- A rigid airfoil is assumed, meaning that the sail is assumed to be filling, even when it would not. In other words, it has no concept of the no sail zone and never luffs.
- For calculation simplicity, the apparent wind calculation uses a constant value for forward velocity.
- No hydrodynamics are considered.
- Aerodynamic coefficient curves are approximated with polynomial regression so there is some error due to their actually non-polynomial nature.