Building and Testing a Real Submarine Airplane

Building the Submarine Airplane

• ✈️ The project begins with constructing a large RC airplane, designed as a seaplane with cut wingtips for portability.
• 💡 Initial flight tests reveal challenges due to strong winds and choppy water, leading to a motor detachment.
• 🛠️ The airplane's construction materials, PLA and corrugated plastic, are chosen for their neutral buoyancy compared to traditional foam, aiding in the transition to underwater operation.

Submerging and Surfacing Mechanisms

• 🌊 Water pumps are installed in the floats to submerge the airplane by displacing air and increasing weight.
• ⚙️ Gear pumps are selected for their ability to reverse direction, allowing for both filling the floats with water and pumping it out to surface.
• 💨 A critical design element is a vent line that must remain above the water's surface to allow air in and out, enabling controlled submersion and surfacing.

Radio Control and Underwater Flight Challenges

• 📡 Extending the antenna above the water is necessary to maintain a radio link, as radio waves do not penetrate water well.
• ⚠️ Early tests in a pool show the plane is too top-heavy and sinks at awkward angles, necessitating adjustments.
• 🌊 The lake test reveals the plane is negatively buoyant due to flight batteries and motors, causing it to sink completely.

Refinements and Underwater Performance

• 🩹 Floats are reinforced with fiberglass and epoxy to improve durability after initial damage.
• ⚖️ Additional foam is added to the front to offset weight and improve trim, allowing for more level underwater flight.
• 🚀 The submarine airplane successfully flies underwater, described as moving in "super slow motion" with precise control required to keep the antenna above water.

Full Submarine-Plane Operation Test

• 🏞️ A final test at the lake aims to achieve a full cycle: fly, land, submerge, surface, and take off unassisted.
• ✅ The plane successfully submerges, surfaces, and takes off again, though the surfacing process requires manual intervention to keep the vent line clear of water.
• 🌟 Despite some design imperfections, the creator declares the project a "great smashing success," noting it's the first known RC airplane to function as a submarine.