Different types of cut in wood

Construction and repair of Classical Guitar and related instruments
edcat7
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Different types of cut in wood

Post by edcat7 » Sun Mar 19, 2017 10:29 pm

What are the differences, structural and aesthetic, between: rosewood; figured rosewood and quater sawn and straight grain rosewood? Why the price differences?
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Marcus Dominelli
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Re: Different types of cut in wood

Post by Marcus Dominelli » Mon Mar 20, 2017 12:36 am

Quarter sawn, straight grain is the most stable and therefore reliable grain orientation from the point of view of making guitars which will last the longest, without cracking, distortion, etc.
But straight grain/quartered is getting harder to source all the time. You'll see wood suppliers offering flat sawn sets of rosewood for sale at premium prices these days. I'm not sure if this is because they are finding it hard to source quarter sawn wood, or if it's because they can more easily sell the flashier, flat sawn looking stuff....
Many players do not understand the importance of having nicely quarter sawn wood.

I like the look of quartered wood more than flat sawn. Maybe because I see flat sawn wood as a potential liability...there is a much higher risk of it cracking. But you can laminate the back and sides of these woods, which will help stability, if one gets desperate enough to use flat sawn....or if one day that's all that's left.
Price difference: It will depend on the vendor. Quality and price are not always related. I once visited a tone wood dealer who tried to sell me twisted up sets of flat sawn Brazilian rosewood veneer, which he claimed could be used for "backs and sides." - $500 a set. I could not help laughing. They were barely good enough for headstock veneers!!

Carey
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Re: Different types of cut in wood

Post by Carey » Mon Mar 20, 2017 5:56 am

Worth mentioning too is much greater shrinkage across the grain in flat-sawn wood, and if it cracks, often a more difficult repair.

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attila57
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Re: Different types of cut in wood

Post by attila57 » Mon Mar 20, 2017 7:21 pm

Naturally there's a much greater supply of flat-sawn stock than quarter-sawn. This fact, and the superior tonal and structural characteristics of the quarter-sawn stock, are manifested in the higher price. A lot of flat-sawn ebony is sold these days for tonewood purposes, and used for fingerboards. Its resistance to wear is just as good as that of the quarter-sawn type, but there's a higher risk of warping and shrinkage. (Ebony is sensitive to water anyway!)

In tonewoods generally straight grain is the most preferred from the structural point of view, but aesthetically figured rosewood can be very beautiful, so it's highly prized. Brasilian rosewood (BRW) is a kind of timber where the figured variety can be just as good, from the tonal point of view, as the straight-grained type. However, knots, curls, and other grain irregularities always bear a risk of becoming structurally unstable in time, especially if the storing conditions are adverse (sudden temperature and humidity changes, etc.).

Attila
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Alan Carruth
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Re: Different types of cut in wood

Post by Alan Carruth » Wed Mar 22, 2017 2:26 am

The figure in some tropical woods, such as BRW, is often 'color figure' rather than 'grain figure'. Grain figure would include things like curly, quilt, and birdseye, that are often seen in maple. Stripe figure, which is common in mahogany and other tropical woods, is another type of grain figure, and there are others. All of these exist because the wood fibers are not straight and parallel, but change direction in some way that creatas a pattern in the reflection of light from the surface.

Wood is stiffest and strongest along the direction of the grain. When that varies you generally lose some stiffness and strength. The wild figure in 'stump' wood is picturesque, but is also a tell tale of high built-in stress which can make the wood unstable. In some cases such wood can be quite weak. A well known example of that is 'wind shake'; compression fractures that are caused by a tree hitting something hard as it falls. The cross wise 'crease' lines are actually breaks in the wood; although it can seem solid enough it will fall apart if bent.

Color in wood is usually an adaptation by the tree attempting to fight off some sort of threat using 'chemical warfare'. There are lots of things that try to eat tropical trees, and they have lots of defenses, some quite specific. The 'spider webbing' in BRW is such a response, possibly to insect or fungus attack. If you look closely at it you'll see that the dark lines often don't follow the grain at all, but can meander across otherwise straight grain. This is not always the case; sometimes the black lines can mark discontinuities in the wood, and be weak spots. I have seen such 'ink lines' that contained enough silica to put a notch in a sharp plane iron. No doubt that tended to slow down the chewing of the grub that triggered the defense, but I sure didn't appreciate it...

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