board breaking

[rb]

Where are these board to body equivalences coming from ?

[TKDLadyInSC]

To me, it came from my instructor. For him from his instructor. Some where down the line there was a study done. It was found that it takes certain pounds of pressure to break different bones. Then they measured different boards, different sizes, until they came up with a close equivalent in pounds of pressure to break.

 

Also note, we do not use spacers. If you use spacers, you would have to rework the equations. When spacers are used, you create multiple points of impact. You have the initial contact with the front board. Then it creates a new contact point. In the space is an area for acceleration between the boards.

[ZeRo]

are spacered boards easyer to break?

[Maestro]

yes, spaced boards are easier. For example, if you take three boards and put them next to each other without spacers, then it's nearly the same as having one, triple-thick board (but not quite). As such, it requires that you hit it with the total power necessary to break all three. However, with spacers, you are really only breaking one board at a time, albeit very quickly, therefore you are able to exert your energy over a longer period of time, and so the neccesary power at any given time is less than that of a break without spacers. Also in a spaced break, the first board impacts with the second, so some of the energy used in breaking the first is carried into the second, and not wasted. Someone who can break two boards right together could probably break five with spacers.

[Stold]

I know 1 12x12x1 inch board is equivelant to a floating rib. 2 of these boards is equal to the bones in the lower arm. Try breaking with a defensive move rather than an offensive move. Break 2 boards with a low block. If you can do this, you know if the bad guy punches at your gut, and you block it effectively, he won't be punching anyone anytime soon.

 

To avoid being banned from this site, I will just say two words. "No comment."

[TKDLadyInSC]

Oh, please do comment.

[ZeRo]

i agree, im interested in wht you wanna say. keep it friendly though, dont wanna get this closed.

[rb]

I am curious how this testing was done. Are we talking single bones being broken on a support and what is the moisture content ?

 

The thing about boards and bones is that they are anistropic -that is they don't exhibit the same properties in all directions. During breaking, boards are carefully aligned and strikes are applied in the transverse direction of the board which is the weakest. I don't have the numbers handy but bone is also weaker in the transverse direction.

 

Also be known that bone has been measured to be strongest in the longitudinal direction. So as you move angularly closer to the longitudinal orientation it becomes harder to break. I mention this because I don't think a direct transvere direction stike is always the case so the strength of the bone is intermediary.

 

That's just a single bone. There are two in the forearm. They connected by flexible tissue and also encased in muscle, fat and skin. That makes the forearm quite deformable which serves to disperse incoming energy, quite possibly leaving not enough to fracture the bone(s). Not to mention that the arm is not bound to supports like a holder or concrete blocks and can move with the blow further reducing the energy available for fracture.

 

I don't think the energy absorption and fracture mechanics of the body can be that easily approximated.

 

Note pressure is a measure of force over area.

[Stold]

What he said.

[TKDLadyInSC]

Very intelligently thought out post rb. Made me think . Thank you. I will try to find out the conditions of the study. Here are my thoughts. The following is not anything I have been taught, but my conclusion after considering what I have been taught and what you have just said.

 

It seems that these board to bone ratio would have to be with the bone supported as in a board break. I guess that would make a speed break (board dangled from one hand unsupported) a more accurate measure.

 

Also, you would have to take into account 2 identically sized pieces of the same type wood can be 2 completely different strengths (ie. one may be full of sap or knots), no 2 are the same.

 

Bone is the same way. There are many factors to take into account: bone size (even though many of us like to say we're not fat, just big boned , there are differences from one person to the next in bone size, not just length, but also diameter), age (which would affect bone density), muscular structure support.

 

As martial artists, we are taught to find our opponents weakness. This is why I would take aim at these smaller bones if necessary, but if attacked on the street, my first attack is a side kick to the side of the knee. As a person with knee problems I know how detrimental an injury to the knee is.

 

However, we have strayed far from the subject. Thank you again rb for your thought provoking and informative post.

 

Back to subject, I like board breaks