The training tool and "soul" of practicing Iaido is the Katana, the famous traditional Japanese Sword. However this is more of a popular knowledge term than the actual name of this weapon in Japan, especially when practicing Budo, Japanese martial arts.
With this article I'll try to give some explanations and shed some more light on a sometimes difficult to access topic. Bokuto or Bokken: These two terms, which are basically synonimous, mean "wooden sword". They are reproductions of a Japanese Katana made in wood. They come in many different styles, in many materials (but most often either Red or White Japanese Oak) and finishings. They are used either as a pure training tool, but they are in and of themselves a proper weapon in their own right! The famous Swordsman Miyamoto Musashi notoriously won several duels to the death while using "only" a wooden sword. Iaito: This term indicates as well a reproduction of a Japanese Katana used for training purposes; it uses the very same fittings, scabbard, tsuba, etc. etc., but the blade itself is NOT made of folded steel, it is not sharp, and cannot be sharpened. It is made generally of a metal called Zamal, a mixture of Zync and Aluminum, and it generally weighs less than a true Katana, even if nowadays they exist in every weight, lenght and customization option. The tip is relatively sharp and it is possible to injure oneself or someone else with it, if used carelessly. On a strong impact against an hard object, it will generally bend or dent. Many if not most Iaido practitioners today use a Iaito only, progressing from lighter blades to heavier ones as their experience increases. Shinken: This is actually the name with which a Japanese martial artist will refer to a real Katana. What it means is that it's a true "live" sword and sharpened almost to a razor edge. It is traditionally made by special artisans over the course of 6 or more months, and it tends to be very, very expensive, roughly from 6.000 to 20.000 USD for a modern made one destined to martial arts practice. It is made with folded steel and it is generally way heavier than a Iaito of the same size. Many high-ranked Iaidokas will train with a Shinken, even if not everyday, to hone their focus and attention level, as with a simple and small mistake it will be easy to open small wounds, especially if in contact with the tip area of the sword. It also requires constant manteinance as the steel used is not rustproof at all, so a special cleaning is performed after each Iaido session to guarantee the safekeeping of such a precious and expensive item. Next week we will examine more differences and venture into the legal aspects in Singapore of owning these training tools/weapons and transporting them from home to your training venue.
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In the modern world that everyday surrounds us with its obligations, work, responsibilities, family, with all their positive and negative aspects, one thing that surely we cannot experience if not in Iaido is... cutting with a 75 cm sharp edged Japanese Sword!
In this article we are going to understand the importance of a proper cut of Iaido - and the reason for doing it. First of all, we must always remember that we do not live in medieval Japan and we are not actually Samurai. Then, what is the purpose of studying fencing and dueling with a real Katana? There is a cultural interest and a curiosity aspect, of course, but those must be complemented by something else, something practical or spiritually empowering that we can take home with us after the everyday practice. That something else is... body control. Iaido is the art of mastering and controlling your body movement, position and power as much as it is cutting around with a sharp object. And from the rigorous study of precise, and sometimes punishingly difficult body control we get focus, we empty the mind from everyday's troubles and thoughts and possibly achieve even spiritual growth and control. We also get other physical benefits like a more elegant posture and fluidity in the movements. All things that can be as well achieved by... dancing! What makes Iaido unique and different from dancing is that it is a Martial Art, or Budo as the Japanese call it, and one of the most precise and refined out there. Therefore we must always keep in mind the fact that we are not just making elegant movements in the air with a dead piece of metal in our hands, but we are actually cutting, and that movements we make could signify life - or death - for us or for our opponents. This is why, in our Iaido course here in Singapore, we focus on the technical aspects of every movement: we are cutting air, but that movement should be exactly the same effective, real, full, alive, as we would be cutting an enemy during a duel in 17th Century Japan. With many exceptions, what-ifs, training conventions, of course, but always trying to achieve the proper trajectory, the proper angles, the proper force. Never and empty repetition of historical movements, but live and alive, logical actions in which we try to put all of ourselves! Only like this our practice becomes something more full and fulfilling and can honor our growth and the sacrifices of our predecessors. Recap
In the last installment of this two-part series of articles we discovered that cutting at full speed and with the correct form and angle generates a speed, at the tip (kissaki) of the Katana, of about 40 km/h. While this might not seem, at first glance, a particularly exciting speed, when related to the sword's main objective, which is cutting, we are going to discover something extremely interesting that will change the way you see and practice Iaido forever! Force, pressure and acceleration When evaluating the efficiency with which any blade is cutting, and not counting directly more metallurgic elements like hardness, flexibility and sharpness, the key element is the "specific pressure". This can be defined as the amount of pressure (measured in Kg) that the blade can generate on its smallest surface (the edge). We have to therefore go on with a few more calculations to understand exactly what that value is. To do that, first of all we have to discover the force and acceleration that we apply to the sword when doing a proper cutting movement. Force (F) is obtained by factoring mass and acceleration, and the latter can be calculated by dividing the speed by the time of the cut - and once again we see how important of a factor speed is. We calculated in the previous article that the speed is at about 40 km/h, which converted back in m/s equals to about 11.2 m/s. Taking the standard measure of time for a cut time duration (0.35 s) we will then discover the acceleration: Acceleration: 11.2 / 0.35 = 32 m/s Now that we know the acceleration, we can calculate the actual force applied to the blade, by factoring in the mass of the sword. Let's take as an example a 0.9 kg sword (which is actually on the lower end of a real folded steel Katana, that can easily go over 1 kg, even up to 1.2 kg). Force: 32 * 0.9 = 28.8 N (for Newton, the measurement unit of forces). Notes and approximations Before going on with our calculation, to determine the actual specific pressure that this Force will apply at the moment of the cut, I'd like to point out a few approximations: in reality we are calculating the acceleration of the tip of the sword factored with its mass which should be considered at the balance point of the blade, but this partially re-balances for not accounting for the user's arms mass. There are also implications related to the type of hit (rigid or elastic and in which portion), so we should account also for the kinetic energy of the sword and then proceed in calculating an energy rebalancing at the moment of the impact to really precisely calculate the forces in play but, as we will shortly see, the amounts and dimensions even approximated are so significant that there is not a real need to go to such detail. Specific Pressure Now to finally calculate the specific pressure that is generated at the moment of the cut, we need to try and estimate the surface of the working edge of the Katana. First of all let's say that the Katana is not really used for all of its lenght, but for approximately the half of it, so for 37.5 cm (0.375 m), if we keep the example of a 75 cm sword. To estimate the dimension of the sharp edge it's much harder, as it depends on a few factors difficult to approximate, but to better visualize still the overall amount of the forces we are talking about, let's assume that the edge will have the same size of a common sheet of paper, about 0.05 mm, so 0.00005 m (please note that the edge of an actual fully sharpened folded steel katana might be much smaller than that!). Therefore the surface area of the edge at the moment of the impact will be of 0.375 * 0.00005 = 0.00001875 square meters Conclusions Finally then we can calculate the specific pressure by dividing the Force (F) by this above obtained surface because: Pressure = Force / Applied Area and so: 28.8 / 0.00001875 = 1.536.000 N/m2 Because 1 Newton is equal to about 9,81 Kg, the final result is: 156.628,41 Kg/m2. One hundred and fifty six tons on a square meter!!! We are in front of an extreme and astonishing value: take your body and then throw on it 150 tons of anything and you'll be totally flattened in an horrid mix of blood, meat and bones. Now take that value and put it on the edge of the sword that is cutting you and you'll be very politely and neatly divided in two. This article is based on the work and calculations of Davide De Vecchi, who is fully credited for the original material. Introduction The simple fact of knowing how or why things work, doesn’t take away anything from their charm and at the same time allows for a correct, and ultimately more beautiful use for them. Does the fact that Newton discovered how and why apples fall from the tree negate our pleasure in eating them? Iaido doesn’t escape this rule and it is therefore possible to apply scientific knowledge to its techniques without worrying about unveiling secrets that will reduce its charm but that instead, if at all possible, will increase it even more! Did you ever ask yourself why a sword cuts? The edge, of course, but an edged sword might not be enough or, viceversa an unedged one can still easily kill: Furuichi Sensei (8th Dan Iaido, 7th Dan Kendo) often, during his Seminars, shows that a live katana (Shinken), a training unsharpened one (Iaito) and even a wooden practice reproduction pretty much cut in the same way if used properly. Physical Hypotesis and data Below we will apply some physics principles, with their connected math calculations, to the trajectories that the sword runs from its high starting position to its low arrival point. What we’d hope to demonstrate is that science agrees with a correct form and practice, and that sometimes sensations that lead you to believe that a movement technically not clean would be in practice more effective are actually wrong. We will therefore discover some significant values that scientifically agree with the perfect technical execution of a cut. First of all, let’s calculate how much distance the blade (or, to be more precise, its tip) covers from start to end in a proper cut, as opposed to a inaccurate one, when for example the practitioner moves by initially bending the elbows, then again extending them at the end, to create a sort of... “whipping” movement, which might seem more effective and it is not so – as Senseis teach us and science is going to prove! In these two images, A and B are always the starting point and the arrival point of a cut. RI is the initial radius of the cut. RL is the correct radius achieved by correctly swinging the sword in the widest possible arc. RC is the shorter radius achieved by bending the elbows in a whipping motion during the cut. In both cases, the sword will start from point A and reach point B, but in the correct technique the trajectory will be ABL, and in the wrong whiplike motion it will be the shorter ABC.
Now, given a sword of the standard 75 cm lenght and an added distance for the arms of the practitioner, we will arrive at a 150cm radius (RL) for the correct cut and at a 110cm radius (RC) for the whipping motion, not correct one, shorter to account for the bending of the elbows mid-way. Considering that to calculate an arc you need to multiply Pi*Radius*angle/180 we can approximate the distance covered by the two arcs ABL and ABC, which is respectively of 3.92m and 2.87m. Because speed is the measure of distance covered in a unit of time, and the time of execution of the cut is the exact same (0.35 secs): - Correct trajectory (ABL) is: 3.92/0.35 = 11.2 m/s, or 40.32 Km/h; - Wrong trajectory (ABC) is: 2.87/035 = 8.2 m/s, or 29.52 Km/h. Thus proving that the correct trajectory is sensibly faster (10 Km/h) than the wrong one, even if the practitioner sensation tells him sometimes something different. Incidentally, 10 Km/h is already the speed at which an average human bone will fracture by impacting against a solid surface. In the next installment of this article we will study and calculate the cutting power, pressure and results of a cut against a human body. Stay tuned! This article is based on the work and calculations of Davide De Vecchi, who is fully credited for the original material. We can finally announce the schedule for the Beginner's Course! Any person interested in discovering and trying Iaido, is welcome to come to our dojo location on Saturday 9 of July at 1.30 PM. Of course a forewarning is welcome, please write on our email first, if you can. No special equipment is needed, we will provide everything with the exception of knee protectors: if you already have any, please bring them, if not there is not an urgent need for the very first lessons. The first introductory lesson is completely free, and if after there will be a decision to join regularly the Course, there will be a small annual fee aimed at covering the costs. If you need any more information, please contact us. |
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