Two nine volt batteries will get if off the ground a fraction of an inch. The air has to escape.
A full size helicopter can carry 4 times its rated capacity, but won't get more than 10 feet high.
How do I calculate the frequency of an 8.5 cm diameter bell ?
The bell is cast brass for resonance, but I intend to activate it with a buzzer so sound will last for more than a few seconds. Does the weight affect anything other than volume ? I intend to use it inverted, supported near the "top".
Balsa (Ochroma pyramidale) is native to the tropical Americas.
Kapok (Ceiba pentandra) grows in the rainforests of Africa and the Americas (except the Canadian rainforest). It is lighter and standard in life preservers. You could cut open a worn out life praserver.
Indian Kapok (Bombax, 3...