Thread: Building Light
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Old Dec 19, 2001, 09:34 PM
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in persuit of low wing loading
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Boston, Mass
Joined May 2001
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balsa density

I just calculated density for six sheets of 4x36x1/16 "contest grade" balsa that I ordered from National Balsa. The thickness ranged from 0.075 to 0.066, with 1/16 being 0.0625. The density ranged from 6.4 to 11.5. Only one sheet had a density less than 8. In addition, the assumption that each sheet was exactly 1/16th would have resulted in density measurements that were on average too high by 0.80. I got a similar range of densities for 1/32nd balsa in the same order.

As a completely unscientific sample (I don't have that much other balsa laying around) I weighed one each 1/16th and 1/32nd for SIG and Midwest balsa. The SIG had densities in the 9-10 range, while the Midwest was in the 13-14 range. This is not to slam balsa vendors, but just to show there are differences.

Finally, Indoor Model Supply in Oregon sells "indoor" balsa. I ordered some peanut balsa packs a while back to sample ($25 minimum order on their full sized balsa). Each pack consists of different cuts of balsa (A, B, C) and different densities. In one pack, the lightest sheet had a density of 5.9. This makes me think that if I put in an order for indoor balsa in full sized sheets from them that I would probably get pretty light balsa.

An alternative is to go to the LHS (which in my case carries Midwest) and weigh a whole lot of balsa to hopefully find that rare sheet of low density balsa.

Dave Robelen recommends using balsa in the 4 to 6 pound per square foot range for indoor/micro models. Hmm...

This building light stuff always has one wrinkle after another to learn about. But, "we choose to build small planes, not because it is easy, but because it is hard". (sorry, shades of JFK).
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