View Full Version : Rift sawn wood
05-13-2009, 12:35 PM
I pulled the images below from the web regarding rift sawn wood, and am subsequently confused since the images are contradictory.
Image 1 shows rift sawn as radially cut fully vertical grain. Image 2 and 3 do not. Image 3 indicates QS as fully vertical, while image 1 shows the smaller QS planks will have angular grain.
Help me Mr. Wizzard!!!
05-13-2009, 01:50 PM
This one reflects what most consider rift, quarter and plain or flat saw. But different nomenclature and different explanations are out there to confuse you.
To add to the confusion, the term "Vertical Grain" is used for a mixture of rift and qsawn lumber, but sometimes it's used (incorrectly) for just qsawn lumber.
The origins of the terms come from how the log is sawn on an old-fashioned carriage mill.
In Flat or Plain Sawn, the log is milled through and through like the top half log in the pic.
In Quarter Sawn, the log is either milled radially as the bottom half log in your pic suggests, or more commonly, the log is quartered and the quarters milled on edge to produce lumber with growth rings 90 degrees to the board surface. Both methods are time consuming and expensive.
More commonly, Vertical Grain lumber is produced by halving the log and milling each half on edge to produce a mixture of qsawn and riftsawn wood. This swing-blade mill does the same thing, only without halving the log first.
The reason Vertical Grain stock is desirable for planking is that it is almost twice as stable seasonally as flatsawn stock, minimizing compression set in carvel and splitting in lapstrake. And the reason riftsawn is most desirable among vertical grain stock is that fasteners penetrate multiple growth rings instead of just one, further lessening the chance of splitting.
05-13-2009, 02:03 PM
Thanks Bob. I knew you would have the answer.
So even though fully vertical grain planks will be more stable, you would prefer the rift planks to avoid potential splitting? Is it then true that boatbuilders would avoid the QS planks in favor of the rift planks, or would they use them in a location where the planks are less tortured (like the sheer planks)?
05-13-2009, 02:05 PM
Why your example is so confusing is the editor wherever this image was published doesn't understand what riftsawn wood looks like.
05-13-2009, 02:07 PM
.... or would they use them in a location where the planks are less tortured (like the sheer planks)?
Exactly. Qsawn are best used where there is the least fastener stress.
05-13-2009, 03:10 PM
Yes Bob, I thought it might be a mistake too, but a lot of people must be making the same one because i also found these images:
05-13-2009, 03:25 PM
Technically, the bottom image is correct, because that's how a carriage mill produces qsawn lumber. What is variable is how the lumber is sold...whether the few rift grain boards produced are sold separately from the qsawn boards or not.
But the top image is simply wrong, and reflects radially sawn, not riftsawn stock. New England still has mills that radial saw stock. The best quality qsawn clapboards are milled that way.
Off the track but a quick question for you Bob,
How would you compare wrc with spanish cedar.
Weight, rot resistance, workability, as an underlayment for cold molding?
05-13-2009, 06:32 PM
....Weight, rot resistance, workability, as an underlayment for cold molding?
I've grown and sold WRC since 1975, and have handled some Cedrela but never built anything major with it. What I did handle was very uniform in texture and I'm sure as easy or easier than WRC to work. (For those unfamiliar with it, Cedrela isn't a cedar or cypress but a light weight hardwood similar to mahogany.)
But looking at the engineering numbers, as an underlayment for either epoxy and veneer or epoxy and fabric, they are apples and oranges. Cedrela has properties closer to our heavy cedars suitable for structural use, which I suspect would be excess weight when the hull strength is determined by layers of epoxy more than by wood fibers.
Cedrela is almost a third heavier than WRC, a third stronger, and almost two thirds harder. Resistance to splitting is the only engineering property where they are close, with Cedrela only 10% more resistant. But that also means you'd have to be careful reducing scantling size if substituting Cedrela for a design engineered for WRC. Both glue easily, and both are exceptionally durable, but Cedrela is over a third less seasonally stable, which may impact the longevity of any crossgrain gluing.
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