When building a mini mortar motorboat, the suction cups attached with TAMIYA’s underwater motors adhere well to some bottom of boats, but not to others.
First, since suction cups work by creating a vacuum inside them to generate a pressure difference against atmospheric or water pressure, the permeability of the contact surface to both water and air, is extremely important.
Consider the case of installing the suction cup on a bottom of a boats in the air. Even if you press the suction cup against the bottom surface and create a vacuum inside it, if the bottom plate is thin, the moisture saturation of the mortar plate around the suction cup will decrease, allowing air to flow from the surrounding area into the suction cup, causing the contact force to come loose.(See the below movie)
However, the situation is different when the surface is sufficiently saturated with water. Since the surrounding area never dries out, the suction cups remain firmly attached. Therefore, when test-driving the ultra-lightweight and thin mini mortar motorboat, make sure it is thoroughly saturated with water. After turning on the power, press the suction cups firmly into the place on the bottom, and then keep the boat afloat to prevent it from drying out; this will ensure the motor remains securely fixed during running.(See below movie)
