curved sword vs. straight sword, katana cutting advantage | SBG Sword Forum (2024)

So, it's commonly said that a curved sword is "effectively sharper" because of the way that the blade approaches at an increasing angle as the blade moves deeper into the cut.

-basically, using a straight blade at an angle is sharper because the distance from the edge to the middle of the blade is longer at an angle, meaning that in the blades direction of travel the angle of the blade is more acute.

-also a curved blade has a gradually changing angle as the blade moves straight across a cut and still held at such an angle, because the distance traveled at that angle increases as you move toward the tip of the blade.

However, I don't recall seeing any suggestions that the rotation of the swing of a blade might result in more speed when using a curved blade, ,,,, I'm not saying that it IS that way, I'm merely having thought so just now, having been swinging my sword, that this might actually be true.

when you swing a straight sword, the sword has multiple rotations. It rotates around your body, and also it rotates around your wrist. It also Both of these rotations combined results in a particular speed at any particular part of the blade, which increases linearly due to its own rotation, plus any translation that results from the rotation around your body. (the speed is more like your hand speed plus the speed of the blades rotation, because your swing is not simply the same as a pendulum around your center of balance).

If you swing a curved sword, the sword should effectively hit the target FURTHER from the handle than if you were to hit the same distance of target with a straight sword. Therefore, should the curved sword ALSO result in higher impact speed than the straight sword??

There's been a lot of discussion on this topic in the past, none of the finer details of which I can remember right now.

Basically, the difference isn't that significant. I'll let the smarter people explain why.

One of the dumber people who knows that but would like to hear it explained by a smarter person...

well, on the other hand, and I guess where I'm coming from, , we could be talking about a situation where a tiny increase in energy (because it is concentrated onto a blade, which is a very small surface), is actually quite a large increase in energy.

so, when cutting , it might not take that much more energy to have a much deeper cut.

so, like, what if I cut you as hard as I can with my sword. ,, now, what if I cut you 1% deeper,,, or better question, how much deeper does 1% more energy cut you?? then,, how much MORE damage to the body is 1% deeper (when being slashed with a sword). Also, some material in the body is tough, like bones, but what if I slash the belly,, that little bit more energy might mean several more organs are damaged, or sufficiently cutting important arteries in the armpit ,,, So, although when chopping melons and water bottles, you might not see an impressive difference, perhaps it meant the winner or loser enough times to matter??

I didn't read much because I feel like a lot of the katana cutting power is based on misconception.

The curve, which is slight, of a katana, aids in the DRAW angle. It's stiff blade aids against botched cuts. It's not about contact area. It's not a tulwar. It's about edge hardness and sharpness, it's stuff forgiving blade, and the aid in the draw

If you hit a target with your hand at the same distance from the target, you hit with the blade the same distance from the handle, as measured in a straight line, which is what matters as far as speed due to rotation. With many curved swords (but not all), the sword will need to rotate further before it hits the target, and this can change the speed somewhat (and often lower than higher).

There are advantages when cutting with typical curved blades, but I don't think more speed is one of them. The advantages that are there are not always large enough to matter. Two advantages relate to edge alignment:

• If the centre of mass of the sword is behind a line through the hilt, this helps edge alignment during the swing.


• If the point of contact is behind the centre of mass (and, ideally, behind a line through the hilt), this helps maintain edge alignment during the cut.

One other advantage:

• The edge being at an angle to the impact helps encourage a slicing draw cut.

The first advantage can be lost with canted hilts. This sword, while curved, doesn't have either of the first two advantages:

and the top sword here:

(from www.nps.gov/parkhistory/online_books/popular/2/ps2-2.htm) doesn't have the first.

The middle angled sword here:

will give at least the 1st and 3rd benefits.

Even with a completely straight sword, it's possible to deliver the classic from-the-shoulder draw cut, and some hilts (e.g., Viking hilts) encourage it. This is done by hitting with a more "hand forward" cut, more pulling the sword through the target than chopping into it. This doesn't give the 1st 2 benefits, but does give the 3rd. Cuts like this sacrifice significant impact speed (because there is less rotation of the sword) for more effective slicing, so there's more to doing a lot of damage than impact speed.

A katana isn't curved enough to do much with the 3rd advantage above. Plenty of cutting videos out there with a complete absence of slicing (and these cuts go through tatami, through water bottles, etc.). More strongly curved single-handed swords get more benefit from this, and some videos out there show cuts that start out with no slicing turn into slicing draw cuts due to resistance in the target. So this is a real effect, but the amount of effect varies with the sword. (And it's probably a useful effect if the target is wearing thick clothing.)

Swords are tools designed for specific purposes. None are good at everything. I think it's more important to know the capabilities and limitations of your blade and then properly train with it.

As far as cutting is concerned; put a pot roast on a cutting stand. Hit it with a curved blade, then do the same with a straight one. Look at the damage. Now pretend that the pot roast is your own shoulder. Now ask yourself which blade would you like to be hit with. If the answer is "neither", then you now understand the practical difference between a straight and a curved blade on the cut.

There are probably several factors that come into play making it having no simple answer. Matt Easton included this in one of his videos that I was unable to find unfortunately as it had a simple answer. But in short he said the contact area of a straight blade distributed its force over a greater area thereby decreases the psi (my words not his) while the curved blade concentrated its energy in a smaller area and thereby increasing the psi (again the psi is my word not his). Below are two crude drawings that may help to clarify the above.

As an afterthought this could be likened to the point penetrating so easily as the force is concentrated in such a small area.

Good convo. I think Eastons points are probably some of the least sophisticated though. So much could impact how much of the blade is contacting a target, and skin/muscle isnt a straight line in paint, so by the time a cut starts (if it isnt a draw cut but just a straight forward force being applied) I'm thinking a curved and straight blade wouldnt be impacting significantly different amounts of area on the target.

Edit: that said Pgandy, your comment is very useful to the conversation and helping me think it through. The above wasnt a criticism of your comment or your paint skills

I reccomend reading this book for anyone interested in a look into this topic as it was researched in an era when swords were used and tested for more than recreation.

www.amazon.com/Memoir-Swords-Etc-Classic-Reprint/dp/028225000X

Would you mind sharing with us the findings and insights of this book about this topic?

Of course; but it seems many are under the impression that they're chopping into a flat surface, flatly. Most of what a sword contacts will be round, and the blade should generally contact at an angle, and be drawn across. So it's not like there's a lot of contact area to reduce.

Edge alignment seems easier with curved blades, though, so that may be a greater factor.

A free version: archive.org/details/MemoirSwords/page/n4/mode/2up

Basically, overall, he loves yataghans, and thinks everybody should use them. And that the cavalry should train better, actually cutting and thrusting with their swords.

For cutting, he gives a geometric explanation of why having the blade at an angle to the cut at the point of contact (my third point above in my first post) is good, but this is somewhat pseudo-science. Anyway, he likes draw cuts. Speed matters so light swords are good. He likes Mameluke hilts (i.e., Ottoman-style hilts).

Thanks a lot for the sharing. :D