Force and Power of Okinawan Nunchaku

Dai-Shihan Ben Froidevaux, 6th dan and All-Europe 
representative of Seiyo no Shorin-Ryu Karate
Kobudo Kai

With today's unrest, one might consider carrying self-defense weapons, such as nunchaku. Nunchaku can generate tremendous forces when handled by a properly trained martial artist. But, the weapon must have sufficient mass, and the martial artist using nunchaku must be able to rapidly accelerate the tool to develop necessary kinetic energy to cause damage. 

Those who train at the Seiyo Hombu start with foam-rubber chuks during bunkai (self-defense) and kumite (sparring), or some train with DIY magazine-chuks (see link in list under the blog title). But even foam-rubber and magazine chuks can generate considerable force when handled correctly. 

We had a father and daughter combo in our dojo some years ago, and was able to film her (about 7 years old) creaming her dad with foam-chuks. The father ended hopping up and down on one foot, holding the other foot in his hand, after she had smashed his foot without warning with foam chuks, I asked permission to send the video to America's Funniest Home Videos and told him I would divide the winnings with him because we had a winner - but the father refused. 

In Shorin-Ryu Karate and Kobudo, students are taught not to use their karate or kobudo against another except in self-defense, as nunchaku can produce some impressive forces. According to one source, a nunchaku tip of 6.3 ounces, can accelerate to 88 meters/second (282 feet/second) and generate 350 joules of kinetic energy. According to this source, this would equal the energy generated by a bullet fired from a Colt M1911! But, a nunchaku will not penetrate a body, unlike aerial dynamic bullets with high specific gravity. Luckily, few can generate this kind of force with nunchaku.

Nunchaku made from two magazines and tape

Human bones are strong! For instance, a bone can survive a strike of 10,000 joules of kinetic energy (3,700 foot-pounds of force) as long at the strike is perpendicular to the surface. Additionally, most bones are padded with soft tissue to adsorb the impact. But a strike at an angle of less than 15 degrees can potentially fracture a bone with about 375 joules of kinetic energy (277 foot-pounds of force). Keep in mind that each bone in the human body, had different masses and different amounts of padding.

The impact-force of nunchaku depends on the speed of the nunchaku and surface area of impact. The damage to a person depends on how fast that chuk travels, the mass of the chuk, and the surface area the force is applied to. In addition, if the surface is soft, such as a stomach, the flesh will absorb considerable amounts of kinetic energy. But if the surface is a hard (such as a collar bone with little surrounding flesh) the damage will be greater (Hausel, in prep).

The tip of a Colt M1911 bullet has a surface of 25 square-millimeters, thus the impact force is calculated as 350/25 = 14 joules/square-millimeter. But if a nunchaku strikes the same surface, the impact force will be notably less because of the surface area, or size of nunchaku. So, we might end up with about 350/100 = 3.5 joules/square millimeter, or essentially 4 times lower impact force than a bullet (assuming that the striking area of the nunchaku is about 1 square-centimeter (0.15 square-inch)). This is why octagonal nunchaku are more effective than round nunchaku. Because of the geometry of the octagonal chuks, the chance of hitting a target with one of the eight octagonal edges is relatively high, and such a smaller surface area will result in an increase in impact force. 

Nunchaku-jutsu, Seiyo Hombu in Mesa, Arizona

Because of small bone diameters with minimum amounts of soft flesh enclosing finger and hand bones (as well as many nerve endings), fingers and hands provide good striking surfaces. Other targets with little soft tissue include toes, ankles, shins, elbows, collar bones, and the head. But one should always avoid the head, which has areas that could lead to death if struck with nunchaku.

In the following video, Soke Hausel of Seiyo no Shorin-Ryu Karate Kobudo Kai, demonstrates one of many kata. It is important to learn to handle kobudo weapons, with force, speed and power, but don't try this without proper guidance, as you can easily end up with a serious injury if you strike yourself, or are struck by another person, or receive a strike from a ricochet of nunchaku. And hospitals today, are places to avoid, unless you appreciate violation of constitutional and human rights. 

Hausel, W.D., in prep., Making of a Grandmaster: traditional Okinawan Karate & Koabudo in North America, in preparation.