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Christchurch and District Model Flying Club
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How many “G” could the wing of a standard Goldberg Cub take before it broke? Could you, indeed, destroy the aircraft just using aerodynamic forces?
Take a WAG (wild-assed guess) NOW as to how many bricks I stacked up on top of the now redundant wing of my Cub before it snapped. Each brick weighs 5.75 lbs and the model weighed 7 lbs.
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This is just the start: 4 bricks weigh 23 lbs: the equivalent of 4g. The pilot is puffing hard but the wing just shrugs.
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6 bricks weigh 34.5 lbs—we are up to 5g now. Not a sign of any stress.
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8 bricks, 46 lbs, 6.5g and still no signs of stress from the wing.
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Pulling 8g now and the pilot is blacking out, but there is just a small wrinkle in the covering to the right of the bricks to show that, well, the wing is... feeling a little pain. I changed the camera angle to show that there is no cheating going on!
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69 lbs and nearly 10g on the meter. The pilot is unconscious. Probably a good thing with all those bricks over his head.
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14 bricks, 11.5g. The wing is still breathing easy.
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I had to re-arrange the bricks as they were about to topple over. It’s even more of a point load, and 16 bricks weigh 92 lbs. The wing is pulling over 13g, the covering is badly wrinkled but there isn’t a cheep from the main spar.
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18 bricks is 103 lbs. But not done yet... The stack is really unstable though!
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Bang! 20 bricks, and I had to press down on the stack, because they were so unstable I couldn’t get to the store to add any more. So a standard Goldberg Cub wing, built over 15 years ago by a novice will take a point load of at least 115 lbs, or 16.5g. What a wonderful advert for balsa wood Pro-film and liteply!
Mike Roach
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