Ok the Helicopter rotor noise sound is due to the tire being low on the air pressure and that low pressure is allowing the paddle blades to flex back and forth and causes that rotor noise. Alex you obviously are flexing them back on the hard packed wet sand.
Tim has explained it to me and many customers over the years. If you want more traction you air the tires up so the Paddle blade stays firm and doesnt flex back. I know some guys that say man I aired my tires up and my car slows down. Yep tires bitting the sand better , means you have to much paddle. which everyone does when buying paddles they all want to over paddle. so when the tire is aired down and the torque on acceleration pushes the paddle backward and it doesnt bite hard so its slipping more. Kind of like rowing a boat what pushes harder a straight up and down paddle or a paddle thats angled back skimming along the surface.
