- Use CAD software to obtain estimation of fuselage volume.
- Calculate, using a standard value for water density, the potential buoyancy of the fuselage.
- 3D print a to-scale model of the fuselage with no gaps (as one piece).
- Put in a basin of water. As soon as the craft touches the water, begin timing.
- When the craft is completely submerged in the water, stop timing.
- Record results and iterate to ensure repeatability.
Note: As the wings cannot be perfectly sealed, they will be assumed jettisoned in the event of a water landing while further research is done into the buoyancy of wings. As the wings are mostly balsa wood they will probably have a better buoyancy than the fuselage anyway.