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Anybody have thoughts on the viability of redwood for tops? Especially old growth?

Mike

Filipo,

I really don't know... I thought about that after I posted. What I do know is the piece in question has a mill stamp dated 1890. I do not know for sure, but I would guess comercially available USA red wood is farmed??

Also, this piece is not ideal for guitars as it is 6" on a side.... perhaps better for ukes? It does appear quite nicely quater sawn. I guess one could make 3 piece tops... I am just trying to ascertain if there is musical instrument wood here.

Mike

This is one topic I'm happy to weigh in on. I've used redwood for smaller-bodied steel string guitars since around 1994 and have been very happy with the results. Redwood provides an alternative tonality to the usual spruce. It's less affected by humidity changes. It's beautiful to look at!

There are, however, some things you should be aware of.

Redwood is much more brittle than spruce. It's not as "strong" though please don't ask me to define that! It may be harder to glue. If it is not cut, dried, and processed perfectly, it's likely to give both builder and guitar owner many problems.

Probably the most important thing is that the redwood be free of runout and carefully dried. I suspect that the differences between young trees and old growth are less that those caused by lousy cutting and drying practices. I don't, by the way, use "curly" redwood for steel string guitars. Curl is runout and that's a really bad thing in a stiff, fragile wood like redwood. Some people have built with it; I choose not to.

I generally work redwood a few thousandths thicker than spruce (like .005" - .010"). I keep the bench free of chips, glue blobs, and anything else that can dent the top. (Steaming out dents works but not as well as on spruce.) Bracing is pretty much like a spruce top but with particular care not to weaken structural braces. But very careful to get good, tight glue joints and have reasonable squeeze-out. Redwood seems to suck up more glue than spruce and is known for glue failure (especially bridges) if the joint is less than perfect. Having some chip-out when routing for rosette/binding/purfling is difficult to avoid -- using small bites and climbing cuts will help. The end grain avidly sucks up moisture, including glues, so don't even think of using CA around a redwood soundboard without sealing the grain VERY well! (Just don't do it; there are other glues that work as well without the problems.)

Hope that's helpful! Redwood's great -- it has a rich, chocolate-y tone with incredible sustain. It does require a bit of care to make it work well but it's worth it!

Mike, I love redwood tops. I really like most guitars, but the ones with redwood tops just seem to connect with me on a different level. The one I'm finishing now has a redwood top from Hank Mauel. It's definitely a bit brittle. I used 1/4" x 1/4" lower face braces tapered down on each end rather than scallops to give the area more stiffness as well.

I'll echo a lot of what Rick has to say. You certainly have to be more careful with redwood because it dents and splits so easily. It has to be thicker but it won't be any heavier. Runout can be a problem. There are some great advantages though. It has a lot of the warmth of cedar, but with more punch. It can make a rich sounding guitar top. Certain redwood trees are tougher than others and are more resistant to splitting and denting. The Craig Carter LS tops are a great example of that. Also wood from near the base of a tree can have more of those characteristics. I think a three piece top would be fine, but you might want to cleat it.

_________________
Ken Franklin
clumsy yet persistent
https://www.kenfranklinukulele.com

I'm a committed Euro spruce builder, accept no substitute, but the last steel string guitar I made used one of Hank Mauel's Carter Redwood tops and judging from the ring count this is very old growth. It is an exceptional guitar, (you can see and hear it here: http://luthiersforum.com/forum/viewtopic.php?f=10101&t=19044&st=0&sk=t&sd=a&hilit=redwood, which I wish I could have played for longer.

Yes it is more brittle than spruce, but that just means careful handling and things like using a gramil to define the purfling/binding cut before going to the laminate trimmer, but the end results are worth it.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Redwood is my absolute fab-fav top wood for a warm complex dark toned guitar. It is a pain in the tush to work with because it is brittle and soft and will dent in a gentle breeze. but well worth the hassel.

I've made one redwood top OM and it came out very bright. The bass is there but you it is sometimes hard to find. I found this wood to be very stiff. Most of what everyone else said above is true. You do have to be careful.

Here's a friend playing is on youtube.

Most of the redwood I've tested has been on the dense side. Since the long-grain Young's modulus seems to track pretty well with the density, it ends up being fairly stiff at a given thickness, but for a given stiffness you end up with a slightly heavier top.

Also, for the most part, the redwood I've used has not been as prone to denting as western red cedar, although in may be a little softer than most spruce. It's hard to say.

Redwood usually has good cross grain stiffness, if it's well quartered.

The biggest plus for redwood, IMO, is that it seems to have about the lowest damping on the average of any softwood. Some samples have damping as low as Brazilian rosewood; they give an exceptionally clear tap tone pitch, and ring on forever.

Now the bad stuff:
Redwood does tend to be quite brittle. All the cautions about chippout and such are true. Don't get carried away flexing it across the grain; it will feel nice and stiff until it fails suddenly, and splits the whole length of the top.

Speaking of splits, another thing that is split about redwood is it's personality. Most of the time it's quite stable, but once in a while you'l find a piece that simply is not. I suspect this is linked to the fact that the trees get so big: there must be a lot of built-in stress near the butt of one of those monsters. I've even seen areas in redwood that look like crush failures. This is one good reason the resaw it and store it for a while before using. I've gone back into my stash and found pieces that had simply split on the shelf: a problem I've never had with other woods. Ken Parker had to stop using redwood necks on the 'Fly' guitars, as they would sometimes worp, even with a CF skin.

Often redwood will look 'dirty'. There's a black, opaque matter in the wood that you can't bleach out or get rid of. It doesn't seem to effect anything, it just looks....dirty.

At times redwood can almost act 'waxy'. It doesn't have wax or oils in it, as far as I can tell, but it seems to when you glue it sometimes. I have found that, for center seams in particular, it's a good idea to plane (not sand) them carefully, go right from the shooting board to glue-up, and leave them in clamps over night.

It pays to use a bridge with a larger footprint. In particular, make it deeper from front to back, along the line of the string pull. This reduces the peeling stress at the back edge. And DON'T cut into the top along the rear edge of the bridge when you 're claening off the finish! Even if you glue it well, the bridge can still peel up a layer of wood. I've seen this hapen on a cedar top (not one of mine, thank goodness), and redwood would act the same way, I think.

Redwood is one of my favorite top woods with walnut or mahogany B&S. I'm just getting the binding on a walnut and LS redwood classical, and the tap tones are gorgeous. Maybe the low damping of the redwood helps make up for the higher damping of the B&S.

Do you talk about regular redwood (aka buckskin) or Sinker redwood ?
I have both at home. For reference sitka spruce is about 445kg/m3 in density. My sinker redwood is about 490 kg/m3 and regular is 320kg/m3.
Regular redwood is very light, and low density, it's seems to be balsa wood, it's afraid me to build something bigger than a 00 with that stuff (I would build a dread with it...).The ring count averages approximately 40 per inch. Please, what is you opinion ?
Thanks.

What does "cleat it" mean?

Oh, and thank you all, I had no idea I was going to get this many replies!

Mike

Cleat it means to put small patches of spruce as reinforcement along the glue joints on the soundboard after you brace it.

Steve

Abredalaforest wrote:
"For reference sitka spruce is about 445kg/m3 in density. My sinker redwood is about 490 kg/m3 and regular is 320kg/m3."

There is a wide range of variation in density in any wood species, and you have to be careful not to draw conclusions based on a few samples. My own data base for either Sitka or Redwood is not as large as I'd like. I show a range for Sitka from 410-485 kg.m^3, and would not be surprised to find outliers from that with more data. The 'regular' redwood I have tested, which came from at least four sources, ranges from 412 to 492 kg/m^3, and the one 'sinker' top at 393. I have seen redwood that was much less dense than these samples, but that was before I started testing.

I also tested a sort of sinker redwood sample once that weighed 736 kg/m^3. It had some kind of mineral deposit in it, and I wonder if it had not been treated for rot resistance at some point.

There is a wide range of variation in density in any wood species, I'm agree with you Alan.
With *my* regular redwood top, I have described, do you think I can do a dread with it or I'm going to have a muddy sound ?

I see no reason why light weight redwood/cedar wouldn't work for a dred, as long as you compensate by making the top thicker. By how much, it depends. It would be handy to have a spruce top, thinned and shaped, to compare weight and deflection.

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Build log

Fun!

My $.02 from a guy with a lot of redwood builds...your dred will be fine, BUT... you will probably not have the headroom typically associated with the spruce family when you really dig in with a flatpick. If you really get into it, a la Tony Rice or any other premier flatpicker, you will most likely overdrive the top and it will muddy up. However if you are going to do fingerstyle or jazz chordings/leads, it ought to work fine. It takes less string energy to get the top moving but it is "rev-limited" at the upper end.
Analogy...redwood is sort of like a Chevy...good off the line but tends to run out of steam at 5,000rpms. Spruces are more like a Ferrari...takes a while to get them going, but then they are good to 8,000rpms!

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Hank Mauel

It seems to me that 'headroom' is in some measure a function of the woods density. Since most of the redwod I've got on hand has high density, I'd imagine it would have a lot of headroom.

I measure the Young's modulus (E) along and across the grain of the tops I use. I figure the long grain E value is the most important for figuring out how thick to make the top, since that's what's resisting the bridge torque. Two tops that have the same E value will have the same stiffness at a given thickness. To work with woods that have different E values, you just need to remember that the stiffness will be proportional to the E value and the cube of the thickness.

Suppose I made a Sitka top that worked well at a thickness of 3mm, and I know the E value along the grain was 14,000 megaPascals (these are metric measurements; you could do the same in any system, or find the conversion factors). I want to make another instrument of the same size, with an Englemann top that has a lengthwise E value of 10,000 mPa. I canuse the numbers from the one that worked to find out how thick to make it.

Since the stiffness is proportional to the cube of the thickness, I'd start by finding 3x3x3=27. Then I multiply that by the E value of 14,000, to get an 'index number' of 378,000. Now I divide that by the E value of the new top, to get 37.8, which is the cube of the thickness in mm that the new top has to be to have the same stiffness. That comes out to a little more than 3.35mm: the Englemann top wants to be a bit more than 10% thicker.

The lengthwise E values of top woods that I've measured tend to scale pretty closely with the density. Wood with an E value of 14,000 mPa usually comes in around 450 kg/meter^3, and the stuff that is at 10,000 mPa is closer to 380 kg/m^3. Thus the Engleman top need to be 10% thicker, but it's a bit less than 85% of the density, so it will end up a bit lighter weight. I'd expect it to be a bit easier to play, but to lack a little in the 'headroom' department.