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Elaine Collinson

Location: New Zealand
Joined: 11 Jun 2007

Posts: 1

PostPosted: Mon 11 Jun, 2007 10:59 pm    Post subject: Sword flexibility         Reply with quote

Hi everybody Happy .

I am new here and am from New Zealand (for those who are geographically restricted, its where Lord of the Rings was filmed Wink ) .I have a simple question that I've been wondering about for sometime now. Over the short time that I have spent in western martial arts, I have noticed that the degree of flexibility in many swords is quite varied. Some sword blades seem to be able to flex right back onto themselves, while others are quite rigid. I understand this can vary with the sword type. My question is, what is the purpose of swords that flex (excessively) ? Are they serious flaws in design present in cheaper end products, or does more flex in a blade offer some sort of advantage against those that are more rigid?

I searched your forums but I couldn't find a similar thread. Thanks for any replies in advance.
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Bram Verbeek

Joined: 27 Mar 2007

Posts: 217

PostPosted: Tue 12 Jun, 2007 3:09 am    Post subject:         Reply with quote

As I understand it, flex in a sword will do several things,
First, it will distribute the blow more equally over time, so as to spare your hand from the full brunt of a steel to steel impact
Second, it will cause a sword to bend, converting the impact to bending, thus lessening the chance of damage in (for instance) parries and locks

Furthermore it is important to note that a realtively flat surface (a sword blade without a riser for instance) will flex unevenly, flexing more on the flat and less on the edge (I think parries should be performed on the flat), and that later sword types need less flex, so as to be more decisive on the thrust, and are generally less able to cut because of the shape needed for that.

If a blad flexes exessively, it could damage all components of the sword, exess is never good.
What should be noted as well, is that an exessive flex might result in a parried weapon sliding through (I for one, often try to redirect in stead of parry weapons, if my sword would flex too much, a weapon could still go to places I don't want it to go.

I think that exessive flexes are a result of cheepness on the side of the creator, though I am not sure how a rapier or smallsword should react, I am no expert in those weapons
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Michael Clark

Location: Welland, Ontario
Joined: 31 Mar 2007

Posts: 45

PostPosted: Tue 12 Jun, 2007 3:15 am    Post subject:         Reply with quote

Also worth noting, it is more desireable for a practice sword to contain relatively more flexability than an authentic sword. This is primarily for safety concerns, but also for durability of the weapon.
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Adam Simmonds

Joined: 10 Jun 2006

Posts: 135

PostPosted: Tue 12 Jun, 2007 3:40 am    Post subject:         Reply with quote

hi Elaine,

while I might not have a whole lot to add, i thought i'd chime in as it's rare to communicate with someone else from this part of the world on this forum.

as mentioned above, an inherent flexibility allows a blade to absorb and distribute shock from blows and parries etc, without shattereing or cracking as a non-flexible, excessively brittle steel could do.

excessive flexibility, however, unless you're wanting safe practise blades (ie fencing foils), is not helpful, as when you hit something with such a blade it is likely to vibrate and wobble excessively and lose much impact force thereby.

also, some rigidity is needed in order to be able to thrust effectively with a blade.

the idea (from the movies) that bending a blade near in half is a good test of quality is false. such 'testing' can be damaging to the blades composition and is not a good idea as far as preserving your blade is concerned.

as with so many aspects of a good blades design, alot is to do with finding the right balance and harmony between often conflicting needs. for example, a blade needs a certain flexibility in order to remain straight without sustaining bends or breaks when struck, yet it also needs to be rigid in order to be effective in the cut and the thrust. the japanese, for example, overcome this conflict by giving a blade a relatively soft, flexible, shock absorbing spine, and a very hard, inflexible cutting edge. there are many ways that these conflicting issues have been dealt wtih in various swords in accordance with the various designs, materials and intended uses etc

blade design seems a complicated subject, with many variables. There are some excellent articles on this site, in the features section, and many more at, where you can lean all about it.

cheers, adam s
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George Torma

Joined: 16 May 2006

Posts: 7

PostPosted: Tue 12 Jun, 2007 4:51 am    Post subject:         Reply with quote

Well, I'm certainly not an expert, but being spent a year studying mechanics as an engineer student, I do understand a little bit of blade physics. When parrying, the blade can absorb the kinetic energy, either by bending or moving. Moving is not good since when blocking, one wants to stop the whole thing Happy .
However, we also do not want the blade to bend too much - not the whole blade, but the most stressed parts in the cross-section. When th blade is bent, there will be some strain rising up in most parts of the cross-section. Some parts get more stress, others get less. The crucial thing is to keep the highest stress below the limit when the material would have a permanent change in geometry. What worsens the case, is that heat-treated steel has a tendency not to change its shape but to simply break under stress. That's it - a tiny crack appears at some dangerous place, maybe smaller that you could see, starts to grow - and your sword is doomed.
This is why european blades have so complicated cross-sections. The smith of the era has empirically created a shape that can distribute the stress, while keeping the bending as small as possible, has ideal mass, as well as maintaining a good cutting edge, etc. As mentioned above Wink .
Bending is not good. When a blade bends - in my opinion - is entirely not good. It is necessary. For blades that are created basically for thrusting, it is even more vital to get a rock solid shape that nearly cannot bend.
If only we would have a material that is not bending at all, than we wouldn't have to fuss about blade harmonics and the like. Too bad it's physically impossible Cry .

Sorry for my poor english knowledge, unforutnately I studied mechanics in a diffrent language. I hope my post was worth reading through.[/i]
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