Saturday, July 17, 2010

DIY Foam Swords, Part 1: Construction

Here's my take on foam practice swords, which are more commonly known as boffers. They are basically foam insulation or pool noodles with a pvc pipe core. Since you can find plenty of boffer construction articles online, i will be focusing on the design options which make it suitable for martial arts practice. Also, my approach is minimalist, what is the minimum work/materials needed to make it because i am making 23 foam swords for a group battle. The material cost per sword is ~ $3 making it cheaper than official martial arts practice swords or nerf swords (at least $15)


You'll need:
-Foam pool noodles or Foam pipe insulation (1/2" and 1")
-1/2" white pvc pipe, schedule 40?
-Duct tape (colored is cooler)
-Electrical tape
-Peel & Stick Foam sheets from walmart or something else for grip.
-1 1/8" Rubber chair tips

Tools you might not already have:
-PVC pipe cutter (you should have one, makes cutting PVC a breeze, seriously)
click to zoom

Long sword dimensions:
based on my wooden boken (two-handed katana), we want a blade length of 30" and total length 40". For a two-inch safety tip, this means the PVC pipe should be 38". (the foam is of course 30" in length). This sword is also suitable for lightsaber practice, as they are based off of japanese sword dimensions as well.

Short sword dimensions:
based off of my kung-fu broadsword (one-handed saber), we want a blade length of 25.5" and total length 32". For a two-inch safety tip, this means the PVC pipe should be 30". (the foam is of course 25.5" in length).

In practice, this will still feel a bit longer than the regular sword because of the width of the foam. Also the rubber chair tip adds ~0.5" so you could cut the pipe a lil shorter on the handle side.

Martial arts and safety
Because we are using these swords for training purposes, 1/2" pvc pipe is the best size to use as it strikes a good balance between flexible enough to not hurt much on impact and stiff enough to solidly block without bending. The problem with most toy swords and commercial practice foam swords is that they bend too much (so you won't get hurt and sue the company). They also have poor tip designs making them dangerous for thrusting attacks.

do this if using pipe insulation
Foam pool noodles from the $1 store are the fastest way to make the swords. Avoid the larger and strangely shaped ones. With my dimensions, you need 1 pool noodle per sword. When you can't get the pool noodles (say during the winter) pipe insulation from a home improvement store works, but since it is thinner you need two layers: 0.5" pipe insulation and 1" pipe insulation to go over it. Arrange the insulation to overlap the gaps and fill the outer layer gap with extra pieces (see diagram). 3 or 4 bands of duct tape along the blade will keep it together. In my opinion, you don't need to cover the entire piece with duct tape. It takes too long, makes the sword heavier, and it takes away from foam's ability to rebound because the duct tape is air-tight. I haven't had a problem with durability since the bare foam itself is pretty robust.

When sliding on the foam pool noodles on the pvc pipe, spray adhesive is a pretty good idea. The foam will be solidly locked on the pipe. (pipe insulation has adhesive already). I didn't do this, instead i just hot glued the pvc pipe to the foam (i roughed up the pipe surface with sandpaper for better adhesion) and duct tape to lock it down (a strip on opposite sides, and a ring on the hilt and on the blade to lock it).


Tip Design
Because thrusting/jab/stab is an important part of martial arts training with swords, we want to ensure the sword tip is safe. Also note that a whack from the side of the sword has some give from the pvc flex. A thrust does not have any give so this part is important do right. I opted for a 2" deep buffer zone. First, cap the tip of the pipe by hot glueing a penny to the tip. If you don't do this, the sharp edge of the pipe can cut through the buffer zone padding. This also makes sliding the foam pool noodle onto the pipe easier. Mark the pvc pipe the blade-length - 2" from the tip and slide your foam to the mark to ensure a 2" empty buffer. Fill the buffer zone with a piece of foam (cut at least a 2" long and ~1/5 portion of the foam ring and stuff it into the hole). You want to have to compress the foam plug so you have a bit more density there. If you are using thinner pipe insulation, you can cut a 2" length piece and fold the width in half to plug the hole. Having a little bit stick out is okay and may even be desirable. Cap it off with a strip of duct tape across the tip, then a ring around the sides to lock it in place.

Finishing the handle
The handle is a bit thin and hard on the hands. I've used some vinyl fabric ribbon before (with double-sided tape) but the best option i found was Peel-&-Stick Foam sheets found in the Walmart craft section. 40 sheets for $5 makes it great grips for mass-producing foam swords. A single sheet wrapped is good for the long sword. Cut it in half lengthwise for the short sword. The colors are nice too. The foam will probably peel-up over time so fix it in place with hot glue, bands of electrical tape, or a ribbon grip. Finish off the sword pommel with a rubber chair tip to cover the hard pipe end (if you have the foam grip, the 1 1/8" size fits perfectly).
rubber chair tip not shown

There you have it! With this design, i can make a sword in 10 min. I made sets of 6 swords per blade color but with all different hilt-grip colors. The blade color would signify the team, but the hilt color could give individuality when a person choose their sword. I made mostly long blades, but made all short swords blue blades, so people can tell visually.

2 comments:

aliah said...

PVC is very commonly used in construction.PVC pipe is very effective in construction projects. i like the colorful pictures you shared here..looking beautiful.
plastic fabricators

Foam-By-Mail said...

Wrapping the handles in a thin closed-cell foam sheet will make them softer and easier to grip. You can even use something like an old yoga or camping mat for this.