Safe training swords part 2: measuring flexibility

Keith Farrell and Robert Schwartz
Keith Farrell and Robert Schwartz fencing with the longsword at Edgebana. Photo by Thomas Naylor, 2015.

This is the second part of a short series of articles on safety features on swords. It builds upon the definitions that I gave in the first part of the series, about “tipping solutions” for the point.

How to measure flexibility of training swords – this is a question that I have been asked several times by different people, over the years. It is most often related to the issue of being able to thrust safely during training, but most usually related to tournaments, where organisers try to standardise the kinds of swords that may be used in the event, to ensure that all the swords meet at least a minimum standard of safety. I support this notion strongly: I feel it is important to ensure a safe environment for all fencers, and one of the ways of doing that is to make sure that no one has a ridiculously stiff and unforgiving sword.

A few years ago, FEDER (the Polish federation for HEMA) developed a method for testing the flexibility of swords, involving the use of clamps, weights, measuring of angles and performing calculations based on the length of the blade and how far the blade bends when a weight is applied. This method has been adopted (sometimes with modifications) by various other organisations and events, with varying degrees of success.

Unfortunately, this method is not always easy for people to measure at home by themselves, as they may not possess the right equipment (such as the clamps) or the understanding of what they are trying to achieve. Then, when taking a sword to a tournament, people can be disappointed when they find that their sword does not pass the test at the event, and they are not allowed to use it. I have seen this happen a few times, and it can lead to quite a lot of grumpiness, especially when the parameters of the test mean that swords that are usually perfectly safe and valid for the majority of events are then forbidden in one event. Generally speaking, it is good to know that, for example, a standard Regenyei feder will pass most of the flexibility tests at most events – however, when you go to an event and your standard feder fails the test, that can be quite annoying.

It would be helpful to have a method of measuring the flexibility of swords that is easy to do at home, and easy to understand, so that more people can make their own measurements in advance to see if their sword is likely to pass or not at a specific event. Ideally, the test should also be fast to perform, with a minimum of hassle or equipment required, to make it easier for event organisers to perform the formal testing at events and to reduce queues.

One such method that I have been playing with recently was developed by Black Fencer, the Spanish company that manufactures the well-known synthetic training swords. They call it “static flexibility”, and it is an incredibly simple method, requiring only a set of digital scales capable of measuring up to 20-25 kg (so a set of digital bathroom scales would be fine).[1]

The method is to switch on the scales, let the display settle at 0, and hold the sword just above the scales with both hands on the pommel. Then, place the tip of the sword on the scales, and gently increase pressure downward towards the scales. Once the blade begins to flex and is no longer straight, read the display on the scales, and use this as the measurement for the sword.

A more flexible sword will start flexing with less pressure, and so the reading will be lower. A stiffer sword will need much more pressure before it begins to flex, and so the reading will be higher. The method may not be a proper test for a physics classroom, measuring a specific variable that can be fed into calculations and formulae, but it is a swift and easy test that gives a measurable and reproducible result, that people can do at home as well as at events.

After testing a variety of makes and models of longswords at home and at my school, I have been able to put together the following table of test results to show how the test performs. The table describes when swords have different points and external tips,[2] and also records when the measurements were performed by different people.[3]

This table shows that the more flexible swords do have a lower score for this test, and the stiffer swords to have a higher score for this test. This means that, regardless whether or not the test is “good physics” or if it “measuring the right thing” or not, it does nonetheless allow us to measure and rank swords by flexibility in a very similar way to how fencers will typically test a sword for flexibility when picking it up for the first time. The method is also very fast and very easy, and digital scales are not difficult to find.

Given the results in the table above, I would suggest that for a longsword, a “safe” range of flexibility would be around 6-14 kg, although a score beneath 7 kg may indicate that the sword is somewhat floppy. Swords scoring above 13 kg are perhaps a bit too stiff to be entirely safe, particularly in a tournament setting where adrenaline is running high and people are likely to throw themselves forward with as much explosive force as they can generate, to try and score the point. While of course any sword can be used safely during training, by reducing the intensity of the practice, tournaments are renowned for being high intensity environments.

While it is unlikely that even a very powerful thrust with a very stiff sword will result in a penetrative injury through the jacket, it is entirely possible that too strong a thrust with too stiff a sword will result in a broken rib, or a broken sternum. Furthermore, the mesh of the masks is only rated to withstand up to 600 N or 1000 N of force (CEN levels 1 and 2 respectively);[4] the stiffer the sword, the more force will be transmitted directly from the thrust to the fencing mask (and to the head within the mask, potentially causing a whiplash effect or even concussion)[5] and the higher the chance of the mask failing; the more flexible the sword, the less force will be transmitted in a thrust, and therefore the lower the chance of trauma to the brain and the lower the chance of a mask failing.

Since thrusts to the face are a common technique in HEMA, it would be a mistake to ban such actions. However, it is clear that it is also a mistake to let people with superb athletic ability throw themselves at each other as fast as they can, stabbing each other in the fencing mask, with stiff and unforgiving blades. As with just about everything in life, moderation is the key. Since people will push themselves to move as fast as they can in a tournament, the equipment needs to help keep people safe. Therefore, the swords must be able to flex. They should not be wobbly and whippy, as that will have a negative impact on other elements of the fencing, but they should flex under a reasonable pressure; hence the need for a “safe” range of measurements.

If you would like to contribute to this article, and especially if you have a type of longsword that is not represented in the table, please do measure your swords according to this method, and send me a note of all the relevant details. I will include it in the table above, and hopefully we can make available a broad list of values for better discussion of the topic.

Footnotes:

[1] The original video from Black Fencer to explain what they mean by “static flexibility” can be found on YouTube: Understanding Black Fencer Flexibility

[2] Please see my article “Safe training swords part 1: tipping solutions” for an explanation of the terminology I prefer to use for points and tips.

[3] Different people performing the measurements will of course come up with slightly different values depending on their scales and what they decide to count as the blade “no longer being straight” during the measurement. Therefore, each line in the table is marked to show where the measurement came from. “TVC” means The Vanguard Centre (part of the Academy of Historical Arts) in Glasgow; “SdA” means La Sala delle Armi in Turin; “MCG” means the Medieval Combat Group in Belfast; “SotW” means Swords of the West in Galway; “CB” means Cork Blademasters in Cork. My thanks to my friends in these clubs for adding their measurements to the table and giving me their thoughts on this article!

[4] For more information on the construction of fencing masks and what the different ratings mean, please see my article on the subject: Construction of a Fencing Mask (.pdf download)

[5] For more information about concussions and “dementia pugilistica” in HEMA, please see my article on the subject: Dementia Pugilistica in HEMA (.pdf download)

KeithFarrell

KeithFarrell

Keith Farrell is one of the senior instructors for the Academy of Historical Arts. He teaches HEMA professionally, often at international events, and has an interest in coaching instructors to become better teachers. He has authored "Scottish Broadsword and British Singlestick" and the "AHA German Longsword Study Guide", and is one of the regular contributors to the Encased in Steel online blog. He has been a member of HEMAC since 2011, and was awarded a HEMA Scholar Award for Best Instructor for research published in 2013.
KeithFarrell