12. Properties of Swords
12.1 The Basics
12.1.1 Sword Performance
|How a Swordsman Looks at Sword Performance|
|What defines the
quality of sword? If we consider its
fighting value and not its prestige value, it can only be its performance in a
sword fight with another sword bearer. Swords for showing off or for hacking
defenseless people into pieces need not to be particularly good and thus are of
no interest here.
John Clements, an experienced swordsman, made a list1) for essential swords properties, here are the major points:
This is the blade's capacity to deliver powerful shearing
and cleaving edge blows. The
katana, with its
living tradition of practice, is well known for demonstrating its cutting
power. Its single, hardened, wedge-like edge has long been shown to be capable
of extraordinary sharpness.
The longsword, has not acquired a similar reputation. It is certain that both weapons successfully faced opponents wearing soft and hard armors without great difficulty. Nonetheless, a curved blade is mechanically superior to a straight one at delivering edge blows to produce injury. And due to its hardness, the single curving edge of the katana is very good at penetrating even hard materials with straight-on strikes. Verdict: Katana.
I wonder why John does not consider wootz blades, also famous for extreme sharpness and cutting power. From a metallurgical point of view, you don't just want a sharp edge, you want it to stay sharp when you hit something, and you want it not to break. That calls first for a hard material, and second for a material with the ability to disperse a considerable amount of energy released in a small area / volume without fracture or much deformation. That necessitates a large "fracture toughness" and thus a material that is first uniform and free from small defects like microcracks or micro-inclusions and, second, somewhat deformable or ductile and not completely brittle. No steel offers both properties equally well, so for cutting ability alone you tend to go in the "ultrahard but somewhat brittle" direction, i.e. for a katana.
|Thrusting ability: This is the capacity for a weapon to make penetrating stabs with its point. Whether against armored or unarmored opponents, a thrust has long been recognized as more difficult to defend against, easier to deliver a fatal wound with, and quicker and farther reaching than a cut. As has been known since ancient times, the geometry of a straight weapon means its thrust hits more quickly and deceptively than does a curved or semi-curved one. Verdict: Longsword.|
This is the weapon's ability to be moved to ward, parry,
and block the assorted strikes of other weapons it had to face in combat. Its
design affects the physical mechanics of how the object can be wielded
defensively and the resilience and toughness of the blade is a component in
this. All things being equal, the inherent
defensive potential then comes down to the tool's geometry, or shape. Verdict:
Much of what John relates here (and I have considerably shortened it) also applies to the 4th point "speed".
|Speed: Speed is the velocity at which any hand-weapon can perform defensive and offensive actions to deliver hits or impede blows. The quickness of a hand-weapon depends partially upon the user's own prowess, as the weapon itself does not move, the swordsman moves it. Since the relative weights of both sword types are nearly equal, the issue comes down to the geometry of how each can be moved. A shorter curved blade can slash more quickly, but a longer, narrower, straight blade can certainly thrust more quickly. The slashing cut of a shorter curved weapon wielded in strong fluid motion can be more maneuverable than the less oblique cuts of a longer straight blade similarly used. Verdict: Katana.|
|Technical Versatility: This is the mechanical utility the weapon has for being employed in distinct offensive and defensive actions. Surely the most controversial category to rate any sword on is its fighting capacity. The katana is the extreme single-edged cutting performer while the longsword is an excellent multitasker. Both are capable of numerous slashing, slicing, and stabbing techniques. Both weapons utilize counter-striking and defensive displacements. However, straight double edges permit cutting along 16 different lines of attack compared to eight with a single-edged curved blade. Verdict: Longsword.|
|Durability: Durability in a fighting sword refers to its general tenacity
and its resilience and in delivering blows and receiving impacts over time
without breaking or becoming bent. The more resistant to brittle catastrophic
failure a sword blade is, however, the more malleable it becomes - meaning the
easier a bend will set in.
The katana required more rigidity for its hard-cutting design, while for its utility the longsword was more of a spring. The katana's edge leaned towards more brittleness while its spine was more prone to bending. In both weapons, cross sectional shape compensated for weaknesses while capitalizing on strengths. Flexibility, or the ability for a blade to deform but return true, though regularly exaggerated in modern times, was actually of very little concern for swords intended for serious combat, and does not enter into the criteria here.
No sword is indestructible. All are produced as perishable tools with a certain expected working lifetime. Which blade historically could possibly be called the more durable in combat is then an exceptionally complex issue to address and perhaps unanswerable. Verdict: Unknown.
|Those points are important for the
user of a sword. However, they leave the materials scientist or even the maker
of a sword somewhat puzzled. How can you grade these properties? That means you must produce
a number, that comes from an objective
measurement. How are you going to do this?
The answer is simple: you won't. The properties expressed in the key words above relate to many "technical" aspects of swords and to "properties" of the person wielding it and there is no way to measure those properties objectively without involving human opinion. A violinist will find a Stradivari or Guarneri violin far superior to "normal" ones but scientists cannot tell how the small differences they might find by making all kinds of measurements relate to the judgement of the experienced users.
My point there is that what counts is the judgment of the user. Nothing will convince him to use the "scientifically" superior sword if it doesn't feel right to him. And that's as it should be.
|However, since I'm not a user of
swords, I only can give you the science point of view. Happily, we are in a
somewhat better position than the musical instrument guys. Science will be able
to come up with some points that do relate rather directly to the performance
of a sword.
So let's look at sword performance now from a scientific point of view. We will distinguish two very basic cases: static properties and dynamic properties. What follows is a general introduction of the meaning of those terms.
|Static Properties of Swords|
|For starters, you could go back to
chapter 3 where I
introduced the definition of major static
material properties and how they are measured. Properties like
Young's modulus or
and we will need that here. But now we are looking at static properties of a
sword, and not just a homogeneous material. What we do, in essence, is to put a
static or fixed load on a sword at rest all the time and consider how it
responds. Look at the picture below to get an idea of what that could mean.
We already know that we can get three fundamental results:
|"Static load" in the most simple version means that you fix your sword at some "point" to something unmovable and then apply forces somewhere. One example of how to do this is shown below.|
smallsword with a
triangular blade was used, the hilt was fixed to a window sill. A (full) beer
bottle provides for a defined force near the tip of the blade. The sword bends
quite a bit but differently if loaded at right angles to the long side of the
triangle defining the blades cross-section (middle picture), or parallel to it
(lower picture). I would guess that nobody is going to be very surprised about
the outcome of this experiment. You have a "feeling" for the kind of
curvatures you get in this case. You also could predict that outcome if I would
have used a more substantial sword, for example a katana: There wouldn't be any
But that's it. If I now would ask you to calculate the exact curve that the sword assumes, you will not be able to comply (with some 99.999 % probability). Few are the people who know how to calculate a "bend beam".
|Let's generalize a bit. For assessing
static properties, we need to first immobilize at least one point of our sword
in order to make sure that it cannot move around or rotate. All it can do is to
bend (including plastic deformation and fracture) if you now apply forces - all
kind of forces - on the "free" parts. Under the influence of the
forces your sword will assume some bend shape, and as long as the forces hold,
nothing changes anymore. That's what static means: Nothing changes.
You might, however, slowly increase the magnitude of the forces and watch what happens.
| One way of doing that would be the good old
tensile test -
clamp it and pull. You would not produce a large effect, however, with a real
swords and forces applied by humans. This is not necessarily true for the
reverse, compressive testing; I will get to this.
The natural way to go at it for starters is to immobilize the hilt and than apply a force at a right angle to the blade near the tip - as shown above.
|We will deal with static properties
in the next sub-chapter. I will look at:
|Dynamic Properties of Swords|
|It may come as a surprise that you
can look at dynamic properties while your sword is still (partially)
immobilized because the hilt is clamped to an immovable object. The blade,
however, can still vibrate. In the simplest way, the tip moves back and forth
with some frequency, in the not-so-simple version a more complex
"vibration mode" might occur. This is seen as a dynamic property,
A quick look at the physics of vibrating sword blades will teach you one thing: Forget it! Calculating anything is rather involved. I will look at vibrations at the end of the next sub-chapter; so let's go for other dynamical properties first.
|Dynamical properties emerge as soon
as you move your sword. We are going at that in three steps:
|But moving your sword without
rotating it is certainly not what you do most of the time. Whatever you do, the
total movement of the sword can best be described by looking separately at the
two ingredients of that movement:
|With ghosts at work, this is still easy to grasp.
Now let's replace the massless but powerful ghost by you. At any point in time during the swing you need to exert specific forces and torques to the sword hilt in order to produce that movement. You do that with your hands but they are attached to the rest of the body by arms and so on. In making the sword move in a certain way, you move your hands, your arms and other parts of your body. To do that, you need to exert proper forces and torques to various parts of your body. And you feel forces and torques in your hands, mostly, but also in other parts of you body.
If you try to make the movement shown above with different swords or with a battle axe, you need to apply different forces and torques, and you will experience quite different feelings, too. With some swords you may not even be able to make the desired movement, or at least not very fast.
|The forces and torques you experience by "body feel" thus are always a combination of what it takes to move and rotate the swords plus what it takes to move your body parts. When you swing your old and familiar sword you are so used to it that your body exertions don't register much. When you test a new sword by swinging it around, getting a feeling for its "speed" and so on (see above), you notice the differences in what your body now has to do relative to what it's used to. In particular you notice possible limits you might encounter. If, let's say, a swift rotation of 90o takes and effort of 90 with your familiar sword, with your limit at 100, than a sword that would need a 110 seems "unmovable" to you. In physical reality the new sword takes only about 20 % more effort for the move difficulty but for your feeling the difference is much larger. That's why swords that are not all that different from a technical point of view might feel very different to you.|
|We now progress to the last and most
complex part of sword dynamics: We hit something! Three basic questions come up
in this context:
|I'll do my best but don't get your hopes up too much. You will have to put up some effort too.|
|At this point it is time to introduce the major contributions that you can find in the Net (or with the links given below and elsewhere) for sword properties in general and for dynamic properties in particular.|
|1.||George L. Turner:Dynamics of Hand-Held Impact
George Turner's work is rather amazing if not all that easy to read. It is actually a 150 page book with plenty of equations. I would vote for awarding him a German Ehrendoktor", a Ph.D "honoris causa", for this work. I learned much from it and used it throughout of what follows.
Chevalier has published several outstanding "papers"
in the Net; some you cna access from here 3).
He also offers a "Weapon Dynamics Computer" in the Net, a tool designed to compute and document the dynamic properties of swords and other hand-held weapons. You can access it through Vincent's homepage. Peter collaborated here with Peter Johnsson (see below) who provided design insights and precious sword data, during the preparation of the exhibition The Sword Form & Thought" 4).
|3.||Peter Johnsson, sword maker, contributed to the
"The Sword - Form and Thought" book 4) that documented a
special exhibition (Sept 2015 - Fbe. 2016) in at the "Deutsches
Klingenmuseum" in Solingen, Germany.
Peter supplied fetching graphics that relate to a special geometrical analysis of the swords shown in the exhibition, and the result of the calculations done for most of these words by Le Chevaliers with his computer program.
|The first two authors found it
impossible to explain major dynamical properties of swords without resorting to
equations (and, of course, assuming that the reader has some working knowledge
of physics and math). I tend to agree with their point of view but are
nevertheless sticking to my
Since there is no such thing as a free lunch, you will get a lot of words instead.
"Longsword and Katana Considered", The Association for Renaissance
Martial Arts (ARMA), Internet Essay (1999).
John has some experience in using a sword (in sports only), in contrast to me, and seems to know what he writes about.
|2)||George L Turner: Dynamics of Hand-Held Impact Weapons, Sive De Motu, Association of Renaissance Martial Arts (2002) posted on the pages of "ARMA - the Association for Renaissance Martial Arts". The book can be directly accessed here|
|3)||Vincent Le Chevalier; selected
papers, all accessible via his
home page: or
directly if links are given below:
|4)||"Das Schwert - Gestalt und Gedanke ("The Sword - Form and Thought"). Hrg.: Barbara Grotkamp-Schepers et al. The book to a special exhibition at the "Deutsches Klingenmuseum Solingen", Sept. 2015 - Feb. 2016.|
© H. Föll (Iron, Steel and Swords script)