Last Update: 12/18/09

Balsa Wood Testing

Below is a testing method used to document various densities and stiffness of balsa wood.

Seven balsa samples will be tested. The dimensions are 1/8"(0.125") x 3/8"(0.375") x 13 15/16"(13.9375").

I purchase my balsa from Jake Zimmer at www.specializedbalsa.com.Balsa from this supplier comes in several densities:

Extra Light Balsa (6 or less pounds per cubic foot)
Light Balsa (6-10 pounds per cubic foot)
Medium Balsa (10-14 pounds per cubic foot)
Heavy Balsa (14-19 pounds per cubic foot)
Extra Heavy Balsa at (19+ pounds per cubic foot)

Samples are assigned letters for identification and are weighed using a gram scale. The suppliers density classification follows the weight in grams. Sample "C" was not labeled by the supplier so it has a "?" for its density classification. It is interesting to see that Sample "D" which is classified as Heavy is actually lighter than sample "E" which was cut from a "Medium" labeled balsa sheet .

Balsa Sample Density Classification

Balsa
Sample		Weight
in Grams		Supplier
Classification		DensityRevised
Classification
A 0.88g Light 5.13 lb/ft3 Extra Light
B 0.88g Light 5.13 lb/ft3 Extra Light
C 1.45g ? 8.45 lb/ft3 Light
D 1.49g Heavy 8.68 lb/ft3 Light
E 3.5g Medium 20.40 lb/ft3 Extra Heavy
F 4.35g Extra Heavy 25.36 lb/ft3 Extras Heavy
G 4.49g Extra Heavy 26.18 lb/ft3 Extra Heavy
A sample with the above physical dimensions (volume) should weight between 1.030g and 1.716g to fall under the classification of "Light" density(6-10 pounds per cubic foot).

Stiffness testing using a 100g weight, balsa set upon two aluminum angles 12" a part and a dial indicator in the center. The deflection is indicated in the chart below. Samples with the least deflection are at the top.

Balsa Sample Density Classification
and Stiffness Testing

Balsa
Sample		Weight
in Grams		Supplier
Classification		DensityRevised
Classification		Deflection
E 3.5g Medium 20.40 lb/ft3 Extra Heavy 0.007"
G 4.49g Extra Heavy 26.18 lb/ft3 Extra Heavy 0.008"
F 4.35g Extra Heavy 25.36 lb/ft3 Extras Heavy 0.009"
D 1.49g Heavy 8.68 lb/ft3 Light 0.031"
C 1.45g ? 8.45 lb/ft3 Light 0.032"
A 0.88g Light 5.13 lb/ft3 Extra Light 0.089"
B 0.88g Light 5.13 lb/ft3 Extra Light 0.110"

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