|
|
#16
01-16-2018, 09:05 AM
|
|||
|
|||
To the OP....
Wood is a natural product and thus imperfect. As such - you will have to make trade off's based on what is more important to you vs what is less important to you. Cost is one factor in this discussion.... Work with your wood supplier. The fellows cutting the wood generally have a pretty good idea of how to find something that matches what you are looking for. 
|
|
#17
01-16-2018, 01:53 PM
|
|||
|
|||
|
I believe that the angle of the reflected light bar is a sign that the tree grew with a changing twist. I often see tops where the tree started out growing straight, and became more twisted over time. In a case like that a 'heart match' will line up the reflection across the two halves at the center join, because there is less, or no, runout there. If the tree grew with the same run out the whole time the stripes on the two halves of the top would be straight across, but in different places. In practice I'm not sure you'd see that very often.
'Stripe' figure, which you often see in tropical woods, is caused by a periodic change in run out. I have also seen this in a less pronounced way in Red spruce from time to time. Those always seem to be good tops.
|
|
#18
01-16-2018, 06:40 PM
|
|||
|
|||
|
I took a pic of this tree in New Mexico years ago just to illustrate a point when discussions come up like this. There are a lot of theories as to why this happens and probably more then one reason why including heliotropism, in defense of dry climates and water distribution at the base of the tree, flexibility against wind and or the weight of snow and so on.
I have heard that heliotropism or phototropism is the cause of striped wood like mahogany that grows close to the equator where it twists in one direction to get the sun then twists back in the other. Interesting stuff. Needless to say if you were to cut a board out of the tree below you would have some serious runout. 
|
|
#19
01-17-2018, 03:04 AM
|
|||
|
|||
|
The real problem is that suppliers keep growing this stuff outdoors. How can they expect to get a perfect product when they can't control growing conditions? Today's consumers are so much more sophisticated than those in the past, but the growers just haven't kept up.
They should take a tip from the pot farmers: you want a first-rate product, you grow indoors, under lights, controlled air circulation, the whole deal with no shortcuts. Stop treating your product like it was the last millennium, with those moon-phase myths and other superstitions. This is the 21st Century. You can't fool today's buyers who know what perfect really is.
__________________
"Still a man hears what he wants to hear, and disregards the rest." --Paul Simon Last edited by Howard Klepper; 01-17-2018 at 03:10 AM.
|
|
#20
01-17-2018, 08:25 AM
|
|||
|
|||
|
Quote:
|
|
#21
01-17-2018, 09:12 AM
|
|||
|
|||
|
Quote:
Supply Chain Management should get right on it...
|
|
#25
01-17-2018, 11:47 AM
|
|||
|
|||
|
Quote:
In recent years, internet discussion forums have made famous the term "runout". Most players don't know what it is or what significance it might have: they only know that other internet discussions have said it is bad. Very, very, very few guitars are "compromised" tonally or structurally due to having a guitar top that has some runout. (Far too many braces have lots of runout, leading to split braces, but that hasn't become an internet discussion topic. One-piece necks display poor "runout" at the head, leading to many broken heads, but that hasn't caught a lot of internet discussion attention either, despite being a common practice on even the most famous brands.) Runout is one of the criteria that should be considered in wood selection by the maker: it should be of little concern to the player or buyer. Most instruments come with warranties that ought to provide the buyer peace of mind regarding the structural integrity of the instrument one buys, and recourse should there be issues with it. Last edited by charles Tauber; 01-17-2018 at 12:41 PM.
|
|
#26
01-17-2018, 01:12 PM
|
|||
|
|||
|
Here is a pic of one of my vintage guitar. It's an S.S. Stewart from about 1925 and has some pretty pronounced runout. You can see that the left half is lighter then the right half as Charles mentioned. It tends to bother some people probably more then it should.
|
|
#27
01-17-2018, 01:12 PM
|
|||
|
|||
|
Quote:
I think the headstock deal with Gibsons is not run-off per se, but a short grain condition. Though it wouldn't be much of an issue with a headstock overlay on each side. I think the standard for a wing spar on an airplane is 1:25, so even a little run-off is acceptable on an airplane wing. Of course the main thing with close to zero run-off for a top is that it can generally be worked thinner..
|
|
#28
01-17-2018, 01:26 PM
|
|||
|
|||
|
Thanks Charles.
As I see it, run out in the top does two things that you don't want. One is that it reduces the long-grain stiffness, as compared with wood from the same tree that has no run out. This is not a large effect unless there is a lot of run out. The second is that it seems to contribute to problems when the bridge peels up. Assuming the run out changes direction at the center join; on one side it seems to reduce the strength of the glue line between the bridge and the top, so that it peels up more easily. As the loose area reaches the center line the top wood starts to stay glued to the bridge, and to split downward into the top. Again, this is not a problem so long as the run out is not too pronounced, but when it is a problem it can be a big one. It seems to make it more likely that the bridge will come up, and that it will do more damage when it does. I don't know of any individual maker who would use a top with that much run out on the center line, but I see them from the factories. 'Phototropism' has become such a standard 'explanation' of twist in trees that I suspect it's futile to try to counter it. Still, the Don Quixote in me can't resist. First, sunflowers twist around to track the sun, trees don't. It's possible that the leaves of trees do, but it might be hard to demonstrate that. There is some evidence that the twist in the fiber direction on a tree responds to changes in stress. This is a fairly complex deal, but it seems likely that if this is the case what the tree is doing is trying to not twist around, so that it can keep its branches where they are. Any unbalanced load that that might cause a tree to lean induces changes in the way the wood grows to counteract it. This sets up stresses in the wood that help to pull the tree up straight, or keep it from leaning any more. The mechanism involved may also introduce a twisting moment on the trunk, and to counteract that the tree would actually shift the fiber direction of the new growth to cancel out the twist. Tropical trees do 'see' the sun on different sides as the year progresses. In response to that they could put out more leaves on the sunny side, and drop those that are shaded. This would change the bending load on the trunk, and could lead to changes in twist of the fiber direction. It would also cause changes in built-in stress in the wood. I have seen evidence of this is pieces of striped mahogany. Cutting brace stock from one such piece recently I noted that when the brace had a lot of run out wood it tended to bend toward the outside of the tree when it was cut off, while wood where the fiber direction was aligned with the axis of the tree didn't do that. I have set forth a hypothetical model here, based on some reading I've done and the few observations I can make on lumber I've gotten. Somebody with access to tropical trees could find out a lot more.
|
|
#29
01-17-2018, 02:01 PM
|
|||
|
|||
|
Quote:
Quote:
|
|
#30
01-17-2018, 02:04 PM
|
|||
|
|||
|
Quote:
Both good points for makers and repair people but neither is particularly relevant to the player/buyer. The change in runout direction should be considered by repair people when removing a bridge (and, possibly, a fingerboard glued to the top).
|
