Bass Boomwhackers!

This project demonstrates how to create bass Boomwhacker tubes out of large drain pipes. I made this set for an elementary music classroom to supplement the set of manufactured Boomwhackers they already use. With this set, even Kindergarteners can play the big bass tubes by lifting and dropping them on the carpeted floor along to a beat.

The idea for the instruments came from two existing bass tubes that were slightly out of tune. I used these as models, recalculated and re-tuned their pitches, and added more to the collection. This set is a B-flat pentatonic scale, which allows the kids to play in the keys of C, F, and G, on scale degrees Do, Fa, and Sol in each key. I had extra pipe left over, so I made an E2 tube as well.

Materials:

• Drain pipe tubes (4 in. x 10 ft. white solid triple-wall; $20 at big box stores)
• PVC Pipe Cap, 4 in. ($4 each)
• 5-minute epoxy
• Cans of spray paint (various colors)
• Goo-gone (Optional, but helpful)

Tools:

• Mitre saw
• Tape Measure
• Speed square
• Marker
• Orbital sander

Safety:

• Eye protection
• Facemask

The most complicated part of this project is calculating pipe lengths accurately. To find the desired pitches for your scale and their frequencies and wavelengths, consult this resource. The scale I chose was a Bb pentatonic scale with the following pitches: Bb1, C2, D2, F2, G2, Bb2, C3, and D3.

The physics of closed-end tubes is explained here. To calculate the effective lengths of the tubes, you must calculate 1/4 of the wavelength. But this result is a theoretical distance where the sound wave reaches a node outside the tube. The diameter of the tube matters in determining the location of the node, so you must do an end-correction calculation, which is .3 x the diameter of the tube. Therefore, to find the actual length of the tubes we need to cut for this project, you must subtract the end correction from the calculated effective length.

In the case of this set of pipes, the end correction is 3.09 cm. For my scale, I calculated the table above, where the right column shows the lengths of my pipes in cm. I chose to use metric measurements because it was easier to work with decimals.

For the next step, I used a tape measure and a speed square to find and mark the cut locations for each pipe. The trick is keeping the tape measure perfectly in line with the pipe, so I laid it on a vertical board next to the pipe and used the speed square's 90-degree angle to make each line with a permanent marker. Precision is important so the pipes are perfectly in tune.

I used a compound miter saw to make a cut on each line, making sure to account for the thickness of the saw blade (1/8") so my calculations remained precise. Be sure to check the measurements many times. (As they say, "Measure twice, cut once!")

The length calculation doesn't change once the end cap is glued on because the sound wave will resonate inside the tube, bouncing off the cap.

I first tried PVC Cement to secure caps on the pipes, but that didn't hold. So I ended up using 5-minute epoxy, which was perfect. Use rubber gloves to avoid skin contact with the glue and a facemask and good ventilation to avoid the noxious fumes. Mix the epoxy and apply it with a paintbrush to both the inside of the cap and the base of the pipe's outer wall. Push the cap onto the pipe, twist it gently into place, and hold the connection for about 30 seconds. You want to make sure the cap goes on tightly against the pipe ending when you glue it in place so the tuning and acoustics are not altered from the precise length measurement. Leave the glue for a few hours to set it permanently.

To remove the labels and adhesive on each pipe and cap, I used Goo-gone.

PVC is very smooth, so to get paint to stick, you need to scuff up the surface to prepare for painting. I tried a rasp at first, but it was slow and laborious. Since it's a lot of material to work on, I ended up using an orbital sander. Be sure to wear a facemask to avoid inhaling PVC dust. Afterward, clean all of the PVC dust off before painting--an air compressor works well to blow off all the dust.

Before painting each tube, I used adhesive stencils to label the pitches on the bottom of each tube.

Boomwhackers are color-coded according to their pitch. C is red and they proceed through the color wheel as the notes ascend through the chromatic music scale, as shown above. I painted the tubes according to the Boomwhacker color chart. After painting each coat outdoors, I stood them up on posts to dry. Two coats of paint were enough.

After the paint dries, remove the stencils carefully.

Once the paint is dry, they are ready to play.

The bass tubes sound impressive. Below are a couple of clips, but they don't capture how good they sound. In-person, they are very resonant--even more so than regular Boomwhackers. They are a great addition to an existing set of Boomwhackers and allow for a wider range of sounds.

Enjoy a brief clip of music teachers playing an arrangement of "Don't Worry, Be Happy" on Bass and regular Boomwhackers!