This article refers to KidWind Balsa Blade Sheets (KW-BBS10) and KidWind Balsa Blade Sheets (KW-BB100)

Balsa wood is a natural material, and the density of any given piece may vary from 100 kg/m³ or less, up to 450 kg/m³ or more. It is natural that several pieces of balsa wood that are the same dimensions would have differing masses, and the masses of two 3″x12″ pieces can be different by 10 grams or more.

In creating turbine blade sets, two or more blades are needed. Ideally, the blades should be balanced and have the same dimensions, shape, and mass. It is easy to cut two pieces of balsa wood to the same length and width, but to change the mass is more tricky.

We recommend adding tape to the balsa wood blades to increase the mass for small amounts of mass. To determine the mass per length of tape, use a sensitive balance (sensitive to at least 0.01 g). Then follow these steps:

1. Cut a piece of paper to about the same size as the balance pan.
2. Place the paper on the balance pan.
3. Tare the balance.
4. Cut a length of tape. Use a short length for heavy tape such as duct tape, and a longer length for light tape such as transparent “magic” tape. Measure the tape as you pull it off the roll and record the length.
5. Place the tape on the paper. Since you have already measured the length, the tape can be rolled into a ball or crumpled to fit entirely on the balance pan.
6. Record the mass of the tape.
7. Divide the mass of the tape in grams by the length of the tape in centimeters. Record this number as the mass per unit length of tape.

Once you know the mass per length of tape, you can determine how long a piece of tape you need to add a specific mass to a balsa wood turbine blade.

If you need to add many grams of mass to a turbine blade, consider adding paper clips or coins under the tape. Use a sensitive balance to determine how many paper clips or coins to use.