Combat Physics

[J.Amiel_Angeles]

Wait, wait, I thought that the British cavalry arm of the 19th century did experiments with this and figured the best kind of sword was a half-and-half tulwar-shaped saber? Does this mean (what I've always suspected) that sword curve and shapes was mostly dictates by taste or aesthetic preference?

[Casper Bradak]

I don't know about that, but I do know there is no best sword. There are no less than 3 articles in the articles/essays section dealing with this topic, more or less.
And yes, in real life, it does only come down to a taste/preference/culture issue, as they'll both get identical results.
There's no telling what they believed though, which could've effected their tastes/preferences of course.

I do believe they could've very well judged a single edged curved sword as the best for their purposes, seeing as how they did not have an in depth swordsmanship curriculum, and they did not face body armour, negating need for a false edge which would allow greater technique variety, a straight point to work around armours or accurately thrust, which takes more training than do sturdy downright blows.

Also, all of the above said in these posts, I'm not saying that a blade was unfortunately never wrenched away when entangled in a victims body and brought the wrong angle/direction somehow, but it's a sure thing the shape of the blade would have nothing to do with it.

[Stacy Clifford]

I think I can consider my argument sufficiently refuted at this point. Still, since this argument remains a common one, I wouldn't mind seeing somebody who has both curved and straight sharps trying to demonstrate what we've discussed here with some test cutting.

Something else just occurred to me which might have some bearing on the case. For light cavalry at least, equipment weight matters. A slim blade weighs less, but slim straight blades don't cut well (see past rapier discussions). A curved blade seems like it would have greater structural strength for cutting than a straight sword of the same width, allowing you to make a narrower and lighter weapon with nearly the same effective cutting strength as a heavier straight blade. To an armored knight this wouldn't matter, but maybe to a fast-riding Mongol or Arab it makes a difference. This is just a hypothesis, so don't take it too seriously, but I'm already throwing ideas out there, so might as well run this one up to be shot at too.

[Casper Bradak]

I don't know how it would effect the strength of the blade, but it still wouldn't effect its cutting ability.
If you take a narrow straight blade, and a curved blade of identical width and edge geometry, it won't effect the cut. This is addressed in the sword motions and impacts article.
The cut will only improve if you give the sword a geometry more inclined for it along with the proper mass distribution, but that has nothing to do with the curve.
The curved sword would have to be more curved (or make that bent at 90 degrees) than any sword ever used in order to place any more backup mass behind the point of impact, and if that were so, they'd probably turn it around to use as a pick instead.

[Stacy Clifford]

What you say is absolutely right, but I think I may have been a little unclear with my point on this one (darn lunchtime posts). I didn't mean that the cut would be any stronger as a result of a curved blade, but that the curved blade should have greater structural rigidity to withstand a strong blow against a hard target than a straight blade of similar dimensions. I'm reminded of some test cutting we did where, at the end of the day, we took an old longsword to a cinder block just to see what would happen. The longsword snapped, and when you looked at the damage on the block, you could see that both corners were damaged while the flat of the block was untouched, meaning that the longsword edge actually wrapped around the block, and this wasn't a particularly narrow blade. Granted this was an extreme test, but I have my suspicions that a curved blade might have survived that a little more intact. (The edge would still be shot, but that's what grindstones are for.) The same thing might happen across the peak of a helmet or breastplate. Geometry aside, a blade that can withstand a stronger blow can be used to deliver a stronger blow without fear of damaging the sword. Again, this isn't much of a concern with beefier blades, but with lighter ones it might mean being able to survive a bit more hard use and abuse. Still just a hypothesis, but I'm having fun playing devil's advocate this week. <img src="/forum/images/icons/wink.gif" alt="" />

[Casper Bradak]

I see. I'm just speculating here, but a straight sword striking a flat, hard target parrallel with the edge will spread the impact over the entire surface as you said.
A curved sword striking the same target at the same angle will strike with a reduced amount of edge depending on how dramatic the curve is, putting more stress on a smaller area and be more likely to snap. But, given the curve of most curved swords, the amount of edge laid on a target that size would still not be much less than that of a straight sword.
Either sword, striking a real life hard target, like a helmet or other plate armour, will strike with the same amount of surface area due to a curved target, cutting technique not considered.

[Stacy Clifford]

I don't believe the sword struck the brick quite squarely on the flat. The nearer corner showed more damage, which would explain the bending force on the blade that led to its demise.

A curved sword striking the same target at the same angle will strike with a reduced amount of edge depending on how dramatic the curve is, putting more stress on a smaller area and be more likely to snap.

This sounds correct, but remember that a convex curve is more resistant to an opposing force than a flat surface, regardless of the curve's diameter. I believe the forces also dissipate differently in a curve as well. This is about the point where my command of physics seriously fades and George Turner steps in with lots of math to determine which of us deserves a severe beating with a slide rule. Unless he peeks out from under his pile of books and sees this however, I think we can give this argument a rest. Heck, curved swords probably became popular because people thought they were pretty.

[Casper Bradak]

Yeah, well that's a step just beyond where my knowledge fails <img src="/forum/images/icons/wink.gif" alt="" />
I was just thinking though, that the curve of a sword may not make a difference with the amount of force applied to it. Like an arch, it can support more weight on one point than something flat, but the 2 ends of the arch are supported.
With a sword, neither two ends are supported and they will flex towards the direction of impact, curved or not.
Yeah, anyway I think it's just rambling now, we've probably gone well beyond the realm of practical application.

[Mike Habib]

As a quick aside on this, you may want to consider that blade shape may be related to where on the blade you usually cut. You'll see in the impact force essays that many sabers are built (based on balance and weight distribution) to strike a 1/3 from the tip, while most of the longswords seem to strike 'best' closer to the tip (best here has more to do with handling than cutting ability, see the essay for details).

If true, it would mean:
1) neither curved nor straight blades cut better objectively
2) neither type cut better with the portion of the blade used to cut. Performance was identical.
3) the portion of the blade used to make said cuts was slightly different, and was based simply on the traditional training by region. There are simply several ways to cut well.

Cheers,
--Mike Habib