apprised of your progress, Kathy. It's always a treat to follow your work.

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George :-)

With the wood sealed I am not sure the CA would do anything but I agree it would be safer. I think if you carefull gluing on the top and routing the binding channels it will not split. The few times I used it I did not find it that bad, WRC is easier to spit.

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http://www.Harvestmoonguitars.com

Thanks, George! What do you mean when you say that it was difficult to keep it flat when scraping/sanding?

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Kathy Matsushita
San Jose, CA USA
http://theamateurluthier.com
Facebook: https://www.facebook.com/kathy.matsushita

I mean that it was unusually difficult for me to get the redwood top plate flush where it met other, harder materials, i.e., my ebony rosette and purfling/binding scheme. I believe this was due to me requiring a bit of a learning curve with redwood, when I was accustomed to using spruce.

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George :-)

Personally, I didn't have any problems with the Redwood. It worked just fine. It is a little chippy, but i had no problems routing channels at all.
Here's a pic.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

LOVELY!!!!

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Kathy Matsushita
San Jose, CA USA
http://theamateurluthier.com
Facebook: https://www.facebook.com/kathy.matsushita

I agree. CA will only help if you let it penetrate and stain. It might actually look kind of cool though. That top already has some mineral stain coming up the endgrain from the bottom anyway.

Splittyness is just another of the variable properties of redwood. It's usually significantly more brittle than spruce, but nothing requiring endgrain treatment. The main danger, as always, is humidity. And you'd have to soak the entire thing in CA to strengthen it against splits from drying out.

But that is another thing. You can glue the braces at lower RH than usual, since redwood's humidity expansion is much less than spruce. Bracing at 30% and taking it into a 90% environment, it will still have less stress on all the glue joints than a spruce top braced at 40% and taken into a 90% environment. Nearly impervious to humidity problems then