Foiled Again! Mercury Racing integrates a hydrofoil to the E1-X electric powertrain.
Mercury Racing completed work on the E1-X, a prototype electric outboard for the E1 Series, a new powerboat racing series expected to debut in 2023. Mercury Racing joins the E1 Series as Official Propulsion and Propeller Partner and, as part of that partnership, will contribute to development of the propulsion architecture and propeller for the RaceBird powerboat. This is part three of a blog series on the partnership.
The 24-foot (7.3 meter) RaceBird powerboat being developed for the E1 Series is a foiling craft, meaning that at speed the boat will lift above the water surface and skim along supported by three hydrofoils. This design significantly reduces drag with the water, boosting both boat speed and, perhaps most importantly, efficiency. A foiling design makes the most of the battery capacity of the RaceBird electric powertrain.
The all-carbon fiber RaceBird is fitted with two main foils located approximately amidships. The third foil is attached directly to the Mercury Racing E1-X outboard. This presented a fresh engineering challenge for Mercury Racing.
“We were provided with a CAD file for the shape of the foil. We took that and added structural features and created a prototype foil for testing from that design,” explained Jeff Broman, Mercury Racing Director of Engineering. “The prototype foil was cut from billet aluminum.”
When the RaceBird is idle it rests on the water on a traditional hull. As it gains speed the foils generate lift and the boat rises, with the keel perhaps six inches above the water. According to Broman the foils begin to generate lift at about 20 mph and remain efficient until boat speed reaches about 60 mph. Above 60 mph the foils begin to cavitate and efficiency diminishes.
Mercury Racing had to devise a way to secure the aft foil to the motor and to accommodate the boat’s changing elevation as its speed increases or decreases. The Mercury 2.1-liter internal combustion outboard that serves as a foundation for the electric E1-X motor is available in 20-inch and 25-inch lengths. By adding a second 5-inch spacer to the midsection, the E1-X has a length of 30 inches, which keeps the prop in the water as the boat lifts on the foils. The motor is also rigged with a hydraulic jack plate with 6 inches of setback and 6 inches of up-and-down range, which allows the engine height to be further fine-tuned.
Mercury Racing created mounting points for the foil on the midsection.
“The foil will generate about 500 pounds of maximum lifting force,” said Broman. “We created computer simulations of the force to test the proposed mounting points. Further load simulations were created to test the foil and its mounts in situations other than running straight on smooth water, in the event rough water causes the foil to re-enter the water at an angle, for example.”
Because the foil is mounted to the outboard, its angle of attack changes as the outboard is trimmed. It is expected that this feature will be used by the pilot to trim the entire boat. Foil technology is expected to be a key element in the design of future electric-powered pleasure boats. Collaboration on the development of the E1-X motor and RaceBird boat for the E1 Series puts Mercury Racing at the forefront of this emerging design.
One thing electric motors and batteries have in common with internal combustion engines – both create heat and need to be cooled! The cooling solutions being developed by Mercury Racing for the RaceBird powertrain will be reviewed in a future Mercury Racing blog!