Board Breaking!

[sensei8]

To have spacers or to not have spacers? That is the question!

Your thoughts?

[bushido_man96]

I think spacers make the breaks easier. With the boards or bricks all stacked together, you have to drive enough energy through all of them at once, where as with the spacers, the break of the one above can help facilitate the one below, and since the one above isn't braced by the one below, I think it requires less energy.

Or something like that....

Perhaps someone with knowledge of the physics involved could chime in, because I know I sound like a total incompetent right now.....

But I think I know what I am trying to say...

Maybe...

[Wolfman08]

You're right. I cann't remember the details myself, but spacers do make the break much easier because of some highly detailed physical laws.

[DWx]

]I think spacers make the breaks easier. With the boards or bricks all stacked together, you have to drive enough energy through all of them at once, where as with the spacers, the break of the one above can help facilitate the one below, and since the one above isn't braced by the one below, I think it requires less energy.

Think you're right. Spaced boards are easier because you're basically breaking one board and then the next board in sequence rather than having to generate a large amount of force and each board is only supported on a small area. Spacers mean less force but you have to maintain it over the distance. Stacking boards without spacers effectively creates a block of wood. To break it you need much more power but you don't have to maintain it over the distance. With spacers each board flexes in turn before it finally snaps. With an unspaced stack, it acts as one and the entire lot flexes first before going.

Its a bit old but there's this old video of GM Rhee breaking with a little mechanics explanation voiceover:

Not got stuff on spacers but does tell you that you expend enough energy to work a "dozen electric toasters"

[Wastelander]

Basically breaking with spacers is applying the force to break one board across the distance of the top of the top board to the bottom of the bottom board, while breaking without spacers is applying the force to break one board approximately multiplied by however many boards there are across the distance of the top of the top board to the bottom of the bottom board. Clear as mud?

[sojobo]

In your opinion...

What's the most important part of board breaking?

My guess is that it is technique and mental resolve.

My style of karate does not tend to feature it - apart from some groups you dust it off for embu.

Referred to in Japan as Tameshiwari (wood test), it draws some parallels with Tameshigiri (test cutting (with a sword)) which I have done with my Koryu group.

The original purpose of Tameshigiri was not the test the swordsman, but to test a new blade. However in more modern times it has become a way to manifest ones skills.

Given that a karateka's weapon is his/her hands then I would suggest that Tameshiwari is a test of one’s technique both physically and mentally.

On the re-breakable vs natural wood debate – I’m kinda with Sensei8 here. As I say – I don’t do breaking, but I can understand (through my Tameshigiri) the added dimension of a “natural” target each time as opposed to one that you have broken several times before. After you have broken something once, the mental barrier is gone – where as every natural wood board is (potentially) different.

Sojobo

[sensei8]

Spacers promote the material under the first one, and it dominoes after that!

So, if I stack 5 boards with spacers, am I breaking 5 or just 1 in reality? Imho, I'm only breaking 1. However, am I releasing enough energy for that 1, or am I releasing enough energy for all 5?

That's why whenever I see tameshiwara demo's of 20, 30, or 40 stacks of concrete, I'm laughing because they didn't break 20 and so on, no, they broke 1 or maybe 2.

Now, break a stack similar WITHOUT any spacers; that's energy transferred through and through.

That's why a stack of 5 boards without spacers is far more difficult than a stack of 5 SPACED boards.

IMHO!!