Hopefully, a different kind of runout question???

[IBKuz]

Didn't want to interrupt the ongoing discussion in the other thread about custom ordering concerns. The comments about runout did bring a question to my mind that I thought some of the luthiers here might be able to answer.

I understand what runout is but was questioning whether this is only visible in Spruce tops or can it be present in Cedar, Redwood or Mahogany as well? When I thought about this a bit, I could not remember seeing visible signs of runout on anything other than spruce tops. Could be wrong on this, as I have not made anything other than a cursory study of the subject. It may be that it only shows up visibly on the lightest coloured tops.

As a secondary question, a form of runout is likely present in B/S sets. If this assumption is correct, are there physical/visible signs? If this does occur, what are the signs? Any pictures would be appreciated.

[mcgr40]

yes, you can see this effect in other woods. It is a greater percentage of end grain "running out" of the viewed face of the wood. The endgrain tends to absorb finish differently, hence the darker color. I will see if I can find a pic somewhere.

[ChuckS]

I'm not a luthier, but here are a few examples of runout:

The ribbon figure often seen on mahogany is alternating bands of runout; runout in one direction alternating to the other direction. One of my guitars has ribbon figure on its spruce top; as far as I'm concerned this is a preferable characteristic of its top.

Fiddle back (curly) figure, often seen in maple and mahogany and redwood, is a form of runout.

[rob2966]

My custom flamenco negra with cedar top has some runout on the top. I have absolutely no issue with this, the top was chosen for its overall quality and nice straight grain.

Definitely not specific to spruce.

Later
Rob

[Bruce Sexauer]

Run out means the wood fiber is not in line with the milled surface of the wood. It occurs is all woods. Because trees typically grow in a spiral there is arguably some degree of run out is virtually all sawn lumber since cutting a straight line through a curved medium means that the line can only be parallel to the fiber at one spot before theory and reality begin to diverge. On very large trees such as Sitka spruce, unless the tree is unusually twisted, it is possible to make many tops appear run out free, though they are not actually. On smaller trees with normal twist (generally EuroSpruce and Adirondack spruce) a luthier must be both diligent and lucky to align the truest part of the top toward the middle of the belly to get the appearance of no run out, and this is assuming the sawyer was VERY good at their work. It can be very difficult to assess a top for this quality, and even the best luthiers, if this is the most important attribute to them or their customer, are not going to nail it every time.

Structurally and tonally, run out in a spruce top is not an issue until the fibers are at least over a 10 to 1 incline to the surface IMO. This is probably conservative, and I think an otherwise sound top can actually go up to around a 5 to 1 ratio before there is real trouble. Seat of the pants, I think a ratio of 25 to 1 or so is where run out can become visible, but that is a guess. I have been surprised many a time where I thought the material was aligned well enough to avoid the visual signs, and yet there it was when the finish went on.

[CE Sobel]

Originally Posted by Bruce Sexauer

Structurally and tonally, run out in a spruce top is not an issue until the fibers are at least over a 10 to 1 incline to the surface IMO.

Your criteria brought to mind the old Army regulation for "aircraft grade" spruce, which specifies about a 12:1-15:1 ratio for allowable runout in spruce which will go into a plane. The stresses are definitely higher in a plane and there is a lot more at stake haha.

Here is a link to the old manual, it's an interesting read: http://www.westcoastpiet.com/images/...t%20Spruce.pdf

To the OP: the reason you tend to see runout more in spruce tops is because spruce in general has more of a tendency to grow with a spiral pattern than cedar or redwood does. I have a luthier friend who does a lot a hiking in the Carpathian mountain range in Europe and he says the trees pretty much all have some kind of twist to them. I rarely see a cedar tree around here with any significant twist to it. Engelmann spruce seems to grow pretty straight as well. This is a broad generalization I know, just my observations.

Chris

[IBKuz]

Originally Posted by mcgr40

yes, you can see this effect in other woods. It is a greater percentage of end grain "running out" of the viewed face of the wood. The endgrain tends to absorb finish differently, hence the darker color. I will see if I can find a pic somewhere.

My quick search of images of Cedar guitars did not show any of the 2-Tone look that I have seen in Spruce. I would appreciate your posting an image of this

Originally Posted by ChuckS

I'm not a luthier, but here are a few examples of runout:

The ribbon figure often seen on mahogany is alternating bands of runout; runout in one direction alternating to the other direction. One of my guitars has ribbon figure on its spruce top; as far as I'm concerned this is a preferable characteristic of its top.

Fiddle back (curly) figure, often seen in maple and mahogany and redwood, is a form of runout.

I like it too and was aware of this as being considered Runout. I was more interested in this 2-Tone appreance of the two matched halves occurring due to the spiral growth pattern.

Originally Posted by rob2966

My custom flamenco negra with cedar top has some runout on the top. I have absolutely no issue with this, the top was chosen for its overall quality and nice straight grain.

Definitely not specific to spruce.

Later
Rob

I myself like to see it minimized, though I would not reject a guitar outright over it. On my current build I asked for none but understand that there is a chance after finish that it may show up. Visually for my build I just though an even homogenous creamy appearance would look best.

[IBKuz]

Originally Posted by Bruce Sexauer

Run out means the wood fiber is not in line with the milled surface of the wood. It occurs is all woods. Because trees typically grow in a spiral there is arguably some degree of run out is virtually all sawn lumber since cutting a straight line through a curved medium means that the line can only be parallel to the fiber at one spot before theory and reality begin to diverge. On very large trees such as Sitka spruce, unless the tree is unusually twisted, it is possible to make many tops appear run out free, though they are not actually. On smaller trees with normal twist (generally EuroSpruce and Adirondack spruce) a luthier must be both diligent and lucky to align the truest part of the top toward the middle of the belly to get the appearance of no run out, and this is assuming the sawyer was VERY good at their work. It can be very difficult to assess a top for this quality, and even the best luthiers, if this is the most important attribute to them or their customer, are not going to nail it every time.

Structurally and tonally, run out in a spruce top is not an issue until the fibers are at least over a 10 to 1 incline to the surface IMO. This is probably conservative, and I think an otherwise sound top can actually go up to around a 5 to 1 ratio before there is real trouble. Seat of the pants, I think a ratio of 25 to 1 or so is where run out can become visible, but that is a guess. I have been surprised many a time where I thought the material was aligned well enough to avoid the visual signs, and yet there it was when the finish went on.

Thanks for the info Bruce. It never ceases to amaze me at the ingenuity that people use to figure out these complex issues with basically simple tools and a little bit of hard work. The foresters of the woods you use and the luthiers all show amazing skills in the work that you do. As wood working is literally as old as the hills, it has played a very integral part (and still does), in the development of the hunan race.

Originally Posted by CE Sobel

Your criteria brought to mind the old Army regulation for "aircraft grade" spruce, which specifies about a 12:1-15:1 ratio for allowable runout in spruce which will go into a plane. The stresses are definitely higher in a plane and there is a lot more at stake haha.

Here is a link to the old manual, it's an interesting read: http://www.westcoastpiet.com/images/...t%20Spruce.pdf

To the OP: the reason you tend to see runout more in spruce tops is because spruce in general has more of a tendency to grow with a spiral pattern than cedar or redwood does. I have a luthier friend who does a lot a hiking in the Carpathian mountain range in Europe and he says the trees pretty much all have some kind of twist to them. I rarely see a cedar tree around here with any significant twist to it. Engelmann spruce seems to grow pretty straight as well. This is a broad generalization I know, just my observations.

Chris

I would like to someday see a large spruce to see this spiral growth. The Cedar I have seen looks fairly straight, yet they are not that large here in Eastern Canada. Of the largest White Pine I have seen, I again can not see any spiral pattern to the growth. I will have to look a little closer next time to see if I can discern the pattern.

[Bruce Sexauer]

While the spiral can sometimes be seen on the outside of a tree, it is not really usually all that obvious. If it is that easily seen, it is pretty much a pass for me when I am in the forest. Where the spiral IS easily seen is when one splits the wood with wedges or a froe making shakes. If one does split the wood before sawing it, there is a much greater chance of getting no visible run out. While many say they do this, it is time consuming and by no means the rule for the millwright who is trying to make their living. This is the great advantage of buying wood from one of the several small suppliers such as Old Standard, the Hampton Brothers, or Rivolta (for instance) in Italy. But these sources tend to be much more dear than the novice builder is willing to go, and I might PAY as much as $500 for a truly great top direct from the cutter. . . though not often. And there is still no guarantee that there will be no surprises as it is wood that grew wild and there is a part for luck to play despite great skill on every side.

I once built a house on the west coast of Vancouver Island and split all the shakes myself from bolts I cut from huge (6' diameter? long time ago) Western Red Cedar down falls. All of these shakes had a noticeable twist in them, so I am pretty sure cedar has similar twist to Spruce.

[printer2]

The first acoustic guitar I built with a cedar fence board as a top. It was a three piece top and I did not know anything about runout. I thought it would look better with the grain lines of the boards matching its neighbor piece so I flipped the middle piece top to bottom. The runout was not apparent until the finish was on. Here you can see the middle section is lighter than the sides.

[IBKuz]

Originally Posted by Bruce Sexauer

While the spiral can sometimes be seen on the outside of a tree, it is not really usually all that obvious. If it is that easily seen, it is pretty much a pass for me when I am in the forest. Where the spiral IS easily seen is when one splits the wood with wedges or a froe making shakes. If one does split the wood before sawing it, there is a much greater chance of getting no visible run out. While many say they do this, it is time consuming and by no means the rule for the millwright who is trying to make their living. This is the great advantage of buying wood from one of the several small suppliers such as Old Standard, the Hampton Brothers, or Rivolta (for instance) in Italy. But these sources tend to be much more dear than the novice builder is willing to go, and I might PAY as much as $500 for a truly great top direct from the cutter. . . though not often. And there is still no guarantee that there will be no surprises as it is wood that grew wild and there is a part for luck to play despite great skill on every side.

I once built a house on the west coast of Vancouver Island and split all the shakes myself from bolts I cut from huge (6' diameter? long time ago) Western Red Cedar down falls. All of these shakes had a noticeable twist in them, so I am pretty sure cedar has similar twist to Spruce.

Not sure if this is related. In the summer of 2012 we had one of the strongest summer storm on record in the Ottawa Valley. Many trees where uprooted, lots of damage to the forest. There where two of the largest White Pine trees in the area (30 - 36' Dia.) that while not knocked down they flexed/bent so far by the wind that they received what I would call stress fractures. Here is a picture of one of the trees -



One thing I remember when I was looking at the trees was that the fractures twisted up the trees slightly (likely more than the ratios you were mentioning). In this picture it is not as noticeable as it was on the second tree. This fracture was in a spiral and was not waving back and forth or straight up the tree. Do you think this would be an example of this spiral growth? Whenever splitting wood for the fire (Pine, Maple, Birch, Oak), I always remember the splits being straight but the billets are usually short so a slight twist may not be noticeable. I will have to examine the pieces more carefully next time.

[Bruce Sexauer]

Even though the outside of the tree spirals, the center, being a theoretical straight line, does not, and point in between are interpolated more or less evenly. So a plane in line with the grain on the outside and projected to the middle of the tree will become decreasingly grain aligned as in goes toward the center of the tree. In fact, a very limited number of such planes can be projected into the middle of the tree as they have thickness and cannot be overlapped. Thus such a plane (we could call it a half of a top plate) can ONLY be grain aligned on one side at best.

I mentioned it before, but it is important to understand that even the grain aligned outside edge of this "plate" cannot be grain aligned from one end to the other under typical circumstances. This is because we are imposing a straight line onto a circular spiral, which really is a contradiction of terms.

The point is that anyone who insists on a wooden object with no run out is not grounded in actual reality. This is not a snarky comment, it is mathematical truth. What they are actually looking for is the illusion of no run out, and that requires a magician, some luck, and usually some form of distraction.

There are localized places in many trees where the spiral is uneven causing straighter areas or even retro spriral. Trees are rarely actually round or straight. But generally, if you split a piece of firewood and then lay the split facet on a flat surface you my notice that two opposing corners touch down and the piece can be rocked, assuming the facet is flat enough. If you do this to several pieces you will notice that is is almost always the same direction for the twist in the surface. It will not matter what species you are splitting, the twist will be in the same direction, at least in the northern hemisphere.

[Alan Carruth]

Run out reduces the long-grain stiffness of the wood a bit, so it could be compensated for by simply leaving the top a little thicker if that were the only consideration. The main issue, IMO, is what happens when you glus a bridge down to a top with run out.

Basically, the torque on the bridge is trying to peel it up from the back edge. If the run out is such that the grain is rising toward the front of the bridge the glue line is not as strong along the back edge as it could be, and the bridge will start to peel up sooner than expected.

Of course, the run out reverses as you go across the join line, so that on that same top the grain will be sinking toward the front of the bridge. As the peeled up area on the 'rising' side reaches the center join the wood tends to split downward into the top. If the run out is bad it can actually split most of the way through the top.

Since it's fairly common for trees to start growing with the fibers aligned with the axis of the trunk, and become more spiral as they get older, the usual 'bark match' of top halves tends to bring out run out. In that case a 'heart match' can salvage an otherwise nice looking (and frequently expensive) top that might not be useful otherwise. Again, as Bruce points out, a lot depends here on the sawyer.

Aside from spiral run out, you can also have run out that is caused by things like knots and bear claw, or other things that vary as you go up the trunk. Often this sort of wood is quite attractive, and makes an 'interesting' top. IMO (and others may disagree, of course) this is not a problem so long as the spot where the bridge is glued down has little or no run out. This can require some careful layout work at the beginning, of course.

When I started building most top wood came as rough sawn pieces, and it was relatively easy to see the run out. These days everybody sands them, and it's much more difficult because the surface is not as relfective. If one were a cynic one would say that this makes it easier for the suppliers to pass off tops with run out as higher grade, but, of course, we all know they wouldn't do that...

[mcgr40]

Originally Posted by Bruce Sexauer

The point is that anyone who insists on a wooden object with no run out is not grounded in actual reality. This is not a snarky comment, it is mathematical truth. What they are actually looking for is the illusion of no run out, and that requires a magician, some luck, and usually some form of distraction.

as I like to say, "it used to be a tree."