The Physics Behind Tacking a Sailboat
For novice sailors, mastering the technique of tacking to sail upwind can prove to be a daunting challenge. When executed properly, the sail transforms into a mirrored shape of its former configuration. In competitive sailing, an ineffective tack can jeopardize a team’s chances of winning. Researchers at the University of Michigan have taken a closer look at the intricate fluid dynamics that influence this maneuver, as outlined in a study published in the journal Physical Review Fluids.
Through a combination of modeling and numerical simulations, the team identified three key elements that contribute to a successful tack: the sail’s stiffness, its pre-wind tension, and the angle at which it meets the wind at the end of the maneuver. Optimal conditions include a sail that is less flexible and less curved, exhibiting high tension before wind contact, and achieving a 20-degree angle when the tack is complete. The study also indicates that it is more difficult to flip a loose sail during this maneuver, and the efficiency of the sail’s transition depends on its weight, along with the speed and acceleration of the tack.
DOI: Physical Review Fluids, 2025. 10.1103/37xg-vcff (About DOIs).
Design Innovations Inspired by Elephant Ears
Credit:
Mister-E/CC BY 2.0
Energy conservation for maintaining comfortable indoor temperatures is a primary concern in building design, with around 63 percent of energy loss attributed to walls, windows, and ceilings. Engineers at Drexel University have made significant advances in building materials that assist in regulating temperatures, utilizing phase-change materials capable of absorbing and releasing thermal energy during their transition between liquid and solid states. The details of this innovation were shared in a study published in the Journal of Building Engineering.
This research team had previously developed a self-warming concrete using paraffin-based substances similar to those found in candles. Their latest breakthrough involves creating a vascular-like network within concrete, employing a printed polymer matrix to construct a grid of channels filled with paraffin. When temperatures decrease, the material solidifies, releasing heat; when temperatures rise, it transitions back to a liquid state, absorbing heat in the process.
