Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB

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Introduction
Water-filled plastic bottles are perhaps the most widely-used target for test-cutting all over the world. It can be
obtained anywhere, costs almost nothing to prepare, and can be easily cut free-standing on any kind of flat surface.
However, its relative softness limits its utility for systematic training, especially for longer blades that have
inherently more cutting power.
Bamboo, on the other hand, is one of the oldest and most respected test-cutting materials available. When green,
its shape and density is considered very similar to live bone, and offers a higher level of challenge for the serious
cutting practitioner. However, even if one has a reliable source for fresh green bamboo, storing them for continuous
Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB) FOR TEST CUTTING
practice is quite problematic as it hardens quickly with age and moisture loss, dramatically increasing their
difficulty to cut, as well as the risk of damage to one's blade (Southren, 2007). They require specialized stands in
order to be cut reliably, and even then most of these stands suffer from vibration and shock absorption issues with
most users. Short segments of free-standing bamboo can be consistently cut only by the best-trained swordsmen,
and having a person hold larger pieces of bamboo out for someone else to cut is simply not safe nor feasible outside
a formal dojo setting. Additionally, relatively long lengths of bamboo are required for a rather lower number of
possible cuts, compared to tatami and beach mats.
But what if there is a way to combine the best properties of both materials, in a way that is easy and accessible
for both the casual and the serious practitioner?
You will need:
- Bamboo
- Plastic bottles
- Hacksaw
- Glue Gun
- Pencil
- Water (not shown)
Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB) FOR TEST CUTTING
1. Saw off one end of your bamboo.
Make your cut as straight as possible, so that it rests more securely on the bottle. The hacksaw really is more
suited for this, even just the detached saw-blade by itself.
Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB) FOR TEST CUTTING
2. Look for the center of the bottom of the bottle.
There is usually a round indentation atop an inverted cone allowing for a nice snug fit. Take care not to damage
this in any way.
Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB) FOR TEST CUTTING
3. Place one end of your bamboo onto the center, press down firmly.
But not too forcefully. Make sure it is pointing straight down, and exiting the mouth of the bottle as vertically
as possible.
Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB) FOR TEST CUTTING
4. Mark your bamboo with a line at the exact same level as the mouth of the bottle.
Perhaps up to a couple of extra millimeters' allowance is advisable, as this will result in a slight downward push,
making it more secure. In any case, you can file away any excess length, but not easily add more if for whatever
reason it comes up short later on.
Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB) FOR TEST CUTTING
5. Saw off your bamboo at the line you just made.
Again, as straight as possible. This is more crucial at the top end, since the bottle-cap that it will be against is
flat, unlike the inverted cone at the bottom.
*At this point, you should have a short segment of bamboo that has no cracks whatsoever, as well just one, or no
nodes at all. But sometimes, you will end up with a segment that has two nodes. This means that you now have a
water-tight chamber that will soak very poorly. To fix this, find a small but sturdy push pin or thumb-tack, and
carefully prick / bore smooth tiny holes within the length of the closed chamber, one or two at each opposing end
close to the nodes. Do not use nails or a powered drill-bit, as this may have the same effect as cracks on the
bamboo: compromising the integrity of the entire segment and messing up your cut.
Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB) FOR TEST CUTTING
6. Apply molten glue liberally at the bottom end of your bamboo.
There should be enough glue on the inside, outside, and rim of the cut; otherwise the bamboo will come off.
Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB) FOR TEST CUTTING
7. Slide your glue-tipped bamboo straight down the center of the bottle.
All that glue is liable to drip or inadvertently stick to the mouth or sides of the bottle, so be sure to use a
precise, fluid motion for this step. Breathe out gently while doing this.
Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB) FOR TEST CUTTING
8. Press down firmly until glue sets. Fill with water.
Rotate the bamboo ever so slightly back and forth once or twice around the indentation to ensure proper
alignment, during the brief moment that the glue is still gooey. When you start filling, the incoming water will
solidify the glue much faster, but you have to make sure to keep the bamboo vertical the whole time, otherwise
it will end up in a slant.
Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB) FOR TEST CUTTING
9. Apply molten glue liberally at the center of the bottle-cap, and replace onto the bottle whilst still
hot.
Again there should be enough glue to more or less encapsulate the top end of the bamboo while leaving a solid
inverted “base” on the bottle-cap. Screw on the cap briskly and securely. The glue will solidify faster this time
since it will immediately come into contact with the water, but it also helps to quickly invert the entire bottle
once after covering.
Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB) FOR TEST CUTTING
10. Soak for 24-48 hours. Your BWB is now ready for cutting!
Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB) FOR TEST CUTTING
Types of Bottle and Thickness of Bamboo
In trying to illustrate the steps above, oversized bottles (6000 mL) and bamboo of medium thickness (20 mm) have
been used to show the details more clearly. However, it is more practical to use 500 mL soda or juice bottles that
can accommodate thin bamboo of around 15 mm diameter, as one is more likely to be able to accumulate these in
sufficient numbers for a worthwhile cutting session, especially in collaboration with community or workplace
recycling and segregation efforts. (Please ensure proper hygienic standards, especially if one is preparing BWB's for
other people.) Paradoxically, bottles smaller than 500 mL become somewhat more difficult to cut, as there is more
pressure inside which makes them more rigid (Southren, 2007).
Bottles for drinking water may also be used, however these are usually made of thinner plastic and are less satisfying
to cut. They have the roughly the same sized mouth and bottle-cap as soda and juice bottles, and can accommodate
similar diameters of bamboo. Do not use diameters exceeding 15 mm for water, juice, and soda bottles though, as
that will leave too little space for the water to enter when filling.
Sports drink bottles, on the other hand, have a wider mouth that can accommodate thicker bamboo of up to 20
mm. Whatever the bottle, the important thing is to use the correct diameter of bamboo that leaves enough space
for water to flow in freely.
Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB) FOR TEST CUTTING
Relative Hardness
It quite problematic to objectively describe the density and hardness of various materials as they relate to cutting
resistance. However, some relative values may be given based on expert swordsmen's personal experiences, as well
as the author's own.
Consider some of the cutting materials discussed earlier. Let us assign a hardness value of 100-130 to a tatami mat
soaked in water, and perhaps a value of around 35-50 for the much softer beach mat, with an acceptable standard
of hardness for meaningful sword practice of 55 (Obata, 2005). As the current author estimates the hardness of
500 mL soda / juice / sports drink bottles to be 15-20 (thicker plastic, various shapes), and drinking water bottles
of the same size to be around 10 (thinner plastic, more uniform shapes), these along with beach mats may be
considered suitable primarily as light practice.
Fresh, green bamboo 15 mm thick may be assigned a value of 70, with a larger diameter of 20 mm having a value
of around 80. These values may increase by a factor of 1.5 – 2 with age and moisture loss (Obata, 2005). However,
soaking dry bamboo encased in a BWB for 24 hours brings this factor down to around 1 – 1.2, while a 48-hour soak
or more brings it down to perhaps 0.9 - 1 of the original hardness.
Putting these all together, for a 24-hour soak it is estimated that:
- A 500 mL sports drink BWB will have a hardness of around100
- A 500 mL soda / juice BWB will have a hardness of around 85
- A 500 mL drinking water BWB will have a hardness of around 80
Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB) FOR TEST CUTTING
For a 48-hour soak or more it is estimated that:
- A 500 mL sports drink BWB will have a hardness of around 92
- A 500 mL soda / juice BWB will have a hardness of around 78
- A 500 mL drinking water BWB will have a hardness of around 73
These values are well within the prescribed range of hardness for meaningful sword cutting practice.
It is not recommended to soak BWB's for 72 hours or more, as this will produce a pungent green liquid that even a
panda will find disagreeable.
https://www.youtube.com/watch?v=6yZ1W2ogpzw&list=PLNF04g-u_MwSwEbW19h0WTg3-4YxglXPp
Safety Precautions
When cutting BWB's, please wear safety goggles or any kind of eye-protection. Closed shoes with good traction are
also recommended. It is also advisable to wear a cap and a jacket to keep the water off, especially if you are
exceeding the 48-hour recommended soaking time.
As with standard bamboo targets, horizontal cuts are strongly discouraged, unless you lay the BWB down on its
side. Cutting straight down the bottle-cap parallel to the bamboo may prove difficult to aim but could meet with
less resistance. Diagonal cuts are considered optimal. Trying to cut multiple BWB's stacked together side-by-side is
extremely risky and could result in significant blade damage.
Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB) FOR TEST CUTTING
Further Development
Adding red food coloring to the water as well as wrapping the BWB's in cloth or denim should increase the difficulty
and provide a highly realistic, if slightly unnerving, cutting experience. Similarly, pre-soaked and drained BWB's
may also be filled with ballistics gel, if one has the funds and access to it.
References
Obata, Toshishiro: Shinkendo Tameshigiri (2005). International Shinkendo Federation. San Gabriel, California
Southren, Paul: Introduction to Backyard Cutting (2007). Sword Buyers' Guide. http://www.sword-buyersguide.com/
Pandoy Pulido | HOW TO MAKE BAMBOO WATER BOTTLES (BWB) FOR TEST CUTTING