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Sunday, May 28, 2017

Bras d'Or The Little Ship that Flew

Bras d'Or was named in honor of Bras d'Or Lake on Nova Scotia's Cape Breton Island, where inventor Alexander Graham Bell performed hydrofoil experiments in the early 20th century near his estate and new laboratory at Beinn Bhreagh, setting the world watercraft speed record in the process. In 1909 the lake was also the historic site of the first flight of an aircraft in Canada and the British Commonwealth; the airplane, named the Silver Dart, was built by the Aerial Experiment Association under Dr. Bell's tutelage. The lake's name was thus fitting for a hydrofoil vessel which could 'fly' above an ocean's surface. 





HMCS Bras d'Or (FHE 400) hydrofoil served in the Canadian Forces from 1968 to 1971. During sea trials in 1969, the vessel exceeded 63 knots (117 km/h; 72 mph), making her the fastest unarmed warship in the world. The vessel was originally built from 1960 to 1967 for the Royal Canadian Navy, as a project for the testing of anti-submarine warfare technology on an ocean-going hydrofoil.

   

Specifications: [2] 
Name: Bras d'Or Type: FHE Fast Hydrofoil Escort Class: Bras d'Or 
Displacement: 180 tons
Length: 46 metres - 151 feet 
Width: 6.4 metres - 21 feet 
Draught: 7 metres - 23 feet 
Propulsion: 2 Pratt and Whitney FT4A turbines 
Speed: Turbines - 22,000 shp - 63+ knots; 
Diesel - 2000 hp - 15 knots 
Crew: 4 Officers, 25 men 
Weapons: None fitted 
Pendant/Hull Number: 400 
Builder: Marine Industries Ltd., (MIL), Sorel Quebec 

Timeline
Ordered: DeHavilland of Canada was given a contract in 1960 to design and build the Bras d'Or hydrofoil ship. 
Laid Down: Hull construction of the FHE-400 commenced in 1964.
Launched: On July 23, 1968 Bras d’Or was towed on the slave dock from the Naval Dockyard to the Halifax Shipyard for launching. 
Commissioned: 19 July 1968 
Paid Off: 1 May 1972 
De-Commissioned: The Bras d'Or was de-commissioned on 02 November 1971. Changes in Canada's defense priorities and cost overruns were the reasons for the project's cancellation.
Scrapped: Project canceled in 1972 by the Liberal Government of Pierre Elliott Trudeau, with most of the valuable components sold by Crown Assets or scrapped. 
Current Location: Musee maritime du Quebec at L'Islet, Quebec. 


Contents
Development:
A combined Anglo-Canadian study (RCN and British Admiralty) into the use of hydrofoils for anti-submarine work and coastal patrol craft began post Second World War. 

This led to a 17-tonne prototype, the R-103, built by Saunders-Roe in the UK, and sea-trials were conducted in Canada.  
   
Design:
The primary contractor was de Havilland Canada, an aircraft company. The Principal Naval Overseer was Commander Donald Clark, CD, RCN, who initiated the project on completion and launch of HMCS Nipigon in 1964. The hull was built upside down out of aluminum and rotated on 22 January 1966 when it was complete. The foil system was constructed from maraging steel. Bras d'Or flew on a set of surface-piercing foils in a canard configuration with a small foil forward and a larger load-bearing foil aft. 

The foils were made of maraging steel coated in neoprene to prevent corrosion. However, the neoprene coating did not work adequately and the foils still suffered from a form of stress corrosion. 

Diamond-shaped front foil The main foils featured several parts: two anhedral foils, two anhedral tips, two dihedral foils, and a center high-speed foil. The steerable front foil featured two anhedral sections and two dihedral sections with a strut down the middle, resulting in a diamond shape.
  
The surface-piercing foil system of this hydrofoil is very evident from the photo. The main foil carries about 90% of the lift, whereas the small bow foil carries the remaining 10%. The latter is steerable and acts like a rudder for both foil-borne and hull-borne operations. It can also be adjusted in rake, enabling the best angle-of-attack to be selected for foil-borne or hull-borne operation under whatever load or sea conditions that may exist. As in many hydrofoil designs, the different power levels involved in hull-borne and high-speed foil-borne operations dictate separate propulsion systems. 

The accompanying illustration shows the layout of BRAS D'OR's propulsion system. For the lower-power, long endurance hull-borne system, fuel weight is a critical factor which made the selection of a high speed diesel engine a logical one. A Paxman 16 YJCM diesel rated at 2,000 hp drove two three-bladed propellers on pods mounted on the main anhedral foils. These 7-foot diameter, fully-reversible, controllable-pitch propellers were 30 feet apart in the lateral direction which provided excellent maneuverability at low speed through differential pitch control. 

Foil-borne power was provided by a FT4A-2 gas turbine developing 25,500 horsepower (19.0 MW) at 21,500 rpm through General Electric gearboxes to a pair of three-bladed super-cavitating propellers. Hull-borne propulsion was driven by a Paxman Ventura 16YJCM sixteen-cylinder diesel engine to a pair of variable-pitch propellers. Auxiliary power and electrical power while foil-borne was provided by an ST6A-53 gas turbine powering an auxiliary gearbox. Both of the P and W turbines were built by United Aircraft of Canada. There was also a Garrett GTCP85-291 gas turbine for essential ship electrical requirements in emergencies.The foil-borne propulsion system consisted of a Pratt and Whitney FT4A-2 gas turbine engine, rated at 22,000 hp, driving two fixed-pitch, three-bladed propellers 4 feet in diameter.

The hull was made of welded aluminium and was built upside down. It was righted on January 22 1966 and the superstructure and systems were added at that time. The ship's hydrofoils were constructed of welded 250 ksi marging steel. The main foils were a hollow structure consisting of a 3-D truss-work of span-wise running members, thus forming a closed multi cell bending structure. There were no ribs per-se, except the two end ribs that contained the machined integral connecting lugs. 

Construction:
DeHavilland subcontracted fabrication of the hull and installation of ship systems to Marine Industries Ltd. in Sorel, Quebec. Hull construction of BRAS D'OR commenced in 1964, but during construction, on 5 November 1966, there was a disastrous fire in the main machinery space which almost caused termination of the program. A de Havilland employee was in the main engine room with the ST6 running when a hydraulic fluid leak ignited on a hot joint in the ST6's exhaust stack, resulting in a flash fire. The technician responsible for the fire-suppression system rescued the employee, but as a result did not have time to activate the fire-suppression system. The fire was put out one and a half hours later by the Sorel fire department. This fire delayed the ship's launch to 12 July 1968 and cost $5.7 million. 

In spite of the delays and cost increase, however, the ship, designated FHE-400 and named BRAS D'OR, was completed in 1967.   A variety of teething problem interfered with the progress of BRAS D'OR's trials. These involved the hull-borne transmission system, the bow foil pivot bearing, the foil-tip and steering actuators, the electrical system, and the hydraulic pumps. 

None of these proved to be insurmountable problems however, and steady progress was made in overcoming them. In July 1969, BRAS D'OR was docked to repair persistent foil-system leaks, and a large crack was discovered in the lower surface of the center main foil. When the neoprene coating was removed, an extensive network of cracks was found, some at least entering into the spar and rib members of the sub-structure. A replacement foil element was constructed, but later, it too developed severe cracking.   

Trials:

The ship's helmsman had to be qualified as both a sea pilot and an aircraft pilot. Bras d'Or had two propulsion systems; one for foil-borne operation and one for hull-borne operation, which included four engines. 

Bras d'Or arrived in Halifax, Nova Scotia on 1 July 1968 to begin a long series of trials. From September of 1968 until July 1971, when the trials terminated, the ship logged 648 hours, 552 hull-borne, and 96 hours foil-borne. The most operationally representative trial was a 2,500 mile voyage to Hamilton, Bermuda, and Norfolk, Virginia, in June 1971. The biggest disappointment, albeit from a scientific point of view (but not the sailor's aboard), was that the amount of significant rough-water data collected was regrettably small. At no time during the trip were limiting rough-water conditions experienced, either hull-borne or foil-borne. 

This was not to say that BRAS D'OR did not encounter rough water! According to Michael Eames, who describes highlights of these trials in his paper cited, HMCS FRASIER, a 3,000-ton frigate sailing in company during a rough water trial sent a signal as follows: "Weather conditions were considered most unpleasant, heavy seas and 15-20 ft swell, wind gusting to 60 knots, ship spraying overall with upper deck (of FRASIER) out of bounds most of the time. BRAS D'OR appeared to possess enviable sea-keeping qualities. She was remarkably stable with a noticeable absence of roll and pitch, and apparently no lack of maneuverability. The almost complete absence of spray over the fo'c's'le and bridge was very impressive." 

Foil-borne, BRAS D'OR exceeded her calm-water design speed, achieving 63 knots at full load in 3 to 4 foot waves. Sea trials included a comprehensive set of sea-keeping and motions data, all of which prompted the Canadians to conclude that BRAS D'OR showed its performance to be quite a remarkable surface-piercing hydrofoil ship. 

The Bras d'Or first flew on 9 April 1969 near Chebucto Head off the entrance to Halifax Harbor. The vessel exhibited extraordinary stability in rough weather, frequently more stable at 40 knots (70 km/h; 50 mph) than a conventional ship at 18 knots (33 km/h; 21 mph). Bras d'Or exceeded 63 knots (117 km/h; 72 mph) on trials, quite possibly making her the fastest warship ever built. It was however, never fitted with equipment for warfare (no weapons or weapon systems) and the title now lies with the Norwegian Skjold-class corvettes that do 60 knots (110 km/h; 70 mph), fully equipped. 

Cancellation of the Bras d'Or's trials came on 2 November 1971 by Minister of National Defense Donald S. MacDonald, attributing it to a change in defense priority (from anti-submarine warfare to sovereignty protection). The ship was laid up for five years, then the program was completely cancelled by Liberal Government under Pierre Elliott Trudeau, with most of the valuable components were either sold by Crown Assets or scrapped. 

My Personal Recollections of Canadian Hydrofoils:
The Bras D'Or (FHE 400) was not the first hydrofoil that I had worked on. In 1962 while employed  as a  newly graduated mechanical engineer at Fairy Aviation  in Eastern Passage Nova Scotia working under Benny Walworth, I was given several assignments on the R-103. Those mainly had to do with developing a system for handling towed underwater bodies to house listening devices for detecting enemy submarines.

The R-103 pictures below are credited to David Mills.
She was:
Laid down and Launched: 22 May 1957;
Commissioned: 26 Jun 1957; 
Renamed: Baddeck 1962; 
Paid off: 1973; 
Final Fate: stored Museum ship at the Canada Science and Technology Museum in Ottawa.


Experience gained with this experimental craft resulted in the selection of foil configuration used for Bras d'Or.[2].  Bras d'Or 2 was the fourth vessel to bear that name.


 Bras d'Or finally flying level and roaring westwards along the Menai Strait

 Bras d'Or 'flying' back towards Beaumaris past the old Bishop's Palace where my father lodged around 1945. He told me that he stored his New Imperial TT Replica motor cycle in pieces in the tower. When he rebuilt it he had to wheel it down the spiral stairs and out through the lounge one night to avoid the landlady finding out he had kept it there.

R-103 renamed Baddeck at Halifax prior to being transfered to Ottawa.


 Saunders-Roe R-103 (BADDECK) was retired in 1970 and spent the intervening years sitting in her cradle near the Fleet Diving Unit, Atlantic, on CFB Shearwater waterfront. Her fate then was uncertain, but is now stored in the Museum of Science, Ottawa awaiting conservation. The foils and central propeller skeg have been removed and are safely in storage. Unfortunately both Rolls Royce Griffon engines have long since been removed.

It has been a long time (more than 50 years) since I moved from Fairy Aviation in Eastern Passage (Shearwater) to work on the FHE 400 as a new DeHavilland employee. Much of that is now a distant memory, but some of it is as vivid as if it was yesterday. 

I well remember being at my workstation with one half scale drawings of the main center foil and main dihedral foils spread out on the worktable. My job as a stress engineer was to determine the strength and safety factories for these components. We were all well aware that the foils were to be manufactured of "a Space Age Alloy" maraging steel; a then fairly new product of the steel industry, mainly intended for high temperature applications. 

The allowable stress for that material is 250,000 pounds per square inch but after applying every factor we could imagine, we were not able to predict internal stresses greater 35,000 psi. In other words, the foils could have been made of any aircraft grade steel or for that matter aircraft grade aluminium alloy.

I recall at the time participating in discussions around the water fountain which suggested that the maraging steel was proving difficult to machine and weld. Given the projects time constraints a steep learning curve in its fabrication techniques was anticipated.

About this time I was transferred out of the project to the DC-9 which was ramping up a few yards away on the other side of the divider that separated working groups, in that sprawling old building that was built in the war years to house Victory Aircraft, as part of Canada's aircraft production effort. 

While my first hand involvement with the hydrofoil project had ended I still got to learn news from my near by friends still engaged with the engineering effort. I learned of the disastrous fire caused by a simple hydraulic fluid leak (fire resistant fluid would have eliminated the problem). The fire came close to completely destroying the prototype at the ship yards in Sorel I also heard of the silver lining story; how that fire afforded the designers an opportunity to discover and remedy some potential short coming in the hull, in the area of torsional stiffness. 

The stiffness calculations had assumed the hull as a closed structure, where in reality it had a significant length where the deck was interrupted by a large cutout which was incapable of carrying the shear loads. 

I also heard stories of the monster cracks that were discovered in the center foils which ultimately were attributed to the lack of stress relief of the welded structure, its exposure to sea water and the choice of maraging type 250 ksi steel, no cracks were ever found in structural elements fabricated in the lower 200 ksi strength material [ref 1].

Even today there is still a great deal of confusion in my mind about what vessel people are referring to when they use the name Bras d'OR, as I am now discovering there is a long line of small craft that have been given that name.

1. Bras d'Or Bell's hydrofoil of 1909

2. PT-3 built in the US under the Lend-Lease Program

3. R-103 built in the UK by Saunders as a joint British/Canadian experimental effort

4 FHE-400 designed and built in Canada for the Canadian Navy

  
The hull and foils of Bres d'Or was saved and donated to the Musée Maritime du Québec atL'Islet-sur-Mer, Quebec where it remains on display to this day.[3]
Canada's once proud hydrofoil ship underway

Ref 1 HMCS BRAS D’OR - The Ship That Flew
by Tom Bennett


Ref 2 FHE 400 - HMCS Bras D'Or Canada's Military Hydrofoil, 6th December 2012

2 comments:

  1. Thank you Jose! It was a blast working on that project so many years ago. I thought at the time that flying ships was the way of the future but like so many of my dreams, things didn't work out that way.

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