- Joined
- Feb 22, 2002
- Messages
- 131
For the purpose of clarity I define terms:
The belly is the part of the blade that touches a table when the blade's handle is maintained flat over a table.
The tip is the part from belly to the extremity.
The working area is everything behind the belly to the start of the recurve
The recurve is the part near the handle.
Symptom:
When you whack with the belly, there are good chances the blade will try to turn in your hand, because of the displacement between the edge and the handle, which create a greater than normal torque. Conditions which may accentuate this torque effect are: straigthness of the movement (arched swing or straight swing), perpendicularity of the edge when hitting the material, hardness of the material, change of hardness in the depth of the material.
I had amazing things happening to me when chopping the most noticeable being a bouncing blade that ended in my foot (my position was mostly correct, legs spread 1 yard, hitting a hard wood (dried cherry) cane 40 cm above the ground, placed 50 cm in front of me, at equal distance from my legs, and hold from the top, 45 degrees angle of attack). The bouncing surprised me, as the blade did quit the material with a 90 degres from the original blow, and with same speed! No worry, that was long ago, and just a few stitches (blade stopped in my big toe's bone). Now, that was a light Cold Steel khuk, not a HI, and the damage would surely have been really bad with a HI. Ihad a look to the chip of wood that was removed, and it was a perfect curve (explanation further). This led me to experience more and you are reading here my findings.
A much better way is to use the area behind the belly (the working area, the one the kamis really harden), because the angle of attack will cause the shearing effect, great penetration and no torque in the handle). The tip is also a choice, as it does not create torque.
The recurve is no problem, as the torque in that part of the blade is minimal.
The torque experienced in the handle is non-linear (like all torque, power of 2 to the distance if I remember), and can be quite powerful and surprising, very difficult to control. As it starts, it changes the angle of attack of the material, which creates more torque which changes the angle... You are soon out of control with a blade swinging at a square angle from it's original direction, same speed.
Correction:
If you must hit with the belly, remember to: hold the handle very tight, perform a straight movement, hit the material as perpendicular as possible, and swing away from you (check that you are not in a position were bouncing could catch you). Block shoulder, elbow and wrist from lateral movements and handle axis rotation. In fact you probably do not want this because it is much more tiring.
In all cases a light rotating forward the blade at impact helps penetration, and eases the torque effect, but then, it is a matter of experience, as it also means a more difficult swing.
Another option is to push away when hitting, which also adds to the shearing effect, and also corrects the blow if you hit on the belly when you meant the working area. (not all of us are martial atists and can place a full blow to the half inch). You can combine with the above.
Still another option is to hit with working area flat, handle (and not edge) at an angle, you loose the shearing effect, but you pull, and no not push, you are in a stable equilibrium dynamic, as opposed to an unstable equilibrium (ie light variations bring back to normal instead of away, therefore torque brings the blade back to position, not away).
Last option is leave the blade in the display, but you WILL miss much fun.
Summary:
I hope this will avoid you drawing your own blood. Most of you probably already knew these through experience, but I thought it would be good to formalise it.
Nowadays I always try to wear steel toes shoes when playing with khuks and axes.
May be you also have different point of views or experiences, which I'll like to hear.
Be safe and have fun.
The belly is the part of the blade that touches a table when the blade's handle is maintained flat over a table.
The tip is the part from belly to the extremity.
The working area is everything behind the belly to the start of the recurve
The recurve is the part near the handle.
Symptom:
When you whack with the belly, there are good chances the blade will try to turn in your hand, because of the displacement between the edge and the handle, which create a greater than normal torque. Conditions which may accentuate this torque effect are: straigthness of the movement (arched swing or straight swing), perpendicularity of the edge when hitting the material, hardness of the material, change of hardness in the depth of the material.
I had amazing things happening to me when chopping the most noticeable being a bouncing blade that ended in my foot (my position was mostly correct, legs spread 1 yard, hitting a hard wood (dried cherry) cane 40 cm above the ground, placed 50 cm in front of me, at equal distance from my legs, and hold from the top, 45 degrees angle of attack). The bouncing surprised me, as the blade did quit the material with a 90 degres from the original blow, and with same speed! No worry, that was long ago, and just a few stitches (blade stopped in my big toe's bone). Now, that was a light Cold Steel khuk, not a HI, and the damage would surely have been really bad with a HI. Ihad a look to the chip of wood that was removed, and it was a perfect curve (explanation further). This led me to experience more and you are reading here my findings.
A much better way is to use the area behind the belly (the working area, the one the kamis really harden), because the angle of attack will cause the shearing effect, great penetration and no torque in the handle). The tip is also a choice, as it does not create torque.
The recurve is no problem, as the torque in that part of the blade is minimal.
The torque experienced in the handle is non-linear (like all torque, power of 2 to the distance if I remember), and can be quite powerful and surprising, very difficult to control. As it starts, it changes the angle of attack of the material, which creates more torque which changes the angle... You are soon out of control with a blade swinging at a square angle from it's original direction, same speed.
Correction:
If you must hit with the belly, remember to: hold the handle very tight, perform a straight movement, hit the material as perpendicular as possible, and swing away from you (check that you are not in a position were bouncing could catch you). Block shoulder, elbow and wrist from lateral movements and handle axis rotation. In fact you probably do not want this because it is much more tiring.
In all cases a light rotating forward the blade at impact helps penetration, and eases the torque effect, but then, it is a matter of experience, as it also means a more difficult swing.
Another option is to push away when hitting, which also adds to the shearing effect, and also corrects the blow if you hit on the belly when you meant the working area. (not all of us are martial atists and can place a full blow to the half inch). You can combine with the above.
Still another option is to hit with working area flat, handle (and not edge) at an angle, you loose the shearing effect, but you pull, and no not push, you are in a stable equilibrium dynamic, as opposed to an unstable equilibrium (ie light variations bring back to normal instead of away, therefore torque brings the blade back to position, not away).
Last option is leave the blade in the display, but you WILL miss much fun.
Summary:
I hope this will avoid you drawing your own blood. Most of you probably already knew these through experience, but I thought it would be good to formalise it.
Nowadays I always try to wear steel toes shoes when playing with khuks and axes.
May be you also have different point of views or experiences, which I'll like to hear.
Be safe and have fun.
