Cedar Goban

[msgreg]

Another reference to goban wood, this is the comment on YMImports' Tibet Spruce boards currently on offer.

Tibet spruce wood from Yunnan Province in southern China. This type of wood is called ''picea asperata'' in Latin and is sometimes called ''dragon spruce'' or ''Tibet Spruce''.

[Mike Novack]

From looking at the listing for some species and considering the specific application with which we are concerned I'm not sure that this is the right test.

It isn't really just a test of "hardness" but has a large component of "elasticity". Thus our "osage orange" has a high Janka score. No, osage orange isn't really that hard but it is very elastic (good recovery from severe deformation) which is why it was an excellent wood to make bows from. In other words, the Janka test ball can be pressed in quite hard making a temporary deformation in the wood but that "dent" rebounds when the pressure is released so by the Janka method "didn't leave a dent".

Woods that have a high Janka score for that reason are less likely to break a shell stone than other woods which have a somewhat lower Janka score but are brittle (little to no "give" to them).

I think that evaluating woods for go boards would require results from a test that measured both pressure to leave a dent and amount of temporary deformation for a given load. If the first is too small, the board will dent in use and if the latter is too small likely to shatter breakable stones.

[msgreg]

From looking at the listing for some species and considering the specific application with which we are concerned I'm not sure that this is the right test.

It isn't really just a test of "hardness" but has a large component of "elasticity". Thus our "osage orange" has a high Janka score. No, osage orange isn't really that hard but it is very elastic (good recovery from severe deformation) which is why it was an excellent wood to make bows from. In other words, the Janka test ball can be pressed in quite hard making a temporary deformation in the wood but that "dent" rebounds when the pressure is released so by the Janka method "didn't leave a dent".

Woods that have a high Janka score for that reason are less likely to break a shell stone than other woods which have a somewhat lower Janka score but are brittle (little to no "give" to them).

I think that evaluating woods for go boards would require results from a test that measured both pressure to leave a dent and amount of temporary deformation for a given load. If the first is too small, the board will dent in use and if the latter is too small likely to shatter breakable stones.

The Janka hardness test measures the resistance of a sample of wood to denting and wear. It measures the force required to embed an 11.28mm (.444 in) steel ball into wood to half the ball's diameter. This method leaves an indentation.

Are you really saying that an 11mm ball pushed halfway into a piece of wood would not leave a dent? That'd be amazing wood! [*prepares to be amazed*]

You're probably right that the Janka Hardness Test might not be the absolute best test for evaluating potential goban woods. However, it does appear to be one of the most common tests done on all wood types. And it is a test that we have a large amount of data on for a large variety of woods.

Is there a common test for wood that tests elasticity? Are there any available charts with that information for a variety of wood types, including those used in gobans?

[Mike Novack]

"Are you really saying that an 11mm ball pushed halfway into a piece of wood would not leave a dent? That'd be amazing wood! [*prepares to be amazed*]"

Hee-hee -- no, of course not. But I think you are misunderstanding how this test would behave in practice. Picture this. Somewhat less force is applied, the wood surface dimples in under that load, but recovers when the force is removed. Now what percentage of the Janka score was that?

What I am saying is that for a relatively inelastic wood, once we pass the amount of force that leaves any permanent dent (to say nothing of imbedding the ball halfway) we have exceeded the elastic limit for that wood, catastrophic material failure, and just a little more force will drive the ball well in.

And yes I realize that perhaps we don't have the desired statistic for a large number of woods for exactly what we want of a go playing surface. We want .....

a) A surface that will deflect significantly under a large load but still elastic. The larger the deflection as the go stone hits the surface the slower it is being decelerated (and so less force on the stone). We don't want a fragile stone to break.

b) A surface where the load of a rounded object hitting it can be significant before the elastic limit is exceeded. We don't want a dent left behind.

It actually shouldn't be all that hard to devise a test that would give the results we would want for this purpose. We'd want a device that would measure:
1) What is the maximum impact (of the rounded* hitting object) that leaves no dent? (impact was completely elastic)
2) What was the deflection of the surface for that impact?
For the most suitable woods we want both of those to be high though might need to compromise.

Might be a very good "science fair" project for a go playing high school student. The impact for no dent part easy but measuring the very small deflection not so easy.

* The radius for our purpose should be much larger than the Janka test ball, inches, not a fraction of an inch.

[bogiesan]

Thanks for the links, fun stuff to watch later.

You'd need 9 of those 8"x8" cedar blocks, carefully planed and laminated, to make a full-size go board and apparently the seller only had one.

Ignore all the rantings about appropriate wood stocks for serious go boards. You can make a board out of anything you want to including slabs of concrete or granite or silicone. Go for it, try to have fun, and buy enough stock to build two units; the first one might not work out correctly.

Laying up wood for several years dosnt' really "dry it out." It's a process formally known as seasoning or stabilizing, converting wood taken recently from a tree to stock that can be used to build somehting. Depending on the wood species and several other factors, it can can decades before a huge solid block of wood is less likely to split.

Hey guys,
So, I don't know if any of you guys know of "theduddha2" on youtube, but I personally love his videos. This is his latest video in his "making your own Goban" series - http://www.youtube.com/watch?v=GAZ9Zqrr ... JgVg6IwwJw
Anyways, he's inspired me to want to make my own Goban. What do you guys think of making a floor Goban out of a cedar block? like this one - http://www.ebay.com/itm/Aromatic-Red-Ce ... 0882302699 but bigger?
Do you think it will look nice? Any faults you might think of? What is your opinion in general?
Thanks in advance for your time!

[Mike Novack]

a PS (in case some high schooler wanted to try this)

Trying to measure the depth of the impact depression directly probably too difficult/expensive. But what this depends on is the modulus of elasticity of the material and that you can find other (easier) ways to measure. In other words, your project just needs to defend that the substitution of test method is valid. So ......

a) Impact device to measure resistance to denting (how hard can the wood be hit and leave no dent). Move stock along with gradually increasing impacts and note at which point dents begin to appear.

b) Modulus of elasticity measured by beam deflection or something similar.

[msgreg]

Ignore all the rantings about appropriate wood stocks for serious go boards. You can make a board out of anything you want to including slabs of concrete or granite or silicone. Go for it, try to have fun, and buy enough stock to build two units; the first one might not work out correctly.

*My* rantings are about collecting enough information for wider recommendations on woods, especially those wood types available outside of Asia. If the burden and cost are low, I certainly agree with just trying it (and the advice on building two units). My focus prevented me from this, potently best, recommendation of "just do it". Lots of materials will result in a playable board and I'm sure you'll greatly enjoy your homemade board!

Though I would add that the Janka hardness of the wood might affect what material your stones are made of, whether you risk breaking slate and shell, or glass, or just go with plastic (or wood).