They can cut it - why can’t I?
The tameshigiri-standard: Japanese old/used Tatami-omote versus green/new Tatami-omote and Chinese beach-mats.
What we wanted to find out was how these mats compared to each other when cut either dry; wet; and boiled: the results were quite surprising.
Results, when doing your own testing , may not be the same but - we are sure - very similar.
We build a simple test-rig that would tell us how much pressure in grams or kg was needed to cut through samples of single strands and rolled up mats. We would cut each sample ten-times - get the average - and compare the results.
Each strand was cut 3 times at various length and thickness, thus givingus a good idea of each mat-type’s resistance and how they compared to each other: using the old tatami-omote as a guideline marked 100%.
Cutting-test of wet/damp mats
(fully soaked and drip-dried)
Cutting-test of boiled mats
(boiled for 30min and drip-dried)
Japanese tatami-omote (old/used) are the ones used in Japan for all tameshigiri.
Comparison between damp and boiled:
The old tatami-omote would, surprisingly, soften by 31%, while the green tatami only softened a mere 9% .The big surprise: the beach-mats just stayed the same.
Having collected all this data we then asked ourselves, “What useful information has it given us?”. As Soul said to his Gangster- friends, “Oils ain’t oils”, so we could now say, “Mats ain’t mats” which isn't much of a result after all that hard work. So we set up another little test-rig, and got some better results outright. And - would we have done this test right first time - we would have saved ourselves a lot of time and hassles.
Comparison cutting-test on fully rolled - wet (drip-dried) mats.
Next we made up an other test-rig that, this time, allowed us to cut into the target-mats from a predetermined height with a constant weight; pulling the blade down into the target; similar to suemono-giri: at the same time recording the mats diameter and weight (wet/drip-dried).
Our second test-rig:
The next illustrations shows how deep and wide the blade cut into each target at a 90 degree angle:
A– 1 rolled Tatami-omote (old/used): 8.0 cm diameter -wet (drip-dry) weight: 2836 gr.
No weight-assist (weight of blade only):
Weight assist (weight + weight of blade)
Single strand comparison cutting-test:
First we randomly selected 20 single dry strands from each mat and cut them by recording the pressure (grams) used to force the cutting edge through each single strand.
With all the results and variables associated with those tests, it gave us a much better comparison. The most inconsitent item would be the beach-mat: its quality changing with each shipment received! Years ago one would buy beach-mats that were strong and had volume; now they seem to get thinner with each order.
Our testing was done to proof to ourselves what has been buggin' us for a long time - that two rolled up beach mats don't equal one hard tatami-omote - and that green tatami-omote are softer and easier to cut than the old tatami-omote as used in Japan!
Our personal conclusion:
After having taken into account the data collected, and the actually “feel” one gets when doing tameshigiri we think the illustration below gives a fair idea how the materials compare to each other.
Copyright (C) 2012 SSJS & Sei Do Kan
© 2009 - SSJS, Sei Do Kan All rights reserved.