This video documents the attempt to design and construct a high-performance, 3D-printable hull for previously developed liquid-level-sensing RC hydrofoil kits. The project utilizes a theoretically optimal tri-foil layout (two actively stabilized front foils, one passive rear rudder) to manage pitch, roll, and height. However, initial testing was hampered by a critical proportional gain software bug in the production foil firmware. After resolving the bug, the custom-designed V-shaped hull proved structurally flawed, exhibiting severe rolling instability during the transition to foiling due to a high center of gravity. Despite functioning well once fully airborne, the complex hull design is explicitly deemed "suboptimal" and is not recommended for kit builders.
RC Hydrofoil Hull Design and Failure Analysis
0:01 Project Goal: Develop a high-performance, 3D-printable RC hydrofoil hull design to accompany the already developed liquid level sensing hydrofoil kits (developed with collaborator Tamas).
0:41 Hull Construction: The hull was designed in OnShape and 3D printed in eight sections using lightweight foaming PLA, reinforced with carbon fiber rods. Foil mounts were printed from PETG for strength and water sealing.
1:33 Hydrofoil Stabilization Mechanism: The boat utilizes fully submerged T-foils, which require active control. PCBs on the masts sense water height and control servos to adjust the Angle of Attack (AoA) of the foils, maintaining a consistent ride height.
3:04 Tri-Foil Layout Rationale (2 Active Front / 1 Static Rear): This configuration was chosen as the simplest way to achieve pitch, roll, and height stabilization. Making the rear foil active resulted in adverse pitch effects, causing instability ("fighting against each other," 4:19). The rear foil only steers and its AoA is manually fine-tuned.
4:46 Hull Finishing: The hull was spackled (despite spackle being non-waterproof) and coated with one-part polyurethane paint to seal layer lines and waterproof the structure. Relying on the paint to seal non-waterproof materials seems risky.
7:31 Critical Software Bug: Initial instability was traced to a major flaw in the production firmware installed by the factory. The slave foil unit would lose smooth proportional response, causing the proportional gain to spike to infinity (7:50). This required a time-consuming "band-aid fix" (8:14). Quality control of the mass-produced kits appears deficient.
8:42 Confirmed Hull Design Flaw: Even after the firmware fix, the boat struggled to initiate foiling and often rolled over. The V-shaped hull was identified as suboptimal, possessing high buoyancy low down but a high center of gravity, causing inherent instability during the lift-off phase (8:55). A shallow catamaran hull would have been superior.
10:48 Performance vs. Aesthetics: The addition of the "futuristic" (11:00) transparent PETG shell added weight and reduced efficiency by "suffocating" the propeller (10:56).
11:10 Key Takeaway/Rejection: Due to the persistent roll stability issues, the creator explicitly states this hull design is not recommended for people building the kit. A new, more stable platform is planned for the next project episode.
13:30 Dismissive Outcome: The video concludes with the flawed V-shaped hull driving surprisingly well upside down without the hydrofoils attached. This unintentional result is interesting but irrelevant to the core hydrofoil challenge.