If you are making a rubber band powered plane what rubber band would you buy?

I would prefer not to buy any rubber bands but to make a rubber motor from strip. It would be possible to knot together a number of small bands but the flight results would probably not be very good. This strip material is generally available from model airplane "cottage industry" type sources and comes in widths from 1/8 to 1/4 inch with a nominal thickness of 1/32 inch and lengths up to 50 feet. It is characterized by extreme elasticity and low energy loss which allows many turns (twists) to be applied without breakage. Typically, a loop of 1/8 inch rubber will satisfactorily fly a model airplane weighing up to one ounce and having a wing span of 16 to 20 inches. Unwound, the loop should be around 1 1/2 times as long as the distance between attachment points with the propeller in place.