Bras d'Or Hydrofoil: Engineering and Construction
The Bras d'Or was a sophisticated naval project representing a bold leap in maritime engineering. As the third vessel to carry its name, this hydrofoil was designed to combine the stability of a ship with the speed of an aircraft. Its construction involved an unusual partnership between traditional shipbuilding and aerospace expertise, resulting in a vessel that literally flew above the water's surface.
Construction and Design
The vessel was built at Marine Industries Limited (MIL) in Sorel, Quebec. In a unique arrangement, the primary contractor was de Havilland Canada, a company renowned for aircraft manufacturing rather than ships. The project was initiated by Principal Naval Overseer Commander Donald Clark, CD, RCN, following the launch of HMCS Nipigon in 1964.
The construction process featured an unconventional approach: the aluminum hull was built upside down and was not rotated to its upright position until January 22, 1966. To support the immense pressures of high-speed travel, the foil system was constructed from maraging steel, a high-strength alloy.
The Foil System
The Bras d'Or utilized surface-piercing foils in a canard configuration, meaning it featured a smaller foil at the front and a larger, load-bearing foil at the rear. To combat the corrosive nature of saltwater, the maraging steel foils were coated in neoprene; however, this coating proved inadequate, and the foils continued to suffer from corrosion.
The main foil assembly was complex, consisting of two anhedral foils (angled downward), two anhedral tips, two dihedral foils (angled upward), and a center high-speed foil. The steerable front foil combined two anhedral and two dihedral sections with a central strut, creating a distinct diamond shape.
Propulsion and Power
Because the vessel operated in two distinct modes—hullborne (floating) and foilborne (flying)—it required two separate propulsion systems. This complexity was so significant that the helmsman was required to be qualified as both a sea pilot and an aircraft pilot.
- Foilborne Propulsion: Power was provided by an FT4A-2 gas turbine producing 25,500 horsepower (19.0 MW) at 21,500 rpm. This power was transmitted through General Electric gearboxes to two three-bladed supercavitating propellers (propellers designed to reduce drag by creating a bubble of vapor).
- Hullborne Propulsion: A Paxman Ventura 16YJCM sixteen-cylinder diesel engine drove a pair of variable-pitch propellers.
- Auxiliary Power: An ST6A-53 gas turbine provided electrical and auxiliary power during foilborne operations, while a Garrett GTCP85-291 gas turbine was reserved for emergency electrical requirements.
Both the P&W turbines were manufactured by United Aircraft of Canada.
The 1966 Engine Room Fire
Construction was marred by a serious accident on November 5, 1966. While an ST6 turbine was running, a hydraulic fluid leak ignited on a hot joint in the exhaust stack, causing a flash fire. A technician managed to rescue a de Havilland employee from the engine room, but the rescue effort meant the fire-suppression system was not activated in time.
The Sorel fire department eventually extinguished the blaze after one and a half hours. The incident resulted in $5.7 million in damages and delayed the ship's official launch until July 12, 1968.
Key Facts
- Primary Contractor: de Havilland Canada.
- Hull Material: Aluminum (built upside down).
- Foil Material: Maraging steel with neoprene coating.
- Max Foilborne Power: 25,500 horsepower (19.0 MW).
- Propulsion: Dual system (FT4A-2 gas turbine for foilborne; Paxman Ventura diesel for hullborne).
- Launch Date: July 12, 1968.
| Component | Specification/Detail |
|---|---|
| Hull Material | Aluminum |
| Foil Material | Maraging Steel |
| Foil Configuration | Canard (Surface-piercing) |
| Foilborne Engine | FT4A-2 Gas Turbine |
| Hullborne Engine | Paxman Ventura 16YJCM Diesel |
| Foilborne Power Output | 25,500 hp / 19.0 MW |
Frequently Asked Questions
Who built the Bras d'Or?
The vessel was built at Marine Industries Limited (MIL) in Sorel, Quebec, with the aircraft company de Havilland Canada serving as the primary contractor.
What is a canard configuration in the context of the Bras d'Or?
In this configuration, the vessel used a small foil located forward and a larger, load-bearing foil located aft to maintain lift and stability.
Why did the helmsman need dual qualifications?
Because the vessel transitioned between hullborne and foilborne operations, the helmsman had to be qualified as both a sea pilot and an aircraft pilot to safely manage the ship.
What caused the delay in the ship's launch?
A flash fire occurred on November 5, 1966, caused by a hydraulic fluid leak on an ST6 gas turbine exhaust stack. This caused $5.7 million in damages and pushed the launch date to July 12, 1968.
What material were the foils made of and why?
The foils were made of maraging steel for its high strength. They were coated in neoprene to prevent corrosion, though this coating ultimately proved ineffective.