|
 This information appeared in a 1970s era Sig
Manufacturing catalog that I had as a teenager. Sig also had an extensive article
on balsa tree foresting and harvesting.
They are as useful today as it was many moons ago.
Also, Al and Rod Clark created a very nice set of graphs that plot
balsa density versus weight for
wide variety of balsa sheet thickness, width, and length combinations. There is
also a brief discussion on balsa grain (A, B, and C) and how it affects the wood's
characteristics. It is hosted on the AMA's website.
| Balsa |
8 |
72 |
70 |
75 |
| Balsa |
10 |
100 |
100 |
100 |
| Balsa |
14 |
156 |
161 |
149 |
| Spruce |
28 |
230 |
260 |
289 |
| Yellow Pine |
28 |
222 |
277 |
288 |
| Douglas Fir |
30 |
241 |
291 |
341 |
| Hickory |
50 |
379 |
638 |
514 |
| Oak |
48 |
295 |
430 |
366 |
| Basswood |
26 |
261 |
288 |
288 |
| Black Walnut |
37 |
301 |
506 |
512 |
Balsa is one of the lightest woods available, and in many respects has the highest
strength-to-weight ratio of any wood - even oak. The chart at the right gives a
comparison of a few familiar wood types.
Hobby grade balsa is harvested in the jungles of Ecuador, kiln dried, cut into
large blocks, and shipped to the U.S. for final cutting and sanding. Most balsa
from hobby shops is in the 8-10 lbs/ft3 realm. The rock-hard stock that
nobody wants is sent to the airplane kit manufacturers ;-)
Before being discovered as an ideal source of wood for model airplanes, balsa
trees were cut and assembled into raft for floating down the river. In fact, the
word "balsa" is Spanish for the word "raft." Balsa has been widely used by the military
for air-drop pallets, and in fact, during World War II, balsa wood for models became
scarce because the Army Air Force needed it for operations. Bamboo and other reeds
were tried by modelers as a substitute wood, but it never could replace balsa.
The charts below for weights of standard hobby shop balsa sheets, sticks and
blocks were calculated from a simple formula that takes the density of the of each
piece of balsa and multiply it by the Volume. For 48" lengths, multiply each 36"
value by 4/3 (1.333).
Example:
A 3/16" x 3" x 36" sheet of balsa has a Volume of 20.25 cubic inches (in3),
which is equal to 0.01171875 cubic feet (ft3). A piece of balsa with
a density of 8 lbs/ft3 is the same as a density of 128 oz/ft3.
So, to find the weight of the balsa sheet, multiply 128 oz/ft3 by 0.01171875
ft3 to get 1.500 oz. A 48" length would weigh 1.500 oz. x 4/3 = 2.000
oz.
BALSA SHEETS
Weight in Ounces, Density in Pounds/Foot3
| 1/32"x2" 1/32"x3" 1/32"x4" |
0.125 0.188 0.250 |
0.167 0.250 0.333 |
0.211 0.313 0.417 |
0.250 0.375 0.500 |
0.291 0.438 0.583 |
0.333 0.500 0.667 |
| 3/32"x2" 3/32"x3" 3/32"x4" |
0.375 0.563 0.750 |
0.500 0.750 1.000 |
0.625 0.938 1.125 |
0.750 1.125 1.500 |
0.875 1.313 1.750 |
1.000 1.500 2.000 |
| 3/16"x2" 3/16"x3" 3/16"x4" |
0.750 1.125 1.500 |
1.000 1.500 2.000 |
1.250 1.875 2.500 |
1.500 2.250 3.000 |
1.750 2.625 3.500 |
2.000 3.000 4.000 |
| 3/8"x2" 3/8"x3" 3/8"x4" |
1.500 2.250 3.000 |
2.000 3.000 4.000 |
2.500 3.750 5.000 |
3.000 4.500 6.000 |
3.500 5.250 7.000 |
4.000 6.000 8.000 |
| 1/16"x2" 1/16"x3" 1/16"x4" |
0.250 0.375 0.500 |
0.333 0.500 0.667 |
0.417 0.625 0.833 |
0.500 0.750 1.000 |
0.583 0.875 1.167 |
0.667 1.000 1.333 |
| 1/8"x2" 1/8"x3" 1/8"x4" |
0.500 0.750 1.000 |
0.667 1.000 1.333 |
0.833 1.250 1.667 |
1.000 1.500 2.000 |
1.167 1.750 2.333 |
1.333 2.000 2.667 |
| 1/4"x2" 1/4"x3" 1/4"x4" |
1.000 1.500 2.000 |
1.333 2.000 2.667 |
1.667 2.500 3.333 |
2.000 3.000 4.000 |
2.333 3.500 4.667 |
2.667 4.000 5.333 |
| 1/2"x2" 1/2"x3" 1/2"x4" |
2.000 3.000 4.000 |
2.667 4.000 5.333 |
3.333 5.000 6.667 |
4.000 6.000 8.000 |
4.667 7.000 9.333 |
5.333 8.000 10.667 |
BALSA BLOCKS
Weight in Ounces, Density in Pounds/Foot3
| 1"x1" 1"x1½" 1"x2" 1"x2½" 1"x3" |
2.000 3.000 4.000 5.000 6.000 |
2.667 4.000 5.333 6.667 8.000 |
3.333 5.000 6.667 8.333 10.00 |
4.000 6.000 8.000 10.000 12.000 |
4.667 7.000 9.333 11.667 14.000 |
5.333 8.000 10.667 13.333 16.000 |
| 2"x2" 2"x2½" 2"x3" |
8.000 10.00 12.00 |
10.666 13.333 16.000 |
13.333 16.667 20.000 |
16.000 20.000 24.000 |
18.667 23.333 28.000 |
21.333 26.667 32.000 |
| 3"x3" 3"x4" |
18.00 24.00 |
24.00 32.00 |
30.000 40.000 |
36.000 48.000 |
42.000 56.000 |
48.000 64.000 |
| 1½"x1½" 1½"x2" 1½"x2½" |
4.500 6.000 7.500 |
6.000 8.000 10.00 |
7.500 10.000 12.500 |
9.000 12.000 15.000 |
10.500 14.000 17.500 |
12.000 16.000 20.000 |
| 2½"x2½" 2½"x3 |
12.500 15.000 |
16.667 20.000 |
20.833 25.000 |
25.000 30.000 |
29.166 35.000 |
33.333 40.000 |
BALSA STICKS
Weight in Ounces, Density in Pounds/Cubic3
| 1/16"x1/16" 1/16"x3/32" 1/16"x1/8" 1/16"x3/16" 1/16"x1/4" 1/16"x3/8"
1/16"x1/2" |
16 16 8 8 4 4 2 |
0.125 0.188 0.125 0.188 0.125 0.188 0.125 |
0.167 0.250 0.167 0.250 0.167 0.250 0.167 |
0.208 0.312 0.208 0.312 0.208 0.312 0.208 |
0.250 0.375 0.250 0.375 0.250 0.375 0.250 |
0.292 0.438 0.292 0.438 0.292 0.438 0.292 |
0.333 0.500 0.333 0.500 0.333 0.500 0.333 |
| 1/8"x1/8" 1/8"x3/16" 1/8"x1/4" 1/8"x3/8" 1/8""x1/2" |
4 4 4 2 1 |
0.125 0.188 0.250 0.188 0.125 |
0.167 0.250 0.333 0.250 0.167 |
0.208 0.312 0.416 0.312 0.208 |
0.250 0.375 0.500 0.375 0.250 |
0.292 0.438 0.538 0.438 0.292 |
0.333 0.500 0.667 0.500 0.333 |
| 1/4"x1/4" 1/4"x3/8" 1/4"x1/2" 1/4"x3/4" 1/4""x1" |
1 1 1 1 1 |
0.125 0.188 0.250 0.375 0.500 |
0.167 0.250 0.333 0.500 0.667 |
0.208 0.312 0.416 0.625 0.832 |
0.250 0.375 0.500 0.750 1.000 |
0.292 0.438 0.583 0.876 1.166 |
0.333 0.500 0.667 1.00 1.333 |
| 1/2"x1/2" 1/2"x1" |
1 1 |
0.500 1.000 |
0.667 1.333 |
0.832 1.666 |
1.00 2.00 |
1.166 2.333 |
0.1333 2.667 |
| 3/32"x3/32" 3/32"x1/8" 3/32"x3/16" 3/32"x1/4" 3/32"x3/8" 3/32"x1/2" |
8 8 4 4 2 2 |
0.141 0.188 0.141 0.188 0.141 0.188 |
0.188 0.250 0.188 0.250 0.188 0.250 |
0.234 0.312 0.234 0.312 0.234 0.312 |
0.281 0.375 0.281 0.375 0.281 0.375 |
0.326 0.438 0.326 0.438 0.326 0.438 |
0.375 0.500 0.375 0.500 0.375 0.500 |
| 3/16"x3/16" 3/16"x1/4" 3/16"x3/8" 3/16"x1/2" 3/16"x3/4" 3/16"x1" |
2 2 2 1 1 1 |
0.141 0.188 0.281 0.188 0.281 0.375 |
0.188 0.250 0.375 0.250 0.375 0.500 |
0.234 0.312 0.469 0.312 0.469 0.625 |
0.281 0.375 0.563 0.375 0.563 0.750 |
0.326 0.438 0.656 0.438 0.656 0.876 |
0.375 0.500 0.750 0.500 0.750 1.000 |
| 3/8"x3/8" 3/8"x1/2" |
1 1 |
0.281 0.375 |
0.375 0.500 |
0.469 0.625 |
0.563 0.750 |
0.656 0.876 |
0.750 1.000 |
| 3/4"x3/4" |
1 |
1.125 |
1.500 |
1.875 |
2.250 |
2.625 |
3.000 |
Resources for Balsa Wood on the Airplanes and Rockets website:
Posted January 4, 2012
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