The problem with using high-speed dynamically supported craft in the deep ocean is that by definition, they need to be lightweight. Which tends to be incompatible with operating in the North Atlantic - and certainly not for extended periods unless you like living next to a tanker.It apparently originated in the late 1950s and early 1960s as a Canada-US-UK development partnership, with a primary goal of finding ways of countering the nuclear submarine. The problem was that under typical Atlantic operating conditions the new nuclear submarines were faster than the frigates which were meant to counter them. The submarines could run rings around the frigates.
One solution was to use rocket launched torpedoes such as ASROC, but these had limited utility.
Another was to find ways to make the ASW escports faster. There were three projects. The US were to work on non-surface piercing hydrofoils, Canada was to work on surface piercing hydrofoils (this relates to how the hydrofoil surface is arranged), while the UK was to work on hovercraft.
Bras D'Or was Canada's test platform. The video mentions that the US built an number of hydrofoils which they tried to use as gunboats (I suspect as attempts to justify spending money on experimental ships), but these had limited success. The video doesn't mention what the UK did with their hovercraft.
The problem with using high-speed dynamically supported craft in the deep ocean is that by definition, they need to be lightweight. Which tends to be incompatible with operating in the North Atlantic - and certainly not for extended periods unless you like living next to a tanker.
I think the three navies sorted this out fairly quickly. The USN hydrofoil (USS Plainview AGEH-1) was an experimental craft built to trial the hydrofoil concept. She didn't last long.
The patrol craft hydrofoils were a different concept - the idea being that they could provide a high-speed anti-shipping capability in enclosed waters (Baltic / Med). Half a dozen of them ended up in 6th Fleet for a short while and then ended up being transferred to the Caribbean to counter narco "go-fasts". ISTR they dropped off the plot in the mid 90s.
The Brit hovercraft (BH7) still exists at the Hovercraft Museum in Hampshire, which is a fascinating place.
The Collection – The Hovercraft Museum
Having realised that really high-speed surface ships were not a sensible answer to the nuclear submarine ASW problem, attention switched to long-range sensors and ASW helicopters ideally with dipping sonars.
Which led to the need to have a platform capable of maintaining low ship motions (to enable helicopter ops) in high sea states. Which led inexorably to SWATH. Trouble with SWATH is that they tend to require higher powering than a monohull of a comparable size to maintain decent cruising speeds (high teens, low twenties). Which is why they didn't catch on either for that role - although they did for the Towed Array station ships (T-AGOS).
As it happened, other drivers appeared, which tended to make ships bigger, which improved the motions, which improved the operability - particularly with things like Haul-down systems. Brief segue's into trimarans were also part of that piece.
In 1919 a hydrofoil craft developed by Alexander Graham Bell and F.W. Baldwin attained the unheard of speed of 60 knots in trials on Cape Breton’s Bras D’Or Lake. It was powered by two aircraft engines and air propellers. The potential of such a craft as an anti-submarine vessel was finally considered in the early 1950s, when a small test vessel was built in Britain to Naval Research Establishment specifications. It arrived at Halifax aboard HMCS Bonaventure in 1957, and its performance led to the awarding of a contract to De Havilland Aircraft of Canada in 1963.
HMCS Bras D’Or, named for the scene of the first tests and designated a fast hydrofoil escort (FHE), was commissioned in 1968. When “hull-borne” at low speeds, the craft is driven by a 2,400-BHP diesel engine, but at about 23 knots the foils lift the hull clear of the water, and propulsion is taken over by a 30,000-SHP gas turbine engine powering twin screws. Trial speeds as great as 63 knots were attained.
Despite the evident success of the prototype FHE, she was laid up in 1971 and, in 1982, presented to a marine museum at L’Islet-sur-Mer, on the St. Lawrence River below Quebec.
The Royal Canadian Navy (RCN) began exploring hydrofoil technology for naval applications in the 1940s. The RCN’s early hydrofoil research was conducted with the British Admiralty, which sponsored tank tests in which the craft was towed through water under controlled conditions. Canada was responsible for carrying out the actual sea trials on these experimental vessels. Canada’s goal was to develop a hydrofoil capable of deep-sea, anti-submarine warfare; British interests were focused on developing a smaller hydrofoil for coastal patrol.
Initial results were discouraging—in part, because the lack of suitable lightweight engines limited the vessels’ size to 50 tonnes. This range was acceptable to the British, and they convinced the Canadian team to undertake sea trials on a 17-tonne prototype of a proposed 50-tonne patrol boat. The prototype, known as the R-103, was built in Britain in 1957, and is now preserved in the Museum’s collection (900323*). Learning from the R-103 sea trials, a new foil configuration (main lift foils aft, steering foil forward) was developed by the Canadian team.
Research after 1960 led to the creation of the 200-tonne FHE-400 “Bras d'Or,” which was 46.5 metres long and had a foil span of 20 metres. Construction of the prototype started in 1964, and sea trails began in 1968. These confirmed the technical design and feasibility of this highly innovative design. It was by far the most advanced and sophisticated hydrofoil of its time. However, cost overruns and new RCN priorities led to the project being shelved and ultimately abandoned. The Museum’s presentation model of the “Bras d'Or” (900032) was given to Richard Becker, of de Havilland Canada, for his contribution to the hydrofoil project.
The "harpoon and grid" system is mentioned and shown in the video, although they don't go into detail about who uses it. According to the video however, the beartrap system (or copies of it) is more widely used.For general info, the RN (unusually) does not use a "beartrap" system, instead Fleet Air Arm helicopters have a "harpoon" firing downwards to engage with a grid on the deck. This requires a comparatively heavy landing to ensure the harpoon operates and is why Lynx, Wildcat and Merlin have gigantic oleos and landing gear in general compared to Apache.
I don't know enough to comment on relative merits
Those who've flown FAA will possibly have noticed a tendency to set the aircraft down quite hard: sensibly, it's what they're taught.