<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR><font face="Verdana, Arial" size="2">Originally posted by Ewan:
<B>
My question is this: If force = (mass x velocity) how can I tone down the force while still maintaining the speed I need to penetrate someones defense?
</B></font><HR></BLOCKQUOTE>
The physics definition of force is:
force = mass x accelerationWhat you are refering to is momentum:
momentum = mass x velocityThe data collected by Sir Pieter (the current Midrealm Crown Prince) shows that SCA sword impacts can be modeled as an
inelastic collision which preserves momentum. You can read an analysis of Sir Pieters' data
here.
There are several factors which affect how much momentum transfer occurs and thus how hard the blow is:
1. The speed of the sword (velocity).
2. The weight of the sword (typically 2 to 4 pounds = 1 to 2 Kg).
3. Your momement (toward or away from your opponent).
4. Your opponents movement (toward or away from you).
5. Where you are hitting your opponent (is there any armour there?).
6. Where on your sword you hit your opponent (if you hit near the center of mass it results in a much more effective momentum transfer since in minimized the rotational torques generated in the impact).
The final factor that I am going to mention is:
7. How hard you hold your sword at the moment of impact.
To show the effect of this last factor, I'll perform a couple of quick calculations.
I'll start by estimating that a typical SCA sword is between 2 and 4 pounds (1 to 2 Kg for those that use the metric system). I'm going to use 3 pounds (1.5 kg) as my "average" sword for the following calculations.
From the analysis of Sir Pieters' data, a 12 pound bowling ball (~5.5 kg) in a average impact will have an initial velocity of ~200 cm/sec. This implies that the "average" velocity of the center of mass of the "average" sword is ~730 cm/sec.
FYI - 730 cm/sec = 7.3 meters/sec = 285 inches/sec = 24 ft/sec (appoximately).
The momentum of the sword is 7.30 (m/s) x 1.5 (Kg) = 11 Kg-m/sec.
Sir Pieters' data shows that the ratio between "low average" and "high average" is a factor of 2.
Now figure that the typical SCA fighter weighs ~220 pounds when in their armour - this is 100 Kg. If they were able to maintain rigid grip on their sword - they would increase the effective mass hitting their opponent by a factor of
SIXTY.
There are many factors which will prevent a fighter from being able to hit with a totally rigid grip - but a factor of at least two can be achieved by simple changes in how they grip the sword.
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR><font face="Verdana, Arial" size="2"><B>
There are people I fight that want the higher calibration (that is what I want as well from my opponent) but there are fighters that I do not need to hit as hard.
The challenge for me is that when I started I wasn't hitting like this. My style has changed and my technique has gotten better so now I'm hitting harder.
</B></font><HR></BLOCKQUOTE>
Your improvement in technique and body mechanics has certainly allowed your sword shots to be faster (higher velocity), and your body mechanics are such that you are likely being more efficient in moving both your body and sword in a coordinated attack. You have increased your speed (sword velocity) which results in your getting around or past your opponents guards which is good. Unfortunately when combined with your improved body mechanics the result can be upset opponents.
The answer to how to hit your opponents "lighter" and "harder" is not lighter swords or slowing down your blows, but rather learning how to control your grip on your sword. Putting this into practice will entail a fair bit of work for you on training.
First - Assure that your sword grip is comfortable and sized correctly for your hand. If it is not, then you will naturally grip down harder on the sword in order to maintain your control. I recommend a "egg" or "hammer handle" shaped grip cross section to the fighters that I train.
Second - You have to practice controlling your grip on the sword throughout the strike.
I start my sword blows with a firm but relaxed grip on the handle. The thumb and index finger form a firm "iron ring" grip on the sword, and the three lower fingers (middle, ring and pinkie) are relaxed.
As a launch the strike, my thumb and index finger remain in the "iron ring" grip, and my three lower fingers twitch in in a similar fashion as done with a fly casting fishing rod.
Just prior to the impact on my opponent I slightly loosen the grip of my lower three fingers (pinkie, ring, and middle finger).
If my strike is clean and my opponent responds "light" - that translates into "hit me harder" - all I have to to is not loosen my grip as much on the next strike. If I am facing an opponent that needs even more than that, I can increase the impact even further by tightening the grip of my lower three fingers as my sword strikes them.
I find this technique to be quite effective in controlling how hard I hit my opponent.
-Keith/Austin
(Ph.D in Physics, University of Rochester 1984).
(25+ years of SCA fighting experience).
