Drop Testing For Evaluation Of Potential HEMA Protective Material

In the early days of HEMA equipment (before people were even really calling it HEMA) there were virtually no manufacturers producing products explicitly designed for things like our modern longsword sparring. The general ‘close enough’ products that people could draw inspiration from were historical gambesons and modern olympic fencing equipment. (Specifically MOF coaching jackets, which have more padding to take repeated strikes from students in the course of teaching.)

The modern HEMA solutions are somewhat of a fusion between the two, and have been evolving along with the explosion in popularity that HEMA has enjoyed. But this brings us to an important point: how many alternative materials and designs have actually been considered? Generally when designing, well, anything, you tend to see established solutions become locked in over time. Improvements wind up being small modifications on the original theme. However if the base solution was good but not the best, there exists an overall ceiling to the level of possible performance. And because the full solution space was not explored prior to starting it is no longer possible

While HEMA is pretty established we are still in the relative infancy of the modern practice. And at this point I think it behooves us to fully explore all possible protective solutions instead of just inheriting a design concept from similar – but distinct – activities. In MOF they don’t need to withstand the kinds of high impulse impacts that we experience when fighting with longswords. And we have materials that historical swordsmen could have never dreamed of.

So I set out to try to test some promising new approaches.

The Test Apparatus

The test design was inspired by the Charpy Impact Test. This is a test which is used to measure the toughness of a material sample by basically swinging a big heavy arm that breaks right through it. 

The Charpy Impact test is used to determine the impact energy absorbed by the sample before fracture (aka toughness), which isn’t exactly what we are looking for. Instead the goal is to observe the force dispersion of the jacket material, for a known impact impulse. I did this by dropping a sword (on a rotating arm) onto a target of known consistency.


The target of choice was insulation foam. This was because I was looking for a material that was both consistent (aka manufactured) and able to have big dents carved into it for me to measure. So I put the test material on and gave it a shot…

Whelp, what I forgot to think about was the fact that I had a box of 2.5” screws sitting next to me while building, instead of the 3” that I would normally be using. And with the way I have the sword wedged between the two pieces of wood there is a gap, and the 2.5” screw has very little purchase into the other piece of wood. And hence snapped. (Which is kind of like a Charpy Impact?)

So with the screws swapped out for more appropriate ones we try again.

Well that’s not what I expected. Apparently 6 sheets of insulation foam (the package they come bundled together in) is too much for a sword drop to deal significant damage to, even without the protection applied. So I tried again with only 3 sheets.

Success! Based on this I chose 3 sheets of foam insulation as the standard to use, and this result serves as the baseline test result to compare it to.


The Material

In terms of longsword protection we want a solution which can both withstand impact and is light to facilitate mobility. In general it is best to look at how mature industries handle these problems, as they have had thousands of engineering hours invested into the solutions – and have been able to delve a great deal into the problem. An industry that has solved these problems with flying colors is the global shipping industry. (Something that has also exploded along with HEMA.)

And so in this article I test the lightweight super material that has facilitated billions of parcels shipped all over the world:

Test: Duck Large 

First up, Duck Brand Large Cushion bubble wrap.

This was layered a single ply thick and placed over the impact target foam. The sword was dropped as before.

And it basically smashes through like nothing. 

You’ll note that a large chunk of the foam has broken off between the two drop locations. This is because styrofoam is not an inherently ductile material. Having the sword smash down will also create compressive stresses on either side of the impact location, as the sword is pushing the foam apart as it passes through. In this case the amount of material in between the two impact locations wasn’t big enough to handle this loading, and failed as a result. Which means I need to make the impacts further apart. (And use more material up while testing. 😒 )

So basically a single ply of large cushion bubble wrap does nothing. Got it.

Test: Duck Large x3

Next up was to see what the Duck Large Cushion could do when layered. The sword was dropped on 3 layers of the bubble wrap.

Success! We have finally stopped the sword. Inspecting the damage after the bubble wrap is removed shows a noticeable impact, but the foam has not actually collapsed.

Test: Duck Original x3

Now we see what difference the cell size of the bubble wrap makes. 

The bubbles on the “original” are much smaller, and I assumed because it was thinner overall it would perform worse. The results of 3 layers of normal sized bubble wrap:

Though the sword did bite into the foam deeply (while the equivalent large cushion layer stopped it entirely) it was an improvement over not having anything. (Or a single layer, which is basically nothing).

Test: Duck Original x5

Time to up the game. 5 layers of bubble wrap! (If they can have a dozen-layer armored jacks in period, I think I’m allowed to do this.)

And it worked! The sword was stopped by 5 layers of bubble wrap. Now let’s have a look at how deeply it dented the foam underneath…

Uh, that’s a bit ugly. It’s hard to say exactly how much energy fracturing the entire length of the test medium took out of it, but I’ll go ahead and say that this was worse than the 3x large cushion layer. (This happens because the impacts can’t be perfectly perpendicular, and the foam isn’t exactly strong against lateral strength.)

Test: AIRPlus Air Pillows

Next up was a different type of air/bubble based packaging. This time it was large air pillows by the manufacturer AIRPlus.

I started with a single layer and I didn’t have much faith in its ability to stop the sword.

And I was right.

Test: AIRPlus Air Pillows x 3

So as things go, we add layers. Once I get to 3 deep of the air pillows it was able to successfully stop the sword. 

The impact is probably smaller than the 3x large bubble wrap location (which I would hope, considering this is like 10 as bulky).

What is interesting is we see multiple impact dents. This is because the action went as follows:

  1. Sword comes down with a ton of energy and pops bubbles and dents foam slightly.
  2. Sword bounces up off the impact.
  3. Sword comes down from a short fall onto unprotected foam, denting it slightly.

If the dents were of appreciably different sizes we could be in trouble. As you then have to figure out which went deeper, the primary or the secondary impact. As they are about the same we are fine to not know which is which.

Test: AP Light

So that was good fun, but to close out I thought I should test out a fencing jacket to show how good of a job it does. So I pulled out my SPES AP Light jacket and set it on the test rig. Ready to show how the padding in a real HEMA jacket works…

So, it looks like the sword really bit into the foam right through the AP Light jacket. I had it set up so the impact sight was basically right on top of the collar bone (or as close as I could get. This setup is not exactly a precision machine.)

I would evaluate this as slightly deeper than the normal bubble wrap x3 depth. Which is crazy, and I was not expecting in the slightest! You heard it here first folks, a few layers of bubble wrap is apparently more than an AP Light jacket. 

Test: AP Standard

Welp, after that it’s time to bring in the big guns. My much more robust SPES AP Fencing Jacket. And in a shock to no one it is able to completely stop the sword.

The targeting isn’t 100% identical, but it’s as close as I could get given the cut on the jacket seems to be different.

Though the foam didn’t get off scot free. It looks like the denting is still deeper than the 3x air pillow layers, but better than the 3x large cushion bubble wrap impact.

Bonus Test: Amazon Packaging

So as an extra bonus, I decided to test the air pillows that amazon needed to pack my order of bubble wrap with. 😅

You know the one, it’s the air pillows that feel super flimsy in your hands. Almost like they are made out of cling wrap and you think they will deflate if you squeeze them too hard as you move them from your package box to the garbage.

So let’s throw a triple layer of this junk onto the test rig to see how deep we can cut.

Yes, that’s right. The cheap ass Amazon packaging absolutely destroyed the test. Literally not a single one of them popped on that impact! And there are only two dents on the foam, both from the secondary impacts of the sword bouncing off after the air pillows fell off after the initial hit. (I didn’t imagine I would need to secure it.)

AirSpeed, apparently you do amazing work.


After this very rigorous testing we can now plot the protective value of our test materials.

And clearly, somehow, I guess if you want to up your game you replace all the foam insert panels in your jacket with the cheap air pillows that come in your online shopping purchases? ¯\_(ツ)_/¯

SwordSTEM is a science publication intended for information and entertainment purposes only. The reader assumes any and all liability for injury sustained while implementing hypothetical solutions proposed.

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About Sean Franklin 119 Articles
Sean has a Bachelor's Degree in Mechatronic Systems Engineering, and is currently employed as a Controls Engineer. He is passionate about developing more analytical ways to view sword fighting, wishing to develop evidence based standards for protective gear and rule sets informed by tournament statistics. His martial arts history includes competitive success, medaling in international competitions for Longsword, Messer, Grappling, Rapier, and Cutting. In addition to competition Sean has been invited to instruct at a number of events across North America and Europe. For non-STEMey coaching topics Sean posts on https://www.swordstuff.blog/